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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How do we know Dark Matter isn't simply Neutrinos?
What evidence is there that dark matter isn't one of the known types of neutrinos?
If it were, how would this be measurable?
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Are modified theories of gravity credible?
I'm a statistician with a little training in physics and would just like to know the general consensus on a few things.
I'm reading a book by John Moffat which basically tries to state how GR makes ...
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Has the speed of light changed over time?
Could someone judge my (stoner) hypothesis that the speed of light has changed over time -- i.e. as the universe has expanded in volume light has slowed down, perhaps going so far as back to the big ...
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What if the universe is rotating as a whole?
Suppose in the milliseconds after the big bang the cosmic egg had aquired some large angular momentum. As it expanded, keeping the momentum constant (not external forces) the rate of rotation would ...
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The age of the universe
Many times I have read statements like, "the age of the universe is 14 billion years" . For example this wikipedia page Big Bang.
Now, my question is, which observers' are these time intervals? ...
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How can something finite become infinite?
How can the universe become infinite in spatial extent if it started as a singularity, wouldn't it take infinite time to expand into an infinite universe?
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Why did the universe not collapse to a black hole shortly after the big bang?
Wasn't the density of the universe at the moment after the Big Bang so great as to create a black hole? If the answer is that the universe/space-time can expand anyway what does it imply about what ...
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What does the cosmic neutrino background look like today, given that neutrinos possess mass?
This question is inspired by (or a follow-up to) the threads Where are all the slow neutrinos? and Is it possible that all “spontaneous nuclear decay” is actually “slow neutrino” induced?
The cosmic ...
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Photons in expanding space: how is energy conserved? [duplicate]
If a photon (wave package) redshifts (stretches) travelling in our expanding universe, is its energy reduced?
If so, where does that energy go?
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How can a quasar be 29 billion light-years away from Earth if Big Bang happened only 13.8 billion years ago? [duplicate]
I was reading through the Wikipedia article on Quasars and came across the fact that the most distant Quasar is 29 Billion Light years. This is what the article exactly says
The highest redshift ...
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Do the laws of physics evolve?
Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure ...
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Sympletic structure of General Relativity
Inspired by physics.SE: Does the dimensionality of phase space go up as the universe expands?
It made me wonder about symplectic structures in GR, specifically, is there something like a Louiville ...
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Shape of the universe?
What is the exact shape of the universe? I know of the balloon analogy, and the bread with raisins in it. These clarify some points, like how the universe can have no centre, and how it can expand ...
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Did time exist before the Big Bang and the creation of the universe? [duplicate]
Does time stretch all the way back for infinity or was there a point when time appears to start in the universe?
I remember reading long ago somewhere that according to one theory time began shortly ...
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What has been proved about the big bang, and what has not?
Ok so the universe is in constant expansion, that has been proven, right? And that means that it was smaller in the past.. But what's the smallest size we can be sure the universe has ever had?
I ...
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