Questions tagged [cosmology]
The study of the large-scale structure, history, and future of the universe. Cosmology is about asking and answering questions about the "big picture" - the extent, origin, and fate of everything we know.
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Expansion of the Universe: is new space(time?) being created or does it just get stretched?
Is new space(time?) being created as the Universe expands, or does the existing spacetime just get stretched?
If it just gets stretched, why do galaxies move along with the expansion instead of just ...
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Doesn't dating the universe violate the concept of spacetime's inseparability?
It would seem that measuring an age of the universe from the big bang requires separating spacetime into a 3D coordinate system and a time track. I fail to understand why it is appropriate to take ...
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Do new universes form on the other side of black holes?
I have four questions about black holes and universe formations.
Do new universes form on the other side of black holes?
Was our own universe formed by this process?
Was our big bang a black hole ...
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Superluminal expansion of the early universe how is this possible?
Is this a postulate? I get the expansion of the universe, the addition of discrete bits of space time between me and a distant galaxy, until very distant parts of the universe are moving relative to ...
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Equation for Hubble Value as a function of time
I am trying to write the equation for the situation where the Hubble parameter $H$ would be changing over time. In other words, it would represent an accelerated expansion of the Universe. That is, $...
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How do we know the universe is expanding, and not that its contents are shrinking?
Is there a physical reason why not to think that instead of space expanding, all physical constants and parameters are shrinking (including of course the instruments we use to measure the constants) ...
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Why is quantum gravity non-renormalizable?
The book The Ideas Of Particle Physics contains a brief treatment of quantum gravity, in which the claim is asserted that if one attempts to construct a model of gravity along the same lines as QED, ...
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If spacetime itself is expanding, how could we ever tell?
If space is the measured distance between 2 objects, then saying the space expanded is nonsensical unless we have a measuring stick outside of the space fabric to measure the expansion. 2 objects ...
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Why does dark energy produce positive space-time curvature?
My understanding is that dark energy, or equivalently a positive cosmological constant, is accelerating the expansion of the universe and I have read that this gives empty space-time positive ...
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If the observable universe were compressed into a super massive black hole, how big would it be?
I understand only a little of general relativity, but that's why I'm here! :)
Consider the hypothetical situation of some extra-terrestrial intelligence pushing all the mass in the observable ...
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Where is radiation density in the Planck 2013 results?
I've been looking at the Planck 2013 cosmological parameters paper, trying to update my toy cosmology simulator with the most recent data. Most of the interesting values such as $H_0$, $\Omega_m$, ...
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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 ...
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How many bits are needed to simulate the universe?
This is not the same as: How many bytes can the observable universe store?
The Bekenstein bound tells us how many bits of data can be stored in a space. Using this value, we can determine the ...
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Why does the low entropy at the big bang require an explanation? (cosmological arrow of time)
I have read Sean Carrol's book. I have listened to Roger Penrose talk on "Before the Big Bang". Both are offering to explain the mystery of low entropy, highly ordered state, at the Big Bang.
Since ...
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What is our location relative to the Big Bang?
Given what we know about space, time and the movement of galaxies, have we or can we determine what our position is in relation to the projected location of the Big Bang? I've read some introductory ...
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