[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 : 208 points
Date : 2023-01-12 20:45 UTC (2 hours ago)
(HTM) web link (skyandtelescope.org)
(TXT) w3m dump (skyandtelescope.org)
| cwoolfe wrote:
| Obligatory xkcd: https://xkcd.com/2622/
| 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?).
| 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.
| [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.
| 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]
| 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.
| 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?
| 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
| 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.
| 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.
| 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?
| 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?
| 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.
| 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]
| 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.
| 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.
| 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.
| [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
| xwdv wrote:
| Ok, so if the Big Bang Theory is bunk, what's the next leading
| alternative creation theory?
| 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
| airstrike wrote:
| Speaking of unpopular pet theories from the 1940s, I'm a fan of
| the https://en.wikipedia.org/wiki/One-electron_universe
| 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.
| 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.
| 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.
| 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.
| 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.
| 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?
| 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
| 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.
| 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.
| 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?
| 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.
| 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.
| 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
| _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?
| 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.
| 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
| 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.
| 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.
| 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.
| 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."
| 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.
| [deleted]
| jpttsn wrote:
| At that point why not call it "witchcraft;" a sciencey word
| for something is not an explanation.
| 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.
| 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.
| 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.
| 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.
| 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? :-)
| 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/
| 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.
| 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.
| [deleted]
| 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
| throwawaymaths wrote:
| Worth noting: For a very long time MOND has been predicting
| earlier galaxies than LCDM.
| 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.
| 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.
| 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!
| 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:
| 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?
| 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.
| jscipione wrote:
| RIP Big Bang Theory
| 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.
| 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.
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