All Questions
8
questions
0
votes
0
answers
26
views
Is there an estimate for how many monopoles would be produced in the very early universe?
The question really hits it with this one. I haven't really found some good numbers other than the whole “It'd be so many (per Hubble vol) to recollapse the universe”. I don't know if that comes of as ...
- 33
2
votes
1
answer
319
views
Size of the universe 13 billion years ago
When wee look at the sky in opposite directions, we can see early galaxies that were formed about 13 billion years ago. At that time, the distance between two such galaxies at the opposite ends of the ...
- 466
18
votes
2
answers
4k
views
How long ago was the Universe small enough for interstellar travel?
Currently, even the nearest stars are lightyears away, and impossible to reach in our lifetimes. If space is always expanding, and was once infinitely smaller, then at what point in the past was space ...
- 719
2
votes
1
answer
609
views
How close can we calculate back in time to the instant of the big bang? (until, presumably we need a theory of quantum gravity?)
I've heard a few times in my 5+ decades that we can only calculate the "state of the universe" (loosely speaking, I don't know any math close to that high) back to very close, but not right ...
- 21
2
votes
0
answers
234
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How to derive number of nucleons in Universe?
I understand that there are roughly $N=10^{79}$ nucleons in the visible Universe. This number comes from adding up the nucleons of $100$ billion stars in $100$ billion galaxies in the visible Universe ...
- 5,925
-2
votes
1
answer
300
views
How many Planck times would there be from the Big Bang to the Big Rip?
How many Planck times would there be from the Big Bang to the Big Rip? (approx.) Does this number have any numerical significance to mathematics?
If you had a CPU clock which had a timer counting ...
user84158
0
votes
1
answer
69
views
When did the universe become lighter than water at 1 g/cm3 [closed]
Did the universe become lighter than water before light could travel through it?
What temperature was it at the time where matter was roughly 1g/cm3?
- 33
8
votes
3
answers
1k
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What was the density of the universe when it was only the size of our solar system?
What was the density of the universe when it was only the size of our solar system? Did it approach neutron star density? Is it physically correct to even ask such a question?
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