All Questions
5
questions
2
votes
1
answer
98
views
What exactly does $k\sigma$ mean in astrophysics and cosmology?
In statistics, $\sigma$ or $1\sigma$ is the standard deviation. For the normal distribution, approximately $68\%$ of the values lie within $1\sigma$ range, $95\%$ within $2\sigma$, and $99.7\%$ within ...
- 451
2
votes
0
answers
84
views
Would we know if the universe was rotating?
I was wondering what we would observe if the universe had a small rotation. My conclusion was that galaxies on the equatorial plane of the universe would be slightly more redshifted than galaxies than ...
- 373
1
vote
2
answers
177
views
Since the Hubble Constant changes over time (it's a variable parameter), why can't the conflicting values of 67.4 and 73 both be right?
Are the conflicting values from the 'early universe' (Planck) method and the 'late universe' (Distance ladder) method actually compatible? Since during the latter period of the universe 'dark energy' ...
- 5,307
1
vote
1
answer
102
views
What exactly is the estimated distance to a far-off object when they say '50 Mpc/h' or '50 Mpc h^-1'? Is it less than 50 Mpc? Do you ÷ by 67 or 74?
Several recent arxiv.org papers I read mention distances to very distant objects in Mpc (megaparsecs) divided by Hubble's 'constant'....
Does that mean we should divide the Mpc or Gpc (gigaparsecs) by ...
- 5,307
14
votes
1
answer
1k
views
How is the Hubble constant determined from gravitational waves?
We know there is a discrepancy between measurements of the Hubble constant, $H_0$. On one side there is the method of the Planck mission, where they use the CMB and the $\Lambda$CDM model to determine ...
- 402