All Questions
352
questions
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What is meant by "spontaneous creation" in this paper?
I have some questions in regard to the paper "Spontaneous creation of the universe from nothing". If I am not mistaken it is akin to Alexander Vilenkin's proposed cosmological model that has the ...
CommunityBot
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60
votes
4
answers
8k
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Does the universe have a center? [duplicate]
If the big bang was the birth of everything, and the big bang was an event in the sense that it had a location and a time (time 0), wouldn't that mean that our universe has a center?
Where was the ...
- 3,860
-1
votes
1
answer
174
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Is the observable universe analogous to a white hole?
My instinct is no, but my lack of understanding with respects to white holes doesn't tell me why. My thinking is this: The universe is expanding and the further away from us the faster it is expanding....
1
vote
1
answer
71
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Age of universe vs Hubble time in Milne universe
Consider an empty universe where energy density $\varepsilon = 0$, thus the Friedmann Equation can be reduced into:
$\dot a^2= -\frac{kc^2}{R_O^2}$
$k$ is the curvature of space, $R_0$ is the radius ...
- 2,550
1
vote
1
answer
410
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Curves on LCDM spacetime diagram
I have a question concerning the LCDM spacetime diagram on this Physics Stack Exchange post.
How are the set of curves for $z = \text{constant}$ (1, 3, 10, 50, etc) constructed or calculated, i.e. ...
CommunityBot
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2
answers
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Does the expansion of the Universe into a higher dimensional space imply that 4D objects are real?
It is my understanding that objects in the Universe are not just getting farther apart but space itself is expanding and so in some real sense, higher-dimensional geometry is "real" -- if so, on a ...
7
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3
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5k
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If we consider the spacetime of the universe to be four-dimensional, does the Big Bang lie in its center?
Apologies for the (hopefully now somewhat less) clickbait-y title. Now, of course, I know that the Big Bang did not happen at any point connected to a single point in our current $3$-dimensional ...
- 12.1k
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If an area in 2D cannot be curved and finite is the same regarding the space of our pressumed 3D universe?
Is the sentence in the title right that our universe is infinite? And if so does it mean that stars are not evenly distributed along our universe but they all move from a populated centre to a fairly ...
- 2,255
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4
answers
1k
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Infinite Universe and Big Bang
A common view now in the physics community is that the Universe is infinite in extent (which makes Hubble sphere an infinitely small part of the Universe).
On the other hand, there is the Big Bang ...
CommunityBot
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33
votes
9
answers
9k
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Is space really expanding?
In a book called "Einstein, Relativity and Absolute Simultaneity" there was this sentence by Smith:
There is no observational evidence for a space expansion hypothesis. What is observed are ...
- 6,404
2
votes
1
answer
123
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Could the universe have a form of a $T^3$-torus?
Cosmological measurements suggest that we live in a flat universe. However, what might be less clear is its topology. So could the flat universe have the form of a $T^3$-torus, i.e. the torus whose ...
- 207k
5
votes
5
answers
2k
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The inner workings of the Olbers paradox
A long time ago I was told that the universe is finite. The provided "proof" (or reasoning), known as Olbers' paradox, was that on infinite universe there would be an infinite number of stars, and ...
- 112
1
vote
1
answer
80
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Cosmic web shape
Does anybody know why the cosmic web is shaped like a web? I feel like it would be more likely that it is more like a galaxy with a supermassive black hole in the center, if that were true, what would ...
- 207k
0
votes
0
answers
73
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Are there any ways to conceptualize the relationship between gravity and space-time other than curvatures?
This might sound like a random question, but it came to me while I was trying to conceptualize the size of the universe and started thinking of entire galaxies resembling grands of sand floating ...
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answer
34
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Question about light and distance
If we see into the past with light and distance travelling so we can’t see things how they are currently, only how they were in the past; and James Webb took a photo from the beginning of the universe ...
- 56.4k