All Questions
Tagged with space-expansion energy-conservation
66
questions
2
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48
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Does gravitational redshift conserve energy?
It is claimed that redshift due to cosmological expansion doesn't conserve energy. Does this exception also apply to gravitational redshift? Why or why not?
1
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1
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76
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Why is the First Law of Thermodynamic related to Fluid Equation?
In Cosmology, there is a equation called Fluid Equation:
$$\dot{{\varepsilon}}+3\frac{\dot{a}}{a}(\varepsilon+P)=0.$$
It is derived by taking time derivative of the First Law of Thermodynamic:
$\dot{E}...
0
votes
1
answer
37
views
Does the energy of a photon in comoving space change?
Assuming a flat FLRW universe that is expanding: In comoving space, does the energy of a photon decrease or stay constant? A physical argument for this would be nice.
1
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0
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64
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Are there structures or systems that can have a high angular momentun that are not made by protons and/or neutrons?
Cosmic structures such as neutron stars, white dwarfs or black holes can have high amounts of angular momentum (high spin velocities). However, these are all made by protons and neutrons (black holes ...
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2
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75
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Does dark energy get used up in the expansion of the universe?
Now, I am a beginner in Cosmology, so I am not sure if this makes sense.
Since the universe is expanding at an accelerating rate, and thus distant objects are also accelerating away. In that sense, ...
0
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1
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134
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Expansion of Universe and validity of law of conservation of energy [duplicate]
It has been proved by the Red Shift that universe is expanding. But if the universe is actually expanding, it needs energy to do so. I also do not know that with expansion in universe if mass ...
2
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0
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26
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When light gets red shifted by the expending universe it's energy decreases. What happens to that energy? [duplicate]
If a Photon of light is red shifted its wavelength increases and therefore its energy decreases. What happens to that energy as energy should be conserved right?
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1
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221
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Energy conservation in the redshifted light by expansion of the universe [duplicate]
I asked chat-gpt the same question, and this is her answer:
The energy of light that is redshifted due to the expansion of the universe doesn't disappear, it is simply transformed into other forms of ...
2
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0
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78
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Can gravitational waves gain energy in an expanding FRW spacetime?
I was reading this paper (Green's functions for gravitational waves in FRW spacetimes: https://arxiv.org/abs/gr-qc/9309025) I had a specific question about one statement in the paper that I would like ...
1
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0
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55
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Conservation of energy in quasar outflows?
I found this article about the behavior of quasar outflows in cosmology and how they can create a magnetic field.
In section 2.1.4., the authors say that when a quasar produces a "wave" or ...
2
votes
2
answers
224
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Energy from spacetime expansion?
Are there any processes or mechanisms in the universe involving spacetime expansion where energy is produced somehow out of this expansion?
I ask this in part due to this article by Sean Carroll 1 ...
3
votes
1
answer
98
views
Cosmic strings increasing internal energy as the Universe expands?
I was reading an article by Edward Harrison, which tackles the problems of conservation of energy at cosmological scales.
At some part (point 2.4) he cites several article, including one by Rees and ...
0
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1
answer
395
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The expansion of universe releases vacuum energy
The quote below has been taken from the Wikipedia article on cosmological constant, https://en.wikipedia.org/wiki/Cosmological_constant.
Einstein included the cosmological constant as a term in his ...
0
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1
answer
71
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Cosmological energy conservation
The expanding universe is gaining energy through increasing dark energy, and losing energy from red shift. Are these two effects comparable in magnitude?
7
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1
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672
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Energy extraction from universe expansion? [duplicate]
I recently learned that energy is not conserved according to general relativity. Inspired, I went looking for a way to harness this interesting feature of the theory and came across an idea that ...