[HN Gopher] Webb and Hubble confirm Universe's expansion rate
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Webb and Hubble confirm Universe's expansion rate
Author : thunderbong
Score : 180 points
Date : 2024-03-11 20:49 UTC (2 hours ago)
(HTM) web link (www.esa.int)
(TXT) w3m dump (www.esa.int)
| JohnMakin wrote:
| This sort of brushes on it but for a long time there was hope at
| resolving the Hubble Tension by saying that Hubble telescope's
| measurements were incorrect, because that would be the most
| simple explanation. This was not the case, so if anything, the
| mystery deepens. I don't know for certain but I believe Hubble's
| estimation has been widely accepted for a while though, because
| we've been using the 13.8 billion cosmological age estimate ever
| since I started brushing up my layman's understanding of the
| subject.
| orra wrote:
| > we've been using the 13.8 billion cosmological age estimate
| ever since I started brushing up my layman's understanding of
| the subject.
|
| I remembered the age of the universe as as 13.7 billion years,
| but I wasn't sure why that was.
|
| Well, the initial WMAP results in 2003 supported an age of 13.7
| billion years. Later results nudged this upwards to 13.8
| billion years. Of course, all the results have error bars.
| explaininjs wrote:
| > Of course, all the results have error bars.
|
| Not to mention the underlying philosophical assumptions, such
| that the "rate of time" has been constant across all of...
| time.
|
| Aka: How do we know a "year" 13 Billion "years" ago bears any
| resemblance to one now? What would it mean for it not to?
| fooker wrote:
| Philosophical indeed, as it's impossible to define the idea
| of a rate of time, when the idea of rate is defined in
| terms on time itself.
| dartos wrote:
| I'd assume that we have some notion of how the laws of
| physics have changed, if at all, since the Big Bang.
|
| We measure time in vibrations of a cesium isotope IIRC
| db48x wrote:
| No, we measure the frequency of vibrations of _light_,
| not of a type of atom. Specifically, it is light emitted
| by cesium atoms that are transitioning from one specific
| energy state to another specific energy state. Although
| this is arbitrary, it is highly reproducible and would
| give precisely the same measured lengths of time at any
| point since the big bang.
| elashri wrote:
| That assumes that fundamental laws of physics did not
| change (will not change). This is what we believe and
| have no evidence otherwise. This is important since we
| rely on measuring atomic transitions of cesium atoms
| which itself were formed/forming billions of years after
| the big bang itself.
|
| The laws of physics invariance under time is a core to
| our understanding. It would be very disrupting if we
| found otherwise.
| yongjik wrote:
| Fun fact: the Oklo reactor, a _naturally occurring_
| nuclear reactor that was active more than a billion years
| ago, was used to test if physical constants were the same
| in ancient times.
|
| https://en.wikipedia.org/wiki/Natural_nuclear_fission_rea
| cto...
| speak_plainly wrote:
| Time in this context is just an arbitrary measurement. Like
| extrapolating the calendar back to the Big Bang which is
| when space/time began, another way to think about time.
| dwattttt wrote:
| How do we know <anything>? Observations we can make plus
| models that relate those to the things we can't observe
| directly.
| perihelions wrote:
| Here's a graph of the contradictory measurements (JWST data not
| yet included),
|
| https://en.wikipedia.org/wiki/Hubble%27s_law#Determining_the...
| (caption: _" Value of the Hubble constant in (km/s)/Mpc,
| including measurement uncertainty, for recent surveys[54]"_)
| gregorymichael wrote:
| What are the implications?
| kromem wrote:
| Basically it means that we can't regard the Hubble result as a
| mismeasurement and the age of the universe seems to be
| different depending on how you measure it.
|
| From the article:
|
| "The bottom line is that the so-called Hubble Tension between
| what happens in the nearby Universe compared to the early
| Universe's expansion remains a nagging puzzle for cosmologists.
| There may be something woven into the fabric of space that we
| don't yet understand."
| washadjeffmad wrote:
| Sounds like they don't want to spoil everyone's research
| grants!
| jdiff wrote:
| Outside of the tinfoil, it just sounds like the universe is
| complex and not always predictable.
| washadjeffmad wrote:
| I meant it as a comment on the phrasing. Potentially
| jeopardizing a field's cash flow is a legitimate worry,
| and I see a few have felt that, as well.
| bigbillheck wrote:
| There's a whole lot of open problems in cosmology,
| nobody's going to be out of work if they solve this one.
| harywilke wrote:
| It's amazing that barely a 100 years ago The Great Debate
| in astronomy was weather the Milky Way was the extent of
| the universe or things like Andromeda were their own
| 'island universes'. In the 1920s, Edwin Hubble showed
| that Andromeda was far outside the Milky Way by measuring
| Cepheid variable stars. These are the same stars that we
| are measuring today in this debate.
| https://en.wikipedia.org/wiki/Great_Debate_(astronomy)
| techwiz137 wrote:
| I just think it means the expansion rate is not a constant,
| but a variable.
| mr_mitm wrote:
| Either we live in an unusually under dense region of the
| universe or our models are wrong ("new physics").
| amethyst wrote:
| Or it's a simulation and someone keeps pushing changes to
| production.
| cwillu wrote:
| Which would also count as new physics.
| yreg wrote:
| With even more literal meaning of new.
| lajr wrote:
| I wonder if their introspection is good enough to have our
| population on a Grafana dashboard somewhere
| queuebert wrote:
| Somewhere aliens are making fun of how shoddy our
| simulation is coded.
| brcmthrowaway wrote:
| It's definitely a simulation at this point
| ducttapecrown wrote:
| All the expert software engineers agree this is the most
| likely explanation. Have physicists looked into this?
| imzadi wrote:
| Someone keeps running gparted on our partition
| nsilvestri wrote:
| This URL is a stub, and the full article can be read at
| https://www.esa.int/Science_Exploration/Space_Science/Webb/W...
| cwillu wrote:
| Added bonus: it has 50% less animated "responsive" design.
| FredPret wrote:
| Unbelievable how much we can work out from just the odd photon
| hitting us from somewhere in the great unknown.
| golemotron wrote:
| Occam's Razor does a lot of heavy lifting.
| daxfohl wrote:
| It's astounding to me that space is so empty that in the
| billions of light years from here to the edge of the universe,
| there's less total interference than what you get from a small
| cloud.
|
| And if it wasn't, then we'd have no way of knowing about any of
| this.
| CobrastanJorji wrote:
| "The odd photon hitting us" is also a pretty good description
| of eyesight, radio, and fiber optics.
| fooker wrote:
| Clearly the even photon is for parity checking and error
| correction ;)
| westurner wrote:
| Hubble's law: https://en.wikipedia.org/wiki/Hubble%27s_law
|
| Expansion of the universe:
| https://en.wikipedia.org/wiki/Expansion_of_the_universe :
|
| > _While objects cannot move faster than light, this limitation
| only applies with respect to local reference frames and does not
| limit the recession rates of cosmologically distant objects_
|
| Given that v is velocity in the opposite direction, and c is the
| constant reference frame speed of light; do we account for
| velocity in determining whether light traveling at c towards
| earth will ever reach us? v - c < 0 if v>c
| v + c > c if v>0
|
| Are tachyons FTL, is there entanglement FTL?
|
| How far away in light years does a mirror in space need to be in
| order to see dinosaurs that existed say 100 million years ago?
| blackbear_ wrote:
| > do we account for velocity in determining whether light
| traveling at c towards earth will ever reach us?
|
| As far as I know this is not necessary because the speed of
| light is constant regardless of the velocity of both the source
| and the observer (this is Einstein's special relativity:
| https://en.m.wikipedia.org/wiki/Special_relativity)
| tzs wrote:
| A little background based on a few articles about this plus my
| recollection of PBS Space Time videos on this: There are at least
| two ways to try to figure out the rate of expansion of the
| universe (which is called the Hubble Constant).
|
| * From variations in the cosmic microwave background (CMB) which
| are the result of certain conditions in the early universe it is
| possible to figure out what the expansion rate should be now.
|
| * From looking at very distant galaxies and noting how far away
| they are and how fast they are receding from us the expansion
| rate can be calculated.
|
| Theory says that these should give the same expansion rate. When
| the rates were first found using those two methods they gave
| different results, but the error bars on both were large enough
| to overlap. People expected then that further refinement of both
| methods to decrease the error bars would converge to some common
| value.
|
| That did not happen. Refinement of the CMB measurements got to 67
| +/- 0.5, and refinement of the galaxy distance/speed method got
| to 73 +/- 1. Those do not overlap.
|
| This non-overlap between the possible ranges given by the two
| methods is called the Hubble tension, and it is one of the most
| irksome problems in cosmology.
|
| Possible explanations include:
|
| * Some sort of error in how we measure the variations in the CMB.
|
| * Some sort of error in the distant galaxy distance or speed
| measurements, which until the James Webb telescope were almost
| entirely Hubble telescope measurements.
|
| * We're missing something in our understanding of the physics.
|
| These new results add a bunch of data from the James Webb
| telescope, which observes in different wavelengths than Hubble.
| These results fit with the Hubble measurements.
|
| They do _not_ resolve the Hubble tension. What they do is remove
| most doubt that the distant galaxy results involve some sort of
| Hubble measurement error. I believe cosmologists are pretty
| confident of the CMB measurements, and so this will be
| interpreted as telling us that the Hubble tension is not just a
| problem with our measurements. There is either physics that we
| got wrong or physics we need to discover.
| rf15 wrote:
| This, together with the endless philosophising around dark
| energy, dark matter and whatnot paints a pretty strong arrow
| towards our models having some flaws when it comes to their
| large-scale application. I hope to live long enough to see
| where we made our mistake and get a better model.
| pishpash wrote:
| Almost every model we build of more trivial things based on
| observation always turns out to be not really right. I cannot
| imagine why one of the universe that has had multiple version
| updates in the last 100 years to not also be grossly
| mistaken. I also don't expect the full model to be simple or
| beautiful. We may be thinking wishfully based on massive
| extrapolation and cutting corners to suit our narrow view
| into the world.
| rmbyrro wrote:
| The scale of the universe sometimes feels terrifying to me
| swader999 wrote:
| It's not if you consider we can only move at less than the
| speed of light or that we go on forever.
| ChrisMarshallNY wrote:
| The thing that strikes me, is the detailed image description.
| That looks like good fodder for an ML visitor.
| harywilke wrote:
| Dr.Becky goes over this in a video [0] from a year ago about the
| divergent results obtained by the two main ways we measure the
| rate of expansion. Cosmic Microwave Background Vs. Supernovae. As
| the accuracy of each method has improved, the end results have
| diverged.
|
| [0] 'theJWST just made the "Crisis in Cosmology" WORSE'
| https://www.youtube.com/watch?v=hps-HfpL1vc&t=858s
| luxuryballs wrote:
| those are some pretty old energy waves
| arcastroe wrote:
| I've asked this question before, but I don't think I received a
| good answer, so figured I'd try asking again.
|
| How do we know that galaxies are accelerating away from us and
| not moving at constant speed? People often point to the
| observation that the further away a galaxy is, the faster it
| appears to be moving away from us, implying acceleration.
|
| However, wouldn't we expect to see the same observation even
| without any acceleration? Imagine there are some objects in space
| all moving in random directions and speeds, relative to Earth.
| After long enough time, all objects will appear to be moving away
| from Earth, even if they were moving towards it initially. And
| after long enough time, the objects that move fastest should be
| farthest away, by the simple definition of speed!
|
| In short, even if galaxies weren't accelerating, we would still
| see that the further away a galaxy is, the faster it recedes.
| Steuard wrote:
| You're right: the "more distant galaxies are moving away
| faster" point is just Hubble's original observation of an
| expanding universe. It's not an argument for cosmic
| acceleration. (If you see people making that claim, they're
| probably either speaking carelessly or not experts themselves.)
|
| The conclusion that the expansion is accelerating was a quite
| recent result: 1990s, I believe. It's based on careful
| measurements of supernova explosions of a type with computable
| intrinsic brightness in increasingly distant galaxies, and the
| exact pattern seen in their apparent redshifts vs. apparent
| brightness. It was a shocking discovery when it came out, with
| two separate teams announcing the result pretty much neck and
| neck. There's also independent and compatible evidence for
| acceleration from the exact pattern of variations in the
| temperature of the cosmic microwave background seen at
| different points in the sky.
| runeb wrote:
| Their light is more red shifted the farther away they are. I'm
| no expert on this, but I believe in a constant-speed scenario
| they would have equal red shift no matter the distance
| m3kw9 wrote:
| If we can travel faster than light does it blow up the theory
| that the universe expands? Because if we can travel faster than
| light the universe is theoretically be infinite if I can go to a
| point pas the furthest reaches of stars/matter.
| mjfl wrote:
| It is very fortunate that the universe is expanding. This
| provides a virtually unlimited source of energy.
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