If you’re interested in learning more about the rich human history and ingenuity underpinning the Hubble “constant”, please do yourself a favor and scroll through The Cosmic Distance Ladder by Terence Tao of UCLA:
https://terrytao.wordpress.com/wp-content/uploads/2010/10/co...
The slides are delightfully visual and comprehensive yet terse, walking you up the rungs of the cosmic ladder from the Earth through the moon, sun, and beyond. I can almost guarantee you’ll learn something new and fascinating.
What if the universe doesn't expand at all? What if we're completely wrong and redshift is caused by something else entirely, like some yet-undiscovered phenomenon that occurs to spacetime or electromagnetic waves? How can we be so sure it's space that's expanding, not time?
The more I read about this, the more it feels like phlogiston theory[1]. Works great for describing observations at first, but as more observations are made, some contradict the theory, so exceptions are made for these cases (phlogiston must have negative mass sometimes/there must be extra matter or energy for galaxies to spin as fast as they do), and then finally someone discovers something (oxygen/???) that explains all observations much simpler and requires no weird exceptions.
Not possible. Redshift is not the only observation we have. The totality of all the observations we have cannot be explained in any other way than an expanding universe.
> How can we be so sure it's space that's expanding, not time?
Our best current model does not say "it's space that's expanding, not time". It says that in one particular frame (the comoving frame), the overall spacetime geometry can be described using a "time" that always corresponds to the time of comoving observers and a "space" whose scale factor increases with that time.
> The more I read about this, the more it feels like phlogiston theory
This is an extremely unjustified comparison. Phlogiston theory never accounted well for actual observations.
> as more observations are made, some contradict the theory
None of the observations being discussed contradict the general model of an expanding universe. They only pose problems for the indirect methods we use to convert our direct observations into model parameters.
There is a very old theory called the "Tired Light Hypothesis" which supposes that for some unknown reason light loses energy as it travels over cosmological distances. This would reproduce the observed redshifts, but it has issues predicting pretty much every other cosmological observation.
In particular it doesn't explain observed reductions in surface brightness (expansion has the effect of "defocusing" collimated light). And it doesn't explain observed time dilation effects.
We can create and observe doppler shift by making things move towards/away from us. Thus it is proven that if something is moving away from us, it will produce a redshift. In the absence of evidence that something else is causing the redshift, the assumption should be that it is a result of things moving away from us.
As an obvious example, doppler shift often needs to be accounted for to communicate with spacecraft.
>What if the universe doesn't expand at all? What if we're completely wrong and redshift is caused by something else entirely, like some yet-undiscovered phenomenon that occurs to spacetime or electromagnetic waves? How can we be so sure it's space that's expanding, not time?
I suppose that's possible. Does that hypothesis adequately explain our observations?
Is the model we currently have completely "correct"? Almost certainly not. But it appears to be less wrong[0] than earlier models.
If you (or anyone) can show how the above describes our observations better and more completely than our current models, then it's likely "less wrong."
But you offer no evidence or even logical argument to support your hypothesis. As such, it's not much more than idle speculation and essentially equivalent, from a scientific standpoint, as suggesting the universe is a raisin dropped into a sugar syrup solution[1] and absorbing the liquid -- hence the expansion of the universe.
Easiest method is to simply take your idea at face value.
In our first version, imagine all of the stars at rest. Now, we emphatically know this not to be true locally due to all kinds of measurements, but let's go with it. What happens? The moment you let these stars "go," they begin to draw toward one another due to gravity. You would have gravitational collapse. We do not see that.
Next iteration: we throw the stars, and the galaxies, and the galactic clusters away from one another. No expansion required. Here we have two options. In the first, we did not throw with enough speed, they expand out ... slow to a halt ... and the gravitational collapse again. Again, unobserved. Option two, you have thrown at escape velocity and what you would see is an asymptotically decreasing speed, never quite hitting zero, since gravity works "forever away." Also unobserved.
What you're suggesting is basically the Steady State concept, a kind of static universe. This is a very old idea. So old it was given a kind of courtesy term in general relativity, which would eventually be set to zero.
Here is a rule for any armchair astrophysicists: whatever you think of, that was most likely an idea at one point and was eventually ruled out.
For example the entire atomic composition of the stars in the observable universe depends exquisitely on the expansion parameters at the big bang. The ratios can be traced back through the expansion to the quark-gluon soup stage. Changing the expansion rates changes the delicate balance between the particles that form at that stage, and when the various particle fractions "freeze out" during expansion when the temperature cools (btw we're talking about seconds from the big bang here :) which can be subsequently observed in stars all over the universe by spectroscopy. It's pretty beautiful.
There are so many intricate dependencies between these pathways that it's pretty unrealistic to postulate anything else than a big bang + cooldown process IMHO.
This is the equivalent of finding your keys an inch off from where you remember setting them down and concluding that someone broke into your home, stole your keys, took your car for a joyride, and broke back in to place them there.
Expanding universe and Big Bang Theory go hand-in-hand. There are multiple independent observations besides the red shift that make it nearly certain there had to be a BBT event to explain what we see. The universe is too hot, chaotic and clumpy for there not to have been a massive explosion to kick it all into motion. Since there is good confidence BBT happened, transitioning from that event to a steady-state non-expanding universe would require some sort of mechanism to slow then freeze the expansion. Not aware of any support for that model.
I remember reading, a long, long time ago, a paper where the authors suggested if the universe was slightly hyperbolic, it would also cause a redshift effect. I can't seem to find it (and as far as I remember it was purely theoretical), but at the time I thought it was an neat idea.
Not that I have the background to know what else they might not have accounted for to reach this conclusion.
While I don't necessarily think at lot of alternative ideas proposed are correct, I always love seeing alternative concepts being considered. Very cool to see ideas that could solve standing issues even if they themselves could have issues.
My guess is that scientists are considering this, but until now no better theory has been presented.
Part of this is the distinction between what is happening and why the model says is happening. Does any physicist believe they have the perfect model? Or is it that they use the model that best fits the observations and are open to any other model, as long as it is either simpler or produces fewer contradictions than the current model (and is just as testable).
I think too often we hear reports of "science says X is what happens" when the reality is more like "science says that the current model based on X happening is what best describes current data and observations".
Naive question: why should the expansion rate need to be uniform or constant everywhere?
I'm likely misinterpreting the article, but it seems to frame things in a way that first assumes expansion should be constant and it's a question of what the right constant value is between the measured/theoretical discrepancies.
(*yeesh, editing all those spelling errors from typing on my phone)
The controversy is that we get 2 different numbers depending on which method (cosmic microwave background vs cosmic distance ladder) we use to calculate the present rate of expansion. These numbers used to have their error bars overlapping, so we assumed they would eventually converge to the true value. But as we get more data the opposite is happening: the numbers are diverging and their error bars are shrinking such that they no longer overlap.
This tells us that either our model of the universe is wrong (therefore the cosmic microwave background method is giving us an incorrect answer) or that something is wrong with how we're calculating the distances along the cosmic distance ladder. The latter was originally the assumption that should be proven true with more and better data from newer telescopes. This is now turning out not to be the case: our cosmic distance ladder calculations seem to have been very good, so it now seems more likely that our model of the universe is wrong.
Indeed. Some researchers have proposed quintessence, a time-varying form of dark energy [0].
> A group of researchers argued in 2021 that observations of the Hubble tension may imply that only quintessence models with a nonzero coupling constant are viable.
> what should the expansion rate need the be uniform or constant everywhere?
It doesn't.
"The simplest explanation for dark energy is that it is an intrinsic, fundamental energy of space" [1]. That's the cosmological constant.
Dark energy is a thing because we don't assume that to be the case. Irrespective of your dark energy model, however, there will be a predicted global average.
It's not constant (the early universe inflated quite quickly), and it doesn't need to be uniform, but it sure does appear to be. We measure it via redshift, pulsar timing arrays, and the temperature fluctuations of the CMB, and it looks pretty much the same in all directions.
Spacetime is apparently extremely rigid as it supports the transmission of gravitational waves originating billions of light-years away, as detected by the LIGO experiments. This suggests smooth and gradual uniform expansion, at least spatially. Temporal variation (speeding up and slowing down uniformly at all points) might be possible but seems hard to explain.
The issue here is that it's not constant depending on the type of star we use to measure it. It's not a discrepancy in location in space. Or at least that's how I read the article.
That's the first thing that occurred to me too. It could also not be constant even at the same place, i.e. could it not be speeding up and slowing down as the universe expands?
Certainly when I look at convection currents in the ocean or the atmosphere, I see plenty of variation. Shoot, the earth's atmosphere constantly produces moving blobs of relatively high and low pressure.
"researchers started using Cepheids to calibrate the distances to bright supernovas, enabling more accurate measurements of H0."
It seems like if there were some error in the luminosity measurement for cepheids, it would propagate to the measurements with supernovas...
I would expect that stacking measurement techniques (as is common with cosmology, where distances are vast and certainty is rare) would also stack error, like summing the variance in gaussians...
These uncertainties in Cepheid luminosities are accounted for in Type Ia distance measurements. Particularly with Gaia we can now calibrate the luminosities of Cepheids in our galaxy using parallax observations.
(Knowing this field I'm sure there are some astronomers who argue that there are still some systematic uncertainties that are not fully being accounted for, but from what I understand it's pretty hard to account for it with the Gaia results at this point.)
"But according to Freedman, the galaxies’ supernovas seemed to be intrinsically brighter than the ones in farther galaxies. This is another puzzle cosmologists have yet to understand, and it also affects the H0 value. "
The opening sentence of this article is 100% wrong. Hubble was a good scientist and correctly made no assumptions regarding his observations that objects that are further away by parallax are more red shifted.
The assumption that these observations indicated an expanding universe was delivered to us by LeMaitre; if you believe in an expanding universe with a finite age, then give credit where it is due...
One of the frustrating aspects of cosmology is how difficult it is to actually apply the scientific method to it. You can't make a couple stars in a lab and see how they behave, the same way you can for particle physics. Fundamentally, most of cosmology comes down to observation, not true experimentation, where the experimenter is directly acting and comparing that to a control group. There are some experiments that can be done, but there are just some fundamental limitations. This is also the case in the so-called "soft sciences" like economics and psychology. But it's even true in some corners of the "hard sciences" like evolutionary biology.
One thing that’s not mentioned is what error there is in the theoretical calculation and what is the measurement error. From the theoretical POV I’d expect the theory to have an upper and lower limit based on values from initial assumptions. Getting the theory to 8% of the actual value is a pretty big achievement. It’s pretty difficult to predict much simpler, real systems to within 8% let alone something as complex as the expansion of the universe.
Not an astronomer by any means. Just can't see it as a mere coincidence that the stars at the distance of the "age of universe" light years run away with about "c". I.e.
"c" / "age of Universe" = Hubble constant (i.e. "c"/13.7 billions ly / 3.26 ly per pc = 71.3 km/s per mpc.)
Frustrating that all the comments seem to be jumping in to talk about dark energy and quintessence and multiverse pontification, when the actual contention in the linked article is that all of this may turn out to be a measurement error and that the Hubble tension may not actually exist after all.
Did I read it wrong, or does the universe expand at 10% of speed of light!? Could that possible be why the measurements are off? A close object vs an object very far away might look like they are in different places relatively.
The observable universe has a radius of about 14 Gigaparsecs. If H0 is 67.4 km/s/Mpc, then a naive calculation puts the edge of the observable universe expanding at 943,600 km/s, or about 3 times the speed of light. Of course we still observe this as merely "close to" the speed of light, but the point is that most of the universe is shooting away from us so fast that we will never see them as they are "now", even if we wait billions of years. We have no way of ever interacting with most of the "modern" universe, even theoretically. They might as well be in different universes. All we will ever see is their images from billions of years ago, even if we wait billions of years from now.
Rest assured, this has been taken into account. The scientists who spend their life working on this topic have had the same thoughts you had within minutes of learning about the problem. It's extremely basic stuff actually.
It's likely you read it wrong; there is no sense in which the universe's expansion has a fixed speed. The Hubble parameter is speed/distance [the figure's axis is km/s/Mpc, for example]. That is the natural unit to explain an expansion rate: things that are farther away ALSO move away from you faster (because the space between you and them all grows at a fixed rate).
I love this controversy. I swear it's the most exciting thing in modern physics. The thought that there's something fundamentally wrong with the cosmic distance ladder and the way that we measure the expansion of the universe.
I'm no mathematician or physicist, but this stuff just fascinates me. I interpret it something like:
The further one looks, the faster objects in the universe are expanding. However, when one looks out at the universe, they are looking backwards in time, to a time when the universe was expanding at a more rapid pace. Right? Close to the big bang? Because there was a period of rapid expansion after the big bang, so the universe had to have moved faster in the earlier universe? So the only part of space that actually appears to be static would be around our local space, the stars we can see?
Often the universe is depicted as a giant bubble, expanding outwards in all directions. It is how the human mind is built to think, a classic blunder dating back to the days of Ptolemy, where Earth was the center of everything.
At the edge of our observable universe is the beginning of it all. We can fast forward then through time to see the most modern picture of our universe, the reference frame that is our own galaxy. We are not at rest in a static galaxy, so why should the laws of relativity and dilation not apply to massive objects
Everywhere else we look is in the past, and the cosmic background is visible from every direction. So once expanded in 3D space, and accounting for time, all of space would appear to be accelerating towards the cosmic background and point of the big bang?
“[...]But in 1929 astronomer Edwin Hubble measured the speed of many galaxies and found, to his surprise, that all were moving away from us-- in fact, the further away the galaxy, the faster it was going. His measurements showed that space is expanding everywhere, and no matter where you look, it will seem as if all galaxies are receding because the distance between everything is constantly growing. Faced with this news, Einstein decided to remove the cosmological constant from his equations.” -some scientific American article
It’s not moving away from us, it’s moving towards the beginning of time at a faster and faster rate, but only because we’re looking backwards through time. In reality, due to our reference frame, and other subsequent frames of observed bodies, we are the only point in the observable universe that is in the “present”. To that effect, when everything appears to be moving away from us at a faster and faster rate, it is moving away from the origin (big bang) at a slower and slower rate.
Galaxies are not moving away, they are showing an accelerating speed due to the time difference, and the slightly higher cosmological constant several hundred million years in the past, a constant that scales with time and its relation to distance according to metric expansion and the speed of light. It is the higher constant with relation to distance that gives the illusion of a universe whose expansion is accelerating.
It can be assumed then, that as you move between vast points in space, the universe will update; showing that astronomical objects aren’t accelerating away, but are not in fact moving at all. If not moving towards each other and closer together.
So no matter where you travel, it is likely that the bubble of the observable universe travels with you, you do not accelerate away faster the closer you get to the galaxies that appear from Earth or other reference points from Earth to be expanding faster away.
If you look at the night sky from a planet in one of these far away galaxies, the overall structure of the universe would be very similar if not the same to the structure as it appears from Earth. With all galaxies appearing to be accelerating away from each other at a faster and faster rate.
when did it start that the storytelling around every piece of physics news was framed as a controversy? I know it's been a while, but I feel like it wasn't this way 20 years ago...
Fuck, now they've got animated nags that are autoplaying and don't get filtered out by uBlock Origin. One more site that uses dark patterns too chase away visitors.
[+] [-] refibrillator|1 year ago|reply
The slides are delightfully visual and comprehensive yet terse, walking you up the rungs of the cosmic ladder from the Earth through the moon, sun, and beyond. I can almost guarantee you’ll learn something new and fascinating.
[+] [-] grishka|1 year ago|reply
The more I read about this, the more it feels like phlogiston theory[1]. Works great for describing observations at first, but as more observations are made, some contradict the theory, so exceptions are made for these cases (phlogiston must have negative mass sometimes/there must be extra matter or energy for galaxies to spin as fast as they do), and then finally someone discovers something (oxygen/???) that explains all observations much simpler and requires no weird exceptions.
[1] https://en.wikipedia.org/wiki/Phlogiston_theory
[+] [-] pdonis|1 year ago|reply
Not possible. Redshift is not the only observation we have. The totality of all the observations we have cannot be explained in any other way than an expanding universe.
> How can we be so sure it's space that's expanding, not time?
Our best current model does not say "it's space that's expanding, not time". It says that in one particular frame (the comoving frame), the overall spacetime geometry can be described using a "time" that always corresponds to the time of comoving observers and a "space" whose scale factor increases with that time.
> The more I read about this, the more it feels like phlogiston theory
This is an extremely unjustified comparison. Phlogiston theory never accounted well for actual observations.
> as more observations are made, some contradict the theory
None of the observations being discussed contradict the general model of an expanding universe. They only pose problems for the indirect methods we use to convert our direct observations into model parameters.
[+] [-] antognini|1 year ago|reply
In particular it doesn't explain observed reductions in surface brightness (expansion has the effect of "defocusing" collimated light). And it doesn't explain observed time dilation effects.
[+] [-] dotnet00|1 year ago|reply
As an obvious example, doppler shift often needs to be accounted for to communicate with spacecraft.
[+] [-] nobody9999|1 year ago|reply
I suppose that's possible. Does that hypothesis adequately explain our observations?
Is the model we currently have completely "correct"? Almost certainly not. But it appears to be less wrong[0] than earlier models.
If you (or anyone) can show how the above describes our observations better and more completely than our current models, then it's likely "less wrong."
But you offer no evidence or even logical argument to support your hypothesis. As such, it's not much more than idle speculation and essentially equivalent, from a scientific standpoint, as suggesting the universe is a raisin dropped into a sugar syrup solution[1] and absorbing the liquid -- hence the expansion of the universe.
[0] https://en.wikipedia.org/wiki/The_Relativity_of_Wrong
[1] https://en.wikipedia.org/wiki/Compote
[+] [-] at_a_remove|1 year ago|reply
In our first version, imagine all of the stars at rest. Now, we emphatically know this not to be true locally due to all kinds of measurements, but let's go with it. What happens? The moment you let these stars "go," they begin to draw toward one another due to gravity. You would have gravitational collapse. We do not see that.
Next iteration: we throw the stars, and the galaxies, and the galactic clusters away from one another. No expansion required. Here we have two options. In the first, we did not throw with enough speed, they expand out ... slow to a halt ... and the gravitational collapse again. Again, unobserved. Option two, you have thrown at escape velocity and what you would see is an asymptotically decreasing speed, never quite hitting zero, since gravity works "forever away." Also unobserved.
What you're suggesting is basically the Steady State concept, a kind of static universe. This is a very old idea. So old it was given a kind of courtesy term in general relativity, which would eventually be set to zero.
Here is a rule for any armchair astrophysicists: whatever you think of, that was most likely an idea at one point and was eventually ruled out.
[+] [-] mr_mitm|1 year ago|reply
[+] [-] l33tman|1 year ago|reply
There are so many intricate dependencies between these pathways that it's pretty unrealistic to postulate anything else than a big bang + cooldown process IMHO.
[+] [-] jjk166|1 year ago|reply
[+] [-] while_true_|1 year ago|reply
[+] [-] lieks|1 year ago|reply
Not that I have the background to know what else they might not have accounted for to reach this conclusion.
[+] [-] DaoVeles|1 year ago|reply
[+] [-] SkyBelow|1 year ago|reply
Part of this is the distinction between what is happening and why the model says is happening. Does any physicist believe they have the perfect model? Or is it that they use the model that best fits the observations and are open to any other model, as long as it is either simpler or produces fewer contradictions than the current model (and is just as testable).
I think too often we hear reports of "science says X is what happens" when the reality is more like "science says that the current model based on X happening is what best describes current data and observations".
[+] [-] unknown|1 year ago|reply
[deleted]
[+] [-] parkaboy|1 year ago|reply
I'm likely misinterpreting the article, but it seems to frame things in a way that first assumes expansion should be constant and it's a question of what the right constant value is between the measured/theoretical discrepancies.
(*yeesh, editing all those spelling errors from typing on my phone)
[+] [-] chongli|1 year ago|reply
This tells us that either our model of the universe is wrong (therefore the cosmic microwave background method is giving us an incorrect answer) or that something is wrong with how we're calculating the distances along the cosmic distance ladder. The latter was originally the assumption that should be proven true with more and better data from newer telescopes. This is now turning out not to be the case: our cosmic distance ladder calculations seem to have been very good, so it now seems more likely that our model of the universe is wrong.
[+] [-] diob|1 year ago|reply
See https://en.wikipedia.org/wiki/Cosmological_principle
Basically, if this weren't to hold true, a lot of astronomy would fall over, even physics.
[+] [-] isolli|1 year ago|reply
> A group of researchers argued in 2021 that observations of the Hubble tension may imply that only quintessence models with a nonzero coupling constant are viable.
[0] https://en.wikipedia.org/wiki/Quintessence_(physics)
[+] [-] JumpCrisscross|1 year ago|reply
It doesn't.
"The simplest explanation for dark energy is that it is an intrinsic, fundamental energy of space" [1]. That's the cosmological constant.
Dark energy is a thing because we don't assume that to be the case. Irrespective of your dark energy model, however, there will be a predicted global average.
[1] https://en.wikipedia.org/wiki/Dark_energy
[+] [-] itishappy|1 year ago|reply
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[+] [-] AnimalMuppet|1 year ago|reply
[+] [-] BossingAround|1 year ago|reply
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[+] [-] sdenton4|1 year ago|reply
It seems like if there were some error in the luminosity measurement for cepheids, it would propagate to the measurements with supernovas...
I would expect that stacking measurement techniques (as is common with cosmology, where distances are vast and certainty is rare) would also stack error, like summing the variance in gaussians...
[+] [-] FredPret|1 year ago|reply
In 50-100 years they'd get a much better angular fix on stars that are too distant for Earth-orbit-sized angular measurements.
https://en.wikipedia.org/wiki/Stellar_parallax
[+] [-] antognini|1 year ago|reply
(Knowing this field I'm sure there are some astronomers who argue that there are still some systematic uncertainties that are not fully being accounted for, but from what I understand it's pretty hard to account for it with the Gaia results at this point.)
[+] [-] hindsightbias|1 year ago|reply
[+] [-] seanhunter|1 year ago|reply
[+] [-] mcswell|1 year ago|reply
[+] [-] eisvogel|1 year ago|reply
The assumption that these observations indicated an expanding universe was delivered to us by LeMaitre; if you believe in an expanding universe with a finite age, then give credit where it is due...
[+] [-] openasocket|1 year ago|reply
[+] [-] causality0|1 year ago|reply
I think people forget that, due to the longer wavelengths to which it's sensitive, Webb actually has a poorer angular resolution than Hubble.
[+] [-] mmmBacon|1 year ago|reply
[+] [-] jakeogh|1 year ago|reply
[1] https://www.youtube.com/watch?v=8URdhSigzjs
[2] https://news.ycombinator.com/item?id=41101144
[+] [-] trhway|1 year ago|reply
"c" / "age of Universe" = Hubble constant (i.e. "c"/13.7 billions ly / 3.26 ly per pc = 71.3 km/s per mpc.)
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[+] [-] mr_world|1 year ago|reply
I'm no mathematician or physicist, but this stuff just fascinates me. I interpret it something like:
The further one looks, the faster objects in the universe are expanding. However, when one looks out at the universe, they are looking backwards in time, to a time when the universe was expanding at a more rapid pace. Right? Close to the big bang? Because there was a period of rapid expansion after the big bang, so the universe had to have moved faster in the earlier universe? So the only part of space that actually appears to be static would be around our local space, the stars we can see?
Often the universe is depicted as a giant bubble, expanding outwards in all directions. It is how the human mind is built to think, a classic blunder dating back to the days of Ptolemy, where Earth was the center of everything.
At the edge of our observable universe is the beginning of it all. We can fast forward then through time to see the most modern picture of our universe, the reference frame that is our own galaxy. We are not at rest in a static galaxy, so why should the laws of relativity and dilation not apply to massive objects
Everywhere else we look is in the past, and the cosmic background is visible from every direction. So once expanded in 3D space, and accounting for time, all of space would appear to be accelerating towards the cosmic background and point of the big bang?
“[...]But in 1929 astronomer Edwin Hubble measured the speed of many galaxies and found, to his surprise, that all were moving away from us-- in fact, the further away the galaxy, the faster it was going. His measurements showed that space is expanding everywhere, and no matter where you look, it will seem as if all galaxies are receding because the distance between everything is constantly growing. Faced with this news, Einstein decided to remove the cosmological constant from his equations.” -some scientific American article
It’s not moving away from us, it’s moving towards the beginning of time at a faster and faster rate, but only because we’re looking backwards through time. In reality, due to our reference frame, and other subsequent frames of observed bodies, we are the only point in the observable universe that is in the “present”. To that effect, when everything appears to be moving away from us at a faster and faster rate, it is moving away from the origin (big bang) at a slower and slower rate.
Galaxies are not moving away, they are showing an accelerating speed due to the time difference, and the slightly higher cosmological constant several hundred million years in the past, a constant that scales with time and its relation to distance according to metric expansion and the speed of light. It is the higher constant with relation to distance that gives the illusion of a universe whose expansion is accelerating.
It can be assumed then, that as you move between vast points in space, the universe will update; showing that astronomical objects aren’t accelerating away, but are not in fact moving at all. If not moving towards each other and closer together.
So no matter where you travel, it is likely that the bubble of the observable universe travels with you, you do not accelerate away faster the closer you get to the galaxies that appear from Earth or other reference points from Earth to be expanding faster away.
If you look at the night sky from a planet in one of these far away galaxies, the overall structure of the universe would be very similar if not the same to the structure as it appears from Earth. With all galaxies appearing to be accelerating away from each other at a faster and faster rate.
Sorry im high on shrooms
[+] [-] alberth|1 year ago|reply
https://www.youtube.com/watch?v=Y7ieVkK-Cz0
[+] [-] fartsucker69|1 year ago|reply
[+] [-] zombot|1 year ago|reply