All Questions
133
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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
7
votes
3
answers
5k
views
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 ...
- 1,897
1
vote
1
answer
81
views
Do we still not know whether the universe had a beginning? [duplicate]
The Question:
According to Prof. Brian Cox in the first 30 seconds of this YouTube video from 4 years ago, we do not know whether the universe had a beginning. Is it still the case that we do not ...
- 105
-4
votes
2
answers
141
views
What model tells us there is nothing outside the universe?
Is there an existing model or theory that shows there is nothing outside of the universe that interacts with anything inside the universe? Or to put it in other words, is there a model or theory ...
- 4,783
0
votes
1
answer
98
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Does The Big Bang Require An Infinitesimal Point, Or Is Another Shape Possible? [duplicate]
Einstein's Spacetime has four dimensions. If the size of one of these dimensions is zero, then the four-dimensional 'volume' - or whatever the corollary to 3D volume is called in 4D - would be zero.
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- 103
0
votes
2
answers
47
views
Is this the Format of the Observable Universe?
The way I have it is: the Observable Universe looks as follows. In some ball, all the galaxy clusters exist, then in a bigger concentric ball the dark ages exist (no galaxies), then on the surface of ...
- 61
0
votes
0
answers
66
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No symmetries in the universe at the Big Bang...?
I apologize in advance if this is a stupid question but...
According to some scenarios about the beginning of the universe (namely cosmological inflation), in layman terms, everything was born out of ...
- 2,462
0
votes
0
answers
51
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Was Big Bang the "START" of time? [duplicate]
I know that this question has been repeated a lot. But I still don't understand this concept.
Big bang created matter and space but how could it possibly create time?
If Big bang didn't create time ...
- 77
2
votes
1
answer
171
views
Particle horizon in an empty universe
So in this thread,
Can space expand with unlimited speed?,
the author Pulsar made amazing diagrams of different horizons and paths for a benchmark model that describes our current universe, and gave a ...
- 161
18
votes
5
answers
7k
views
How does it make sense for the universe to have started from a big bang?
It has been said that the Big Bang started from a singularity. Think about a balloon radially growing over time. Fix a time $t_0, t_1 > 0$, and let $M_0, M_1$ be two balloons at time $t_0, t_1$ ...
- 301
0
votes
2
answers
91
views
What is there at a point the universe hasn't expanded past yet? [duplicate]
(Please don't mark as a duplicate)
If the universe is constantly expanding that means that there is a point the univese hasn't expanded past, with that what would be past that point? This isn't about ...
- 11
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votes
1
answer
73
views
When we say that the universe is expanding, what is causing this?
I could understand an initial explosion imparting momentum to matter but where is the energy stored in space itself? How does empty space have momentum that causes this expansion?
- 2,238
-1
votes
1
answer
1k
views
Did gravity exist before the Big Bang?
Gravity is one of the biggest mysteries. It is the weakest of the 4 fundamental forces but we have no clue how it works. Einstein never was able to figure it out in his lifetime. There is evidence ...
- 129
0
votes
3
answers
66
views
Detection of Variation of CMB Radiation with Time and Space
According to the standard model of cosmology, the CMBR temperature increased as $T(z)=2.7(1+z)$ at higher redshift. Has there been any study to actually probe the variation of the CMBR with redshift, ...
- 884
1
vote
2
answers
341
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Cosmic inflation and how does it stop?
What conditions make out the probability for the Cosmic Inflation once began to stop. For instance quantum physics says that once the inflation started there was a probability say 80% for it to stop ...
- 697