[HN Gopher] The James Webb Space Telescope is finding too many e...
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The James Webb Space Telescope is finding too many early galaxies
Author : cainxinth
Score : 725 points
Date : 2023-01-12 20:45 UTC (1 days ago)
(HTM) web link (skyandtelescope.org)
(TXT) w3m dump (skyandtelescope.org)
| myaccount0011 wrote:
| [flagged]
| cwoolfe wrote:
| Obligatory xkcd: https://xkcd.com/2622/
| ash wrote:
| This discovery of the early galaxies seems to make "huge-
| looking iPhones far away" xkcd obsolete.
| rubymancer wrote:
| That comic just made my mind bend.
| cwkoss wrote:
| Is it possible that the 'edge' of universe reflects light? Have
| scientists been able to conclusively rule that out somehow?
|
| Does the universe even have an edge? What is our current
| understanding of what the boundaries of the universe might be
| like?
| eganist wrote:
| > Is it possible that the 'edge' of universe reflects light?
| Have scientists been able to conclusively rule that out
| somehow?
|
| It's not an edge the way you think. It's the edge of what we
| can see based on the known age of the universe and how much
| light has reached us. I.e no real boundaries as best as we can
| tell.
|
| The best way you can look at this is that early galaxies are
| being found earlier than expected based on our model of how the
| universe formed. The further you look, functionally the further
| back in time you look (not just further away)
|
| This is an oversimplification and an astrophysics expert can
| give you something better.
| afro88 wrote:
| I guess it's reasonable to assume that there are parts of the
| universe that are far older and much further away (ie, their
| light hasn't reached us yet). Which would mean we can never
| really guess the age of the universe. We can only guess the
| age of our local area?
|
| Which kind of sounds a bit like the whole "everything revoles
| around earth" transitioning to "everything revolves around
| the sun". The universe is what light has reached us
| transitioning to the area of light that has reached us is
| just a small spec of the actual universe?
| ivalm wrote:
| > I guess it's reasonable to assume that there are parts of
| the universe that are far older and much further away (ie,
| their light hasn't reached us yet). Which would mean we can
| never really guess the age of the universe. We can only
| guess the age of our local area?
|
| But older parts of the universe would emit light that would
| have more time to travel. So unless space is not
| continuous, we can confidently say that no older light
| exists. The main counterfactual is that there is an older
| universe that is discontinuous with the observable universe
| (but in what sense is that older universe part of "ours"
| then?).
| afro88 wrote:
| But they can still be far away that the light hasn't
| arrived at us yet (or maybe never will?). It's entirely
| reasonable that space may not be continuous. There may be
| groups of galaxies far enough away from each other that
| they burn out before receiving the other's light.
|
| How can we confidently assume this isn't the case?
| ivalm wrote:
| No, there was a time that all space was hot, and we know
| from microwave background radiation that it is
| homogenous. So it's not just "galaxies are far from each
| other", it would take "space time is discontinuous
| somewhere and this discontinuity is just on the edge of
| our observable universe". There is also no older light
| that can ever reach us, as the amount of universe that is
| observable is actually decreasing (beyond that, CMB will
| always be the oldest light as it predates any
| astronomical object formation). Anyways, CMB really
| constraints the age/homogeneity of the early universe.
| jacobr1 wrote:
| An analogy might be the horizon. There is no fixed horizon,
| it is just the boundary of how far your can view, given both
| the curvature of the earth and the quality of your eyes. It
| is relative to where you are on the earth, and by your
| altitude. So while it is calculable, it isn't a fixed
| boundary like a river, or a wall.
| pwatsonwailes wrote:
| Without getting into lots of detail, this is basically
| correct. It's why we talk about the observable universe.
| There's lots of stuff we can't see because the light from it
| won't reach us.
| oblio wrote:
| I was thinking about something weird right now.
|
| We don't (can't?) even know if there weren't multiple Big
| Bangs, right?
|
| I.e we're just in a specific "universe" we can observe, but
| maybe several of these are just side by side, not
| necessarily parallel as in parallel realities.
| micromacrofoot wrote:
| assuming light from a big bang travels in all directions,
| then another big bang's light could be heading in our
| direction and potentially observable -- the reason we
| can't observe the entirety of our universe is that
| spacetime is expanding in a way where light at the
| beginning isn't traveling fast enough to outpace
| expansion
| chrisweekly wrote:
| wait, no, a big bang doesn't happen IN spacetime, it IS
| spacetime per se. that's part of what makes it so
| confusing.
| godshatter wrote:
| What is spacetime expanding into?
| NineStarPoint wrote:
| Unless we figure out a way to take measurements of areas
| outside of space-time to compare against (which seems
| quite impossible), it's probably a question humanity will
| never answer.
|
| It might be a question with no meaning: The universe
| interacts with nothing else. It spawned out of nothing,
| and its expansion is only meaningful if you're inside the
| universe to see it happening.
|
| It could be a question with a lot of meaning: perhaps the
| universe exists on top of some higher dimensional
| substrate that is conducive to big-bang style expanding
| universes. Maybe the reason the universe expands is only
| possible to answer by having access to the information of
| what it is expanding into.
|
| It could be question impossible to wrap our heads around:
| Maybe the area outside the universe runs on metaphor, and
| our universe expands in a sense that would make more
| sense to a writer than a physicist.
|
| Basically, endless sci-fi can be written about that
| question. But given we are (probably) restricted to
| staying within our universe's laws of physics, it's quite
| likely we'll never really know.
| micromacrofoot wrote:
| as far as we know spacetime is everything that exists
| [deleted]
| GrantS wrote:
| Eternal inflation:
| https://en.m.wikipedia.org/wiki/Eternal_inflation
|
| A more reader-friendly explanation:
| https://medium.com/amazing-science/if-inflation-is-true-
| then...
| SkyMarshal wrote:
| _> because the light from it won 't reach us._
|
| This is one of the most interesting aspects to the
| universe. It's not, _" because the light from it hasn't
| reached us yet but is on the way and will get here
| eventually."_
|
| Rather it's that the rate of expansion of the universe is
| accelerating, so that we're moving away from parts of it
| faster than its light can cover the distance to us. It will
| never reach us.
|
| That's mindboggling.
| Rury wrote:
| I'm still not convinced that the expansion of the
| universe is accelerating based on current evidence.
|
| That argument largely comes from supernovae appearing
| dimmer than we think they should, and more distant things
| appear more red and it looks that way in any direction we
| look. But the thing is, we sometimes calculate how
| distant things are based on redness, so it's kind of
| circular reasoning.
|
| Sure we have other things which help gauge distance, like
| brightness and periods of Cepheids, but if you look into
| history on Cepheids, the association that brightness is
| directly related to periods was built upon an assumption
| that the Cepheids in a galaxy were roughly all the same
| distance away. That may seem probable, but it isn't a
| given, as galaxies can be at various angles to our
| perspective, as well as being different size in various
| dimensions. It also assumes that it is impossible for
| fake Cepheids to exist, which might even confer a reverse
| association. How could we know if we're looking at false
| Cepheids vs real Cepheids, and that there's not multiple
| types of Cepheids with different causes for pulsations at
| various brightnesses?
|
| Next you have to consider movement is relative. It's
| entirely possible a brighter galaxy is moving 2x faster
| away from us, than a dimmer galaxy that is actually
| closer to us. Yet this is hardly considered from distance
| calculations.
|
| Lastly, people also say the Big Bang is not an explosion
| of matter moving outward to fill an empty universe, but
| rather an expansion of space between things. IMO, this is
| mostly just a model, a way of viewing things. The thing
| is, you can still look at things from normal intuition
| (of say an explosion), and it still conforms that
| definition (ie it's objects moving in space over time, vs
| it's space filling in between objects over time). And so,
| if looking further into the galaxy, means looking further
| in time, the dynamics of an explosion suggests that those
| galaxies _will_ be moving faster away from us. As the
| outmost debris of an explosion, is the fastest moving
| debris of an explosion, and speed between two pieces of
| debris, is highly associated to their relative positions
| and tends to increase as distance between them increases,
| even regardless of where they are in an explosion. So
| even if further galaxies are indeed moving faster away
| from us, and it is faster the further we look, and looks
| that way every which way, I don 't see why this would
| necessarily mean the expansion of the universe is
| _accelerating_. As it appears to me, it can be predicted
| by conventional (non-accelerating) explosion dynamics.
| SkyMarshal wrote:
| Considering the two methods for measuring the rate of the
| universe's expansion differ by about 10%, the question
| seems unsettled at best. You're not wrong to question it.
|
| https://youtu.be/hps-HfpL1vc
| Twisol wrote:
| > Rather it's that the rate of expansion of the universe
| is accelerating, so that we're moving away from parts of
| it faster than its light can cover the distance to us.
|
| From my understanding, it's not that we're moving away
| from parts of the universe, but that the distance between
| us is growing so fast that light sent from one part will
| find that after traveling toward us for some amount of
| time, the remaining distance to travel is actually more
| than than when it started.
|
| One way for the distance between two objects to increase
| is indeed for those objects to literally be moving in
| opposite directions through space. But the expansion of
| the universe itself causes the distance between two
| otherwise-stationary points to nonetheless increase. Put
| differently, it's the cosmic yardstick that's shrinking,
| not the entities that must necessarily be moving.
|
| (This is also why two points can be "moving apart" faster
| than light speed, the cosmic speed limit.)
| SkyMarshal wrote:
| _> but that the distance between us is growing so fast
| that light sent from one part will find that after
| traveling toward us for some amount of time, the
| remaining distance to travel is actually more than than
| when it started._
|
| Good clarification, that's what I meant, I guess I didn't
| say it accurately. I don't actually think of us as
| moving, but more like the scale of the entire universe is
| increasing while the ability to traverse it - light speed
| - remains a constant.
| chrisweekly wrote:
| You have it right. My cosmology teacher at UVA a couple
| decades ago used the analogy of points marked on the
| surface of a balloon that's being inflated. (maybe more
| intuitive than other shortcuts to understanding?)
| shagie wrote:
| That rate is "only" approximately 68 kilometers per
| second per megaparsec.
|
| 68 kps isn't that fast (it's about the same speed as the
| Helios 2 solar probe) and a mega parsec is big distance
| (3.2M light years).
|
| Its that there's a lot of megaparsecs between here and
| there and the sum of all of those 68 kps is more than the
| speed of light.
|
| The relevant Kurzgesagt : TRUE Limits Of Humanity - The
| Final Border We Will Never Cross -
| https://youtu.be/uzkD5SeuwzM
| Twisol wrote:
| Yes, true -- the distance between two points doesn't grow
| linearly, but rather proportionally to itself :D
| sfifs wrote:
| So such an expansion phenomenon should affect everything
| uniformly right? Are we (people /animals) then getting
| "bigger"? Over time innthe extreme will it cause problems
| in signal transmission in our own nervous systems (since
| apparently we have a problem seeing light beyond the
| observable limit)
| shagie wrote:
| With the current rate of expansion, no. We're still bound
| together more tightly than the rate. This extends all the
| way out to a fair distance (galactic distance).
|
| If the rate does get to the point where it is noticeable
| the "galaxies can't hold together" you get into the Big
| Rip end of the universe situation.
| [deleted]
| Twisol wrote:
| Gravitational attraction still dominates on even fairly
| large scales, and chemical bonds absolutely dominate over
| anything expansion could possibly do -- it would
| contribute an incredibly light force opposing any bonds.
| So no, we (and our galaxy) are in no danger of being
| inflated from the inside by space itself.
| sfifs wrote:
| Thanks for the explanation!
| denton-scratch wrote:
| > So such an expansion phenomenon should affect
| everything uniformly right?
|
| Apparently not. As far as I can tell (IANAC) cosmic
| expansion affects the empty space between galaxies, but
| not concentrations of mass. Galaxies (and everything in
| them) are immune to cosmic expansion.
|
| I understood that cosmic expansion is a consequence of
| General Relativity; DE is supposed to explain
| _accelerating_ expansion. Is that right? But wouldn 't
| expansion result in there being more empty space and less
| nearby stuff; and therefore in accelerating expansion?
|
| I wish I understood this stuff.
| xenadu02 wrote:
| The strong nuclear force, electromagnetic force, and even
| gravity are strong enough to overwhelm the expansion
| within individual galaxies and even local groups of
| galaxies.
|
| In other words the expansion of spacetime very very very
| slightly tries to shift the atoms of your body apart but
| we can't even detect it because ordinary forces like
| chemical (electromagnetic) bonds are exponentially
| stronger - enough to pull things back where they should
| be. Actually in the current epoch I'm not sure if the
| expansion is strong enough to shift an electron by 0.01%
| of its own width let alone move an atom.
|
| Space is really really big so that tiny amount of
| expansion adds up over long distances.
| sfifs wrote:
| thanks for the explanation!
| paulrouget wrote:
| I don't think that's true. Expansion is not very weak
| around matter, it just doesn't exist. It sounds a little
| counter intuitive to think that expansion "shutdowns" as
| we get closer to galaxy. But that's because expansion and
| gravity are a little more complicated that just a force.
|
| We over simplify what expansion really is, which leads to
| this type of thinking.
|
| Expansion and gravity are results of the same equations.
|
| Einstein equations are difficult to use, so we usually
| split the results in two models, FLRW (empty space) and
| Schwarzschild metrics (around matter). Computing the
| equations leads, respectively, to expansion and gravity.
| And it's not like there's one and the other, with gravity
| fighting expansion. It's "one or the other".
|
| Around matter (in Schwarzschild metric), solving Einstein
| questions, we see zero expansion drifting. If there is
| matter, there is gravity, and no expansion.
|
| Quoting Wikipedia [1]:
|
| > Once objects are formed and bound by gravity, they
| "drop out" of the expansion and do not subsequently
| expand under the influence of the cosmological metric,
| there being no force compelling them to do so
|
| [1]: https://en.wikipedia.org/wiki/Expansion_of_the_unive
| rse#Effe...
| Twisol wrote:
| That makes a lot of sense -- thanks for contributing that
| nuance!
| kgwgk wrote:
| > Einstein equations are difficult to use, so we usually
| split the results in two models, FLRW (empty space) and
| Schwarzschild metrics (around matter). Computing the
| equations leads, respectively, to expansion and gravity.
| And it's not like there's one and the other, with gravity
| fighting expansion. It's "one or the other".
|
| Arguably splitting a complex model of reality in two for
| convenience and saying that it's "one or the other" is
| also an over simplification.
|
| By the way, the same wikipedia entry also says things
| like "gravity binds matter together strongly enough that
| metric expansion cannot be observed on a smaller scale at
| this time."
| kgwgk wrote:
| You don't get larger - just like you don't dissolve in
| water and wind doesn't spread parts of you all over the
| land. There are interactions of matter keeping you
| together.
| ryanSrich wrote:
| Something that's even more mind boggling than that, at
| least to me is that the universe is still within the
| first few seconds (or minutes) of its life in terms of
| relative time we can comprehend. As stars collapse and
| black holes consume everything, the universe will spend
| 99% of its life in complete desolate darkness. An endless
| sea of black holes for billions and billions of years.
| The fact that we exist, in the split second that life can
| exist is unimaginable.
| davidvarela_us wrote:
| Isn't this just the anthropic principle[0]? e.g.
| "conditions that are observed in the universe must allow
| the observer to exist"
|
| [0]: https://en.wikipedia.org/wiki/Anthropic_principle
| kibwen wrote:
| _> Rather it 's that the rate of expansion of the
| universe is accelerating, so that we're moving away from
| parts of it faster than its light can cover the distance
| to us. It will never reach us._
|
| It's actually even worse than that. Because of the
| accelerating expansion of the universe, over time the
| part of the universe that we can observe will get
| smaller, allowing us to see less and less of it.
| Eventually, all that we'll be able to see is our own
| local group of galaxies, where gravitational attraction
| will win out over the universe's expansion. However, this
| won't really be a problem for a few billion years.
|
| Relevant Kurzgesagt video:
| https://www.youtube.com/watch?v=uzkD5SeuwzM
| dalbasal wrote:
| So galaxies are falling off the edge of the universe
| never to be seen again?
| zelphirkalt wrote:
| I know it is considered increasingly unlikely, but: What
| a parallel to flat Earth ideas people had (...) hundreds
| of years ago, until they realized we are on a sphere.
| Maybe in a few hundred years people will laugh about our
| limited ideas of the universe as well.
| alisonatwork wrote:
| This is wrong by an order of magnitude. It was already
| known thousands of years ago that the Earth is more-or-
| less spherical. The idea that people in recent history
| believed in a flat Earth is a myth.[0]
|
| [0] https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth
| midoridensha wrote:
| >The idea that people in recent history believed in a
| flat Earth is a myth.
|
| The way you've worded this, you're incorrect. There are
| people _today_ who believe in a flat Earth, crazily
| enough.
|
| Of course, the idea that most of society (namely educated
| people) believed in a flat Earth is a myth. From your
| link:
|
| "The myth of the flat Earth, or the flat earth error, is
| a modern historical misconception that European scholars
| and educated people during the Middle Ages believed the
| Earth to be flat."
|
| What the typical serf working in the fields thought about
| the shape of the Earth is probably unknown.
| zelphirkalt wrote:
| If we had to guess (of course not good research to be
| guessing): The typical person working on a field probably
| believed what the church told them the world looks like.
| If they ever heard about being on a sphere, they would
| probably laugh and point to the horizon, saying: "How can
| Earth be a sphere? Don't you have eyes to see? Look into
| the distance, all is flat!" and any kind of
| argumentation, that it is simply so huge, that one cannot
| see it, would seem to them like a made up story, a lie to
| further some hidden agenda the explaining person has.
| zelphirkalt wrote:
| That does not really detract from my comment though.
| Thousands of years are also hundreds of years. Just more
| hundreds. So if we are getting technical about that, I
| don't think it is wrong what I wrote. Still, thanks for
| putting the time frame a bit clearer.
| coremoff wrote:
| this has already happened to most galaxies we can see -
| we're seeing the light they emitted before they "fell off
| the edge"
| Iwan-Zotow wrote:
| Yes, that is exactly what predicted to happen in the
| future - dark cold universe
| sampo wrote:
| Lawrence Krauss to Joe Rogan: "Nothing can travel though
| space faster than light, but space can do whatever the
| hell it wants."
|
| https://www.youtube.com/shorts/WGSYKoUqvps
| deanCommie wrote:
| So mindboggling that frankly I refuse to accept it.
|
| The likelyhood that we'll figure this out in my lifetime
| is zero, but I simply can't comprehend a universe that
| accelerates without cause (dark energy) infinitely.
|
| Just as we don't understand the root causes of dark
| energy, I believe it's just as logical to believe that
| something will eventually slow it down.
|
| I have to believe that because only a cyclical theory of
| the universe makes sense to me. It's my faith, I suppose.
|
| The more depressing part to me isn't that I'll never
| know, but rather it's entirely possible HUMANITY can
| never know, any more than an ant can know about General
| Relativity.
| thom wrote:
| I think it's actually quite a simple model to think of
| the universe as a network of discrete nodes, rather than
| a spatial thing that's expanding and within which various
| things are accelerating. It makes the Big Bang simpler -
| we start from a small number of nodes and they grow in
| number, so we don't need to think about what the universe
| is expanding 'into'. And it explains expansion - nodes
| can divide like mitosis, so we don't need to explain some
| force pushing things apart.
| boppo1 wrote:
| What do I have to study to understand all this in
| mathematical terms? Is an undergrad text good enough?
| pc86 wrote:
| Depends what you mean by "in mathematical terms." There
| are YouTube videos that cover the concept with real
| numbers.
| hnuser123456 wrote:
| The universe is 13.7b yo, but due to acceleration of
| expansion, if you could "teleport", it's actually
| currently 93b ly across. So we're already in a bubble
| within a greater universe that we'll never be able to
| escape even if you could instantly reach lightspeed right
| now, and due to the expansion continuing to increase, the
| fractional size of this bubble relative to the rest is
| shrinking. Faraway galaxies that are "currently" on the
| edge of the bubble but expanding away are becoming
| forever unreachable as you read this.
|
| https://en.wikipedia.org/wiki/Comoving_and_proper_distanc
| es#...
|
| https://public.nrao.edu/ask/inconsistency-between-the-
| age-an...
|
| However, the local group/cluster of galaxies is close
| enough to remain gravitationally bound, and we're still
| gonna merge with Andromeda.
| Maursault wrote:
| > The universe is 13.7b yo, but due to acceleration of
| expansion, if you could "teleport", it's actually
| currently 93b ly across. So we're already in a bubble
| within a greater universe that we'll never be able to
| escape
|
| This number, the age of the universe, has changed a few
| times since I learned to read 45 some years ago. What are
| the chances that this isn't really "the" universe, but
| what we know as the observable universe is really a mind-
| bogglingly massive black hole that was sucked out of the
| actual universe, and the actual age of "the" universe is
| incalculably old, trillions of quadrillions of years old,
| and it's only our baby universe is what is roughly
| 13.7Byo? Maybe the Great Attractor hides the mother of
| all singularities. I'm sure there could be a way to
| explain the CBR and what seems like the Big Bang and
| Inflation. Maybe this baby universe only appears to be
| expanding, when it's just a growing black hole.
| nickersonm wrote:
| The number hasn't really changed, it's just been measured
| with increasing precision. It is rather unlikely to be
| wrong given measurements via various methods are all in
| agreement. Summaries about these various experiments are
| available: https://imagine.gsfc.nasa.gov/science/featured
| _science/tenye...
| fnovd wrote:
| It's black holes all the way down. Fun to note that, from
| the reference of someone outside a black hole, the
| singularity contained within hasn't happened yet, and
| never will.
| reptation wrote:
| It's worth pointing out that there is a minority of
| physicists who don't accept the Big Bang as proven beyond
| doubt. An alternative theory would be a 'steady-state'
| universe which, as you suggest, would be much older than
| the ~14 BYO age. If the medium of space itself dispersed
| light for instance, red shifts might be observed that
| explain the astronomical data.
| pmayrgundter wrote:
| Eric Lerner is one of them and he's advocating for the
| idea that the BB never happened and that we'd see plenty
| of old galaxies with JWST. He's since updated his
| thoughts and there was a bunch of controversy:
|
| https://news.ycombinator.com/item?id=32938153
| [deleted]
| bee_rider wrote:
| Just for any future historians: all us normal people are
| aware that the idea of the Big Bang seems a little
| fantastical, but relativity or whatever is, like, way
| complicated. Most of us just have to trust the
| physicists. Of course now that you have the Theory of
| Everything, notation and thought-experiments developed to
| make it obvious, and relativity is just a special case,
| we look pretty dumb. But if you look at the operators
| that your undergrads pull out to solve Theory of
| Everything equations and try to somehow derive them with
| ancient 21'st century math, they are actually really
| complicated!
|
| Actually, having a bit of sympathy now for the folks who
| believed in the Luminiferous aether.
| Calavar wrote:
| > If the medium of space itself dispersed light for
| instance, red shifts might be observed that explain the
| astronomical data.
|
| This is called tired light theory. There's a professor of
| physics at UCLA who has a good breakdown of some of the
| major flaws with that theory.
|
| https://astro.ucla.edu/~wright/tiredlit.htm
| hnuser123456 wrote:
| Better wikipedia link: https://en.wikipedia.org/wiki/Obse
| rvable_universe#:~:text=Th...).
| make3 wrote:
| how can that work if nothing is faster than light in the
| referential of the objects being compared? is it that space
| expands faster than light moves?
| delecti wrote:
| > is it that space expands faster than light moves?
|
| Yes. Picture an ant walking on the surface of a balloon.
| You could conceivably blow up the balloon faster than the
| ant could walk across it. If you were blowing up an
| infinitely stretchy balloon with an ant at the far end,
| you could conceivably blow it up fast enough that the ant
| could never reach you.
| seanw444 wrote:
| Correct, as I understand it. No _matter_ can travel at
| the speed of light, and no light can travel faster than
| the speed of light. But the rule doesn 't extend to the
| rate of expansion of the "field" on which those things
| exist.
| seszett wrote:
| When I read this, it seems to me like this is more or
| less the same as saying that the speed of light is
| decreasing, but I am probably wrong?
| dpkirchner wrote:
| Like if you calculated the speed not in meters per second
| but fraction-of-the-universe per second?
| cout wrote:
| What if space isn't expanding and we are just shrinking?
| jhoechtl wrote:
| Is this something anybody ever thought out to look at
| things this way? Sounds like an intriguing
| Gedankenexperiment
| eigenket wrote:
| Yeah, ideas like this are usually called "tired light"
| models, they have been extensively explored for the last
| hundred years or so. A lot of these models have been
| shown to be false by experiments, but I guess if you try
| you can probably cook up models which haven't been
| falsified by anything yet.
| function_seven wrote:
| I vote we bring back "aether" as a valid term. The aether
| is stretching everywhere, and in so doing it spreads
| distant things away faster than light can overcome.
| micromacrofoot wrote:
| I did a wrong, ignore me
| fknorangesite wrote:
| This is exactly wrong: _c_ is the one speed that _is_
| constant to all observers.
| micromacrofoot wrote:
| oh so, space changes... not the light?
| tetha wrote:
| Ah. So it's a referential thing?
|
| If we had some absolute zero reference outside the
| universe - let's call it a great alien petri dish - we
| probably could find something moving faster than the
| speed of light, in reference to that absolute, out-of-
| universe observation point? But measuring that might be
| hard.
|
| And on the other hand, we might be able to find two
| objects which are static with reference to the universe,
| but actually increasing the distance from each other at a
| speed beyond c or rather 2c, which should be impossible,
| because the universe between them expands?
|
| This is very weird to think about, but accepting your
| reference framework - the universe - changes makes it
| easier.
| thom wrote:
| Think of the universe as some sort of information system.
| The speed of light caps the rate at which information
| propagates, which is a desirable or at least necessary
| property at scale. But there's some discrete substrate
| underlying that propagation of information. That
| substrate can multiply, like inserting nodes in a graph
| or empty spaces in a linked list. That makes it longer to
| traverse from one end to the other. The rate of
| propagation stays the same but the map keeps changing.
| colordrops wrote:
| How does this work with the big bang happening at a specific
| point in the past?
| soulofmischief wrote:
| We have a concept of the Particle Horizon, the max distance
| light could have traveled in the universe, and that is our
| boundary, our effective edge of the universe.
|
| There's the concept of the light cone, which is the total
| volume of observable light which can ever reach an observer,
| or inversely, the total volume ever traveled by a given point
| source. The expansion of the universe means that there is a
| certain boundary, a horizon where the universe expands too
| much for light to ever travel the required distance.
|
| https://en.m.wikipedia.org/wiki/Particle_horizon
|
| https://en.wikipedia.org/wiki/Light_cone
| 8note wrote:
| I wouldn't be surprised if there's a hawking radiation
| equivalent for that edge, but the wavelength is on the order
| of the size of the universe, so basically impossible to
| measure
| [deleted]
| CuriouslyC wrote:
| Talking about the edge of the universe implies space is a
| thing. Physics works just fine if you imagine the x, y and z of
| particles describes an arbitrary set of coupled attributes on
| the particle itself. It is more likely that space is an
| emergent property of the entanglement between information, and
| in that case the idea of a boundary is nonsensical. Under that
| model, "spacetime" would behave like a foam - if one bit of it
| pulled far enough away from the rest it'd shoot off as a
| bubble.
| soiler wrote:
| What is the edge of the universe? How would you define that? In
| most models, the universe doesn't have anything that could be
| called an edge. Unless you are referring to the boundary of the
| local universe, which is defined as the sphere around us at
| which objects are too far away for their light to ever reach
| us. It's not a physical structure that could reflect light,
| it's more like the opposite of that.
| teraflop wrote:
| No, we have no evidence that the universe has any kind of
| "edge" that is topologically different from its interior.
|
| There is a boundary to what we can see. As the early universe
| cooled, it changed from an opaque plasma to transparent gas. So
| as we look farther away, and also backward in time, we see the
| last point at which it was opaque; this is the cosmic microwave
| background. But this isn't a "real" boundary that something
| could hit. And it long predates the formation of galaxies, so
| it couldn't have reflected images of galaxies.
| chrisweekly wrote:
| also (citation needed, this is from memory from university
| cosmology classes over 20y ago, maybe misremembering or info
| out of date) the shape of the universe may be less like a
| sphere and more like a toroid, or a multidimensional moebius
| strip.
|
| so (hand-wavy, impossible IRL but maybe illustrative / fun to
| think about) if you could freeze time and look far enough in
| one direction, you'd see the back of your own head.
| eigenket wrote:
| There are some reasons why cosmologists don't like the idea
| of a universe that loops back on itself, one is that such a
| universe can't be both isotropic (the same in every
| direction) and homogeneous (the same at every point) [edit:
| while also being flat, as observations seem to indicate it
| is].
|
| To get a rough idea of why, imagine taking a 1km by 1km
| square and identifying the opposite sides, you now have a
| homogeneous space (every point is equivalent to every other
| point), but it isn't isotropic because some directions are
| special. If you put a rock on the ground and walk due east,
| you'll have to walk 1km to reach the rock again (assuming
| you start in what used to be the center of the square it
| takes 500m to where the edge used to be, and another 500m
| from the edge back to your starting point). On the other
| hand if you walk south east you have to walk sqrt(2) km to
| get back to your rock (sqrt(2)/2 km to get to what used to
| be the south east corner, and another sqrt(2)/2 km to get
| back to where you started).
|
| So although the torus space is homogeneous there are traces
| of the fact that it used to be a square, embedded in the
| fact that some directions are special (the 4 cardinal
| directions have the shortest distance to get back to where
| you started and the 4 intercardinal directions have the
| longest). Cosmologists think this lack of isotropy is
| essentially ugly, and don't like the idea of living in a
| universe where some directions are special.
|
| Aside from just not liking the idea (which isn't very
| scientific) its also relevant that the universe looks
| pretty isotropic when do observations, we emphatically
| don't see traces of the sort of anisotropy you'd see in a
| toroidal universe anywhere.
| drdeca wrote:
| What's wrong with it being (topologically) a 3-sphere ?
| That seems plenty symmetric to me.
| eigenket wrote:
| Theres nothing massively wrong with it, it's a perfectly
| plausible model.
|
| The one thing that isn't particularly nice is that
| spheres have intrinsic curvature, essentially if you draw
| two parallel lines on a sphere they will eventually
| touch. We can go and look at astronomical data and see if
| the universe has any intrinsic curvature that we can see.
|
| People did this and it turns out that from all the
| astronomical data we have the universe looks incredibly,
| spectacularly flat. No curvature at all that we can
| detect. This doesn't mean it isn't a sphere, but it means
| that if it is a sphere it's a really big one. Much much
| bigger than the observable universe.
| deepsun wrote:
| To be pedantic, there is curvatures, see lensing effect
| of large masses. It's not global, though.
| ben_w wrote:
| The far limit of the visible universe is the cosmic microwave
| background, which is the heavily red-shifted view of when all
| of space was filled with an opaque plasma of similar
| temperature to the surface of a star[0].
|
| The galaxies we're seeing are in front of that.
|
| [0] 3000 K,
| https://en.wikipedia.org/wiki/Recombination_(cosmology)
| lostmsu wrote:
| This is hard to internalize. Why do we continue seeing CMB?
| My understanding is that the early galaxies still produced
| light after recombination.
| cbracken wrote:
| The process that caused the light we see as the CMB
| happened everywhere in the universe roughly all at once. At
| the time, from any given point, you'd just have seen
| blinding light but as things cooled, you'd see a sphere
| expanding around you where this light was dimming, as less
| and less, and finally none was being emitted around you,
| but due to the finite speed of light, light from outside
| that sphere would still continue arriving in your eyeballs.
| That's the situation we're in today; that sphere's just
| really big now.
|
| During recombination epoch ~400,000 years after the Big
| Bang, this light would have been visible. Due to expansion,
| over time that light has stretched to longer and longer
| wavelengths, and we currently see it as microwaves.
|
| Note: It's been ~30 years since I was actually studying
| physics & astronomy; others may be able to offer better
| explanations or correct me.
| ben_w wrote:
| The CMB happened everywhere in the universe at the same
| time[0], so what we're seeing is the light which took
| 13-point-whatever billion years to get here[1] from some
| part of the universe in that direction at that younger age.
|
| > My understanding is that the early galaxies still
| produced light after recombination.
|
| I'm not sure what you're imagining about recombination,
| because I've not heard any suggestion of any galaxies
| existing before it, so they _only_ produced light after
| recombination.
|
| [0] for some definition of the concept, even though
| relativity is formulated with the assumption that there
| isn't any good concept of simultaneousness.
|
| [1] from our point of view. From light's point of view,
| time isn't defined.
| jhoechtl wrote:
| My theory: It's not an edge but we look onto ourselves back in
| time. As space and time evolves, it's hard to identify as such.
|
| One day we will recognize that we essentially were looking onto
| space to see ourselves while starring. The last thing is meant
| metaphorical.
| twawaaay wrote:
| The edge of _visible_ universe is Big Bang. Or more concretely,
| the time couple hundred thousand years after Big Bang when the
| universe became translucent to light.
|
| Things cannot "reflect off of the edge of visible universe"
| because that would require that the light travel back in time
| which is nonsense.
|
| As of this moment we cannot exclude possibility of
| discontinuities in the universe which would be cause for
| example by inflation. But we also have not observed any.
| 0xbadcafebee wrote:
| if time is a dimension, and we can only see the past and the
| present, could it not be that, if one's gaze were shifted,
| one could see the future? effectively looking at the "other
| side" of the dimension of time? looking straight at one
| "side" of time, you can only see the past and present. but if
| you had a galactic set of mirrors set up around "time",
| couldn't you "see" the other side where the future lies?
| effectively you'd be looking at a reflection of the future.
|
| or, time being malleable (relative to things like mass and
| movement), wouldn't it be possible to refract or bend time
| the way light is, such that you could see things (that
| already happened in the past) sooner, even if they are really
| far away? maybe like how bending a race track can allow a
| vehicle to exert more force or go faster, but with light?
| twawaaay wrote:
| Or wait until shrooms wear off.
| pwatsonwailes wrote:
| Time doesn't exist as a thing in the way you're thinking
| about it. It's why in physics we talk about spacetime. (The
| following is not entirely accurate and an
| oversimplification.)
|
| Space and time are one thing, which have to be thought
| about together. Your current thinking imagines that you're
| in a box, with x, y and z coordinates, and that time is a
| thing passing inside it. Instead, it'd be more accurate to
| talk about that you're in a frame of reference with x, y, z
| and a, and all are tied together. There's no sense in which
| you can talk about space and not also be talking about
| time, and vice versa. For a similar idea, a 3d volume is
| not a plane plus a z axis, where you can talk about moving
| through just the x and y axis without the z axis mattering.
| You can talk about a view of that, but it doesn't mean the
| z axis isn't relevant. Ask two planes not colliding whilst
| viewed from above how important a z axis is. (Maths jokes
| are the worst.)
|
| The actual physics involved for discussing this gets
| absurdly complex very quickly, but this is about as simple
| as I can think how to explain it whilst still being in the
| bounds of accurate.
| badrabbit wrote:
| Space and time are intertwined interstingly that way. If time
| somehow loops back or reverses (circular time) the it is not
| unreasonable to suggest space also loops back. Is it possible
| that at a certain boundary of space and point in time you loop
| back and start over at 0:0:0/0:0:0 space/time coordinates. At
| least in this current realm of reality, is it like one big
| space-time movie on a loop?
| [deleted]
| xcskier56 wrote:
| I have a memory from when I was a kid and learning about the
| universe. In my head it definitely had an edge, and it
| resembled a really really big hockey rink with boards. But it
| was also only 2d at that time, which I think I remember knowing
| that wasn't right but not being able to conceptualize a 3d
| universe. So yes, in the universe of my 8yo mind the "edge"
| might reflect light
| SaintSeiya wrote:
| Maybe, just maybe the Universe is infinite and eternal? and the
| big bang never happened?
| xwdv wrote:
| Ok, so if the Big Bang Theory is bunk, what's the next leading
| alternative creation theory?
| sebzim4500 wrote:
| Something which sounds exactly like the Big Bang Theory to a
| layman but whose expansion satisfies a different equation.
| TheOtherHobbes wrote:
| I'm going to be very amused if the Steady State Model - an
| unpopular relic from the 1940s - turns out to be correct.
|
| https://en.wikipedia.org/wiki/Steady-state_model
| marricks wrote:
| There's also more spiral galaxies than expected!
|
| If steady state gained favor that would be super fun, but this
| quote from the article seems to throw a little cold water on
| that.
|
| > At the same time, she notes that yesterday's disks are
| different than modern ones. "They're not today's Milky Way,"
| she notes. "They're turbulent, they're messy, and we need to
| study them more."
| airstrike wrote:
| Speaking of unpopular pet theories from the 1940s, I'm a fan of
| the https://en.wikipedia.org/wiki/One-electron_universe
|
| EDIT: There's also this super fun PBS Space Time episode on the
| theory: https://www.youtube.com/watch?v=9dqtW9MslFk
| Cthulhu_ wrote:
| I love this theory because it's both mindblowing and yet,
| when you think about it, weirdly makes sense. Assuming time
| travel etc, of course.
| brap wrote:
| Since everyone is mentioning their favorite whacky theories,
| mine is the one that says within every particle is a whole
| universe, made up of particles with their own universes and so
| on, and what we call our universe is really just a particle in
| an even bigger universe. And what if all of those universes
| were actually the same universe, like some infinite recursion?
|
| Is there a name for this?
| ckw wrote:
| Animal House: https://youtu.be/JUOGxePBs50
|
| Pascal: [...] But to show him another prodigy
| equally astonishing, let him examine the most delicate things
| he knows. Let a mite be given him, with its minute body and
| parts incomparably more minute, limbs with their joints,
| veins in the limbs, blood in the veins, humours in the blood,
| drops in the humours, vapours in the drops. Dividing these
| last things again, let him exhaust his powers of conception,
| and let the last object at which he can arrive be now that of
| our discourse. Perhaps he will think that here is the
| smallest point in nature. I will let him see therein a new
| abyss. I will paint for him not only the visible universe,
| but all that he can conceive of nature's immensity in the
| womb of this abridged atom. Let him see therein an infinity
| of universes, each of which has its firmament, its planets,
| its earth, in the same proportion as in the visible world; in
| each earth animals, and in the last mites, in which he will
| find again all that the first had, finding still in these
| others the same thing without end and without cessation. Let
| him lose himself in wonders as amazing in their littleness as
| the others in their vastness. For who will not be astounded
| at the fact that our body, which a little while ago was
| imperceptible in the universe, itself imperceptible in the
| bosom of the whole, is now a colossus, a world, or rather a
| whole, in respect of the nothingness which we cannot reach?
| He who regards himself in this light will be afraid of
| himself, and observing himself sustained in the body given
| him by nature between those two abysses of the Infinite and
| Nothing, will tremble at the sight of these marvels; and I
| think that, as his curiosity changes into admiration, he will
| be more disposed to contemplate them in silence than to
| examine them with presumption. For in fact what is
| man in nature? A Nothing in comparison with the Infinite, an
| All in comparison with the Nothing, a mean between nothing
| and everything. Since he is infinitely removed from
| comprehending the extremes, the end of things and their
| beginning are hopelessly hidden from him in an impenetrable
| secret, he is equally incapable of seeing the Nothing from
| which he was made, and the Infinite in which he is swallowed
| up.
| thinkmcfly wrote:
| I dunno, I felt like this was a huge cop out in the movie Men
| in Black
| someotherperson wrote:
| Men in Black marble hypothesis?
|
| https://www.youtube.com/watch?v=OKnpPCQyUec
| brap wrote:
| I also vaguely recall something from The Simpsons...
|
| Edit: ha, found it:
| https://m.youtube.com/watch?v=ycvlJ9XMd94
| karmelapple wrote:
| Which itself is based off the intro the film Contact:
| https://youtu.be/EWwhQB3TKXA
| kepano wrote:
| Which is inspired by the Powers of Ten 1977 short:
| https://youtu.be/0fKBhvDjuy0
| actionfromafar wrote:
| In the 1954 book _Horton Hears a Who_ its entire universe
| is inside a speck of dust.
| dark-star wrote:
| My favorite theory is that the universe is finite, some sort of
| (hyper)sphere or -torus. If we could just look far enough out
| there we would see our own galaxy
|
| What would be even cooler is if it was warped like a moebius
| strip in a higher dimension, so that when we look out there,
| everything is mirrored from "our" reality :-D
| deepsun wrote:
| That assumes that we can somehow see through time, which
| leads to a whole bunch of inconsistencies (aka time travel
| paradoxes). There's no way to look through large distances
| without looking back in time, unfortunately.
| nine_k wrote:
| I don't see how _seeing_ one 's past may lead to paradoxes.
| Meddling withthe past would still be impossible, due to
| the,distance and the speed of light limit. What am I
| missing?
| [deleted]
| delecti wrote:
| That first theory would be interesting, but wouldn't it be
| basically impossible to prove unless the finite repeating
| universe were also pretty small? We see distant objects as
| they were in the past, and I'm not sure we'd recognize our
| own galaxy a billion years ago and a billion light years
| away.
|
| It's actually an interesting thought experiment. _If_ that
| theory were true, and assuming we could see ourselves face-on
| (rather than edge-on), then I wonder how far away and far
| back could we recognize ourselves.
| dark-star wrote:
| Yeah, I realize we're looking in the past and can't "see"
| ourselves (probably not even our own galaxy, depending how
| far out we have to look). But I guess the theory in itself
| is not any more "weird" or "outlandish" as the idea of an
| infinite universe.
|
| And maybe if we actually look both ways, we could find
| another galaxy that could be proven to be the same (because
| of some particularly remarkable stars/quasars/supernovae
| etc. in them). Who knows, maybe the universe _is_ smaller
| than we think and we just don 't recognize the "same"
| galaxies on different images because they are billions of
| years apart?
| satvikpendem wrote:
| You should read the short story _The Tower of Babylon_ by Ted
| Chiang who also wrote _Stories of Your Life_ , the
| inspiration for the movie _Arrival_.
| jadbox wrote:
| That was one of my favorite stories and certainly relevant
| to the theories here.
| Cthulhu_ wrote:
| For all we know it might be - or it might actually be
| infinite - but the trouble is that we're limited by what we
| can see / detect, which is in turn limited by the speed of
| light.
|
| Another commenter asked something like, what if the universe
| is much bigger than the observable universe, because
| everything beyond that 'border' has redshifted out of reach -
| or hasn't reached us yet / never will, because it's moving
| away faster than the speed of light.
| narag wrote:
| The funny thing is that since we've been observing the universe
| for so little time, and we're so small, most of the evidence
| for the big bang and expansion is not _direct_ , but a chain of
| deductions.
|
| I mean that we can't _observe_ the expansion because we can 't
| really triangulate at galactic scale. If there is another
| reason the light from distant galaxies turn to red, kind of a
| long-distance light fatigue, we couldn't really know.
|
| The reason I always heard that would be a confirmation, because
| it comes from a different causal path, was precisely the
| different composition of old galaxies. And now it seems they're
| not so sure.
| cryptonector wrote:
| > If there is another reason the light from distant galaxies
| turn to red, kind of a long-distance light fatigue, we
| couldn't really know.
|
| It's not just red shift that demands an explanation, but also
| that the sky (space) is dark. If space wasn't expanding then
| the skies would be bright white.
|
| Another thing is the second law of thermodynamics, which very
| strongly implies a lot of standard cosmology.
|
| Of course, standard cosmology could be all wrong, but these
| deductions are quite solid as far as the physics that we know
| today.
| ash wrote:
| Why would it be bright white?
| habibur wrote:
| Any straight line you draw from earth to any direction in
| the sky will then reach a star.
| narag wrote:
| _Any straight line you draw from earth to any direction
| in the sky will then reach a star._
|
| Only if you think that there is infinite matter, all of
| it forming the same kind of stars, uniformly spread over
| the infinite space and there is no unknown form of
| atenuation for waves traveling millions or billions of
| years light.
| fartsucker69 wrote:
| Which is insanely far away and all light coming from
| there will have diminished in energy enough to be barely
| visible?
|
| Inadequate explanation. Even if the universe was a closed
| box with perfectly reflecting borders, what you would
| actually see in the sky is something like an average
| brightness of the entire universe with some fluctuations.
| Omin wrote:
| It's not inadequate. Brightness diminishes for two
| reasons. One is absorption from cosmic dust (not that big
| of a factor), the other is that the object appears
| smaller, but the brightness per unit solid angle from the
| object does not diminish. If there were just more stars
| behind that you could see, the sky would have to be much
| brighter.
| cryptonector wrote:
| Photons do not "diminish" in energy except via red
| shifting (where does the energy go? into the expansion of
| the universe!).
|
| Light scatters, gets absorbed and re-emitted, it's true,
| but if distances don't change then the universe would
| still be much brighter than it is today.
| narag wrote:
| _It 's not just red shift that demands an explanation, but
| also that the sky (space) is dark. If space wasn't
| expanding then the skies would be bright white.
|
| Another thing is the second law of thermodynamics, which
| very strongly implies a lot of standard cosmology._
|
| Don't you feel that these evidences just make a case from
| models checked in small scales and tell the whole universe
| what it _should_ do?
|
| I don't mean the reasoning is incorrect or unwarranted,
| just that there could be alternative explanations that
| involve unknowns.
|
| _Of course, standard cosmology could be all wrong, but
| these deductions are quite solid as far as the physics that
| we know today._
|
| When applying Occam's razor, you try to minimize entities
| and simplify. But what appears simpler for a physicist is
| sometimes surprising for the rest of us. The equations
| don't work as expected? No problem, let's say that the
| entire universe is expanding or, even better, that _space
| is expanding_. Or that all the universe was at some moment
| in the space of a tennis ball. Or that big bang happened
| everywhere at the same time...
|
| While some explanation fits the maths, it doesn't matter if
| it's totally alien to common sense. Actually I find all
| those weird explanations strangely appealing, they give me
| a sense of wonder and empowerment. Cosmology feels like a
| superpower :)
| cryptonector wrote:
| > Don't you feel that these evidences just make a case
| from models checked in small scales and tell the whole
| universe what it should do?
|
| Yes, we like to think that the laws of physics we can
| deduce locally are global. That could be wrong, for sure.
| But consider that we understand the physics of our solar
| system (which has a star), and we see other stars in the
| skies which... implies that at least as much of our local
| physics that makes stars possible also applies where we
| see those stars.
| mr_mitm wrote:
| > The reason I always heard that would be a confirmation,
| because it comes from a different causal path, was precisely
| the different composition of old galaxies
|
| And you never heard of the CMB? That's generally considered
| the "smoking gun" evidence for the big bang.
| narag wrote:
| That's attributed to Big Bang because most people believe
| there was a Big Bang. Maybe it comes from another
| phenomenon. Or maybe they're right.
| atemerev wrote:
| Something is wrong with the cosmic distance ladder. Space is
| anisotropic, or gravity interacts with itself somehow. The
| distances are not what they seem to be. I think this will
| eventually be the solution to the galaxy rotation / dark matter
| problem.
| zmgsabst wrote:
| Our who claim that things are isotopic seems in conflict with
| what we see:
|
| https://www.quantamagazine.org/asymmetry-detected-in-the-dis...
|
| https://www.newscientist.com/article/2280743-enormous-strand...
|
| Personally, I think this is strong evidence that primordial
| anyons were inflated -- and we've failed to account for the
| energy these stored from inflation.
|
| https://en.wikipedia.org/wiki/Anyon
| starik36 wrote:
| Does this mean that big bang either didn't happen or happened in
| a different way that we think of it? Or happened far earlier than
| we think it did? Complete layman here.
| russdill wrote:
| Incomplete/unconfirmed data is showing some discrepancies for
| what our tentative models of the early universe predict. The
| data could be wrong or misinterpreted, the models could be
| wrong, incomplete or misinterpreted, or the could be
| fundamental problems with the very foundations of cosmology.
| The models we have of early galaxy formation are very
| incomplete and based on very little data. It's exciting to get
| data that will discover new things about the early universe and
| help refine those models.
| downrightmike wrote:
| We have lots of theories, but we'll never be certain as we will
| never see back to the BB. Everything was hot plasma for 370k
| years after the BB. We can get maybe that close, but no
| further. We are still exploding anyways.
| pndy wrote:
| I'm not an expert but from what I understand, scientists
| observed the very distant galaxies which shouldn't be visible
| according to most popular model of the universe evolution. And
| if these observations will be confirmed then we might get more
| accurate model which totally differs of the most popular one
| the scientists agrees upon.
|
| Far distant young galaxies should be seen as "red", but these
| aren't and that's the issue here - JWST captured these very
| bright. It's possible that the universe evolves in a different
| way and Hubble's law doesn't applies
|
| https://en.wikipedia.org/wiki/Hubble%27s_law
| rossdavidh wrote:
| I think it's safe to say that it is still uncertain, but few
| (not zero) astronomers believe that it means the Big Bang
| didn't happen.
| robg wrote:
| Instead of one big bang, imagine an infinite number of big bangs,
| all colliding on a cosmic scale in time and space. That's not
| necessarily a multiverse, but it is a megaverse with universe as
| the old paradigm.
| russdill wrote:
| https://en.wikipedia.org/wiki/Eternal_inflation
| robg wrote:
| Yes, just why assume a multiverse and not a megaverse? Of
| course, the superhero movies (which I enjoy) give an
| unrealistic view of what a multiverse would be.
| freedude wrote:
| ok, but what caused the big bangs?
|
| ...
|
| Genesis 1:1
| SketchySeaBeast wrote:
| You've just moved the "what caused the..." question up
| another level and then pleaded that your new level is somehow
| more special than the previous level without any actual
| justification. It's turtles all the way down and gods all the
| way up.
| drdeca wrote:
| So what you do is you form a ordinal-indexed hierarchy of
| "why"s, And then you go up a universe level so that the
| class of ordinals in the lower universe level becomes an
| actual set and not just a class, and then you somehow
| (exactly how... remains to be seen) appeal to Zorn's lemma
| , and construct a why-of-all-whys that explains everything
| in the lower universe level.
|
| And you call that thing [ERROR: NOT REPRESENTABLE].
| bruce343434 wrote:
| ok, but what caused Genesis 1:1?
|
| ...
|
| big bang
| jayzalowitz wrote:
| I may be stupid, but considering that the models of galaxy
| stability are based on a universe where we are made from star
| stuff and not energy stuff, is it not possible that they formed
| way quicker with less complication because it was basically only
| hydrogen and empty space?
| jchanimal wrote:
| Thanks that blew my mind, had to go tell the folks in the next
| room. Cool perspective. Where can I learn more?
| astroH wrote:
| I have to say, this article is exceptionally disappointing. As
| someone who works in this space, there are numerous misleading
| depictions about the state of the field. Almost any respectable
| simulation shows that disk galaxies are widely present at very
| early times. This is simply an argument of angular momentum
| conservation and these rotational states are simply more
| transient at early times compared to the local Universe.
|
| "Yan found 87 distant galaxies behind the galaxy cluster SMACS
| 0723" --> this is not true. They found 87 galaxy candidates. To
| be fair to the article, they do note that these await
| spectroscopic confirmation but experts only believe those with
| spectroscopic confirmation. Everything else is tentative and we
| don't yet have good numbers on confirmation rates. Finally, the
| Yan et al candidates are wildly inconsistent with almost every
| other estimate of high-redshift galaxy samples. You can see a
| comparison in Table 4 here: https://arxiv.org/pdf/2212.06683.pdf.
| They claim more than double the number of high-redshift sources
| compared to everyone else. JWST data is still very new and hard
| to both reduce and analyze. One particular problem is correlated
| hot pixels which can appear as very high-redshift sources. I
| don't know if this impacts the Yan et al paper but just an
| example of something that is not 100% straightforward to deal
| with. I highly recommend people take this with a healthy amount
| of skepticism until everything has a spectrum.
| gala8y wrote:
| Honestly, thank you very much for this comment. As a lay
| person, I very often fall into taking such news as solid, as am
| kind of hoping for some great breakthroughs in cosmology
| (broadly speaking). Thanks for providing details. "One
| particular problem is correlated hot pixels" has a nice,
| cooling effect on me and I get the idea that it is an unsolved
| issue (kind of get it). Same with "experts only believe those
| with spectroscopic confirmation" - fair enough. An antidote for
| getting fooled in this way by such articles (or YT video
| beating some popular notions over and over) is to read core
| material (like books) and seek some actual lectures, I think.
| That's a pity you can't skim some topic and have it right. You
| just can't and it only fills you with fake knowledge.
| beefield wrote:
| Sorry for an likely ignorant question, but can someone ELI5 why
| we are confident that evereything in universe is less than 13
| billion years old or whatnot, and not just redshifted beyond
| recognition?
| mr_mitm wrote:
| Because you can literally see the remnants of the big bang.
| Basically, if you look out far enough, you see a wall of plasma
| from a time where the universe was so hot and dense that light
| couldn't travel freely. It's called the cosmic microwave
| background and is impossible to explain in a static state
| universe. Before you get to the wall, you first see younger and
| younger stars (which we can tell by their composition, which
| influences their spectra), then a region which is void of
| galaxies (because it is such a young region of the universe
| that galaxies hadn't yet formed), and then said wall.
|
| Not only that, but the CMB's properties, like its frequency
| spectrum or its tiny anisotropies match what you would expect
| to an astonishing degree.
|
| https://en.wikipedia.org/wiki/Cosmic_microwave_background
| twojacobtwo wrote:
| As I understand it, the most basic calculation came from
| modeling the Cosmic Microwave Background temperature changes in
| reverse time. If I recall correctly, that runs into a
| discrepancy that requires the addition of inflation to account
| for it.
| Synaesthesia wrote:
| One of the great things about JWST is it can observe galaxies
| that are so distant, they're red-shifted that theyre in the IR
| spectrum.
| scotty79 wrote:
| Can you do spectroscopy on images of the galaxies to see how much
| stuff other than heydrogen and helium there was?
| 10g1k wrote:
| A lot of academic/scientific belief is based on ignorance. Hear
| me out.
|
| The entire academic/medical establishment believed the appendix
| was "just a vestigial organ" which served no purpose. It was
| taught in every university, in every textbook. Every medical
| professional knew it was a fact. Why? Because they had not
| identified a purpose. In their ignorance, they adopted the
| position "I don't know what it does, therefore I can state as a
| fact that it does nothing." Except it turned out they were all
| wrong, for a very long time.
|
| The appendix is not the only example of that mentality.
|
| The same has occurred when it comes to estimates of the age of
| the universe.
|
| When the most powerful telescope could see N lightyears, people
| believed the universe was N years old. Tiny gains or new images
| using that telescope adjusted the estimate to N.fraction years.
|
| When the most powerful telescope could see 2N lightyears, people
| believed the universe was 2N years old. Tiny gains or new images
| using that telescope adjusted the estimate to 2N.fraction years.
|
| When the most powerful telescope could see 3N lightyears, people
| believed the universe was 3N years old. Tiny gains or new images
| using that telescope adjusted the estimate to 3N.fraction years.
|
| This happens every time. Yet astronomers and cosmologists refuse
| to learn the lesson, and keep repeating the same mistake.
| deadbeeves wrote:
| Vestigiality is not about having no function, but about losing
| the original function. Vestigial organs are also often in an
| atrophied state when compared to analogs in other species. The
| appendix is indeed vestigial, and while not _entirely_ without
| function, it is almost entirely without one, to the point that
| you can not have it and not even realize it.
|
| >When the most powerful telescope could see N lightyears,
| people believed the universe was N years old. [...]
|
| What are you talking about? Before the 20th century it was
| believed that the universe was eternal. After then, advances in
| determining the age came primarily from theoretical models, not
| improvements in equipment.
|
| >Yet astronomers and cosmologists refuse to learn the lesson,
| and keep repeating the same mistake.
|
| You seem to be under the misapprehension that the goal of
| science is to not make incorrect statements. It's not. It's to
| incrementally (by necessity) learn about reality. There's
| nothing with the statement "by our best current measurements,
| the universe is about 13 billions years old" even if tomorrow
| new findings point to it being twice as old. To demand
| otherwise would mean that no conclusions can ever be drawn,
| because necessarily all scientific conclusions are tentative.
| It is true at all times that tomorrow's evidence may overturn
| today's conclusions.
| [deleted]
| albertgt wrote:
| df = pd.DataFrame( universe )
|
| Warning: Specify dtype option on import or set low_memory=False.
| nuker wrote:
| The Universe AI is trolling us.
| mabbo wrote:
| Ethan Siegel isn't so certain: https://bigthink.com/starts-with-
| a-bang/most-distant-galaxie...
|
| The tl;dr is that we're finding quite a few _red_ galaxies and
| red can mean distant (and therefore old) but you need to follow-
| up and do further direct measurements of each galaxy to be really
| certain that it 's old and not red looking for some other reason.
|
| Some of these unexpectedly red galaxies have been followed up on,
| and some are indeed old, but it's not enough data points yet to
| be certain of anything.
|
| The fun part of science is that either way it's pretty exciting!
| namaria wrote:
| Yes! Beautiful pictures and scientists scratching their heads?
| This telescope is awesome!
| rossdavidh wrote:
| They do talk about that a bit in the article:
|
| "These candidates await spectroscopic confirmation: Their
| redshifts are only estimates for now. But so far, spectroscopic
| confirmations of other galaxies have confirmed the vast
| majority of preliminary distances. Even if only half of Yan's
| selection turn out to be nearby galaxies masquerading as
| distant ones, the latter number would still be unexpectedly
| large."
| luxuryballs wrote:
| I always wonder if light traveled billions of years to get here
| wouldn't it be possible that it got distorted along the way? What
| if all these galaxies are just a sort of a typical pattern of
| what light looks like after an unfathomably long journey through
| space/gravity/time/etc? It could be likely that what we're seeing
| is no indication of what was ever actually out there.
| jesse_faden wrote:
| It does. One effect of light passing through gravitational
| wells is gravitational lensing.
|
| https://en.m.wikipedia.org/wiki/Gravitational_lens
|
| There is also Redshift.
|
| https://en.m.wikipedia.org/wiki/Gravitational_redshift
| hapticmonkey wrote:
| Experiment results that disagree with theory is EXCITING. I hope
| this contributes to progress and I'm giddy just imagining the
| model of the universe we have 50 or 100 or 500 years from now.
| 1970-01-01 wrote:
| I've often wondered if matter from another galaxy is behaving the
| same way it does here on the macroscopic level, but varies at the
| atomic level.
| jfengel wrote:
| It's pretty clear that it's the same at the atomic level as
| well.
|
| The spectra look exactly like they look here. They're red-
| shifted, but the gaps between the peaks are exactly the same.
| That comes from the atomic level, the way the electrons are
| arranged within the atom.
|
| If something were different at the atomic level, it would
| surely change the characteristics of the light they give off.
| The only way to see what we see would be if there were _two_
| things different, that somehow counteracted each other in the
| things we can see but were nonetheless different in some other
| factor we can 't observe.
|
| That's not impossible, but it would be a bizarre coincidence.
| 1970-01-01 wrote:
| Doesn't spectra come from the Rydberg constant, which is set
| by several other universal constants?
|
| https://en.wikipedia.org/wiki/Rydberg_constant#Alternative_e.
| ..
| jfengel wrote:
| Yes. If any of the constants were different, or the formula
| were different, we'd see it.
| eointierney wrote:
| Our scientists are engineers and our artists are logicians.
|
| The telescopes are always amazing
| college_physics wrote:
| I don't know if this instance qualifies as one, but I think its
| fair to say that cosmology is the one domain of "fundamental"
| physics where "discrepancies" or question marks keep piling up
| and not really resolving.
|
| It the pattern of previous science revolutions repeats, there
| could come a point where reinterpreting the large existing body
| of knowledge using a different paradigm would explain an number
| of "oddities" in a more economical way.
|
| I don't know if this generation of telescopes will get us there
| but it feels that this is a plausible outcome over the next 1-2
| decades. Which would be _very exciting_ :-)
| barbazoo wrote:
| > It the pattern of previous science revolutions repeats, there
| could come a point where reinterpreting the large existing body
| of knowledge using a different paradigm would explain an number
| of "oddities" in a more economical way.
|
| Could we train a GPT3 like model with the entire corpus of
| astronomical research and try to answer some questions that
| way?
| Enginerrrd wrote:
| I'd say not a chance.
|
| GPT3 can regurgitate, and, in my opinion, even use knowledge,
| but I don't think it can synthesize knowledge.
| mikepurvis wrote:
| I think it's a bit more subtle than whether it can
| _synthesize_ , because clearly it can produce seemingly new
| work.
|
| But what it definitely cannot do is _seek new
| abstractions_. It can 't be curious about an inconsistency
| and probe its own knowledge for possible resolutions, or
| design an experiment that might shed further light in an
| unknown area. It can't even play a board game after
| ingesting the rules to it, much less identify
| contradictions or problems in such a ruleset. And a board
| game is a tiny microcosm compared with the laws of physics.
|
| It's conceivable that one or more scientists could work in
| conjunction with an AI to help augment their own abilities,
| co-pilot style, but I don't think we have a picture yet of
| what exactly that kind of thing would look like.
| pmichaud wrote:
| I kind of feel like _all it can do_ is seek new
| abstractions. It's clustering the data into what you
| might think of as "concepts," even though we haven't made
| all that much progress on interrogating those concepts
| directly. I just think clustering concepts by their
| latent relationships is sort of what abstraction is.
| mikepurvis wrote:
| Hmm, interesting. I feel like that clustering/grouping
| part is like... the first stage on the way to finding an
| abstraction, but if all you've done is that part of it,
| then you haven't reasoned about what the abstraction is,
| or extrapolated out to a new hypothesis, or grappled with
| the other consequences of the grouping.
|
| Thinking of mathematics, an abstraction is only as
| valuable as what it can tell us about the underlying
| system-- a laplace transformation into the frequency
| domain isn't particularly interesting unless we either a)
| happen to care about some frequency domain property of
| the function, or b) we can manipulate the transformed
| function and then un-transform it afterward, yielding a
| novel insight in the original time domain.
|
| My layman's assessment is that the current state of the
| art for machine cognition is about on the level of
| _identifying that such a transformation might be
| possible_ , but not actually applying it or doing
| anything about it, much less unapplying it afterward.
| pmichaud wrote:
| I think I get the gist of your point which I would
| handwavily summarize as "there is no _there_ there,"
| which I agree with. But I'm thinking that in terms of
| functionality, there is no real distinction here. Like If
| I train a model to do video game physics, and reward it
| for getting the tank shell missile to land on arbitrary
| targets, then in some sense the system must have an
| abstraction of gravity or at least parabolic movement or
| at least a functional equivalent of that, and it must be
| able to "hypothesize" about the consequences of its model
| because that's what it needs to do in order to hit the
| target, ie, "everything I've seen before leads me to
| believe tank missiles move like _so_ , therefore if I
| apply the following forces, it should hit the goal"--the
| degree to which it wins at this task is exactly the
| degree to which it can form working models of its
| environment and reason about the cause and effect of the
| actions it can take. But of course all those words in the
| previous sentence are wrong because it's not exactly
| doing any of that, just something functionally equivalent
| and automatic.
|
| Maybe we disagree about whether that last point means it
| can meaningfully "do abstraction" or not.
| largbae wrote:
| Already done. They came back with the answer: "42"
| quickthrower2 wrote:
| They haven't but they will
| RosanaAnaDana wrote:
| You're really not going to like it
| foolswisdom wrote:
| But what was really the question?
| sdiupIGPWEfh wrote:
| "What is the Matrix?"
| salawat wrote:
| Mu.
| Karellen wrote:
| ChatGPT-3: What do you get if you multiply six by nine?
|
| ChatGPT-4: How many roads must a man walk down?
| purpleblue wrote:
| If you give GPT3 code with a bug in it, and ask it to find
| the bug, it can't really do that. I'm pretty sure giving it
| all the data and asking it why things aren't working the way
| it should, it wouldn't have actual knowledge.
|
| There's a depth to explaining things that GPT still can't do.
| It's still astonishing, and has completely changed my idea on
| what AI can do, like write plays with very incredible context
| (better than most humans!) but there are still major limits.
| yreg wrote:
| It can definitely find and fix bugs. Of course it's not
| great at it and cannot be relied upon.
| RosanaAnaDana wrote:
| >If you give GPT3 code with a bug in it, and ask it to find
| the bug, it can't really do that.
|
| The hell are you talking about? I've been doing this
| literally any time I need something fixed and it does just
| fine.
| dinkumthinkum wrote:
| It doesn't solve non-trivial bugs. It can bugs that match
| patterns that have been asked a lot if Stackoverflow or
| something like that.
| RosanaAnaDana wrote:
| I love the sound of goal posts as they go whooshing past.
| KMag wrote:
| I think it's more likely a problem that the GP poorly
| worded their initial statement, rather than actually
| moving the goalposts. They were probably having trouble
| with a few thorny bugs, tried ChatGPT, got nowhere, and
| forgot to qualify their initial statement with "for the
| few non-trivial bugs I tried".
|
| From the external point of view, the goalposts moved, but
| from within the GP's poorly expressed mental model, they
| haven't moved. But, that's just a guess.
| soulofmischief wrote:
| The article mentions that they're training neural networks to
| classify these objects. Give it a decade and this kind of
| high level number crunching will be as common as calculators
| are today. Transformers will find their place in all of this,
| and I am confident we will have a breakthrough in a few years
| regarding novel synthesis.
| anon291 wrote:
| FWIW, I've tried asking ChatGPT to walk through some thought
| experiments.
|
| Things like, what happens if I shoot two bullet at c/2 in
| opposite directions on a train going at c/2? Now suppose, I'm
| an outside observer. And then trying to introduce quantum
| gravity.
|
| My thought was that perhaps it could 'reason through'.
| Unfortunately, it was unable to. Eventually, it said that
| this is an unsolved problem. In other words, it 'recognized'
| the thought experiments. Perhaps if you use a phrasing that's
| not in the literature.
|
| EDIT: Actually, just checked again, and chatgpt can't reason
| through relativity anymore:
|
| Me: Imagine I'm on a train traveling at half the speed of
| light. I'm in the middle of a car and I fire bullets going at
| half the speed of light towards the front and back of the
| car. Do the bullets arrive at the front and back of the car
| at the same time?
|
| ChatGPT: No, the bullet fired towards the front of the car
| will arrive at the front of the car first, while the bullet
| fired towards the back of the car will arrive at the back of
| the car later. This is because the front bullet is moving in
| the same direction as the train and the back bullet is moving
| in the opposite direction of the train. The relative velocity
| of the bullet and train will determine the time it takes for
| the bullet to reach the front or back of the car.
| quickthrower2 wrote:
| It is going to be like a drunk Michael Ross (the fictional
| character). I.e. great memory but too drunk to think beyond
| what can be recalled. If it's corpus has the answer it will
| shit it out.
| college_physics wrote:
| well, you could. And it might not be a complete waste of
| time. I would not expect any directly useful answers(...).
| But producing a semi-random collation of sentences that spans
| the corpus of cosmological facts and models and asking
| scientists to review / draw "inspiration" from it might
| remove some of the biases of the average cosmologist (like
| having to follow the latest publish-or-perish fad). This
| would only be useful if the answer is sort of hidding in
| plain sight (within the published stuff) and you tweak the
| algorithm not to ignore weird observations or theories that
| are not cited a lot.
|
| But the beauty of science (and the human mind driving it)
| that important progress happens with creative jumps that
| invent completely new things (e.g., new mathematics) and
| frequently bear little resemblance to the past
| luisapic wrote:
| [flagged]
| Cthulhu_ wrote:
| I think chatbots can probably answer known things, but we'll
| still need smart humans for original ideas.
|
| That said, I can imagine a chatbot can help as a rubber duck,
| bring up things that weren't considered yet, or be so wrong
| as to kickstart the human into a breakthrough.
| _Algernon_ wrote:
| GPT3 cant even play tic tac toe properly (at least in my
| attempts). What makes you believe it can build and manipulate
| a model of the universe, and then answer questions about that
| model in a way that goes _beyond_ what humans can do?
| odieldomanie wrote:
| There is the esoteric "Cosmological Natural Selection" theory
| that predicts the discrepancies. This guy at
| https://theeggandtherock.substack.com/archive explains his
| version of this theory (albeit in an emotional way) that I find
| a pleasant read.
| EZ-Cheeze wrote:
| It's an amazing theory that I now share.
|
| F R A C T A L H A T C H E R Y
| User23 wrote:
| There's a joke that calling Computer Science Computer Science
| is like calling Astronomy Telescope Science, but part of what
| makes it funny is the ring of truth to it. Our instruments
| really do limit our observations. The advantage Computer
| Scientists have is that we can glimpse a world of Platonic
| Forms[1], where Functions, and Sets, and Information exist, or
| something close enough for government work, merely through the
| intellect. Astronomers have no such luxury.
|
| [1] Or whatever circumlocution you prefer to express the same
| general concept.
| AstixAndBelix wrote:
| Computer Science doesn't get the pass, unfortunately. First
| of all because it's a branch of maths, so in reality it
| doesn't have any instruments to worry about. Secondly,
| applied CS relies on an incredibly simple instrument: binary
| logic gates. The computers we have today are just a mesh of
| stuff that flips on and off with no intermediate states.
| That's pretty primitive as a means of expression and
| computation compared with the rest of the universe
| Taniwha wrote:
| Oh, let me introduce you to metastability ....
| bpye wrote:
| Is that computer science or is that physics though?
| Taniwha wrote:
| well a bit of both - if someone hasn't given you the
| scary meta stability lecture you haven't really done
| computer science :-)
| bombolo wrote:
| > The computers we have today are just a mesh of stuff that
| flips on and off with no intermediate states.
|
| Only when things are working properly and there isn't too
| much cosmic radiation, interference, strange patterns
| accessing memory, someone turning on a light...
| mnw21cam wrote:
| A lot of people think that computer science is just a
| branch of maths. But when I was doing my doctorate, I was a
| computer scientist, and my three supervisors were a
| mathematician, an engineer, and a meteorologist. The
| difference between us was much more than the stuff we knew
| - it was the way that we thought, and therefore approached
| a problem. Supervision meetings were interesting - it very
| much felt like four people speaking four different
| languages.
|
| On a very broad level (and I'll get loads of people
| disagreeing with this, because both mathematics and
| computer science divide further into different
| specialities), mathematics is primarily about proving
| logical truths, whereas computer science is about managing
| complexity. That's a massive cognitive difference, even if
| many of the problems the two fields tackle are the same.
| raxxorraxor wrote:
| Astronomers probably should go on the quest for immortality
| since otherwise you are basically condemned to look at a
| still image. Even if that image contains a story from the
| earliest universe until now. It is a million states, but no
| real process.
|
| What I find so fascinating is that the observations are still
| quite precise. How do you know the outer rims are rotating
| too fast? Couldn't this be some gravitational lensing and
| stars are actually much closer to the core than they appear?
|
| How do you even begin to estimate the mass of a galaxy? How
| do you weight the behavior of a disc and combine it with
| keplers law to even see that something is wrong here? As a
| layman I would be perfectly happy with how galaxy are
| rotating... I find it fascinating that much is so precisely
| determined that we have to miss something.
| freedude wrote:
| Fields of science should always be willing to change based upon
| empirical evidence.
|
| I think there are several other scientific areas where we know
| less than we ought.
|
| 1. The sub-atomic level
|
| 2. The cellular level
|
| 3. Ocean biology
|
| 4. Geology, particularly effects of earthquakes and volcanic
| activity
|
| 5. Weather patterns over time
| yreg wrote:
| What are the indicators we have marine biology wrong to the
| level of the other mentions?
| NovaVeles wrote:
| I feel for the Weather pattern folk. All of the one I have
| spoken to over the years are pretty cool. They are trying to
| model an insanely complex system - oh but thanks to global
| warming they are struggling to make models that work for
| longer than a few years because it all keeps changing!
| abtinf wrote:
| If "it all keeps changing", which thwarts their attempts to
| "model an insanely complex system", then wouldn't that mean
| any claim about "global warming" is actually a claim to
| possessing a priori knowledge?
| TillE wrote:
| We know very well how carbon dioxide interacts with
| infrared radiation (easily tested with an IR
| spectrometer), and we know human activity releases
| enormous quantities of carbon dioxide into the
| atmosphere, which does not magically disappear.
|
| Precise predictions are hard, but the general direction
| of travel cannot be seriously disputed without arguing
| against the above simple facts.
| Cthulhu_ wrote:
| > Precise predictions are hard, but the general direction
| of travel cannot be seriously disputed without arguing
| against the above simple facts.
|
| To add, the predictions re: global warming seem to have
| been too optimistic, and they were already gloom and
| doomsaying enough decades ago. I scoffed when I read a
| headline saying something about a specific glacier being
| gone in 100 years - I'm sure it'll be much sooner than
| that.
| eru wrote:
| Carbon dioxide is actually a relatively weak greenhouse
| gas. At least compared to water vapour, or even methane.
|
| Btw, CO2 does 'magically' disappear. Into the oceans.
| Alas, from what I've read it'll take about 2,000 years to
| do so.
|
| > [...], but the general direction of travel cannot be
| seriously disputed without arguing against the above
| simple facts.
|
| I don't want to argue against global warming, but I want
| to argue that can't argue against global warming without
| arguing against your 'simple facts'.
|
| Your 'simple fact' about CO2 could be true, but global
| warming could still be a myth. (I don't think it is; but
| your argument is far from sufficient. It's a complex
| system. Eg from time to time volcanic eruptions produce a
| lot of CO2, but they are typically associated with a
| cooling of the climate, because of other factors.
|
| Similarly, burning coal releases a lot of CO2, but it
| also used to release a lot of SO2. Locally, SO2 is pretty
| bad (ever heard of acid rain?), but SO2 converts to
| sulfuric acid aerosols that can block solar radiation.
| These days most coal fired power plants have measure to
| avoid spewing so much SO2.
|
| It's conceivable someone could find a coal so 'dirty'
| with sulphur, that burning it would decrease
| temperatures. I don't think it's very likely, but it's
| conceivable. So you need more empirical observations,
| than just your simple facts to make your argument.)
| craftsman wrote:
| I understood their point to be that that based on our
| understanding of basic physics and chemistry, the energy
| balance is such that the Earth system is gaining energy,
| and that this will lead to increased temperatures among
| other things. Certainly there are all kinds of
| complexities about how that energy will be distributed
| and what the effects will be, but just in terms of a
| simple energy balance model based on well understood
| physics, it would be difficult to make the case that
| warming won't happen.
| eru wrote:
| > Certainly there are all kinds of complexities about how
| that energy will be distributed and what the effects will
| be, but just in terms of a simple energy balance model
| based on well understood physics, it would be difficult
| to make the case that warming won't happen.
|
| There are lots more effects. When lots of volcanoes
| erupt, we also see more CO2, but we see the climate cool
| down.
|
| That's because the effect of the CO2 is outweighed by
| other factors. But exactly that there are lots of factors
| is my point.
| craftsman wrote:
| Not in the long run. If CO2 levels are increasing and the
| energy balance into the Earth system is positive, then
| the basic physics that the original poster referred to
| will result in warming. The net energy increase of the
| system will result in a higher equilibrium temperature.
| michaelhoney wrote:
| No. That the planet is warming is incontrovertible. What
| this might mean for highly interdependent, chaotic
| systems is harder to predict. Will the Greenland ice
| sheet melt? Looks like yes. Will that affect the Gulf
| Stream? Probably. Will that make Spain colder? again,
| probably, but the error bars are bigger, and so on.
| thereisnospork wrote:
| It just sounds like global warming is giving them good
| test data. A comprehensively accurate model should be
| able to take e.g. a Greenland ice sheet melting in
| stride.
| Cthulhu_ wrote:
| It's a lot of factors that they didn't even consider in
| the first place; decades ago, the Greenland ice sheet
| melting wasn't a consideration. Similar things: The north
| pole ice cap melting causes less sunlight to be reflected
| back into space, adding to the warming effect. Or the
| huge areas of permafrost melting (not so perma now, but
| for earlier models they would have considered permafrost
| not an issue), which causes sequestered biomatter to
| start decomposing and releasing tons of methane.
|
| Forest fires were probably in the model, but they seem to
| be intensifying due to (mis)management and droughts. The
| Amazon rainforest probably has a significant impact on
| weather and weather models, but under Bolsenaro a lot of
| it was cut down and burned. And it goes on.
| NovaVeles wrote:
| No as has already been answered. The example I can
| directly think of is modelling of specific weather
| patterns across Australia. A model that works in
| predicting weather 2 weeks out may work today but not
| work so well in 5 years.
|
| Global Warming is happening, that is not just a realm of
| modelling but is directly observable today. The models on
| a broad scale look to be working very well, specific
| locations and reactions not so much.
|
| It is possible to make broad engines that work but also
| get the finer details wrong. Signal : Noise ratio and all
| of that.
| mmusson wrote:
| It may be more a question of a new generation of physicists,
| willing to consider that particle dark matter is not the
| explanation for the acceleration discrepancy.
| dylan604 wrote:
| Sadly, I'm to the point that unless we call it the Kardashian
| Space Telescope, the draw to new generations will not be
| there. We're closer to Idiocracy future than Interstellar
| future.
| Cthulhu_ wrote:
| I think you're overly generalizing, I don't believe today's
| generation is much different from previous generations when
| it comes to interest in STEM and the like. Sure, their
| attention spans are different - I mean "ours" are due to
| the advent of the internet etc - but I don't believe their
| ambitions are that much different. It's just that they want
| to become youtubers instead of movie stars / musicians.
| sebzim4500 wrote:
| I think this says less about cosmology and more about the
| incredibly effectiveness of the standard model in the regime we
| can test directly on earth.
|
| If we compare LCDM to most other scientific theories it doesn't
| look so bad in terms of discrepancies. Certainly there are many
| unexplained effects in solid state physics, there isn't even an
| accepted explanation for why rubbing a balloon on your head
| makes it stick to a wall and that's an experiment you probably
| did as a child.
| vl wrote:
| >Certainly there are many unexplained effects in solid state
| physics
|
| Wait for it... Why ice is slippery?
|
| Usual explanation is completely incorrect. Actual semi-
| conclusive research just recently happened.
| kgc wrote:
| Link to the research?
| hutzlibu wrote:
| It is not, because ice has a smooth surface and that
| probably the surface layer melts a bit because your shoes
| are warm?
|
| That would be my reasoning, but it likely seems to be
| wrong, well why?
| Sharlin wrote:
| The usual hypothesis is that a microscopic layer of the
| surface melts, not because your shoes are warm, but
| because of the pressure. But the pressure is not enough
| to do that.
|
| That said, as anyone who has been in icy conditions can
| attest, it is clear that ice at ~0deg C is vastly more
| slippery than at, say, -20degC.
| darkerside wrote:
| My understanding is that, at the borders, master is
| constantly changing between its states. A boiling pot has
| water molecules turning to steam, as well as vice versa.
| It just has more of the first probabilistically.
|
| Maybe the same happens with ice and water.
| kortex wrote:
| That's more or less it, as far as I understand. There's
| the hexagonal lattice of solid water ice, where hydrogen
| bonds form a 3D tetrahedral structure which is very
| stable. At the boundary, there are no molecules "above"
| the solid latice, so those water molecules are held less
| tightly. The exact dynamics are challenging to predict
| because we can't exactly see what's going on (most
| simulation based).
| hutzlibu wrote:
| ", it is clear that ice at ~0deg C is vastly more
| slippery than at, say, -20degC."
|
| There is nothing more slippery in my experience, than
| rain on the street, that just turned frozen. But ice at
| -20degC is usually older and has not such a smooth
| surface anymore, so hard to compare in non lab settings.
| usrusr wrote:
| The pressure from well distributed static load divided by
| area is not, but on the tiny scale where the difference
| between grippy and less grippy surfaces happens there
| isn't so much "well distributed" going on. And once you
| add lateral force to the mix all bets are off: there will
| always be a point getting better grip (is surface
| interference the correct term?) than others, see a local
| force concentration and when that causes a tiny spot of
| phase transition there will very soon be a new point of
| least local slippyness getting all the attention of
| lateral force.
| skykooler wrote:
| If that were the case, then cold things wouldn't slip on
| ice, but they do (for a demonstration, pick up a rock
| that's been sitting out in the cold and note that it
| still slides on ice)
| __alexs wrote:
| I'm not sure a cold rock sliding across very cold ice
| will slide any better than if the ice was another very
| large smooth rock. Ice is hard and smooth. Hard smooth
| things have low friction.
| rajamaka wrote:
| Wouldn't that just be due to the low coefficient of
| friction?
| FPGAhacker wrote:
| > Wouldn't that just be due to the low coefficient of
| friction?
|
| You mean, its slipperiness?
| o_____________o wrote:
| You're talking about the "2D gas vs liquid" discussion?
| emptybits wrote:
| I had to look that up. Here's research[1][2] from 2019
| about "why ice is so slippery", including some of the
| apparent surprises. I dunno. I'm not a physicist so some of
| the surprises seem like very minor things to me.
|
| Spoiler: According to this research, ice is slippery
| because of a thin layer of water. (As we expected, no?) But
| the water layer is 1) thinner than expected, 2) more
| viscous than expected, and 3) contains bits of ice which
| help make it extra slippery.
|
| > "Usual explanation is completely incorrect."
|
| Only for an unusual definition of "completely" IMO. Again,
| IANAP.
|
| [1] https://phys.org/news/2019-11-ice-slippery.html
|
| [2] https://journals.aps.org/prx/abstract/10.1103/PhysRevX.
| 9.041...
| __alexs wrote:
| Ice isn't slippery, water is. If anything I'd say ice is
| actually pretty sticky. A very cold ice cube will easily
| stick to your skin.
| medstrom wrote:
| That's just because your skin has water molecules that
| freeze on contact with the ice cube. If you use tongs to
| put an ice cube on your desk, it doesn't stick at all,
| right? And the friction is very low so it's easy to kick
| away -- things like a leather wallet stick much better to
| your desk.
| __alexs wrote:
| I've not tried it but intuitively I'd expect it to slide
| about as well as other very hard things of the same
| shape.
| lukas099 wrote:
| I've dropped ice cubes on the floor before and they
| definitely slide a lot more than most objects of the same
| shape.
| m463 wrote:
| I remember listening to joe rogan when he interviewed
| neil degrasse tyson and he had some fascinating insights
| into the behavior of water with relation to pressure and
| temperature.
|
| I can imagine ice on an iceskate wanting to be solid, but
| because that takes up too much space it becomes a liquid
| instead.
| dumpsterdiver wrote:
| > Only for an unusual definition of "completely" IMO.
|
| Agreed. While the "usual explanation" may lack the
| details that actual testing provided, deduction and logic
| in this case were pretty much harmonious with the
| findings. The water layer being thinner or more viscous
| than expected doesn't invalidate the basic assumption,
| and that's where all science starts, right? Some basic,
| yet to be disproved* assumption.
| vl wrote:
| Exactly, this it's the new research. Standard (incorrect)
| explanation is because ice melts because of the pressure
| from the object put on it. Robert Wood showed it to be
| untrue at the beginning of the twentieth century, but
| "popular scientists" didn't get the memo.
| JumpCrisscross wrote:
| > _contains bits of ice which help make it extra
| slippery_
|
| Wait, why would bits of ice make it extra slippery if
| it's the water that makes ice slippery?
| lukas099 wrote:
| Maybe the ice molecules move through the water with less
| resistance, since the ice molecules are already 'tied up'
| in a lattice structure and therefore do not form as
| strong of hydrogen bonds with the neighboring water
| molecules.
| coryrc wrote:
| I assume like walking on marbles or ball bearings.
| gmadsen wrote:
| which part. how is that not electostatics and van der walls
| forces?
| foxyv wrote:
| > there isn't even an accepted explanation for why rubbing a
| balloon on your head makes it stick to a wall
|
| You mean dielectric moments and static electricity?
| Electromagnetism is the one thing we know the most about.
| It's that spooky gravity junk that makes us scratch our
| heads. It never seems to behave quite right and doesn't mesh
| with all the other forces.
| gwd wrote:
| > You mean dielectric moments and static electricity?
|
| You're confusing _what_ with _why_. My understanding is
| that everyone knows it has something to do with electrons
| collecting on the balloon; but nobody quite knows why
| rubbing rubber against hair causes the electrons to do
| that.
| foxyv wrote:
| I think I got confused because I was thinking about why
| it stuck to the wall, rather than why it accumulated
| charge. I know why electrically charged objects stick to
| things. The why of how they got like that is a bit
| different as you mentioned. Triboelectric effect is
| spooky, but there are some theories. It's one of those
| non-linear messy quantum things that's a pain in the neck
| to solve.
| moloch-hai wrote:
| > _It 's one of those non-linear messy quantum things
| that's a pain in the neck to solve._
|
| That is exactly equivalent to "dunno, maybe something".
| foxyv wrote:
| > That is exactly equivalent to "dunno, maybe something".
|
| Yup! It's like understanding the why of weather and
| people. They are messy and have so many factors you can't
| account for. It's like saying, why are the clouds shaped
| like that. You can why your way down, but it's turtles
| all the way!
|
| When it comes to non-linear junk, the why becomes mixed
| up because the causes are so numerous. There are so many
| tiny interactions you can't really say there is one
| individual cause. Often times you have phenomena that
| occur at specific energy levels that aren't really caused
| by any one thing. Even something as simple as a double
| pendulum is unpredictable.
|
| One thing that is kind of mind blowing is strange
| attractors. Systems that are so random you cannot predict
| them even a few moments later can exhibit seemingly
| ordered patterns. They seem to have a cause, but they are
| literally just statistical mechanics. A slightly more
| likely outcome out of un-countable numbers of other
| outcomes.
| throwaway09223 wrote:
| Exactly.
|
| Often the gap between what and why is enormous. Humanity
| began curing meats to protect against microorganisms
| around 3000BC. The effect of _what_ was going on was
| immediately observable, but it wasn 't until 4500 years
| or so later that we discovered the _why_ of
| microorganisms.
| WalterBright wrote:
| > there are many unexplained effects in solid state physics
|
| Looks like there is plenty of opportunity for newly minted
| physicists to make their names and careers!
| AnIdiotOnTheNet wrote:
| Also there's that whole "worst prediction in the history of
| physics" thing with the Vacuum Catastrophe.
| WithinReason wrote:
| The relevant XKCDs:
|
| https://xkcd.com/1867/
|
| https://xkcd.com/2682/
| tim-fan wrote:
| Relevant xkcd: https://m.xkcd.com/2682/
|
| And from the alt-text:
|
| "Friction-driven static electrification is familiar and
| fundamental in daily life, industry, and technology, but its
| basics have long been unknown and have continually perplexed
| scientists from ancient Greece to the high-tech era. [...] To
| date, no single theory can satisfactorily explain this
| mysterious but fundamental phenomenon." --Eui-Cheol Shin et.
| al. (2022)
| moffkalast wrote:
| Reminds me of this one https://xkcd.com/1489
|
| "Of these four forces, there's one we don't really
| understand." "Is it the weak force or the strong--" "It's
| gravity."
| azalemeth wrote:
| My favourite example of the intractabilities of some theories
| is that magnetohydronamics apparently can't predict the
| formation of streamer jets when you put your finger on a
| kid's plasma ball - i.e. the main point of the toy is beyond
| the most advanced theory that lies behind NIF, JET, ITER,
| etc...
| Buttons840 wrote:
| At this point in the thread, I'm wondering if we do a
| disservice to physics students by making it appear we have
| it all figured out.
| mr_mitm wrote:
| Who do you think makes it appear we have it all figured
| out? That is not my impression at all. All the scientists
| I know are extremely aware of the limitations of their
| field.
| flockonus wrote:
| Calling mental models "laws of physics" is the biggest
| linguistic disservice to science itself, so in a way,
| yes.
| treeman79 wrote:
| If it was all figured out why get into the field? Sure
| some do it just to know. But the hunt is what drives
| most.
| maegul wrote:
| So much this! There's surely a huge argument that all of
| scientific education is a massive disservice.
|
| The point should be to learn and appreciate the method or
| process of scientific investigation of uncertain and
| mysterious or hard to understand phenomena.
|
| Instead we get dogma as a proxy of measuring intelligence
| with little regard for what the fundamental tools are of
| being a scientist.
|
| I've gone all the way through to Grad School and came out
| astounded at just how little commitment to or a sense of
| the essence of scientific investigation and what's
| expected of the investigator there is in the system. They
| don't prepare you for it because they themselves weren't
| prepared. You can try to leverage some meta understanding
| of the "process" in conversation or debate, but so often
| the conversation falls flat because few are prepared or
| accustomed to it. Research is often done, IMO, in
| philosophical poverty by people eking out a living in the
| gutters of novelty and paradigmatic safety, averting
| their gazes from the sky (flourishes aside, you get my
| point).
|
| Putting aside the health of actual research. If the
| general public is to benefit from education and pass that
| benefit into their society (that's the point right), it
| needs to be more than soon to be forgotten and often
| useless fallacies.
| cwalv wrote:
| > There's surely a huge argument that all of scientific
| education is a massive disservice.
|
| > If the general public is to benefit from education and
| pass that benefit into their society (that's the point
| right), it needs to be more than soon to be forgotten and
| often useless fallacies.
|
| I realize this is hyperbole, but still I think it's
| obvious that there _is_ more than soon to be forgotten
| and often useless fallacies.
|
| I do generally agree though that current models/paradigms
| are usually presented more as "the final word" vs "a
| useful mental model".
|
| Esp. when paradigms are challenged by, or conflict with
| untestable traditional explanations, ppl tend to get
| irritated and overstate the confidence of their own
| understanding
| maegul wrote:
| Agree. I'm guilty of descending to hyperbole at times!
|
| Nonetheless, while I agree with your pushback, I do
| wonder how much utility there is in the "dogma" approach.
| There's a lot of "facts" being thrown around in
| education, from what I've seen, that are often forgotten
| or become vague memories. How much better would it be to
| focus on skills and practice and concepts? Especially in
| the digital age where a fact is easily discoverable,
| provided one has the appropriate research skills.
| zinclozenge wrote:
| I don't think I've ever, out of all my physics classes up
| to grad seminars, been given the impression we have
| everything figured out. In fact, it was hammered into us
| that all we have are "effective" theories, at least when
| it comes to high energy physics, and that's not even
| talking about grand unification (electroweak + strong
| force unification), let alone Theory of Everything
| (electroweak + strong + gravity).
| epicureanideal wrote:
| Maybe not where you studied, or at the level you studied,
| but in upper division undergrad physics at a top tier
| California school I definitely was given the impression
| that I should just crunch the numbers and not think too
| much about how it might be working.
| njarboe wrote:
| Was this a quantum mechanics class? Thinking about how it
| might be working leads to strange things like the Many-
| Worlds Theory[1] and other very weird ideas. "Shut up and
| calculate" is the usual method of dealing with these
| deeper questions.
|
| Beware; deep rabbit hole.
| [1]https://plato.stanford.edu/entries/qm-
| manyworlds/#:~:text=Th....
| moloch-hai wrote:
| It is easy for children to come up with questions for
| biologists that none can answer, and that none has even
| tried to answer.
|
| Biologists are almost unique among scientists in being
| happy to say how little they still know about their
| subject. Up until last year nobody had thought to see
| whether anything eats viruses! Turns out some do.
| eru wrote:
| > Biologists are almost unique among scientists in being
| happy to say how little they still know [...]
|
| Citation needed.
|
| > Up until last year nobody had thought to see whether
| anything eats viruses! Turns out some do.
|
| Nah, lots of things eat viruses. It's nothing unusual at
| all. You eat viruses, I eat viruses. They are everywhere,
| after all.
|
| The novel finding was a critter that lives / can live
| solely on viruses.
| abudabi123 wrote:
| > Nah, lots of things eat viruses. It's nothing unusual
| at all. You > eat viruses, I eat viruses. They
| are everywhere, after all.
|
| When an engineer walks in front of an idling jet engine
| you don't say the jet eats viruses.
| eru wrote:
| To be more precise, viruses are just made up of proteins
| and DNA / RNA. Your normal digestion that can handle
| proteins and DNA/RNA from animals, plants etc doesn't
| have any more problem breaking down virus proteins into
| amino acids and absorbing them.
| whatshisface wrote:
| I think the OP was talking about the bacteria that derive
| non-negligible sustenance from viruses.
|
| > _Moreover, our foraging trials demonstrated robust
| growth in the Halteria population with only chloroviruses
| as food (rint = 0.66 +- 0.26 [SD], black lines, Fig. 1A),
| with minimal to no growth in the controls (with
| chloroviruses filtered out; rint = 0.22 +- 0.12 [SD],
| blue lines, Fig. 1C). The abundance of the larger
| Paramecium did not increase in treatment or control
| trials (Fig. 1D), indicating that not all ciliates can
| grow on chloroviruses in these conditions, even when they
| consume them._
|
| https://www.pnas.org/doi/10.1073/pnas.2215000120
| eru wrote:
| Yes, I know. That's why I wrote
|
| >> Up until last year nobody had thought to see whether
| anything eats viruses! Turns out some do.
|
| > Nah, lots of things eat viruses. It's nothing unusual
| at all. You eat viruses, I eat viruses. They are
| everywhere, after all.
|
| > The novel finding was a critter that lives / can live
| solely on viruses.
| moloch-hai wrote:
| You wrote it, but it was what we all understood already,
| making writing it nothing but an exercise in snark.
| eru wrote:
| Not sure.
|
| Eg creatures that eat plastic are still news, even if
| plastic is not their sole diet.
| moloch-hai wrote:
| Yet, you are eating plastic every day.
| DiggyJohnson wrote:
| > Citation needed
|
| How could you possible find a citation for that? It's not
| even pretending to be a scientific or totally objective
| claim. Asking for a citation for this type of statement
| is no way to have a discussion. Do you not see why?
| eru wrote:
| Eh, 'Citation needed.' was my admittedly somewhat snarky
| way of calling bullshit.
|
| Most any scientist will happily babble all about the
| stuff they don't know yet in their discipline, because
| that's exactly where the excitement lies for them.
| moloch-hai wrote:
| Some do. Many don't.
|
| Much of Wikipedia is "curated" by retired professors
| carefully scrubbing mention of anything new that makes
| their graduate thesis look ill-conceived.
| [deleted]
| brotchie wrote:
| Intractable in the analytic sense, or intractable
| numerically... or both?
| azalemeth wrote:
| Both!
| moloch-hai wrote:
| Magnetohydrodynamics is, specifically, the "easy part"
| carved out of plasma fluid dynamics. It is inadequate to
| almost all applications, with only rare, precious
| exceptions, mostly manufactured. Devices that rely on
| plasma fluid dynamics to work are carefully designed to
| keep the plasma in the domain where MHD can be used to
| model them.
|
| Astrophysicists, as a rule, hate to be obliged to consider
| phenomena that involve plasma fluid dynamics, even what can
| be shoehorned into MHD. Such phenomena are thus orphaned,
| and you won't find anybody talking about them.
|
| The exception is _solar physics_ , where nothing can be
| done at all without fully general plasma fluid dynamics.
| Solar physicists have the largest gonads in science, on par
| with rocket propellant chemists.
| HPsquared wrote:
| Is it called "hydrodynamics" because of an assumption of
| incompressibility (like regular hydrodynamics vs
| aerodynamics)?
| srcreigh wrote:
| Is plasma fluid dynamics the most important hated
| obligation of astrophysicists?
| moloch-hai wrote:
| I think most consider it "somebody else's problem". I
| know some don't like to think there is anything to it
| beyond MHD, so they call anything involving plasma "MHD".
|
| Are there other phenomena they see but don't like to talk
| about? Maybe?
| comicjk wrote:
| My understanding is that the standard model likely does
| predict static electricity, but since it's a phenomenon
| bigger than a few molecules, we have no way to actually run
| the simulation. The physics is willing but the computers are
| weak.
| bardworx wrote:
| This seems incorrect as it's just an imbalance of charge
| and isn't a strange phenomena.
|
| Can you provide a reference, please?
| Eduard wrote:
| > there isn't even an accepted explanation for why rubbing a
| balloon on your head makes it stick to a wall
|
| But the accepted explanation is "static electricity", no?
|
| Or do you mean we don't "really" know when asking a couple of
| follow-up "why?" questions further?
| beambot wrote:
| This is the triboelectric effect, and the low-lying
| mechanisms are poorly understood & poorly characterized.
| Eduard wrote:
| Reading
| https://en.m.wikipedia.org/wiki/Triboelectric_effect , I
| have the impression the mechanisms are not _that_ poorly
| understood, at least from my layman's perspective.
| JimBlackwood wrote:
| It's in the lines:
|
| > The triboelectric effect is very unpredictable, and
| only broad generalizations can be made.
|
| > The mechanisms of triboelectrification (or contact-
| electrification) have been debated for many years, with
| possible mechanisms including electron transfer, ion
| transfer or the material's species transfer.
|
| > Recent studies in 2018 using Kelvin probe microscopy
| and triboelectric nanogenerators revealed that electron
| transfer is the dominant mechanism for
| triboelectrification between solid and solid.
|
| > For a general case, since triboelectrification occurs
| for any material, a generic model has been proposed by
| Wang, in which the electron transfer is caused by a
| strong electron cloud overlap between two atoms for the
| lowered interatomic potential barrier by shortening the
| bonding length.
|
| So, still very much misunderstood. There is an experiment
| showing the dominant mechanism (so still only explaining
| a part!) between solid-solid and a generic model proposed
| that can be used to explain other interactions (solid-
| liquid, liquid-liquid, etc).
|
| Unless there's a tested model with predictable results,
| I'd say we're not really understanding it properly.
| bardworx wrote:
| > So, still very much misunderstood. There is an
| experiment showing the dominant mechanism (so still only
| explaining a part!) between solid-solid and a generic
| model proposed that can be used to explain other
| interactions (solid-liquid, liquid-liquid, etc).
|
| This seems like a very large part, no?
|
| I mean, we know it works, we get the majority of it, and
| it doesn't seem super necessary to spend a lot of dollars
| and brain power to satisfy an internet debate on a theory
| of rubbing a balloon on one's head.
| [deleted]
| jpttsn wrote:
| At that point why not call it "witchcraft;" a sciencey word
| for something is not an explanation.
| vaidhy wrote:
| We do not call it witchcraft, because that is the end of
| the discussion and the answer. We call it unknown because
| it is knowable and is the beginning of the experiments.
| dylan604 wrote:
| >We do not call it witchcraft, because that is the end of
| the discussion and the answer.
|
| Also, we'd have to eliminate the practitioners for
| clearly being witches. We've had that period and history,
| but it seems some modern day people are content to bring
| that very time period back.
| dmitriid wrote:
| Hail science https://youtu.be/tl55gVXsBZE
| moffkalast wrote:
| Clearly you've never recalibrated the thermal
| interferometery scanner so you can reverse the polarity
| of the neutron flow in the isoneutronic pulse wave
| carrier.
| TeMPOraL wrote:
| That's technobabble - a pejorative term for a technical
| word salad that usually _is_ an explanation, just not a
| very good one.
| alfor wrote:
| You need a plumbus for that.
|
| Everyone need one.
| voldacar wrote:
| A good retroencabulator helps a lot here.
| Sharlin wrote:
| "Static electricity" as an explanation without follow-up
| "why?" questions is just a curiosity-stopper [1] or
| guessing the teacher's password [2].
|
| [1]
| https://www.lesswrong.com/posts/L22jhyY9ocXQNLqyE/science-
| as...
|
| [2] https://www.lesswrong.com/posts/NMoLJuDJEms7Ku9XS/guess
| ing-t...
| [deleted]
| TillE wrote:
| My favorite poorly understood phenomenon in basic physics is
| the Mpemba effect, where hot water can freeze faster than
| cold water under certain circumstances. It's just phase
| changes of water in a simple experiment you can do at home,
| and I think there's still no widely accepted explanation.
| thaumasiotes wrote:
| You might want to find a phenomenon that everyone can agree
| exists. Failing to explain something that doesn't happen
| isn't very mysterious.
|
| https://en.wikipedia.org/wiki/Mpemba_effect
|
| > the actual occurrence of the Mpemba effect is a matter of
| controversy
|
| > In 2016, Burridge and Linden defined the criterion as the
| time to reach 0 degC (32 degF; 273 K), carried out
| experiments, and reviewed published work to date. They
| noted that the large difference originally claimed had not
| been replicated, and that studies showing a small effect
| could be influenced by variations in the positioning of
| thermometers: "We conclude, somewhat sadly, that there is
| no evidence to support meaningful observations of the
| Mpemba effect."
|
| > In controlled experiments the effect can entirely be
| explained by undercooling [water may cool below the
| freezing point without actually solidifying] and the time
| of freezing was determined by what container was used.
| NavinF wrote:
| That's because nobody's replicated that effect in a real
| lab. People who claimed to observe effect didn't even
| bother to bypass the freezer thermostat and force the
| compressor to stay on, nor did they measure power
| consumption. It's just shoddy science.
| simonebrunozzi wrote:
| > LCDM
|
| Lambda-CDM Model [0], for the ones like me who haven't heard
| it before.
|
| [0]: https://en.wikipedia.org/wiki/Lambda-CDM_model
| Dopameaner wrote:
| I always wondered if we could somehow get a James webb
| telescope revolving around all planets of our solar system in
| the next 1000 years. That should give us pretty awesome
| visuals.
| eru wrote:
| Huh, why would you want to do that?
|
| If you have the resources to spare, you can do much better
| than replicating James Webb style telescopes. See eg
| https://en.wikipedia.org/wiki/Solar_gravitational_lens
| Cthulhu_ wrote:
| I want to venture that 1000 years is pessimistic. I just hope
| governments or private entities open up their wallets to
| build and launch more and better telescopes.
|
| I'm reading the whole JWST project is estimated to cost $10
| billion. That's about 4.4 overpriced Twitters, 77 US
| Department of Defense budgets (just for 2023), and 11.7
| Facebook annual revenues.
|
| We have the technology and the means, what's lacking now is
| the will.
| mkl wrote:
| Your maths is upside down, I think. $10 billion is 10/44
| [?] 0.227 overpriced Twitters, 10/816.7 [?] 0.0122 US DoD
| budgets, etc.
| positr0n wrote:
| What would be the benefit of the telescope orbiting other
| planets than earth?
| midoridensha wrote:
| I can't imagine any, besides redundancy and more
| observation time.
| throwawaymaths wrote:
| Interferometry.
| mnw21cam wrote:
| There's definitely a benefit to placing a decent telescope
| outside the asteroid belt. From Earth, we get a lot of
| light reflected from the Sun from dust orbiting somewhere
| between Earth and 2 AU from the Sun, which pollutes our
| space images - it's called the Zodiacal Light [0]. A
| telescope outside this light pollution would be able to see
| faint objects much more clearly and easily than Webb.
|
| [0] https://en.wikipedia.org/wiki/Zodiacal_light
| jackmott42 wrote:
| I don't think it is fair to characterize cosmology as not
| making progress no. Stuff is far away and occluded and hard to
| measure and see. Each improvement in observation causes a need
| to refine previous ideas, as expected. There are of course the
| two big mysteries that have lingered for a long time: Dark
| Matter and Dark Energy, but other areas of physics have
| lingering mysteries as well.
| teawrecks wrote:
| I almost had the same reaction, but technically they didn't
| say anything about cosmology not making progress. It's
| entirely reasonable to assume a scientifically minded person
| describing a field as "piling up question marks" means they
| think it's making a LOT of progress. Imagine a field that
| answers questions more often than it finds new ones; that'd
| be a pretty stagnant field to be in.
| sho_hn wrote:
| This is how I understood OP, too. Last time we had a
| "crisis in physics", it was the early transition from
| classical physics to quantum mechanics, when some good new
| ideas had been coinceived of, but trying to reconcile them
| with the classical way of thinking and with experimental
| evidence required increasingly convoluted hacks in the
| models to make it all work - until folks like Heisenberg,
| Born, Jordan and Dirac found more holistic and clean ways
| to approach the problem space.
|
| The number of question marks piling up in cosmology does
| feel similar. It will help to shape new theories that
| reconcile all this experimental evidence.
| dylan604 wrote:
| Sometimes the questions keep piling up until someone
| happens up on just the right question. That question
| itself wouldn't have been thought of except for the
| thinking of all of the previous unanswered questions.
| Then the big Eureka!! moment and someone gets a Nobel
| prize 20 years later.
| hutzlibu wrote:
| "Imagine a field that answers questions more often than it
| finds new ones; that'd be a pretty stagnant field to be
| in."
|
| Funnily enough, that's what the science community of the
| ending 19. century thought about physics, before they
| started to look deeper.
|
| Max Planck was advised against a career in physics,
| because:
|
| "In this field, almost everything is already discovered,
| and all that remains is to fill a few holes."
|
| He rather found some more holes.
| moloch-hai wrote:
| Nobody says cosmology is not making progress.
|
| People dunk on cosmology because cosmologists have
| consistently, over decades, insisted, in public, that they
| knew more than they did, and are continually obliged to
| abandon what they insisted they knew. If they were more
| forthright about how much they don't know, they would get
| less criticism. They have much to learn from the biologists,
| who know they know practically nothing (even though massively
| more than you), and are happy to say so.
|
| The health of a branch of science may be read from how eager
| its researchers are for you to know about what they have no
| clue about.
| JacobThreeThree wrote:
| >cosmologists have consistently, over decades, insisted, in
| public, that they knew more than they did
|
| Exactly, and each time the theories are proven wrong, it's
| explained as a never-ending series of "oddities", yet the
| theories are never altered in any meaningful way other than
| ad-hoc additions to explain each "oddity".
|
| At some point there needs to be a reckoning that, for
| instance, the current theories of star formation are
| essentially completely wrong.
| somenameforme wrote:
| This is exactly what pushed me away from pursuing
| cosmology. One of the most important 'discoveries' in
| cosmology was that of cosmic inflation [1]. The issue is
| that if you model the big bang, what it creates is
| nothing like what we see. Regions of space that wouldn't
| have had time to have become causally connected (nothing
| could have gotten between them even traveling at the
| speed of light since the time of the big bang) _are_
| causally connected.
|
| So the solution? There was some very specific period of
| acceleration, faster than light acceleration to some very
| specific degree, at some specific point right after the
| big bang which then ended at some other very specific
| point, at which point everything returns back to normal.
| What's the logic for it? Well if we do this, then what we
| see matches what we _expect_ to see. It 's an absolute
| retrofitting of numbers to make a model fit reality. And
| not only does that constitute good science in cosmology,
| it was sufficient to win a Nobel Prize.
|
| It is literally unexplained magic being taken as a
| fundamental concept of science. And the worst part of it
| all is that it's completely unfalsifiable. We only have
| one universe to observe. So if it turns out that the
| discrepancy is actually being caused by many smaller
| effects we stand near 0 chance of ever discovering
| because each one of those small effects will have a
| million flaws, while the perfectly retrofitted inflation
| theory has "none." At worst they'll even get absorbed
| into the inflation theory model magic. Just add more
| epicycles!
|
| [1] - https://en.wikipedia.org/wiki/Inflation_(cosmology)
| mr_mitm wrote:
| > It's an absolute retrofitting of numbers to make a
| model fit reality.
|
| That's just called science. What else do you propose?
| Give up because you didn't get it right the first time?
| moloch-hai wrote:
| It is one thing to identify a mechanism and show how in
| operation it must produce the numbers seen. It is
| entirely different to invent a name for a presumed
| mechanism, with no hint of how it happened to come to the
| numbers seen.
| moloch-hai wrote:
| Galaxy formation, anyway, or maybe galaxy supercluster
| formation.
| fartsucker69 wrote:
| not surprising imo, because of how limited our observational
| capabilities are. we'd probably progress quicker if we could
| look at far away stuff up close instead of from billions of
| light years away.
| gibolt wrote:
| The number of possibilities are countably infinite. Makes sense
| that we will keep finding things we don't understand for a long
| time.
| suetoniusp91 wrote:
| The simulation gets less cohesive the farther from earth you
| look.
| peatmoss wrote:
| I was just thinking about video games where vegetation,
| animals, and hills spring into existence when you get close
| enough. Far away, and they don't bother to render the little
| things.
|
| Depending what generation tech we're running on in the parent
| reality, JWST may be causing a noticeable jump in system
| load.
| yreg wrote:
| Whatever JWST can see should be trivial to convincingly
| mock compared to the complexity of simulation of the scenes
| here on Earth.
| dylan604 wrote:
| And now you have come to the reason GPU prices have been so
| high. Crypto was just a cover story.
| wruza wrote:
| I had the same idea about magic. Back in the day people
| could do things that we can't because nobody looked into
| details and the universe had enough "possibility space" to
| allow it. Once you turn your gaze into atomic or galactic
| workings, this space shrinks tremendously and further
| research becomes much harder because you glued the puzzle
| from its sides in a particular way and there's not much
| left to hope for, except for solving it to the center in a
| bizarrely complex way. We may have painted ourselves into a
| horrible corner.
| peatmoss wrote:
| This is an excellent sci-fi premise. Also an interesting
| thought experiment to think of what an optimal research
| approach would be if you knew a priori that you were
| living in a universe in which the implementation details
| don't exist until observed. Come to think of it, quantum
| physics is actually like this in some respects.
| ordu wrote:
| It is a v0.93 of simulation, which was run a long time ago.
| Software was patched since and now simulation is much
| smoother.
| 77pt77 wrote:
| Everyone knows that general relativity is broken.
|
| Plus cosmology has the problem that you can't really conduct
| reproducible experiments.
| pantsforbirds wrote:
| Would you bet that we'll see a paradigm shift of a similar
| nature to the classical physics -> quantum mechanics /
| relativity paradigm change, but for Cosmology in our lifetimes?
| jacquesm wrote:
| The answer to that will highly depend on how old you and the
| GP are.
| gitfan86 wrote:
| Yes, we are in the middle of a huge shift in the definition
| of intelligence. AND that could have enormous impact on our
| perception and ability to see reality.
| UltraViolence wrote:
| So there could've been civilizations that are literally BILLIONS
| of years ahead of us? Imagine what these people know about the
| universe!
|
| This reminds me of the Star Wars lead-in: "A long long time ago
| in a galaxy far far away." It really could've happened you know!
| mixmastamyk wrote:
| The first ones are beyond the rim now.
| yreg wrote:
| Earth came quite late to the party and it spawned life
| relatively soon after.
|
| That's why it's strange we haven't discovered any Dyson
| spheres/swarms (in any galaxy).
|
| Either life is indeed absurdly rare, or Dysons are impractical
| for some reason, or there is a way to mask heat.
| tuatoru wrote:
| Earth life uses lots of different elements - at least two
| generations of supernovas required. Not really that late if
| you allow for that.
| yreg wrote:
| Didn't that happen within like the first 2B years? First
| Sol-like systems were I think at 5B years, which would
| still make Earth ~3B years late to the party.
| foxyv wrote:
| What's even crazier is that those civilizations could have
| built and advanced for a 100 million years and we would never
| know about it because they are so far away. The light from
| Canis Major, our closest galactic neighbor, is older than our
| civilization (25,000 years). The average distance between
| galaxies is 1 million light years. For all we know, there have
| been billions of civilizations that have lasted longer than the
| lifetime of our solar system and we haven't even seen the light
| from them yet.
|
| The universe is huge!
| scotty79 wrote:
| I don't know. Life needed almost 5bn years to get to this point
| on Earth. Let's say we lucked out and it almost always takes 3
| times as long. Then we look like early birds in the Universe.
|
| What's more, earlier solar systems had a bit boring chemistry.
| We need a lot of supernova made stuff to really function so
| this narrows the time window.
|
| You might think that near galactic core there's a lot of really
| cool stuff made but I think interstellar environment might be
| less stable because of that and maybe life doesn't even have a
| 5bn years of quiet time to develop there.
| UltraViolence wrote:
| You don't know that. Life might be possible with simpler
| chemistry too.
|
| Chemistry was sufficient 100 million years ago for
| intelligent life to evolve, so some other solar system
| could've easily have had intelligent life for that long or
| even longer if they were lucky.
|
| Our lives have changed beyond recognition in the last 500
| years. Imagine a civilization that's thousands, tens of
| thousands or even hundreds of thousands of years ahead of us.
| scotty79 wrote:
| > Life might be possible with simpler chemistry too.
|
| Yeah, but we since we know of only one instance of life
| developing we don't really know what's actually possible
| and what only might be possible.
|
| > Chemistry was sufficient 100 million years ago for
| intelligent life to evolve, so some other solar system
| could've easily have had intelligent life for that long or
| even longer if they were lucky.
|
| What I'm saying is that time it took life to develop on our
| planet is so close to the age of the universe (not even one
| order of magnitude of difference) that it's entirely
| possible that we were the lucky ones and the next
| intelligent life (or even eukaryotic life) in the universe
| won't show up for another few billions of years. Although
| it will inevitably show up.
|
| > Our lives have changed beyond recognition in the last 500
| years. Imagine a civilization that's thousands, tens of
| thousands or even hundreds of thousands of years ahead of
| us.
|
| However technological capabilities of life didn't change at
| all in last 4 bn years despite it being in control of the
| whole planet for that long. Technology seems to need a
| really long runway to fly off.
|
| Another thing is that once technology kicks in as you
| noticed it develops incredibly fast and it influences the
| environment at the same speed. And life doesn't really like
| fast changes to environment so the technology in hundred
| thousand years might make this world completely unlivable.
| jmyeet wrote:
| Cosmology is one of those fields where I suspect we'll _always_
| be finding things that don 't match with theory because we can
| never know nor replicate the initial state of the Universe.
|
| There's also a lot of fundamental questions we don't have answers
| on. For example:
|
| - What does space expanding actually mean? Is space stretching or
| is new space being created? If so, what is the mechanism for
| that?
|
| - Is time a fumdanental property of the Universe or is it an
| emergent property?
|
| - What are the fundamental intereptations of quantum mechanics
| [1]?
|
| And so on.
|
| The cosmic microwave background is our earliest yet observation
| from the Universe. Before this the Universe was really too dense
| and hot for radiation signatures to survive. Interestingly, we
| may be able to peak even earlier than that with the cosmic
| neutrino background [2].
|
| But there are a ton of things about the early Universe's
| formation and expansion we will probably never know and will only
| be able to guess at with models that will always break at a
| certain point.
|
| [1]:
| https://www.southampton.ac.uk/~doug/quantum_physics/interpre...
|
| [2]: https://en.wikipedia.org/wiki/Cosmic_neutrino_background
| cevn wrote:
| Can someone explain to me what would be behind the galaxies if we
| could see it, to the point of 0 seconds after the big bang?
| Black, white, is it even possible?
| b800h wrote:
| There is a wonderful sequence in the (2nd?) Book of Enoch
| (~150AD?), where the viewer is transported up through the
| heavens, past the planets, and finally beyond the stars, and
| eventually sees the incomprehensible face of God lying behind
| it all, visible all across the far end of space.
|
| So perhaps that? :-)
| moloch-hai wrote:
| Great flaming letters spelling out "We apologize for the
| inconvenience".
| soiler wrote:
| We can actually already see that time period, in its present
| form. It's called the Cosmic Microwave Background. It is the
| (now extremely cold) energy which permeated the entire universe
| in that very early time period. The entire universe was opaque
| and extremely hot... then as it expanded, it began to cool
| enough for particles and then atoms to form. Only then were
| stars possible, and later galaxies.
|
| How/why can we see the CMB? Well, it was everywhere. Literally
| every point in the universe was a nearly uniform sea of blazing
| energy. So if you look far enough in any direction, you will
| see the cold echoes of that time period.
|
| edit: Beat to the punch! I hope among our many answers you've
| found something enlightening
|
| edit 2: Important to note that the CMB is not synonymous with
| the beginning of spacetime. It is more like a wall, beyond
| which we can't see anything, and it came down very early in
| time.
| drexlspivey wrote:
| Kinda relevant xkcd that was published today
| https://xkcd.com/2723/
| bpye wrote:
| > and it came down very early in time.
|
| Is this just because we've used it to define the start?
| Tuna-Fish wrote:
| We can't see down to 0 seconds, because very soon after the big
| bang, the universe was filled with dense, extremely hot, opaque
| plasma. The closest we can get is the "recombination epoch"
| [0], which is roughly 370 000 years after the big bang, when,
| because of universal expansion, the plasma got cold enough for
| neutral hydrogen to start forming, at which point the universe
| became transparent.
|
| As protons gain electrons in high temperatures, they don't form
| in the ground state. Instead, the newly minted hydrogen atoms
| are in a highly exited state. As they fall back to their ground
| states, they emit infrared photons at ~3000K color temperature.
| These photons, redshifted by the expansion of the universe to
| ~2.7K, are the Cosmic Microwave Background, the uniform
| ultimate backdrop we have when looking in any direction.
|
| [0]: Which has it's slightly incorrect name (should not have
| re-) because it was named before the big bang became a widely
| accepted or known theory.
| lp4vn wrote:
| What I'm going to ask you is completely dumb, but keep in
| mind I don't know much of physics.
|
| If my understanding is correct, when mass gets dense enough
| inside, a star you have a black hole, that would be like a
| hole in the fabric of space time. Ok, we have black holes in
| the contemporary universe. So how was the primordial universe
| a ball of dense, extremely hot, opaque plasma without
| becoming a huge black hole?
| willbudd wrote:
| Not a physicist at all either; but on a per particle basis,
| I know gravity is by far the weakest of the fundamental
| forces. However, unlike the others, it doesn't have
| spin/charge/polarity that results in their vectors
| repelling each other. As such, black holes form when the
| large scale weak gravitational forces combine into a
| greater force than the strong short scale repelling forces
| exerted by the others (and especially so when nuclear
| fusion is involved). In a hot primordial plasma, the
| particles are by definition extremely energetic; pushing
| each other in all directions with far more vigor than the
| extent to which gravity attracts them. Hence being a big
| bang rather than a big crunch, I suppose.
| deadbeeves wrote:
| Because the primordial universe was in a state of extremely
| fast expansion, while black holes today exist in space-time
| that is almost exactly flat. In fact, if the universe
| really started from a singularity, the expansion was
| infinitely fast for an instant.
| Balgair wrote:
| To hedge the next question then: Why was the universe
| expanding so quickly?
|
| It seems that the expansion must have been so fast that
| it was going faster than light speed, right? Otherwise
| the very dense universe must have gone black-hole.
| deadbeeves wrote:
| The expansion of space itself is not comparable to the
| speed of light, but yes, I would say it's probable that
| it would have caused particles (or whatever there was at
| that time) to spread out faster than light, thus
| disconnecting them causally and preventing gravitational
| interaction. As for the why, answering that would involve
| answering why the Big Bang happened, which given our
| current understanding would veer into metaphysics. As far
| as we can tell, it's just what the universe does.
| cypress66 wrote:
| I have no idea about cosmology, but I think maybe that if
| this dense matter where everywhere, then forces would
| cancel out and that's why you don't get a black hole.
| Jeff_Brown wrote:
| +1! Infinite density => way blacker than a black hole, no?
| cevn wrote:
| Fascinating... so we see the CMB, got it. I wonder if someone
| could take what seems like the random pattern of the CMB and
| reverse it into some vision of the BB..
| seanw444 wrote:
| So if we can see CMB in all directions, why do we really even
| say "the observable universe" as though there could be more
| matter and more galaxies beyond what we can see? If the
| maximum of what we can see is implied to be before all
| galaxies, then shouldn't it be implied that all galaxies that
| exist _can_ be seen?
| sebzim4500 wrote:
| No, because galaxies almost certainly exist which are
| further than the CMB. It's just that the light travelling
| from them has not been able to reach us in the time since
| it was emitted.
| dwaltrip wrote:
| And never will reach us, as the space in between us and
| that distant light is expanding to quickly.
| superjan wrote:
| Well most physicists assume it is massively bigger than we
| can see. It is in principle possible that we see nearly all
| of it, but that would be very coincidental. The only thing
| we know is that it is at least as big as we can observe,
| but it could be hundreds of times bigger, 10^100, or even
| infinite.
|
| There are speculations one could make that imply a minimum
| size, I recall a reading a prediction of 10^50 times bigger
| or so.
| jfengel wrote:
| The "observable" universe is about what we will ever see in
| the future, rather than about the past. If you waited
| around for billions of years, you could watch those early
| galaxies evolve.
|
| There might be galaxies even further away, but you can't
| ever see them, not even in theory. The light from them will
| never reach us because they flying away from us further
| than the speed of light.
|
| The CMB isn't really about galaxies. We know there won't be
| any galaxies past the CMB because galaxies couldn't have
| formed before the CMB was emitted.
|
| In theory we can "see" past the CMB using gravitational
| waves. (There was a thought, in fact, that we'd already
| done that, but that appears to have been faulty.) The CMB
| is just kind of a practical limitation rather than a
| fundamental matter of spacetime: you can't see because it's
| too cloudy.
|
| The question of whether galaxies beyond the observable
| universe "exist" is kind of a matter of metaphysics rather
| than astrophysics. As an astrophysicist, you basically just
| say they don't exist and you're done with it. But if you
| want to know where the universe "came from" (whatever that
| turns out to mean), you try playing around with notions
| like "our universe is an observable sub-part of a wider
| ensemble, which we'll never detect, but here's a pretty set
| of equations which explain our universe in terms of it".
| KMag wrote:
| Due to accelerating cosmic inflation, some galaxies are
| receding from us at faster than the speed of light, so
| their light will never reach us. The majority of galaxies
| (everything outside of our local cluster, IIRC) will
| eventually be receding faster than the speed of light and
| be beyond our vision forever.
|
| Yes, this means most galaxies will appear to actually pass
| through/into the cosmic background, from our point of view.
| Jeff_Brown wrote:
| I thought the logic of inflation had no limit, and
| eventually, everywhere, even atoms themselves would come
| apart.
| KMag wrote:
| I don't think we understand enough about the dark energy
| driving inflation to say that. If the force is constant
| for a given pair of particles at a constant distance, and
| the atoms are currently stable, that would seem to imply
| that the force from dark energy pushing the atoms apart
| will be the same as they are now.
|
| However, as I said, I don't think we know enough about
| dark energy to say anything about its effects on the
| atomic scale either now or eons hence.
| [deleted]
| deadbeeves wrote:
| You're describing the Big Rip. It's now thought that the
| acceleration of expansion is not high enough for that to
| happen. Gravity is strong enough that the particles
| inside galaxy groups will stay causally connected
| indefinitely. Long enough into the future, whole groups
| will become disconnected from the rest of the universe,
| though.
| seanw444 wrote:
| Ah, I had never thought of it that way for some reason.
| Duh. Thanks.
| dougmwne wrote:
| Here's the important point I think you are missing. You are
| looking in TIME, not in space. When you look very far away,
| you are looking back to the beginning of time, back to a
| singularity where all matter and energy existed at a single
| point. In every "direction" you end up looking back to the
| same time and the same place, the beginning of everything.
| There's nothing "beyond" that, it is the beginning.
|
| If you ask, what exists today, beyond 13.7 billion light
| years from earth, the plausible answer is "mature galaxies
| like ours" but there is no possibility of collecting data
| or evidence of what is there, since the evidence would take
| more than 13.7 billion years to reach us, and in fact would
| never reach us because the expansion of the universe means
| that distances are getting larger between 2 points all the
| time.
| tomp wrote:
| But if we're looking in the _direction_ of a galaxy far
| far away (i.e. 14bn ly away) (which we don 't know it's
| there, but let's assume it is, because likely _some_
| galaxies must be there), how come we see the CMB, which
| is 13.7bn years old, and not the galaxy itself, which is
| (by definition) _less_ than 13.7bn years old?
| scotty79 wrote:
| Because what we see from that direction are the things
| that were there in the last 13.7bn years. But the farther
| we look we see older images. So while we can see image
| from 10bn years ago of something that's 10bn light years
| away, when we try to see something 13.7bn light years
| away we just see microwave soup because that's what was
| there 13.7bn years ago. And if we try to see something
| 14bn light years away we see nothing from there because
| 14bn years ago there was nothing there.
| [deleted]
| deepsun wrote:
| To "what exists today, beyond 13.7 billion light years",
| I'd rather say that "it doesn't exist yet". Because,
| otherwise, it assumes there's some "global universe time"
| like UTC or something. But all there is is our light
| cone.
| dougmwne wrote:
| That is fair. We are veering into metaphysics or religion
| if we talk about what exists there today, or even if
| there could be any relationship between our "today" and
| their "today". By definition there is no causal
| connection. I'll get back to you on that once I finish
| inventing my Time Machine.
| Jeff_Brown wrote:
| Is it true that space had no volume at the Big Bang? I
| understand that density rises without (known?) bound as
| we approach the Big Bang, but even if you compress
| infinite space by an infinite factor you might still have
| infinite space -- infinity divided by infinity is
| undefined.
| dougmwne wrote:
| If you run the density backwards far enough, eventually
| everything in the visible universe is effectively at a
| single point, in some theories this was modeled as an
| actual infinite singularity, but it's quite possibly
| unknowable since our first evidence is the CMB 380k years
| into the whole thing. As we rewind time from there things
| being to get highly speculative.
| [deleted]
| pseudobry wrote:
| > the uniform ultimate backdrop we have when looking in any
| direction
|
| Is the CMB exactly uniform in every direction? Or is this
| early light slightly more redshifted when we look up versus
| when we look down or left or right? Does the oldest light we
| see in any given direction vary slightly in color?
|
| I'm imagining the universe expanding as a sphere from a
| central point, but we're located off-center. Wouldn't the
| early infrared photons emitted from the other side of the
| central point of expansion from us be observed by us now as a
| slightly different color than the early infrared photons
| emitted closer to the edge of the early expanding universe?
|
| A rabbit hole of questions: - When did space start expanding?
| - Did it have to rapidly expand for 400k years as extreme
| forces propelled matter apart? - Was that expansion faster or
| slower than the current expansion of space between galaxy
| groups? - Is expansion uniform across the universe? - Or is
| expansion slower closest to the original center of the
| universe? - Maybe there's a central point in the universe
| that's not moving relative to a reference frame outside our
| universe? - Is space discrete or continuous? - As space
| expands do new "units" of space appear between units of space
| that have grown farther apart? - If not, wouldn't physics
| work differently for areas of space where the units of space
| have grown farther apart than areas of space where the units
| of space aren't as far apart?
| saberdancer wrote:
| Better to think of expansion as being a 2D dot on a
| balloon.
|
| As balloon expands, in all directions there is same rate of
| expansion. You are not inside the balloon close to one side
| to observe the difference.
| kzrdude wrote:
| The CMB is famously not exactly uniform https://www.esa.int
| /ESA_Multimedia/Images/2013/03/Planck_CMB
|
| I have not read that any particular directions are evident
| in the sense you suggest though.
| mr_mitm wrote:
| There is a very obvious dipole in the CMB due to our
| peculiar velocity. This has been removed in almost all
| images you saw because it's just an artifact of our
| particular movement and not physical. It's just the
| Doppler effect.
|
| This page has three pictures:
| https://wmap.gsfc.nasa.gov/universe/bb_cosmo_fluct.html
|
| The first is the actual observation. It's boring and
| looks completely homogeneous.
|
| So you subtract the average value, which brings you to
| the second picture. Its temperature is 0 on average, but
| shows the obvious dipole.
|
| When you remove the dipole, you get the last picture,
| which show only the physical temperature fluctuations.
| kzrdude wrote:
| that is a very clear explanation
| mandevil wrote:
| As everyone has already pointed out, the Cosmic Microwave
| Background Radiation is as close as you can get to the Big
| Bang.
|
| But to the larger point, these galaxies were suspected before,
| based on Hubble work. You see, the COBE satellite from 1989 to
| 1993 mapped the microwave background radiation very precisely
| (two of the Principal Investigators on COBE won the 2006 Nobel
| Prize in Physics for this work). And they found that while
| there are minute fluctuations in the radiation, those
| fluctuations are measured at the parts-per-million level of
| difference. But the Hubble has found that the farthest back
| galaxies it could see were some of the largest and most massive
| things ever witnessed. So we had this gap between 'everything
| everywhere is the same to parts per million' and 'there are
| some supermassive galaxies' and so the Webb telescope was
| specifically designed to find the things that were redshifted
| so far they were out of the visible spectrum (so Hubble
| couldn't see them) but not so far that COBE could see them in
| microwave: in the infrared spectrum that lies between those
| two, that's where Webb is supposed to focus and help us
| understand how these galaxies form.
|
| Because this question of what happened between the CMBR and the
| visible light range is the biggest question left over from
| Hubble, so it is what drove the design of the Webb. This is how
| astronomy has worked for centuries: you build a new telescope
| to answer some questions, but that leaves you with more
| questions, so you need to build new telescopes to answer those
| questions, GOTO 1. That's what's been happening ever since
| Galileo looked through that telescope at Jupiter all the way
| back in 1610.
| ajross wrote:
| The very early universe can't be observed with visible light.
| It was filled with ionized hydrogen and thus opaque over long
| distances. The oldest light is from the era of "recombination",
| when things had cooled enough (c. 370k years after the big bang
| by consensus models) to permit light to travel. This is just
| the thermal glow of the universe, redshifted (way, way) down
| into the radio spectrum. And we can see it just fine; it's the
| cosmic background radiation and has been very well studied.
|
| It's the region between recombination and the currently-
| visible-to-telescopes galaxies that Webb is particularly well-
| suited to study.
| rjrodger wrote:
| Visible light was scattering off densely packed electrons up to
| about 300k years after the Big Bang - so I guess - white.
| ben_w wrote:
| White, redshifted so hard it's the blackest black we ever
| experience.
|
| (I want to add a H2G2 joke here, but I can't figure the right
| way to reference making God disappear in a puff of logic
| related to the Babelfish...)
| shadedtriangle wrote:
| We can see it and it's called the Cosmic Microwave Background
| https://en.m.wikipedia.org/wiki/Cosmic_microwave_background.
| It's not t=0.0000001 though as the time before the cosmic
| microwave background the universe was opaque to photons, you
| wouldn't be able to see anything.
| klodolph wrote:
| Correct me if I'm wrong.
|
| Cosmic microwave background is behind the galaxies, and we can
| see it. The universe is mostly transparent these days, so light
| can travel across the universe from a distant galaxy to our
| eyes or telescopes. Long ago, the universe was full of ions-
| free electrons and protons-and these are very effective at
| scattering light, so the universe was effectively opaque at
| that point. The universe became more transparent as the
| universe shifted towards hydrogen atoms instead of free
| electrons and protons.
|
| Whatever the universe happened to look like during that
| transition period, from opaque to transparent, is still what we
| see. It's the cosmic microwave background. Anything from before
| that time got absorbed.
| jfengel wrote:
| Yep. That is all correct.
|
| It's conceivable that we could observe gravitational waves
| during that period before the CMB, because they're not
| blocked by the un-recombined electrons and protons. If we
| ever get there, it could help explain the small variations in
| CMB from place to place. But that's a long way off.
| feoren wrote:
| Not an expert here but it sounds like you might be describing
| the Cosmic Microwave Background. This is basically the remnant
| of the early opaque plasma cloud that filled the entire
| universe. As we look far away/back in time, the photons
| reaching us have redshifted due to the expansion of the
| universe. That's why these originally extremely high-energy
| photons are now just low-energy microwaves. The "background", 0
| seconds after the Big Bang, is in all directions, and presents
| as the Cosmic Microwave Background. Or so I understand.
|
| https://en.wikipedia.org/wiki/Cosmic_microwave_background
| Pxtl wrote:
| There's always a relevant xkcd for every science question,
| and in this case it's one of the first ones:
|
| https://xkcd.com/54/
| limbicsystem wrote:
| But oddly the most recent one as well https://xkcd.com/2723
| yreg wrote:
| It's incredible how Randall seems to be able to come up
| with an endless number of fun ideas even after all these
| years.
| throwawaymaths wrote:
| Worth noting: For a very long time MOND has been predicting
| earlier galaxies than LCDM.
| rqtwteye wrote:
| As far as I know , MOND is not compatible with some
| observations. So dark matter and MOND have to be tweaked to
| agree with what we see.
| 6nf wrote:
| MOND is not compatible with all observations but neither is
| dark matter. A lot of scientists think MOND is a better
| explanation than a new particle that we've not yet observed.
| Have a look at Sabine Hossenfelder's work for some of those
| arguments.
| rsj_hn wrote:
| Which researchers (as opposed to pop-sci pundits) think
| MOND is a better explanation than Dark matter?
|
| That is a very, very fringe alt-science view that so far
| exists in various pop-sci blogs and informal youtube
| discussions, rather than in mainstream conferences,
| journals, and research centers.
|
| I'm not saying it's bad to speculate or write whimsical
| blog articles about these topics, there's lots of room for
| creative speculation, but MOND does not respect Lorentz
| invariance which is basically a deal breaker for virtually
| all serious researchers. Fewer things have more robust
| empirical support than Lorentz invariance, so discarding it
| forces you to say that your violation is always just over
| the horizon of what is testable (and this horizon keeps
| getting pushed back). That's generally a discrediting
| feature of any theory and a huge red flag. Much better to
| say "you don't know" than to postulate something which
| requires such massive fine tuning to always be just beyond
| the horizon of what is testable, but close enough to that
| horizon to have explanatory power for observed phenomena.
|
| https://phys.org/news/2017-11-evidence-violation-lorentz-
| inv...
|
| https://asfriedman.physics.ucsd.edu/Papers/Friedman+2020a.p
| d...
| [deleted]
| throwawaymaths wrote:
| He's passed, but jacob bekenstein?
| rsj_hn wrote:
| Bekenstein wrote an interesting paper on MOND in 2010
| here: https://arxiv.org/abs/1001.3876
|
| But again, the 2017 experimental data [cited previously]
| in support of Lorentz invariance and the 2016 bullet
| cluster data in support of dark matter basically killed
| MOND in the eyes of most researchers.
|
| As I said before, nothing wrong with writing papers
| exploring the consequences of MOND or trying to come up
| with alternatives, science does not work by consensus,
| but the bar for dropping Lorentz invariance is really
| high given the experimental support for it.
| sebzim4500 wrote:
| First, it might be 'a lot of scientists' in absolute terms
| because this is such a fertile field, but it is a tiny
| minority of cosmologists who believe MOND is the best
| explanation for these effects.
|
| Secondly, even the proponents of MOND concede that you need
| to introduce some amount of dark matter in order to explain
| e.g. observations of the Bullet Cluster. So the competition
| isn't between new particle vs MOND, it is between MOND +
| new particle vs new particle.
| 6nf wrote:
| Sabine says the Bullet Cluster is a problem for dark
| matter EVEN MORE than it's a problem for MOND!
| puffoflogic wrote:
| Yeah, but is it even worth saying that when the response will
| inevitably be "so what?" by the entrenched anti-MOND orthodoxy?
| JetSetWilly wrote:
| This is not unusual. There's many predictions made by MOND
| ahead of the fact that are borne out by reality. But don't
| worry - dark matter will be "retrofitted" so that it fits the
| facts and everybody will suffer collective memory loss again.
|
| Edit: see for example table 1 on page 12 here:
| https://arxiv.org/pdf/2110.06936.pdf from a review of prior
| expectations by both MOND and dark matter vs how they turned
| out against reality for a large variety of astrophysical
| scenarios.
| thereddaikon wrote:
| Dark matter is the umbrella term for the observed
| discrepancies. MOND is one possible possible explanation for
| DM. The paper you linked doesn't compare MOND to DM, because
| that doesn't make any sense. It compares MOND to LCDM which
| is a competing explanation.
| sebzim4500 wrote:
| Am I understanding that paper correctly that their suggested
| solution to explain the Bullet Cluster using MOND is too
| introduce an additional kind of matter which can not be
| detected on earth and doesn't interact with light (namely
| sterile neutrinos)?
|
| Is this satire?
| aeneasmackenzie wrote:
| "dark matter but not as much" is still an improvement if
| you replace it with something better. If MOND predicted
| these observations and LCDM didn't it's reasonable to say
| that it is better.
| sebzim4500 wrote:
| Yeah that's fair. I guess it could also explain why DM
| has been so hard to pin down, if both MOND and DM are
| true then there might be DM candidates that have been
| unfairly ruled out.
|
| I do think it significantly hurts the (more
| philosophical) argument that MOND is simpler or has fewer
| parameters than DM though.
| throwawaymaths wrote:
| So the ongoing problem with LCDM is that the parameter
| space for allowable particles keeps getting pushed back.
| We keep falsifying classes of potential particles that
| could be WIMPs. MOND+ some standard model-adjacent
| particle (like say right handed neutrinos), if we can
| have a phenomenological estimate of how much of them
| _should_ exist, would at least be credible on account of
| having a constrainable set of parameters, whereas the
| density of WIMPs in normal LCDM has no constraint besides
| the same measure that we have to infer its existence
| (gravitation)
| varjag wrote:
| But MOND itself is a "retrofit" to make it agree with the
| data, isn't it? It's in the name.
| rcme wrote:
| Every theory is a retrofit. A useful theory is also
| predictive.
| rqtwteye wrote:
| MOND is not compatible with some observations. It and
| dark will probably be tweaked until both agree with
| observations. At that point they will be the same.
| throwawaymaths wrote:
| That's a false equivalence. MOND has made several
| predictions before they were observed (external field
| effect, linear Tully fisher relationship, early
| galaxies). I think LCDM's made fewer if any predictions.
| varjag wrote:
| MOND has its share of failed predictions. It also _still_
| requires a certain amount of DM to work.
|
| This is fine for work in progress that all frontier
| science is but the issue is far from settled.
| jononomo wrote:
| I've always wondered where the universe is.
| djfobbz wrote:
| Thanks to Adobe, the universe and all of its galaxies have now
| been found!
| xyzal wrote:
| Articles like these make me want to stop doing everything and
| isolate in the basement for several months to study physics. Then
| I realize I have a family to feed and elderly parents to take
| care for.
|
| Sigh, so many beautiful mysteries in the world, and only one
| life.
|
| edit: A friend told me germans have the word "Sehnsucht" to
| describe such a feeling. So I guess it might be somewhat
| universal.
| yipbub wrote:
| Same, but I imagine doing it in a country house with a table
| looking out into a lovely garden, and a mountain path nearby
| for long walks thinking about things.
| Cthulhu_ wrote:
| I'm sure there's a catchy phrase for that kind of thing,
| intellectual cottagecore maybe?
| siva7 wrote:
| Wanderlust
| jstummbillig wrote:
| It was beautiful and unexpected that this was not a
| "but"-one-up or "but"-and-here-is-why-you-are-wrong.
| ankit219 wrote:
| I have kind of done that for last few months. Chat GPT helped
| immensely with that. I recently even asked if it's worth it to
| go back to academia. Still exploring that.
|
| A few things that I recently understood or read about.
|
| - Fermi Paradox - with help of chatgpt
| https://imgur.com/a/LuVV6iK
|
| - How the age of universe was calculated.
|
| - Redshift
|
| - How age of solar system was calculated. I previously thought
| just like the universe is expanding, so is solar system. Turns
| out that is not the case. The distances have been more or less
| fixed. (i thought sun would be losing some mass, weakening
| gravitation for that to happen, nothing like that).
|
| - Exo-planets.
|
| - a lot of nuclear physics.
|
| - Parallel universe theory according to quantum mechanics.
|
| - gravitational waves (how to measure ripples in spacetime
| https://www.wired.co.uk/article/catching-cosmic-rays-
| virgo-i...)
|
| - Theories around nuclear fusion and how ML, High Temp super
| conductivity and more precise chips are making advances
| possible.
|
| And so on.
|
| Will add one special mention to this:
| https://www.quantamagazine.org/why-this-universe-new-calcula...
| (this universe exists because it has the highest entropy is a
| layman summary of the article)
| smcnally wrote:
| Anton Petrov regularly covers topics like these and
| encourages sharing with people interested in space and
| sciences.
|
| https://youtube.com/@whatdamath
| ankit219 wrote:
| Love it. Bookmarked. Thanks for sharing.
| [deleted]
| lnkl wrote:
| Seems like https://www.edx.org/xseries/astrophysics?index=pro
| duct&query... would be of interest to you.
| go_elmo wrote:
| Chances are significant that some explanations received are
| just not true as chatgpt does that too, unfortunately.
| ankit219 wrote:
| Not all of it is from chatgpt. It's a good starting point,
| and essentially tells me what to google and how to read
| further. When I get something, I anyway want to read more
| so would google around the topic. The ability to ask a
| cross question is what makes learning easier. If the answer
| is not true, i will end up finding that out anyway from
| google or other science publications.
| kettleballroll wrote:
| Interesting approach. Aren't you worried that chatgpt is
| feeding you bullshit without you noticing? I'd imagine
| chatgpt read as much science fiction content as science one,
| so there's no way to know if it tells the truth or
| hallucinations. How do you deal with that?
| ankit219 wrote:
| It's a good starting point. It may get some things wrong,
| but that's where my ability to research and truth seeking
| lies. I usually google more anyway because i want to go
| deeper than what chatgpt offers. I will eventually get to
| the truth. But the basic questions are well answered. I
| once asked it to explain the whole "Field has momentum"
| theory in a way a Feynman lecture would. It did it
| surprisingly well. I had some background so I kept asking
| more questions, and it was alright. Augments the curiosity,
| and make the topic seem simpler. Tools I use are: Google,
| science publications, and archive to see if there is text
| around it.
|
| One small thing, the idea that chatgpt will feed bullshit
| is possible, so you have to be a bit skeptic and check the
| info, but it gets things right most of the times. Fun fact:
| I confused chatgpt about static electricity ie "Why does my
| hair get a static charge by rubbing a balloon?" It kept
| saying positive charge or negative charge, with transfer of
| electrons. Truth is, it's still poorly understood. [1] this
| paper highlights the conundrum.
|
| For a beginner in college level physics, chatgpt is an
| excellent resource for understanding concepts.
|
| [1]: https://www.researchgate.net/publication/360674587_Der
| ivatio...
| saboot wrote:
| For me, it's been learning about the topic of last year's nobel
| prize in physics. Shedding light on Einstein's famous "God does
| not play dice" through, literally college algebra and a
| somewhat mundane experimental setup. The only thing stopping
| people from doing it sooner was obscurity and a comfortable
| attitude towards to status quo!
|
| Now I'm convinced we can understand really fundamental things
| about our reality, and that is so so interesting.
|
| I'm dreaming of going back, getting a math master's, then a
| physics PhD ... Maybe
| acqbu wrote:
| only one life? don't be so sure about it
| [deleted]
| wolfi1 wrote:
| although there is a german word for everything, "Sehnsucht"
| just means "desire"
| mr_mitm wrote:
| I don't know if it's any consolation, but a few months are not
| nearly enough to understand this on a meaningful level. I spent
| almost a decade studying physics, still feel like I don't
| really understand it and could barely wait to get out at the
| end.
| znpy wrote:
| > I spent almost a decade studying physics, still feel like I
| don't really understand it
|
| This is the part that's actually consoling.
| 8bitsrule wrote:
| Some more interesting food for thought:
|
| >The classical big bang cosmological models describe gravitation
| by Einstein's general theory of relativity. These models are able
| to treat the matter content of the universe quantum mechanically
| where appropriate, but they do not take into account the
| interplay of quantum theory and gravity.... The earliest universe
| was presumably quantum mechanical through and through, and we can
| no longer describe its initial conditions in a classical
| language. We must instead treat the whole early universe as a
| quantum system and formulate its initial conditions in the
| language of quantum mechanics.... Quantum gravity theorists have
| not shied away from the challenge. At present there are some half
| a dozen contenders...."
|
| https://www.einstein-online.info/en/spotlight/quantum_cosmo_...
| [deleted]
| dave333 wrote:
| [flagged]
| BillSaysThis wrote:
| I'm not the least bit qualified to judge this but if true, mind
| blown.
| Beltalowda wrote:
| That entire site reads like "what if Elizabeth Holmes set up a
| power generation company?"
|
| Reading up on the company on Wikipedia, it seems to be pretty
| much exactly that.
|
| https://en.wikipedia.org/wiki/Brilliant_Light_Power
| ajross wrote:
| Yikes, it's BlackLight! I had no idea this joker was still
| around. For reference: this was popular snakeoil on USENET
| back in the 90's when I was in college. This is some really
| crufty nonsense, and I'm kinda shocked it's still being
| recycled.
| dave333 wrote:
| The theory has not changed much since the original work by
| Mills in the 1990s but the experiments and engineering have
| overcome a lot of hurdles and there are now many
| experiments that match the predictions of the underlying
| theory and prove the existence of hydrinos.
| dave333 wrote:
| Read the talk page too - there's been a lot of dispute about
| that page
| lalalandland wrote:
| I watched a few videos about variable speed of light. I know
| nothing about this but it is fun to ponder different
| explanations for Dark Matter, Dark Energy etc.
| HideousKojima wrote:
| You may like my silly theory (made with zero evidence) to
| bring back the Big Crunch Theory. Imagine that spacetime is a
| sphere, and the Big Bang happened at the "north pole" so to
| speak. All matter will eventually meet back together and
| recombine at the "south pole" after which a new Big Bang will
| happen. Absolutely zero evidence for my idea and it's
| probably impossible to prove anyway but it's fun to theorize.
| Tuna-Fish wrote:
| This doesn't work. The universe was opaque for the first few
| hundred thousand years, even if there is a cycle, we cannot
| possibly see it.
| dave333 wrote:
| We are not looking back into the past cycle, but we see
| mature galaxies that date from the previous cycle.
| kolinko wrote:
| What you're saying doesn't make sense - not even according
| to the bizzaro theory you mentioned. Even if there was a
| previous cycle, there would be no galaxies left from it to
| witness.
| dave333 wrote:
| I think you are assuming a big crunch?
| kolinko wrote:
| No.
| idlewords wrote:
| This was predicted by astronomer Stacy McGaugh on his super
| interesting blog as a natural consequence of modified Newtonian
| dynamics (https://tritonstation.com/2022/01/03/what-jwst-will-
| see/).
|
| McGaugh came to support MOND over dark matter reluctantly for
| just such reasons--MOND routinely predicts things in advance that
| dark matter struggles to justify ex post facto, usually by adding
| additional moving parts to the model.
|
| Whether or not you find the evidence persuasive, McGaugh's blog
| is worth a deep dive just to appreciate the subtleties and
| complexities of this kind of observational astronomy.
| astroH wrote:
| So MOND does predict more galaxies at high redshift however it
| also predicts earlier reionization than LCDM which it turns out
| not to be true and the mass function of clusters is not what we
| see purely based on X-ray temperatures. So getting one thing
| right at the expense of many others doesn't make this
| particularly viable.
| schiffern wrote:
| Any publications indicate whether Refracted Gravity (RG)
| predicts the same thing?
|
| RG has always fascinated me, since it neatly explains flat
| rotation curves[1] without messing up the equations for gravity
| too much. If some refractory effect (TBD) causes gravity to
| bend toward mass concentrations, then this effectively
| "confines" gravity into a plane. Then the propagation law
| becomes 1/r rather than 1/r^2.
|
| In effect it becomes a galactic analog of the SOFAR layer in
| the ocean.[2]
|
| Intuitively the "self feeding" effect on disk formation should
| accelerate the process, but I'd be interested to see a full
| treatment.
|
| [1]
| https://www.aanda.org/articles/aa/pdf/2020/05/aa35950-19.pdf
|
| [2] https://en.wikipedia.org/wiki/SOFAR_channel
| whatshisface wrote:
| > _without messing up the equations for gravity too much. If
| some refractory effect (TBD) causes gravity to bend toward
| mass concentrations, then this effectively "confines" gravity
| into a plane. Then the propagation law becomes 1/r rather
| than 1/r^2._
|
| There are objects like globular clusters and dwarf galaxies
| that lie outside the galactic plane, but are not that far
| away. If our galaxy's gravity was confined to its plane, you
| would expect nearby external objects to move differently from
| how they are observed to move. See illustration:
|
| https://cdn.britannica.com/23/4423-050-964A0A08/Distribution.
| ..
| schiffern wrote:
| I was hoping someone would mention globular clusters! I
| couldn't find a way to integrate it naturally in my post.
|
| I don't see any information about globular cluster
| _movement_ in that image. Naturally the confinement wouldn
| 't be 100%, and some amount of gravity would still "leak
| out,"[1] so the mere existence of globular clusters isn't
| proof one way or another.
|
| Surveying globular clusters offers a good test. RG might
| (or might not) explain why globular clusters are
| mysteriously 1) preferentially orbiting perpendicular to
| the primary galaxy's rotation, perhaps due to stability,
| and 2) preferentially aligned with each-other in their own
| plane, perhaps due to mutual (lensed) gravitation. Both of
| these observations are otherwise unexplained (or require
| numerous free parameters) under dark matter.
|
| We won't know until someone does a survey, and probably
| some simulation work. Sadly MOND soaks up most of the
| oxygen in the Modified Gravity field, leaving almost none
| for RG.
|
| [1] see Figure 16 https://arxiv.org/pdf/1603.04943.pdf
| jquery wrote:
| It seems to me, as a layperson, if MOND was hypothesized first,
| it would be the dominant theory. It's so elegant and simple
| with so much explanatory power. However, because it was
| hypothesized much later, the fact it matches past predictions
| is given no weight, despite its simplicity.
|
| I think this is a bit of a mistake. I believe that simplicity
| itself is evidence. Dark matter theory is starting to feel like
| the epicycles of Copernicus.
| moffkalast wrote:
| I was pretty convinced that dark matter is made up nonsense
| and that RelMOND is probably correct, but then I learned of
| the Bullet cluster.
|
| https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to.
| ..
|
| Two clusters collided, with most of the observable objects
| being just past the middle point right now, however most of
| the mass seems have already shot way out to the edges, as if
| it passed right through everything. It's pretty hard to
| explain with anything else other than that there's something
| there that has mass yet can't interact with anything else
| that passed through everything when the collision happened.
| Adjusting equations doesn't really work in this case, there
| must be something physically there.
|
| I'm not sure why this isn't mentioned first thing every time
| in dark matter discussions because it's literally the only
| thing that's pretty hard evidence imo.
| bmitc wrote:
| > however most of the mass seems have already shot way out
| to the edges, as if it passed right through everything.
| It's pretty hard to explain with anything else other than
| that there's something there that has mass yet can't
| interact with anything else that passed through everything
| when the collision happened.
|
| It is my understanding that dark matter _does interact_
| gravitationally, so I am confused by this.
| fartsucker69 wrote:
| MOND mispredicts many, many past discoveries. This would have
| people scrambling for alternative explanations immediately.
| Dark matter is simply a better fit for what we see.
|
| Second, I don't know why MOND seems simpler and more elegant
| to you than literally something that doesn't modify the laws
| of physics at all but just increases the mass you use in
| computations.
| messe wrote:
| I'm not a MOND proponent, but Cold Dark Matter also
| literally requires modifying the laws of physics, by
| positing new particles.
| nickelpro wrote:
| If MOND completely described observable phenomenon it would
| supplant dark matter, but it doesn't. MOND still requires
| dark matter, just less of it. Or, to quote Milgrom, "some
| standard matter in some form that has not been detected"[1].
| Which, IMHO, is nearly isomorphic to DM as far as statements
| go.
|
| So until we figure out what the missing mass is, MOND is
| widely viewed as an unnecessary complication. There _is_
| missing mass, if we figure out the nature of DM or discover
| this hitherto unknown "standard matter" _then_ we can talk
| about modifying universal gravitation.
|
| [1]: https://web.archive.org/web/20160721044735/http://www.as
| tro....
| throwawaymaths wrote:
| The explanatory power of dark matter is so weak though.
| With the right clumping of LCDM you could probably also
| explain various reports of poltergeists around the world.
|
| Then you could claim that reports of poltergeists are
| evidence of LCDM over MOND because it's another phenomenon
| that MOND can't explain.
| ndsipa_pomu wrote:
| However, there is plenty of evidence to suggest that it
| does exist.
|
| The distribution of dark matter being uneven is evidence
| that something functioning like dark matter has to exist
| as MOND doesn't easily replicate that. Colliding galaxy
| clusters show a distribution of matter that differs from
| the distribution of visible matter, so the simplest
| explanation is that there is invisible matter that reacts
| gravitationally.
| throwawaymaths wrote:
| The evidence that it exists boils down to: gravitational
| anomalies. It's not multimodal, which is a problem
| because you're saying "it must exist because of x
| therefore it must exist" versus "it must exist because of
| x, which has a side effect of y, which aha also we see".
| That's why it's weak.
|
| > the simplest explanation is that there is invisible
| matter that reacts gravitationally.
|
| That's the whole point of the poltergeist example. If
| someone said: "Oh, that urn on your mantle just fell
| over? Must have gotten knocked over by a rogue ball of
| dark matter. The simplest explanation is that dark matter
| must exist". You would think they are insane.
| ndsipa_pomu wrote:
| You can think of dark matter as gravitational anomalies
| that aren't distributed uniformly. If we assume that
| physical laws are constant throughout the universe, then
| it becomes difficult to account for those anomalies
| without saying that there is "something" there that is
| influencing gravity. Obviously, we've labelled that
| "something" as dark matter and figured out what
| properties it can and can't have.
|
| With your poltergeist example - if it was relatively
| common for urns on mantle to be knocked over, then it
| would make sense to come up with a hypothesis. If objects
| around the urn were affected gravitationally just before
| the urn falls over, then dark matter would appear to be a
| rational hypothesis.
| Beldin wrote:
| The simplest explanation is that there is regular matter
| which we fail to detect. Not weird, given the huge
| distances involved - there almost assuredly is mass that
| we didn't detect (e.g. planets).
|
| The point where fairy matter comes in, is that we can
| guess how bad we could be at not detecting matter.
| Basically, regular matter that we didn't observe can't
| explain everything - we would've observed it otherwise.
| ndsipa_pomu wrote:
| That's not the simplest explanation as our current
| theories limit the amount of normal matter that can exist
| and galaxies behave gravitationally as though there must
| be a lot more than normal matter. Normal matter that is
| invisible to us is not a viable solution to the evidence.
|
| There some discussion of regular (baryonic) matter vs
| dark matter here: https://www.livescience.com/how-much-
| dark-matter-universe
| bmitc wrote:
| > The simplest explanation is that there is regular
| matter which we fail to detect. Not weird, given the huge
| distances involved - there almost assuredly is mass that
| we didn't detect (e.g. planets).
|
| What is the difference between that and dark matter?
|
| > there almost assuredly is mass that we didn't detect
| (e.g. planets).
|
| Don't planets give off light and thus contribute to the
| distribution of light observed?
| throwawaymaths wrote:
| Sorry, There are currently hard constraints on the
| lumpiness and size on that matter which basically exclude
| all reasonable possibilities for "normal matter we fail
| to detect". It's certainly possible something strange is
| happening though, or our statistics could be wrong.
| saberdancer wrote:
| Problem that I see with dark matter is that it is
| unfalsifiable.
|
| If you can have arbitrary amounts of dark matter in
| arbitrary positions - how can you falsify that?
| dTal wrote:
| It's not as if dark matter doesn't follow any rules at
| all - hypothetically, it obeys gravity like any other
| matter. So you can't have arbitrary amounts in arbitrary
| positions - you have to explain what attracted the dark
| matter to that position.
| mr_mitm wrote:
| This argument seems to pop up on HN every time dark
| matter is discussed. Unfortunately, it stems from a
| fundamental misunderstanding of how modern cosmology
| works.
|
| The exact spatial DM distribution is not a parameter of
| the cosmological standard model. Instead, you assume an
| initial condition (pretty much a smooth distribution with
| only quantum fluctuations, which are parameterized by one
| or two parameters), apply the laws of physics to evolve
| this state some 14 billion years and compare the
| statistics of the theoretical and observed distribution.
|
| In fact, DM suffers from the dwarf galaxy problem. Our
| theory predicts more than we observe. It's a bit of a
| challenge for DM, and considering how fuzzy our knowledge
| of galaxy formation is and how much other evidence for DM
| there is, it's not falsifying it yet. But if this is
| cemented by future observations it might very well be a
| blow to DM.
|
| Besides, DM was hypothesized after measuring the famous
| rotation curves of galaxies. DM could have been easily
| falsified if we made gravitational lensing measurements
| afterwards and didn't see any DM. But we saw DM. Same
| thing with baryionic accoustic oscillations in the cosmic
| microwave background angular power spectrum. We looked
| there after we already thought that DM should be there,
| and the power spectrum looks just like if there is DM. It
| could have easily falsified DM, but didn't. The list goes
| on. DM could have been falsified may times, but passed
| almost all tests so far. Well, except for the ones in the
| lab, unfortunately.
| cdogl wrote:
| I am too ignorant to weigh in on MOND vs dark matter, but
| this seems entirely possible.
|
| In all domains - not only physics - there are many possible
| models that seem to match our observations. They're
| continually adapted over time in order to meet to perceived
| needs and reality (see: the medieval European church).
|
| Paradigm shifts can happen incremental or explosively. With
| the enormous sunk cost in our existing models - not least the
| millions of people educated in them - incremental change
| becomes harder. If MOND or any alternative theory is "true",
| it faces a distinct challenge: there are decades of
| experiments and observations that have been fit to our
| existing model. To take over, it needs to answer _all_ of it
| - or provide so much utility that the incentives shift.
|
| Success can be paralysing. In tech, a new idea can come along
| and shake everything up by showing results and solving a
| problem. The only way a new model of physics can do that is
| by generating a practical breakthrough. I hope I'm wrong!
| ilitirit wrote:
| I've been out of the loop for a while. Can MOND satisfactorily
| explain gravitational lensing?
| hackernewds wrote:
| It doesn't entirely, but Refracted Gravity does.
| Spkeat wrote:
| This can further reinforce the idea that the unobservable
| universe was always there and that the big bang is only a pattern
| of movement of the cluster of galaxies and it is only the
| information that has managed to arrive from our position.I want
| to see how big bang theory falls into an optical illusion.
| WXLCKNO wrote:
| I don't know which idea is harder for me to conceptualize.
|
| That something has _always_ existed or that it came to exist
| out of nowhere-ish.
| SV_BubbleTime wrote:
| I suspect this is why simulation theory is popular.
| tommoor wrote:
| Much like god, that just pushes the question up one level
| whaaswijk wrote:
| While I agree that simulation theory pushes the question
| up a level, that is not the case for the God of classical
| theism.
| bbreier wrote:
| Ok, I'm curious. How does the explanation for
| everything's existence being "God did it" not simply push
| the question up a level to wondering how to explain God's
| existence?
| panza wrote:
| The general idea is that the set of all contingent things
| can only be explained by something non-contingent (ie
| necessary).
|
| A necessary thing, by definition, is its own explanation.
| "I am what I am" etc.
|
| From there, classical theists attempt to connect that
| necessary thing to what you'd commonly understand as God.
| deepsun wrote:
| I just noticed that if you replace "God" with "Big Bang",
| it's pretty much the same question.
|
| The answer to Big Bang is that before it, there was no
| time itself, so there's no notion of "before" (or if you
| wish, it's an error in the question itself that assumes
| there was "before").
| mansoon wrote:
| Once you factor time out of your pre-universal reality, these
| are compatible.
| not2b wrote:
| This is good. If we merely confirm what we expect to see, then we
| don't learn anything new.
| echelon wrote:
| Not so sure. If we're not early ourselves, the likelihood that
| the universe is swimming in intelligence -- if not already part
| of an enormous computational fabric -- is higher. That naively
| seems like it would place an upper limit on Earth-originated
| intelligences.
| Jweb_Guru wrote:
| Would that be such a bad thing?
| jscipione wrote:
| RIP Big Bang Theory
| DesiLurker wrote:
| Cue Laugh Track
| timmg wrote:
| I have no idea if it is the end of the Big Bang Theory, but I
| think it would be super fun if it is:
|
| * It doesn't have a negative effect on anything if it turns out
| to be wrong (other than some theses).
|
| * It would be pretty cool to get a sense for how fallible we
| are
|
| So I'm rooting against Big Bang Theory just for the experience
| of it :)
| sebzim4500 wrote:
| Depends what you mean by the big bang theory. The theory that
| the universe expanded almost from a point will probably survive
| forever, but LCDM might not survive the decade.
| bcaulfield wrote:
| Great news. Finding stuff that doesn't fit into the current model
| and we need smart people to get to work understanding may be the
| surest sign that the JWST is invaluable.
| xp84 wrote:
| Same - I really like seeing things like this.
|
| Not only because it means we're about to learn some big stuff,
| but also because it would be completely *preposterous* if
| humans at our puny stage of development had already correctly
| figured out every last detail about insanely complex things
| like the exact size, age, and origin and age of galaxy-sized
| things that developed tens of billions of years ago, billions
| of light-years away from the tiny rock we stand on. Getting
| things wrong shows that people are actually doing science
| honestly!
| Teever wrote:
| What stage of development do you feel is necessary to acheive
| what you're describing?
|
| How can a human at this puny stage know this?
| Waterluvian wrote:
| This reminds me of how when you're right, you don't learn much.
| When you get it wrong, you learn a ton.
| pleb_nz wrote:
| You learn more from mistakes and being wrong no doubt about
| it.
|
| I remember some billionaire saying 15% of the decisions you
| make each day should be mistakes otherwise your not trying
| and you're not learning.
| gitfan86 wrote:
| We have known that the current model of physics is wrong for
| a long time. But the main focus has been on math. "If only we
| could figure out this formula, then we would understand
| everything"
|
| It seems much more likely that we are not missing a formula
| but a basic understanding of reality. Much like the early
| astronomers trying to find a formula for the movement of the
| sun and planets that put Earth at the center of the universe
| andrei_says_ wrote:
| I really like this comparison. But isn't the case with
| modern physics that we are getting something like 8 of 10
| things right? So that's a lot of correct triangulation -
| and throwing the current understanding out would throw all
| of that away - and potentially rearrange things.
| gitfan86 wrote:
| The Ptolemaic System was also mostly correct at
| predicting the movement of celestial bodies.
|
| https://en.wikipedia.org/wiki/Geocentric_model#Ptolemaic_
| sys...
| naikrovek wrote:
| I don't know why articles are titled like this. it's annoying,
| though, I'll tell you that
|
| we are finding the exact correct number of galaxies of the exact
| correct ages; our expectations are wrong, or how we determine
| what we've found is wrong. generally, our understanding is wrong.
| not the rest of the entire universe.
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