All Questions
12
questions
6
votes
1
answer
354
views
How would the universe look like without matter?
I was wondering how the universe would look like if it would have been perfectly symmetrical in terms of matter and antimatter. If I understand correctly, there would be no "particle" but ...
- 357
2
votes
1
answer
93
views
Total number of particles in the universe (according to Planck Surveyor measures, 2018)
Recently, Marco Ajello et al. (2018) has estimated the total number of photons in the whole observable universe as:
$$N_\gamma \approx 4\cdot 10^{84}.$$
On the other hand, the ratio of baryons to ...
- 1,640
0
votes
1
answer
41
views
How the universe is expanding? [duplicate]
If universe is expanding with the velocity of light then why the distance between earth and sun is constant? Also why the distance from one Galaxy to another remains constant? And so on...
0
votes
3
answers
40
views
Are the constituents of the known universe matter (including antimatter) and electromagnetic radiation?
Is it correct to say that the constituents of the known universe are matter (including antimatter) and electromagnetic radiation, leaving aside the comparatively hypothetical ‘dark’ entities? This is ...
- 135
2
votes
1
answer
81
views
Amount of matter in two infinite universes [closed]
I don't know exactly where to find any other information on this question so I thought I would ask here. If there were two infinitely large universes one where 20% of the space in the universe was ...
- 21
0
votes
1
answer
104
views
Are there other theories than gravitational attraction taken into account as a reason for the extreme accumulation of matter in the universe?
This question is about how small the interstellar density is (less than 1 atom per cubic centimeter).
But although the interstellar density is very low, matter tends to extremely aggregate in certain ...
- 282
3
votes
3
answers
204
views
Expansion of space or contracting of matter? [duplicate]
Can the expansion of the Universe effect be explained by contraction of the overall matter instead? That is, all material objects are in fact contracting, due to what the universal space seems (and ...
- 31
2
votes
0
answers
46
views
Is every object in the universe really expanding? Even small scale objects like humans? [duplicate]
So I was asked a question by someone that "if everything in the universe is expanding, then the lens we use to look at stellar objects is expanding as well, meaning we shouldn't be able to tell the ...
- 121
0
votes
1
answer
614
views
As space expands does the density of matter remain same or increase? [duplicate]
I learned that space is always expanding. Even between sun and earth, it's just gravity is stronger.
Imagine space as graph paper and there is a square object that fills it.
Space expands, 1x1 cell ...
- 2,645
4
votes
2
answers
492
views
Intuition for why matter dominated expansion is faster than radiation domination?
In a matter dominated universe $a_{\rm mat.}(t)\sim t^{2/3}$, while in a radiation dominated universe, $a(t)_{\rm rad.}\sim t^{1/2}$. Therefore, a matter dominated universe is expanding more quickly, ...
- 3,492
1
vote
1
answer
756
views
How does mass affect the expansion of space?
I'm a layman and I'm curious to understand how mass affects the expansion of space and whether the expansion of space is uniform everywhere in the universe.
From looking at redshifts it seems we have ...
- 11
0
votes
1
answer
464
views
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