All Questions
Tagged with electromagnetic-radiation cosmology
55
questions
3
votes
1
answer
107
views
Gravitational wavelength shift of microwave background radiation
I can't find this precise question answered. It is basically a two part question.
Would the microwave background radiation, as well as light travelling to us from stars in an expanding universe ...
- 533
18
votes
3
answers
2k
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Is the amplitude of the Cosmic Microwave Background (CMB) correctly predicted or just its spectral shape?
I see this beautiful graph of the CMB in Wikipedia
Apparently the measured data-points match the theoretical curve for black body radiation very exactly and the discrepancies and error-bars are simply ...
- 2,403
0
votes
0
answers
36
views
Changes to an EM-wave that is propagating in an inflating space
I am trying to get an easier picture of what happens to an em-wave considering space expansion. My question is: If a star in a non-inflating space emits light recorded at a certain distance of the ...
- 1,815
4
votes
1
answer
228
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How much energy is in the Universe as photons? [duplicate]
The mass of Universe in kilograms is about 10 power 53.
But how much energy exists in the Universe in form of photons?
And if they would all be converted into mass, how much mass that would make?
Dark ...
- 233
1
vote
1
answer
3k
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Why are there fewer lines on the absorption spectrum than on the emission spectrum for some gases?
I don't know if this is right, but I think that it is because:
when the gas is heated, the electrons get 'excited' and move up to an energy level (lets say an electron moves up 4 energy levels).
...
- 220
4
votes
1
answer
114
views
What is the energy spectrum of all photons in the observable universe?
Does anyone know what the energy spectrum for the entire universe looks like? In other words, what would the graph look like if you plotted the number of photons on the $y$-axis and frequency on the $...
- 555
2
votes
1
answer
268
views
How/why did the Thomson scattering by early plasma of the CMB create a particular polarization?
I understand how Thomson scattering polarizes EM radiation, but why/how did particles of the early universe create a particular polarization pattern of the CMB? (E-mode polarization)....
I mean, the ...
- 4,509
0
votes
0
answers
169
views
Infinite universe and the impossibility of monochromatic light and infinite plane waves
I recently asked a question relating to this excerpt from the textbook Optics, fifth edition, by Hecht:
Mathematically, the plane wave extends out to infinity in all its directions, and, of course, ...
- 889
0
votes
1
answer
47
views
What does a universe look like where light cannot lose energy and is emitted all the time? [closed]
In a universe where light cannot lose energy, and is emitted all the time, what is the result?
- 1
4
votes
1
answer
178
views
How to justifiy that $\rho_{\text{rad}} \approx \rho_{\text{mat}}$ at recombination time?
In standard cosmology, the recombination time is estimated to be $t_{\text{rec}} \approx 380~000~\mathrm{years}$ after the Big Bang, when matter and electromagnetic radiation becomes decoupled. It's ...
- 7,592
14
votes
1
answer
4k
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What percentage of the mass/energy of the universe is in the form of electromagnetic waves? [duplicate]
Is there any theoretical framework or model that would lead to a prediction, either precise or approximate, about how much or what proportion of the universe's total mass is in the form of photons, or ...
- 533
0
votes
0
answers
70
views
Matters Including Resolution of Olbers' Paradox
Is there evidence for galaxies receding from us faster than the speed of light? If so,that might help resolve Olbers' paradox, though other factors must also be taken into consideration. Could such a ...
- 1,710
15
votes
1
answer
4k
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Why can’t you see at the start of the Big Bang?
I’m quite confused with regards to photon emission throughout the creation of the universe.
From what I’ve heard, there was no light (of any frequency) in the universe until 300,000 years after the ...
- 2,356
2
votes
2
answers
244
views
What happens when the wavelength of light becomes as large as the observable universe? [closed]
Say the wavelength of a photon became so large that it approached the size of the observational universe. Does something unexpected happen?
-2
votes
2
answers
278
views
Could photons decay into Dark Matter? [closed]
So, we can "see" 13.7 billion (intentionally not including expansion) light years in all directions and we "see" a red shift.
What if, the reason we can't observe photons beyond this limit is that ...
