All Questions
125
questions
0
votes
1
answer
78
views
Could cosmic rays induce a vacuum decay in the future?
I've been told that very energetic cosmic rays could cause a vacuum phase transition or vacuum decay (and even could cause a true vacuum level to go "uphill" to a false vacuum) due to their ...
- 2,462
0
votes
1
answer
62
views
What is the total mass-energy of baryonic matter?
From what I understand, conservation of energy does not apply to the total energy of the Universe, because it constantly expands and the new, created space has a constant non-zero energy of its own. ...
- 413
3
votes
0
answers
80
views
Noether's Theorem in relativistic cosmologies [duplicate]
Is Noether's Theorem valid within the context of relativistic cosmology? If not, does this mean that the universe does not conserve energy on cosmological time and distance scales?
- 95.5k
10
votes
1
answer
1k
views
What fraction of the universe's energy is contained in photons?
From each point in the universe, the light of billions of stars, galaxies, supernovae etc. can be detected. So there seems to be a lot of energy/momentum "in flight".
Is it possible to ...
- 347
0
votes
0
answers
42
views
Up-tunneling of vacuum with high-energy events?
I was reading these papers by Sean Carroll (https://arxiv.org/abs/1405.0298 ; https://arxiv.org/abs/1505.02780) in which, among other things, he argues against vacuum up-tunneling occurring in the ...
- 2,462
0
votes
1
answer
69
views
Why does the total gravitational potential in the universe exactly equal the total mass energy RIGHT NOW? [duplicate]
In the zero energy universe model, the gravitational field has negative energy, and this negative gravitational energy of all the distant mass exactly balances and cancels the positive mass-energy in ...
- 278
1
vote
0
answers
75
views
What means Alan Guth's Free Lunch Principle for the universe?
Alan Guth calls the universe the ultimate free lunch. What does he mean by this?
Does he mean that the total energy of the universe is zero? So the total energy of all particles is the negative of the ...
- 450
3
votes
1
answer
500
views
Does energy exist on its own? [closed]
So to my understanding as a layman is that energy transfers from one material to another (I guess that's why there's potential and kinetic energy), for example photons to solar panels. Now my question ...
- 149
4
votes
1
answer
94
views
Why thermodynamic arrow of time will not reverse during the big crunch (considering our universe is above the critical mass)?
As the question states, Why thermodynamic arrow of time will not reverse during the big crunch (considering our universe is above the critical mass)?
The doubt arised because I thought the ...
- 159
12
votes
10
answers
6k
views
Why don't the first two laws of thermodynamics contradict each other?
The second law of thermodynamics states that the entropy of the universe increases over time and this has lead to theories like the heat death of the universe and the big rip. What this means in ...
- 255
2
votes
2
answers
113
views
Cosmology model with equation of state $P=\epsilon / (\epsilon+1)$
In my cosmology course I came across the universe with the equation of state
$$
P=\frac{\epsilon}{\epsilon+1},
$$
where $P$ is the pressure and $\epsilon$ is the energy density. The task was to ...
- 976
0
votes
1
answer
87
views
Kinetic energy being transformed into other types of energy in cosmology?
Spacetime expands at an accelerated rate and the particles with movement associated to this expansion are said to be coupled to the Hubble flow. In many papers that I've read, objects coupled to the ...
- 2,462
2
votes
5
answers
424
views
Why can infinite quantities not be shown in an experiment or observed in physics?
To modern physicists knowledge, there are no truly infinite quantities that can be shown with an experiment or observation. Time is not infinite, it had a beginning. Matter and energy is finite (...
- 49
1
vote
1
answer
74
views
Avoiding heat death in an accelerated expanding universe?
Would there be any way to avoid heat death in an accelerated expanding universe?
https://en.m.wikipedia.org/wiki/Heat_death_of_the_universe
Is the heat death of the universe completely unavoidable in ...
- 2,462
1
vote
0
answers
77
views
Energy harvesting in expanding universe? [closed]
There has been much discussion (in Physics Stack Exchange for instance) about how could we (theoretically) extract energy from the accelerated expansion of the universe.
However, the only ...
- 2,462