B Black hole at the beginning of time

Click For Summary
The discussion centers on why the universe did not collapse into a black hole at the beginning, despite all matter being condensed. It emphasizes that the Big Bang did not originate from a single point but occurred uniformly throughout space, preventing the formation of a gravitational gradient necessary for a black hole. The early universe was filled with expanding matter rather than a static region surrounded by vacuum. Misinterpretations of the Big Bang concept are common, leading to confusion about its nature. Overall, the early universe's isotropic and homogeneous conditions are crucial in understanding its evolution.
  • #61
PeterDonis said:
Is impossible as you state it here since, as @vanhees71 has correctly pointed out, isotropy about only one point does not imply homogeneity.
It's clear from the context that "isotropic" means isotropic at every point. That must be the default terminology in any case.
 
Physics news on Phys.org
  • #62
Well, it's obvious that isotropy around only one point is not enough. It's however also pretty intuitive that isotropy around all points implies homogeneity (but not the other way, i.e., homogeneity does not imply isotropy around any point). Weinberg's definitions and proofs in Gravitation and Cosmology (Chpt. 13) is also not too difficult to follow.
 
  • #63
PeterDonis said:
No global chart in any curved spacetime can be inertial.
Yes that's is true in general, in the particular case of chart described in #56 the reason behind it should be that pointed out there, I believe.
 
Last edited:

Similar threads

I If electrons can be pointlike particles, why can't black holes?
  • · Replies 16 ·
Replies
16
Views
2K
B How can a black hole absorb matter?
  • · Replies 31 ·
2
Replies
31
Views
1K
I You can't actually enter a blackhole?
  • · Replies 40 ·
2
Replies
40
Views
3K
I Falling through the event horizon of an evaporating black hole
  • · Replies 51 ·
2
Replies
51
Views
4K
B Theories about light and time near a black hole
  • · Replies 20 ·
Replies
20
Views
2K
B Question about the Entropy of a Black Hole Singularity
  • · Replies 17 ·
Replies
17
Views
3K
I Do any real macroscopic black holes have a singularity?
  • · Replies 11 ·
Replies
11
Views
2K
I Black hole formation and infinite redshift
  • · Replies 8 ·
Replies
8
Views
1K
B Entering a black hole -- I know I must be wrong (Help me understand why)
  • · Replies 29 ·
Replies
29
Views
3K
B A photon always travels in a black hole
  • · Replies 9 ·
Replies
9
Views
1K