All Questions
107
questions
1
vote
3
answers
86
views
Does the fact that we are able to see CMBR implies that universe expanded faster than light?
Supposedly, the universe underwent rapid expansion immediately after the big bang, surpassing the speed of light. If we can detect remnants from that era, does this suggest they moved faster than ...
- 21
1
vote
1
answer
75
views
Are there any observations from the beginning of the universe until the CMB?
The question that concerns my mind is that in the time period before the cosmic microwave background, did humans have any observations or not? I mean, are all the materials mentioned in physics about ...
- 21
11
votes
2
answers
1k
views
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
3
votes
2
answers
153
views
Does neglecting dark matter solve the Hubble tension?
If the total mass of the universe is smaller than estimated by neglecting the gravitational pull of dark matter, the estimated expansion rate should be greater.
Does this consideration in the CMB ...
- 476
0
votes
0
answers
13
views
CMB anisotropies due to moving clusters/voids?
Apparently, there is an effect where a moving overdensity/underdensity (or an object, e.g. a galaxy, moving in an overdensity/underdensity) that is going through an evolution of its gravitational ...
- 2,462
0
votes
2
answers
39
views
Can we measure temperature in an isothermal Universe?
It is envisaged that ,in the future ,Universe can end in a big freeze, where there will be no energy gradient. It is also theorised that Universe was isothermal(with some irregularities I guess) in ...
0
votes
0
answers
26
views
What is the change in vision and measurement between curved space and flat space, especially for measuring cosmic background radiation?
In a curved space, the light bends as it travels and acts like it is going through a lens. In a (positively) curved universe, a small object appears larger. If we know the actual size of an object, ...
2
votes
2
answers
147
views
Value of $H$ at the emission of the CMB
According to the lambda CDM model, $H_0$ is around 67.7. If this value was calculated from a value for $H$ at the emission of the CMB, what was it, or do we have constraints on its value at that time?
- 85
1
vote
0
answers
59
views
How big was the surface of the cosmic background radiation?
The cosmic microwave background radiation is the furthest and oldest visible light in the universe. But the universe has expanded considerably since that light was emitted. At the time that that light ...
- 897
0
votes
0
answers
62
views
Does inflation theory assume a finite universe?
Inflation theory has it that the early universe was causally connected, and could “mix”, hence explaining relative homogeneity of the CMB. The universe then rapidly expanded and became causally ...
- 139
-3
votes
1
answer
90
views
Why is the cosmic background 4K? Where are the other photons? [closed]
The cosmic background is 4K. Where are the other photons? A 4K photon produced at the big bang is detected by our detector. Time stops for the photon and hence we are seeing the big bang. Shouldn't we ...
- 43
0
votes
1
answer
48
views
Energy lost by CMB since recombination from energy density and scale factor
To calculate the energy lost by CMB since recombination from energy density and scale factor, one should compute today's energy density of CMB * a^-1 or today's energy density of CMB * a^1 with a ...
- 476
3
votes
3
answers
700
views
What's so "quantum" about quantum fluctuations in the CMB?
I've heard that fluctuations in the CMB provide support for inflationary theory, as they are thought to be amplified quantum fluctuations of the inflaton field. My question is, what is so "...
- 373
-1
votes
1
answer
104
views
If Inflation never happened before the CMB, and the present expansion were projected backwards, how old would the Universe be since the Big Bang?
The Cosmic Microwave Background Radiation is the oldest thing we can directly observe. To explain the near uniformity of temperature of the CMBR and the flatness of space, Cosmic Inflation was ...
- 11
2
votes
1
answer
98
views
What do WMAP CMB Temperature map values represent exactly?
I understand that Cosmic Microwave Background Radiation Map provided by WMAP survey in HEALPix pixelization format is nothing but an array of temperatures associated with the cmb radiation coming from ...
