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.
5,566
questions
3
votes
1
answer
146
views
Cyclic Universe Problems
In Penroses's hypothesis, at the end of each iteration the universe undergoes a conformal transformation, meaning distances are rescaled. If I am right, it implies that a planet from the previous ...
- 1,161
0
votes
2
answers
68
views
Homogeneous and Isotropic But not Maximally Symmetric Space
Is this statement correct: "In a homogeneous and Isotropic space the sectional curvature is constant, while in a maximally symmetric space the Riemann Curvature Tensor is covariantly constant in ...
- 1,161
9
votes
4
answers
651
views
Understanding expansion of the Universe as things flying apart
Say that we have a Universe uniformly filled just with matter (let's not bring dark energy into this). And say that we fill it with very light particles (so that the gravitational interaction between ...
0
votes
0
answers
21
views
About redshift and distant objects observation
I did a few Time&Length dilation factor calculations. This is for a distant clock away from any field and a clock on Earth on the equator with the moon passing over clock coordinates, the factors ...
0
votes
1
answer
78
views
Could cosmic rays induce a vacuum decay in the future?
I've been told that very energetic cosmic rays could cause a vacuum phase transition or vacuum decay (and even could cause a true vacuum level to go "uphill" to a false vacuum) due to their ...
- 2,462
0
votes
3
answers
73
views
Are there universes where "symmetry breaking" went differently? [closed]
What have happened with other possible variants of asymmetry?
Are there other universes being run in parallel to our universe where the ball is not at C, but at B?
Stephen Wolfram told
I have found ...
- 129
0
votes
2
answers
111
views
Is it true that $\dot{H}(t)\sim H(t)$, and if so, why?
In the context of working with the FRW metric in Cosmology, I'm trying to reproduce the results of a paper where an expansion of the metric in terms of perturbations is performed. The author gives a ...
- 293
0
votes
1
answer
76
views
Black Hole Formation -- How Can an Event Horizon be Observed to Grow? [duplicate]
This is a question about black hole formation. To be clear, I’m not suggesting that black holes don’t form. It’s that I’m having trouble with the accepted explanation so there’s a flaw in my logic ...
- 21
-1
votes
1
answer
55
views
Relation between Earth's and Sun's magnetic axis relative to their paths of travel and relative to each other?
Pretext
As non-educated citizen with no academic background, and based on watched PBS Space Time's latest video I've got curious, what's the relation between Earth's and Sun's magnetic axis relative ...
- 530
0
votes
0
answers
47
views
Inflation in background free models of the universe
There are many authors who are attempting to construct a model of physics that doesn't rely on the objective existence of spacetime. This is part of the work in quantum gravity. This leads to things ...
- 1,430
3
votes
2
answers
143
views
How can we model the primordial Universe while the interior of a neutron star and comparable states of matter are still mostly unknown?
There is something I never quite understood about the physics of the primordial Universe. There are states of matter at high temperature/high pressure that are still, today, poorly understood. The ...
- 1,109
11
votes
2
answers
513
views
Why is nonzero net charge density incompatible with the cosmological principle?
In an answer to a question about the overall charge-neutrality of the universe, benrg writes,
A nonzero net charge density is incompatible with the cosmological
principle. Unlike the gravitational ...
rob♦
- 91.5k
1
vote
2
answers
69
views
Can Bose-Einstein condensates and Fermionic condensates survive for long periods of time in space?
Imagine we have a cold region of the universe, almost devoid of matter and radiation. Or perhaps in a future universe where the CMB has "cooled" down to sufficiently low "temperatures&...
- 2,462
5
votes
3
answers
414
views
Why is the universe charge-neutral?
The positive charges (such as from the protons) of the universe are almost neutralized by the negative charges (such as from the electrons).
Is there an explanation for this neutrality? Does it ...
- 4,452
1
vote
2
answers
530
views
Please help me with this paradox [closed]
Physicists believe that some galaxies are moving away from us at faster than the speed of light. A galaxy that is moving away from us at faster than the speed of light would be moving backwards in ...
- 53