All Questions
5
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98
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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, ...
1
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3
answers
130
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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
4
votes
1
answer
178
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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
10
votes
2
answers
973
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Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
Due to the mass-energy equivalence, both matter and EM radiation bend spacetime, and both are capable of forming singularities (black hole, white hole/kugelblitz). In light of this, why do photons ...
user40753
3
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2
answers
436
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Do electromagnetic fields gravitate?
It's well known that electromagnetic fields contains energy but do they gravitate?
When we talk about the composition of the universe it's now accepted that the 74% is dark energy, the 22% is dark ...
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