All Questions
39
questions
7
votes
3
answers
2k
views
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 ...
- 171
0
votes
1
answer
92
views
Does a cosmological redshift occur within our local group, of galaxies?
I know that it is not supposed to be expanding but space is space and it is expanding everywhere else outside it so why not inside it too, and gravity just holds everything back.
I suppose if it is, ...
- 171
2
votes
1
answer
134
views
Why are distant type Ia supernovae dimmer than expected?
Why are the (extremely) distant type Ia supernovae dimmer than expected?
Relative to what? Their cosmological red shift? Well, what else.
Please don't just say "Because the expansion is ...
- 171
18
votes
2
answers
3k
views
Could we (Earth, Humanity, Solar System) be falling into a black hole?
With the expansion of the universe, all objects far away from us appear to be moving away (ie: exhibit Redshift). With distance, this acceleration / redshift also seems to increase (~73,000 (m/s) / (...
- 297
1
vote
0
answers
87
views
If astronomers didn't know about redshift could we still determine the universe is expanding?
What other evidence is there for the expansion of the universe?
Would the equations of physics look wrong without it?
user51209
3
votes
3
answers
1k
views
Could the redshift of all incoming photons be explained by a massive ring of distant masses pulling the sources of the photons away?
ChatGPT and wikipedia have informed me that the primary evidence for the theory that the universe is expanding is the fact that photons that arrive to our planet from all directions are being ...
- 231
2
votes
1
answer
149
views
Can the expansion of the universe cool my beer?
So the expansion of the universe stretches the light traveling through the void, as demonstrated by the cosmic microwave background radiation. These photons are lower energy than when they are ...
3
votes
0
answers
69
views
How do we know universe is expanding and not light slowing down? [duplicate]
We tend to take some things for granted, for example the light of speed is constant, but what if it isn't? How can we know that light is not slowing down at great distances for example, or that light ...
- 31
2
votes
1
answer
693
views
Why is the CMB's redshift so high?
It is pretty well-established that the CMB was originally emitted around 380,000 years after the Big Bang, at a redshift of ~1100.
The most distant known object is HD1, the light from which was ...
- 284
5
votes
1
answer
320
views
How far away from us was Earendel star when it emitted the light that is just now reaching us?
From what I've read, the look back time is about 12.9 billion light years, and the current distance to the Earendel star is approximately 28 billion light years...
How close to us was it when it ...
- 5,307
18
votes
11
answers
5k
views
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
views
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 ...
- 175
6
votes
2
answers
187
views
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....
1
vote
1
answer
221
views
Intuitive explanation for why the Doppler effect (and red-shift) happens?
I was looking for an intuitive explanation as to why the Doppler effect happens. I haven't found any, but this is what I thought:
-Waves emitted travel at a constant speed
-The source emits a wave
-If ...
- 201
2
votes
0
answers
79
views
Definition of space - to cope with "space expansion"
I've searched quite a lot but found no satisfying definition, so please:
How do we actually define space when talking of "space expansion"? Isn't it just a metric, a dimension we measure, instead of ...
- 31