All Questions
40
questions
0
votes
0
answers
100
views
Movement of galaxies vs expansion of space
I can readily accept the theory that the universe is expanding as a mathematical model to explain the fact that all galaxies are moving away from each other, but I have difficulty understanding ...
- 1
2
votes
5
answers
1k
views
Why is it that the further a galaxy is, the greater is its recessional velocity?
The exam question is:
Explain how red-shift provides evidence for the Big Bang theory.
One of the points in the answer is:
the further away the galaxy is, the greater is their recessional speed
...
- 21
1
vote
1
answer
54
views
What is the rough distribution for number of galaxies with a given mass in the observable universe?
Is there a rough formula for the fraction of galaxies in the observable universe with masses between M and M + dM? Or perhaps a graph that displays the same information? I've looked online but can't ...
- 419
1
vote
1
answer
34
views
Seyfert Galaxies: How does this statistical deduction about the age of their nucleus make sense?
As per this book, An Introduction to Active Galactic Nuclei by Bradley Peterson:
The nuclear emission must last more than $10^8$ years, because Seyfert galaxies constitute about 1 in 100 spiral ...
- 11
1
vote
0
answers
20
views
How long would take for other galaxies to be unobservable due to Cosmic Expansion?
I heard that if Universal Expansion continues at some point galaxies will be so separated that a future civilization would have no way to know there are other galaxies, for them the Galaxy they live ...
- 111
-1
votes
1
answer
40
views
The centre of what we can now see in the universe
If the JWST has just discovered the furthest away galaxies in one place we can now triangulate to where the centre of what we can see
This is observable and appears not symmetric with everything ...
2
votes
3
answers
662
views
Why is the ratio of dark matter to normal matter larger in galaxies than the cosmic average?
There seems to be a discrepancy between the ratio of dark matter to normal matter in the Universe (about 5 to 1 according to $\Lambda$-CDM) and the ratio of the average dark matter halo mass to the ...
- 185
0
votes
3
answers
769
views
Why do they say universe will become cold with expansion?
The Universe is expanding and they say it will eventually become cold, and new star formation will stop.
But galaxies are only moving away from each other, and each galaxy itself stays intact and the ...
- 283
6
votes
1
answer
448
views
Why are the most distant galaxies "only" around 13 billion light years away?
According to Wikipedia's List of the most distant astronomical objects, the most distant galaxy (GN-z11) is estimated to be around 13.39 billion light years away from earth.
However, the observable ...
- 3,778
0
votes
3
answers
176
views
Why is the Andromeda galaxy coming closer to Milky way?
If both these galaxies are on collision path because of their gravity but how could that be?
They are 2.5 million light-years apart now but I imagine they are still n collision path for a long time ...
- 283
0
votes
0
answers
15
views
Galaxy is 8 times closer 13 billion years ago? [duplicate]
Based on below,
How can I calculate the distance of a point from Earth now vs 13 billion years ago? The excerpt below claims it is 8 times further now. Can someone provide relevant equations ?
I ...
- 11
1
vote
0
answers
46
views
Calculate distance of galaxy 13 billion years ago [duplicate]
How can I calculate the distance of a point from Earth now vs 13 billion years ago? The excerpt below claims it is 8 times further now. Can someone provide relevant equations ?
- 11
1
vote
0
answers
51
views
What would happen if our galaxy and an identical anti-matter galaxy annihilated each other?
What would happen if every bit of matter in our galaxy annihilated with an anti-matter equivalent at the same time? Such as that stars completely annihilated with identical antimatter stars, planets ...
12
votes
2
answers
2k
views
Why are galaxies so far apart?
With the Big Bang, one would expect the distribution of mass to be somewhat uniform, but we have galaxies that have billions of stars and there are huge distances between galaxies.
Why is there is so ...
- 283
5
votes
2
answers
181
views
Can one galaxy have a higher dark matter ratio than another?
Dark matter do not interact with ordinary matter and light, it has mass and is affected by gravity. If the distribution of dark matter and ordinary matter is evenly spread at the early universe then I ...
- 13k