All Questions
33
questions
0
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2
answers
95
views
Could Space and Time Be Decoupled Pre- Big Bang?
The traditional view holds that both space and time emerged together from the Big Bang. However, I'm curious about the possibility that time could be eternal, with no beginning, while space began to ...
- 489
2
votes
0
answers
88
views
A problem on cosmic inflation
I analyze inflation in this following scenario: Suppose that at some very early epoch, $t_1 ≤ t ≤ t_2$ (where $t_1 ≪ t_2 ≪ t_r$ and $t_r$ is the time at the recombination epoch), the universe resides ...
- 131
0
votes
0
answers
48
views
Time from big bang to here [duplicate]
New to this so apologies for my ignorance, the simpler the answer the better. Here goes.
Light took 13.5 billion years to get to us from the big bang.
On an imaginary neighboring planet that is much ...
1
vote
2
answers
95
views
Time dilation between now vs right after the Big Bang should imply the universe is much older than 13.8 bn years? [duplicate]
The universe is said to be 13.8 bn years old. But if we go back in time towards the Big Bang singularity time will slow down more and more and eventually stop because of the density of the singularity....
- 11
1
vote
0
answers
68
views
Why is the Hubble law so accurate at scales smaller than galactic voids?
It's possible to derive the Hubble law:
$$v = H_0 d$$
from the FRW metric by differentiation.
Experimentally the Hubble law appears to hold for relatively small distances, say 20 Mpc and smaller. ...
- 841
-1
votes
1
answer
53
views
Big Bang and relativity [duplicate]
Wasn't the big bang's explosion itself faster than speed of light? how does this not violate relativity, I had read an explanation earlier but it wasn't sufficient, can someone explain to me how the ...
1
vote
1
answer
336
views
Did the Big Bang cause an outward push of gravity?
There is a theory that the big bang’s blast caused an outward push, a kind of reverse gravity if you will, of our universe and everything within it.
My question is how could this have happened? If it ...
- 179
1
vote
2
answers
1k
views
When did the Big Bang happen?
Did the Big Bang happen at a point? goes through the fact that the Big Bang happened everywhere at the same time. John Rennie's answer explains this as being a consequence of all points in space ...
- 2,162
13
votes
6
answers
3k
views
Do we know anything about the age of the universe?
I am looking to understand how the age of the universe is calculated according to modern physics.
My understanding is very vague as the resources I have found do not seem to state consistently whether ...
- 255
1
vote
1
answer
71
views
How closely does the analogy of a 2-sphere hold in cosmology?
Two dimensional creatures living on the surface of an inflating 2-sphere are often used to explain general relativity, curved space, and big bang cosmology. For years, though, I have wanted to ask: ...
- 789
7
votes
3
answers
3k
views
Age of Universe from Friedmann Equation - How to actually solve the integral?
The Friedmann equation for a flat universe can be written as
$$
H(t)=\frac{\dot{a}}{a}=H_0\sqrt{\Omega_{m,0}\cdot a^{-3}+\Omega_{\Lambda,0}}=H(a)
$$
To calculate the age of the universe, many books ...
- 938
5
votes
4
answers
420
views
Does the age of the universe depend on the way it is defined?
I was reading some earlier posts on this question in stack exchange. These posts give me the impression that the age of the universe is defined in a certain way following prescriptions such as that:
...
2
votes
1
answer
471
views
How can I compute the scale factor for an open universe?
I'm struggling in obtaining an analytical expression for an open-universe $a(t)$. I know it is usually calculated from the second Friedmann equation, and with respect to the image I know how to ...
- 107
1
vote
3
answers
272
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Is there a contradiction between isotropy and the Big Bang? [duplicate]
Disclaimer: I'm not asking whether the Big Bang happened at a point. I'm asking whether the fact that the universe is isotropic and that the Big Bang happened contradict each other.
To be honest I am ...
user212860
7
votes
4
answers
420
views
Could the spatially flat universe start small?
The global space has been measured flat within a small margin of error. According to FLRW, the flat universe has always been infinite. At the time of the Big Bang the universe was infinitely large ...
- 12.7k