All Questions
Tagged with space-expansion redshift
149
questions
2
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1
answer
48
views
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?
- 804
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votes
0
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95
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Distance needed for visible light to be cosmologically redshifted to microwave
What distance will it take for visible light to become a microwave due to cosmological redshift?
I'm not sure how to calculate this, as I'm never good at complex math. I tried googling but didn't find ...
- 109
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 ...
- 2,462
11
votes
2
answers
1k
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Redshift of the CMB
Has the $z\sim 1100$ redshift of the CMB been actually measured by comparing the fingerprint (absorption spectrum) of the CMB with the theoretical radiation pattern of a $2.725\,\mathrm{K}$ blackbody, ...
- 121
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1
answer
45
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Cosmological redshift and distance calculus
I am somewhat puzzled when it comes to understanding the general relationship between the cosmological redshift of a galaxy and its distance, and none of the other questions in the forum have ...
- 161
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0
answers
42
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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
1
vote
1
answer
190
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Why are physicists not more concerned that there are too many explanations for redshift in the universe?
There are speculative explanations for red shift such as the tired light theory, but I am not referring to those. There are three mainstream explanations
Red shift due the expansion of the universe ...
- 371
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1
answer
57
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Why do successive redshifts multiply rather than add?
I understand the argument presented in the answer to this question on how successive redshifts combine, such that $$1+z = (1+z_1)(1+z_2) = 1 + z_1 + z_2 + z_1z_2 \\ \therefore z = z_1 + z_2 + z_1z_2.$$...
- 37
1
vote
2
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129
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Is cosmological redshift associated with recession velocity when the light left or when it arrived?
Is the cosmological redshift $z$ associated with the recession velocity when the light left, when it arrived, or something in-between?
user300520
-4
votes
2
answers
108
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Would continuously increasing curvature of space explain seeming expansion of the universe? [closed]
Could expanding universe phenomenon be explained by slowly but continuously increasing curvature of space around masses like galaxies and galaxy clusters? In other words, I am curious whether the ...
- 113
1
vote
0
answers
59
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How to derive deceleration parameter in terms of redshift?
How do I get q in terms of $z$ specifically of this form:
I want to derive the second equation from the first but I'm getting an additional $ \frac{a^2}{H^2}\ $ in the second term
$$ q= -\frac{\ddot{a}...
0
votes
2
answers
90
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If the expansion of space causes the elongation of light waves, why isn't this elongation observed within the Milky Way?
The elongation of light waves occurs not because galaxies are moving away from each other, but because light waves are stretching along with the fabric of expanding space (cosmological redshift). ...
0
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0
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45
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Clocks at different redshift: does calculating luminosity distance shift the frame of reference?
Luminosity is energy per time.
When we calculate a luminosity distance, using angular diameter distance times $(1+z)^2$, I think we are correcting the energy (from redshifted photons) by $(1+z)$ and ...
- 821
0
votes
2
answers
78
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Detectability of cosmological redshift in an empty part of universe
I'm pretty new to the concept and I want to get a better idea about it. I've seen a video in which a light wave is stretched since the space itself is stretching. Another analogy is that cosmological ...
- 1,051
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votes
0
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34
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Has the speed of light always been constant? [duplicate]
Is there any evidence to suggest that the speed of light (or its other properties) has been unchanged since the beginning?
The particular curiosity stems from the redshift observed in distant galaxies....
- 287