All Questions
Tagged with redshift hubble-constant
14
questions
7
votes
3
answers
2k
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How do we work out the light travel time on a cosmic scale?
I just read this article in the AUSTRALIAN SKY & TELESCOPE magazine, Nov/Dec 2022 Issue 140, on P16, KEEP YOUR DISTANCE: How far away are the objects we see in the universe? And on P23:
"And ...
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18
votes
11
answers
5k
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Is there physical evidence to distinguish between the expansion of space and an anthropocentric universe?
When we look in all directions, we see distant objects red-shifted, with the size of the red-shift correlated with the distance from us.
As I understand it, the consensus among cosmologists is that ...
- 341
9
votes
1
answer
279
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How distant were the furthest currently-observable cosmic events when their currently-observed radiation was emitted?
(Edited for clarity. Thanks to James K and Connor Garcia.)
This question about the most distant, observable cosmic objects made me wonder if we know the distance that was between us and them at the ...
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6
votes
2
answers
187
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How does the hypothesis of the "inconstant Hubble constant" solve the current crisis in cosmology?
It was published in a paper more or less like two months ago. I'd like to know also if more accurate measurements are necessary to close the gap between the model of the universe and the data reported....
0
votes
2
answers
90
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is there a way to determine a distant galaxy’s speed relative to the Hubble Flow by measuring time dilation effects between there and this galaxy?
As I understand it there is a preferred frame of reference based on the velocity for the CMB and our galaxy is moving in relation to it (at about 600 km/s). I think this is how the Hubble Flow is ...
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0
votes
1
answer
75
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Which redshift is used to determine the Hubbleconstant?
I think they measure cosmological redshift to use in the Law of Hubble-Lemaître together with the distance to calculate $H_0$. Is this correct, or do they use Doppler shift (too)?
$H_0$ indicates how ...
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2
votes
2
answers
209
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Why does the Supernova 2006cm give a very different value for the Hubble constant? Why doesn't it increase error bars for the Hubble constant?
The Supernova 2006cm has a redshift of 0.0153 which translates into a recession speed of 4600 km/s.
It has a distance modulus of 34.71 which translates into a luminosity distance of 87 Mpc.
This ...
- 1,002
2
votes
1
answer
234
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At what cosmological redshift $z$, does the recession speed equal the speed of light? How is it calculated?
At what cosmological redshift $z$, does the recession speed equal the speed of light?
What equations are used to calculate this number (since at large redshifts, $z=v/c$ won't apply)?
[The ...
- 1,002
0
votes
1
answer
75
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Where a database of different z values of redshift can be found?
I was working on reshift details for various galaxies but do not know any database to find the z values given to redshift galaxies. Can anyone help?
6
votes
1
answer
889
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Where can I find a database of galactic spectra?
I was wondering where spectra of galaxies at various redshifts are to be found. I'm looking for ones that can be used to find the recessional velocity of the galaxy and eventually the Hubble Constant. ...
3
votes
1
answer
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Question from Introduction to Modern Cosmology by Andrew Liddle
The exact question goes like this:
In the real Universe the expansion is not completely uniform. Rather, galaxies exhibit
some random motion relative to the overall Hubble expansion, known as their
...
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10
votes
2
answers
2k
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Does the accelerating expansion of the Universe contradict Hubble's law?
Hubble's law gives a linear relationship between the distance to a galaxy and it's recessional speed.
Observations of distant type 1a supernovae showed that their red shift (and therefore their ...
- 215
0
votes
1
answer
1k
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Approximating density of hydrogen in [observable] universe
Let universe be completely made from hydrogen. And also we have redshift $z= 6$. with Hubble constant $H_{0} = 2.1941747572815535\times 10^{-18}\:\mathrm{s}^{-1}$. We also know that density of the ...
- 483
1
vote
1
answer
491
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Question about Hubble parameter (Hubble constant) and measuring it
I see this question in "An introduction to modern cosmology - Andrew Liddle - Wiley Publication":
In the real Universe the expansion is not completely uniform. Rather,
galaxies exhibit some ...
- 483