All Questions
11
questions
2
votes
1
answer
169
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What does the arrow of time and entropy say about the universe and repetition?
This question What is the relationship between how time is viewed in thermodynamics and how time is viewed in general relativity? is close to what I was wondering, but it didn't get into repetition ...
- 123
1
vote
0
answers
192
views
Energy density of particle species in thermal equilibrium
I am reading the book Kolb and Turner "The Early Universe". In the thermodynamics section they mention that the total energy density of different species in equilibrium is
$$\rho=T^4\sum_{\...
user255856
7
votes
5
answers
556
views
Can the "Boltzmann brain" concept inform discussions of cosmology?
The Boltzmann brain was originally discussed as a sort of thought-experiment or aid
to reflection on what might possibly happen in the universe. Its first discussion was
in the context of thermal ...
- 59.6k
10
votes
10
answers
11k
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If we were able to prove that the universe is infinite, wouldn't that statistically prove that there is no other forms of life?
I want to begin my explanation using abstract mathematical explanation to repetition possibility by taking independent samples $X_n$ from some continuous probability distribution: https://math....
- 368
5
votes
2
answers
797
views
Can we really apply the second law to the entire universe?
I do not doubt the second law in general, just if it rigorously applied to the entire universe. Here's why I ask this
2nd law - restricted to isolated systems: "The second law may be formulated ...
- 601
2
votes
1
answer
349
views
Does ΛCDM imply infinitely many Boltzmann brains?
In this paper, Sean Carroll basically argues that the ΛCDM/'flat lambda' cosmological model has to be wrong since it implies that we're probably Boltzmann brains (and therefore shouldn't trust our ...
- 77
1
vote
1
answer
231
views
Estimation of the entropy of the universe
I heard the following way to estimate the entropy of the universe:
using that the entropy is dominated by photons, in particular the cosmic microwave background radiation, which has a wavelength ...
- 9,304
2
votes
2
answers
191
views
Must the universe recur, be infinite, or be infinitely divisible?
When I was an undergraduate, I had this thought: Suppose that everything is made of atoms (I mean, pieces which cannot be separated further) and the universe has a finite amount of space.
Let $N$ be ...
3
votes
1
answer
1k
views
The fate of Poincaré recurrence with the Big Rip
Recently, there has been a lot of talk in the media about the "Big Rip". It most certainly resulted from the paper by Marcelo M. Disconzi and Thomas W. Kephart where they have figured out a ...
- 93
10
votes
7
answers
2k
views
Mathematically possible vs physically probable outcomes
A good buddy of mine and I have had a friendly debate about the origins of the current state of our universe (namely; Earth and life on Earth) and have fundamentally disagreed in our stances with ...
- 201
10
votes
4
answers
3k
views
Why aren't we Boltzmann brains in an infinite universe?
Either space is finite or it is infinite.
a) - If space is infinite in extent, either it is thermal over an infinite volume, or it is in the vacuum state for most of it. If it is thermal, infinity ...
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