The observable universe of a given observer encompasses the volume of space from which information - particles, radiation - could ever (past, present or future) reach that observer.
Questions tagged [observable-universe]
236 questions
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Could the observable universe be bigger than the universe?
First of all, I'm a layman to cosmology. So please excuse the possibly oversimplified picture I have in mind.
I was wondering how we could know that the observable universe is only a fraction of the overall universe. If we imagine the universe like…
A. P.
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Ambiguity in applying Newton's shell theorem in an infinite homogeneous universe
Newton's shell theorem has two corollaries:
The gravitational attraction of a spherically symmetric body acts as if all its mass were concentrated at the center, and
The gravitational acceleration inside the cavity of a spherically symmetric body…
pela
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Is the temperature of the universe rising?
I know the temperature of the universe is decreasing due to it's expansion after the big bang but after I came up with this article in AOP(please note I don't have the access of the journal,so I have just read the abstract) after reading this I am…
David
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As the universe ages, will we see more stars or less?
After a very long time will we see more stars (due to the fact that more light is get to us) or less stars (as the universe expends and light have to pass larger distance)?
In general, can stellar objects go outside of the scope of the observable…
Yair
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The difference between comoving and proper distances in defining the observable universe
"The radius of the observable universe is estimated to be about 46.5 Gly."
If I understand correctly, it means the most distant object that we can see right now is 46.5 Gly away (at present), but it was 13.7 Gly away at 13.7 billion years ago.…
asmani
- 530
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Why is the sky dark at night?
The question is the well-known Olbers' paradox:
If there are so many/infinite stars, in every direction, why is it dark at night? Where goes all the light we don't see?
Discussing with a friend we found different answers.
The first (my friend's…
seldon
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How would the night sky appear at the edge of the galaxy?
In Isaac Asimov's Foundation Series, there is a planet named Terminus which is believed to be the planet farthest from the galactic center.
There are almost no visible stars in its sky, only the huge lens of the Milky Way galaxy
But what would we…
DavRob60
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How do telescopes see many billion light years distant object in our universe?
How do telescopes see many billion light years distant object in our universe?
As an individual with limited expertise in the field of astronomy, my current understanding suggests that the observation of the furthest points in the universe using…
15
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Can light reach far away galaxies in an expanding universe?
I've read that, since the universe is expanding at an increasing rate, light that leaves our galaxy now will never reach far away galaxies. That even though a galaxy is moving away from us slower than the speed of light right now, before the light…
Chris.B
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Will the CMB ever stop shining?
Will we ever reach a point where all the light that was set free by recombination finally reaches us from our point of view and the CMB stops "shining" for observers on Earth?
John
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Understanding the CMB background as a reference frame
We say the Earth is in relative motion with respect to the cosmic microwave background (CMB), causing anisotropies in the CMB spectrum. I have four very simple questions about this.
How is it possible to treat the CMB, a bath of blackbody photons…
SRS
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Is "speed relative to the universe" a well-defined concept?
Prompted by commenting on this question.
I offered the standard "Which frame of reference are you using? Yours? A satellite's? The sun's? The Milky Way's?" observation.
Which prompted me to think ... Is there any sort of Absolute Universal (as in…
Brondahl
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If we were able to prove that the universe is infinite, wouldn't that statistically prove that there is no other forms of life?
I want to begin my explanation using abstract mathematical explanation to repetition possibility by taking independent samples $X_n$ from some continuous probability distribution: https://math.stackexchange.com/q/1739927/
If we applied this same…
Omar Adel
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Can the coordinate of the big bang point be calculated via observed universe or it is impossible?
We know all galaxies spread out after Big Bang theory.The key idea is that the universe is expanding after that theory. Can we play back the scenes via observable universe (galaxies) and can we calculate the coordinate of big bang point as a fixed…
Mathlover
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How many states are there in the observable universe?
If we took a single instant and considered all possible states of all energy and matter do we have any bounds on how much that would be?
Would that number be related to information?
Skyler
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