All Questions
Tagged with electromagnetic-radiation cosmology
55
questions
6
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4
answers
2k
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Accelerating Expansion of Universe - Why Not Caused by Radiation?
As I understand it, dark matter and dark energy are used as an 'explanation' for how universe expansion is accelerating; because without it gravity would be expected to cause a long term shrinking.
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- 181
10
votes
1
answer
1k
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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
1
answer
144
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Mass density of radiation in Friedmann equation?
$$\frac{{\ddot a}}{a} = - \frac{{4\pi G}}{3}(\rho + 3P) + \frac{\Lambda }{3}$$
In the case of matter, pressure $P=0$,
In the case of radiation, pressure $P=(1/3)ρ$,
In the case of cosmological ...
- 117
0
votes
0
answers
95
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How can we use CMB to measure the value of the cosmological constant?
Another mystery facing cosmologists is the accelerating expansion of the universe. In 1929, astronomer Edwin Hubble showed that the universe was expanding, but for this expansion to be justified, ...
3
votes
1
answer
69
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Frequency shift of photon using magnetic field
According to GR, it is possible to redshift the frequency of a photon using a magnetic field as demonstrated by the Gerstenshtein Effect:
https://web.archive.org/web/20210225134450/http://jetp.ac.ru/...
- 183
1
vote
0
answers
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Radiation from a moving charge particle in expanding universe?
Moving charged particles generally emmit energy in form of radiation.
Assume a charged particle that is situated in a zone that can join the Hubble flow and therefore starts moving away from us.
As it ...
- 2,466
11
votes
3
answers
3k
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If we have a cosmic microwave background should't we also have a cosmic radio wave background?
I'm a layman in physics, but here is what I understand:
What we see in the sky with naked eyes is a map of electromagnetic waves in the frequency visible to the human vision.
But that kind of ...
- 111
-1
votes
1
answer
127
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Redshift Due to Expanding Space (not increasing distance) [closed]
Please NOTE: "For example, a question that proposes a new concept or paradigm, but asks for evaluation of that concept within the framework of current (mainstream) physics is OK."
And: "...
- 23
0
votes
2
answers
192
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Why the CMBR redshift is so higher than the redshift of the most distant therefore oldest galaxies in the universe?
Why the CMBR redshift is so higher than the redshift of the most distant therefore oldest galaxies in the universe? We know that cosmological redshift rises with distance from the object but at ...
- 2,245
1
vote
1
answer
34
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If cosmological redshift causes wavelength elongation does it mean the whole emitted signal is elongated?
If cosmological redshift causes wavelength elongation does it mean the whole emitted signal is elongated? Let say we have ten waves on the see hitting the shore.... If we somehow elongate every single ...
- 2,245
1
vote
3
answers
115
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How does light fill the entire universe? [duplicate]
Light is a particle and a particle is discrete. So say light is emitted from a star 7 billion years far, how is it possible that this light particle emitting from a star fills every point in the ...
- 283
1
vote
3
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129
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Can cosmological redshift only decrease photons' energy by increments (that correspond to Planck's constant)?
I have read this question:
The equations that govern quantum mechanics predict that the angular momentum (that is, spinning or orbiting) in a system can't take on any value, but instead come in lumps....
- 29k
1
vote
0
answers
19
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Universe expansion and energy conservation principle [duplicate]
If photons lose energy due to expanding of the universe where the lost energy is stored? Does the energy conversation principle is violated?
- 119
2
votes
1
answer
486
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What is the mean free path (MFP) of a Cosmic microwave background radiation (CMBR) photon?
If the IGM (inter-galactic medium) had a massive particle (proton) every cubic metre, or a carbon grain every cubic kilometre, what would be the MFP of a CMBR photon? The coherence length of the ...
- 304
0
votes
3
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40
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Are the constituents of the known universe matter (including antimatter) and electromagnetic radiation?
Is it correct to say that the constituents of the known universe are matter (including antimatter) and electromagnetic radiation, leaving aside the comparatively hypothetical ‘dark’ entities? This is ...
- 135