All Questions
10
questions
-2
votes
1
answer
213
views
Shouldn't the Friedmann equation take into account the massive extra distance traveled during the time for gravity to travel across the universe? [closed]
I’ve got a question that has been bothering me for the past few years that of the few sources that are only somewhat related to this, none of them say anything about this should be wrong so I can’t ...
- 21
6
votes
1
answer
135
views
Classifying 3C273 as a quasi-stellar object
I am currently reading A Brief History of Time and Chapter 6 about black holes.
Now, here it says
He found it too large to be caused by a gravitational field: if it had
been a gravitational redshift, ...
- 191
10
votes
2
answers
2k
views
Can the gravitational redshift of our sun be measured?
How much of a wavelength change does our sun’s gravity cause in the light it emits? I imagine this could be measured by the shift in its spectral lines. And by extension, does the earth’s ...
- 521
1
vote
1
answer
82
views
Question about redshift and effective gravity at the rotating neutron star surface
For a rapidly rotating neutron star, if consider the star as a sphere, redshift at the equator surface will be larger than at the pole. But if consider the star as an obsolate sphereiod (the ellipsoid ...
- 339
2
votes
2
answers
68
views
Is light emitted from a heavier body more redshifted than light from a lighter body?
Is light emitted outwards from, say, a region very close to a black hole more shifted than light with the same wavelength that began next to a less massive object?
- 823
4
votes
2
answers
3k
views
Gravitational red shift vs Doppler redshift: Is the universe really expanding?
Is it possible that the redshift observed by Edwin Hubble is really from a gravitational redshift and the universe isn't expanding as he has predicted?
What I think I know thus far is this:
Redshift ...
- 479
2
votes
1
answer
95
views
Is there a radius inside of which objects are (doppler) blue shifted?
The Andromeda galaxy is about 600,000 light years away and is doppler blue-shifted. Are there objects closer to us than Andromeda which are red-shifted? Are there objects farther than Andromeda that ...
- 121
7
votes
1
answer
335
views
Dark Energy Expansion
The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...
- 294
8
votes
2
answers
492
views
Why do we have the cosmological constant?
Since the cosmological constant is not required to explain that the universe seem to be expanding, why do we have it?
What other factors cause us to have that constant?
Background:
Without the ...
- 1,197
9
votes
1
answer
1k
views
How does gravity affect the wavelength of light?
If, hypothetically, me and my rocket powered flashlight were falling straight toward the center of a black hole. The flashlight is a few kilometers behind me in our travels toward the center of the ...
- 1,197