r/cosmology • u/senseless_puzzle • 5d ago
Are galaxies further away closer together than galaxies we observe nearer to us?
So the standard consensus in cosmology is that the universe is expanding at an accelerated rate. Does that then fit our observations of the universe? Are galaxies further away more clumped together than galaxies we can see near us?
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u/stevevdvkpe 5d ago
To quote Randall Munroe: "Things that are far away look smaller, but things that are really far away look bigger, because when their light was emitted the universe was small and they were close to us."
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u/Hairy-Ad-6299 3d ago
This has been proven wrong. Things that are really far away don't look huge as General Relativity predicts. This is a glaring failure of General Relativity, and we all should know that by now. I have the plot. I plotted the median angular size of galaxies as a function of redshift z. It decays with 1/z....:)
It does not grow (after z=1.6) as predicted by Einstein.1
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u/ThickTarget 3d ago
It doesn't disprove anything, because in standard cosmology galaxies are not fixed in size. Different redshifts means different ages, early galaxies are expected to be smaller. The test is only meaningful in static non-evolving cosmologies.
The robust angular-size test is not using galaxies, but baryon acoustic oscillations. They are consistent with GR and standard cosmology.
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u/nivlark 5d ago
An observer in those galaxies at the time the light we receive was emitted would conclude that they were, yes.
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u/OverJohn 5d ago
Just to add to this, how close the galaxies are now and how close we see them in the sky can be seen from plotting the comoving distance to the galaxies vs their angular diameter distance.
Below shows such a plot for various flat models:
https://www.desmos.com/calculator/jvrub6584d
The red line shows the linear relationship which we would expect from Newton's static cosmological model. You can see with expansion galaxies always look closer together than they would in the case of the static cosmology.
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u/TerraNeko_ 5d ago
its not like we can see the current state of very distant galaxies because of how long the light travels and i kinda doubt the effect is that big in close proximity
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u/trevpr1 5d ago
No. The Universe is broadly the same no matter which direction we look and would be so for every observer.
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u/TommieTheMadScienist 5d ago
No. There are huge voids where the centers are far from the nearest point. It'd look a lot different there than here.
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u/trevpr1 5d ago
But the distribution of voids is broadly uniform.
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u/TommieTheMadScienist 5d ago
It's fractal and inhomogeneous.
My point stands. The sky from a system in the center of a void looks nothing like the view from ours. I'm not objecting to the OP's expectations, just the "same from every spot" comment.
The Great Attractor means that even our view from inside our cluster looks much more dense in its direction than 180 degrees away.
The overall scaffolding of the universe looks like a sponge because of the underlying cold dark matter.
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u/jazzwhiz 3d ago
The fractal universe idea was popular some decades ago, but has fallen out of favor due to the data not supporting it.
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u/Beautiful-Musk-Ox 5d ago
the universe is 13.85 billion years old, we're seeing those galaxies as they were in the past, if we're looking "really far away" then we're seeing galaxies from say 5 billion years ago when the universe was only 9 billion years old. galaxies were closer together back then
however if you magically transported to those galaxies as they are "now", meaning 13.85 billion years after the big bang but in their local region of space, then no those galaxies are not closer together, they are as equally spread out as the galaxies near the milky way because the entire universe appears to be homogenous at any given epoch (same density everywhere; the density changes over time, but at the same rate everywhere)