All Questions
Tagged with big-bang space-expansion
321
questions
4
votes
1
answer
663
views
Why don't we see the big bang?
excuse my understanding, my brain is melting.
So I understand that pictures of far away objects is like viewing the past.
and I think I pretty much get that the big bang was in every direction since ...
- 973
3
votes
1
answer
86
views
How can we still see the CMB? [duplicate]
May seem stupid but i cant wrap my head around it. if a star explodes we eventually see it when the light gets here. but once its got here we see the event and the star is now gone, we cant see it ...
-1
votes
1
answer
113
views
Is HD1 Galaxy a potential Big Bang theory killer?
I have heard some first explanations of why the farthest ever galaxy discovered about 13.27 Bly away the HD1 appears so UV active and about the population III stars inside this galaxy made only from ...
- 4,170
0
votes
2
answers
113
views
If there was an infinite amount of matter at big bang to form an infinite universe how it was possible for a so huge amount of matter to expand?
If there was an infinite amount of matter at big bang to form an infinite universe how it was possible for a so huge amount of matter to expand? Is it better to think that the universe is spatially ...
- 467
1
vote
1
answer
55
views
Higher order terms in Big Bang derivation
You can easilty proof that an SEC fluid gives a big bang by looking at the second Friedmann equation:
$$
\frac{\ddot{a}}{a} = -\frac{4\pi G}{3}(\rho + 3P) \le 0
$$
This implies that $\ddot{a} \le 0$ ...
- 351
2
votes
2
answers
236
views
If CMB came from the big bang, how come we got to where we are before the CMB arrived? [duplicate]
I have read that the cosmic background radiation was formed 380,000 years after the big bang, when stuff changed from being opaque to light, because of free electrons, to becoming transparent.
However,...
- 145
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
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
3
votes
1
answer
236
views
Deriving the age of the universe
I am trying to work out the solution to exercise 8.4 from An Introduction to Modern Cosmology by Andrew Liddle. I could derive the Friedmann equation as below,
$$\dot{a}^2 = H_0^2 \left[\Omega_0a^{-1} ...
1
vote
0
answers
60
views
Why is the age of the universe $=D/v$, despite that $v$ is not constant with time?
I am watching a series of lectures by the Noble prize laureate Brian Schmidt and Paul Francis and in this episode (at 4:20) they make the simple assumption that a galaxy receding from us due to the ...
- 157
0
votes
0
answers
77
views
What if cosmological inflation never stopped?
If inflantionary theory is correct, the universe ceased to expand after just $10^{−32}$
seconds. Imagine a scenario where cosmic inflation never actually stopped.
At the extremely accelerated ...
- 2,987
1
vote
2
answers
153
views
Can the age of the universe be much bigger than 13.8 billion
If observable universe is only a small fraction of the existing universe, does it imply that the age of the universe is much more than 13.8 billion years or the expansion of the universe is much ...
- 57
1
vote
0
answers
29
views
Could our universe still work if either one of $c$, $h$, $q$, $G$, permeativity, permeability or $H_o$ were slightly different? [closed]
Could our universe still work if either one of c, h, G, q, permeativity, permeability or Ho were slightly different? Also all of them are thought of as being constants for the whole history of the ...
- 2,255
1
vote
0
answers
54
views
How is the expansion of the universe measured if redshift depends on the expansion itself? [duplicate]
To me this seems like a bit of a chicken egg problem.
Based on the redshift of light (plus the assumption that physics worked the same way back then and there as it does now and here), we can ...
1
vote
2
answers
194
views
Can dark energy dominate from the Big-Bang?
I'm studying the age of the universe for a universe dark energy dominated. Using Friedmann equation
$$
\left( \frac{\dot{a}}{a} \right)^2 = H_0^2 \left[ \Omega_R \cdot a^{-4} + \Omega_{NR} \cdot a^{-3}...
- 317