All Questions
45
questions
1
vote
1
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66
views
Would "gravity" and the "law of gravity" have a meaning in a universe without matter?
I was discussing the fact that if there was no matter in the universe, just vacuum and radiation, can we say that anything called gravity wouldn't exist?
In that universe, the Friedman equations ...
- 93
0
votes
1
answer
464
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Solving the Friedmann Equation for a specific universe
Suppose instead of the cosmological constant there is a quantum field with equation state parameter $w = -1/2$. Assume also it is a flat universe with only this quantum field ($Q$) and with non ...
- 21
6
votes
4
answers
598
views
Which one is more fundamental in nature: matter or radiation?
I am following a geometric perspective on abelian gauge theory as done in the lecture notes by Timo Weigand, chapter 6, pp 165-167, here:
http://www.thphys.uni-heidelberg.de/~weigand/QFT1-13-14/...
user56963
12
votes
2
answers
2k
views
What is the physics definition of space?
When astronomers, physicists say that space is expanding, does the definition of space include matter, energy and the particles within?
Or is space an empty 'stage' in which all of the above exist?
...
- 11.7k
2
votes
1
answer
488
views
Is the expansion of space universal or local?; does matter impede the expansion of space?
Michael Strauss in his recent book "Welcome to the Universe" with authors Tyson & Gott describes that space is NOT expanding within galaxies but rather between galaxies. So then the expansion is ...
- 11.7k
0
votes
2
answers
259
views
Don't rulers expand at the same rate as the universe they measure? [duplicate]
If you placed a giant ruler between the sun and our nearest star for example, wouldn't the divisions on the ruler expand at the same rate as the universe - therefore maintaining a constant distance? ...
- 7
0
votes
1
answer
59
views
Space is expanding but the space around me isn't [duplicate]
Everyone says space is expanding and distances between galaxies growing. But space isn't limited to outside of the earth. Space is everywhere on earth and around me. However I don't notice any ...
- 101
1
vote
1
answer
652
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Why does dark energy seem to push things apart? [duplicate]
Ordinary matter acts to slow down the expansion of the universe. That makes intuitive sense, because the matter is exerting a gravitational force, acting to pull things together.
Moreover, dark ...
3
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3
answers
2k
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Does our universe have an even distribution of matter in every direction
It occurred to me that it does since gravity in the space I exist appears to be uniform Ie there is no net movement of objects I observe in a particular direction. I maybe speaking from classical ...
- 101
1
vote
1
answer
332
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What is the identity of Dark Matter?
What is the identity of dark matter?
Is it a particle?
Is it the lightest superpartner (LSP)?
Do the phenomena attributed to dark matter point not to some form of matter but actually to an ...
- 659
3
votes
1
answer
567
views
What is the difference between matter & spacetime? [duplicate]
If the universe is expanding why doesn't the matter in it expand proportionally making it seem as if the universe is static? Alternatively, as spacetime expands why does it not just slide past matter ...
23
votes
1
answer
9k
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How do we know Dark Matter is non-baryonic? [duplicate]
It seems widely stated, but not thoroughly explained, that Dark Matter is not normal matter as we understand it. Wikipedia states "Consistency with other observations indicates that the vast majority ...
- 3,241
5
votes
3
answers
2k
views
Creation of matter in the Big Bang
I appreciate your patience to my neophyte question. I am working on my dissertation in philosophy (which has nothing or little to do with physics) about the "problem of naming." Briefly what ...
- 59
194
votes
15
answers
31k
views
Why does space expansion not expand matter?
I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for.
So here is my question: One often hears talk of space ...
- 2,055
50
votes
8
answers
7k
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Why isn't dark matter just ordinary matter?
There's more gravitational force in our galaxy (and others) than can be explained by counting stars made of ordinary matter. So why not lots of dark planetary systems (i.e., without stars) made of ...
- 603