All Questions
5
questions
-2
votes
1
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163
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Why is v lowercase and D uppercase in $v=H_0D$?
Why is v almost always written in lowercase and D in uppercase in $v=H_0D$?
OK, v is in lowercase, as usual, but then why is D in uppercase? What's so different/special about it?
In my physics school ...
- 171
1
vote
2
answers
1k
views
How can Hubble's original data show that the universe is expanding?
The diagram from Hubble's original data only goes from 0 to 2 Mpc (see here), and yet our Local Group is not supposed to be expanding and it is 1.5 Mpc in radius. How can the data show that the ...
- 171
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
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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