All Questions
16
questions
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125
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What if gravitation was the only force? [closed]
This is a follow up of Interactions within constituents of dark matter .
I wonder about dark matter, and, naturally, compare it with our observable world.
If gravitation would be the only force acting ...
- 1,028
1
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0
answers
44
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Effects of dark energy in the kinetic energy of a body?
If I launch a ball into the sky it would reach a distance after which it would return into the ground transforming the potential energy into kinetic energy as it hits the ground
This is similar to ...
- 2,462
0
votes
2
answers
44
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Age of the universe due to expansion
"If gravity working on matter is the only force at work on large scales, then the attactive force of gravity will act to slow the expansion. In this case, the universe was expanding more rapidly ...
2
votes
1
answer
71
views
Can empty space 'press' galaxies?
If gravity slows the effects of time, then empty space will see greater expansion than space inhabited by massive objects. So the space within a galaxy will be expanding more slowly than the space ...
9
votes
1
answer
356
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Why are galaxies much closer spaced (relative to their size) than stars?
I have read this question:
So the average spacing is somewhere in the range of 10 - 100 times the size of the biggest galaxies. The peas I had for lunch today were (at a guess - I didn't measure them!...
- 29k
5
votes
2
answers
387
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Gravitational binding energy as alternative to dark matter?
Pondering this question: Casimir effect and negative mass
and, in particular, the response of John Rennie "as the mass of any bound system is slightly less than the mass of its parts" I ...
- 113
1
vote
1
answer
55
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Galaxy Superclusters
Okay quick question... why is it that when galaxies group together in superclusters they form a sort of branch-like shape? I personally would think they’d all just group together in some sphere or ...
- 31
1
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1
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225
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How to calculate the strength ("space force") of dark matter within galaxies?
Let's first have a look at the observed speed within galaxies (source):
On the left side we can see the speed of celestial bodies within galaxies derived by gravity only (gravity is usually created ...
- 282
1
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1
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128
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At which point in the universe history will inflation prevent galaxies feeding from intergalactic matter?
It's my understanding that galaxies formed from accretion of intergalactic matter around supermassive black holes. As the universe expands the amount of matter entering a galaxy decreases, until at ...
2
votes
0
answers
140
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How does dark matter distribution help to identify it's composition
A question regarding this recently released data,
and the paper https://arxiv.org/abs/1708.01538 that details it's distribution:
Abstract:
We use 26 million galaxies from the Dark Energy Survey (...
user163104
3
votes
3
answers
784
views
Is there 'gravitational force of repulsion'?
According to hubble's law of universal expansion, the velocity of a galaxy moving away from ours is directly proportional to the distance between the two. Now velocity is increasing in direction away ...
- 706
6
votes
1
answer
171
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Do galaxies have a halo of neutrinos and cosmic microwave background?
If virial arguments as in "How can dark matter collapse without collisions or radiation?" allow concluding that dark matter could collapse to galactic halos purely gravitationally, then is this true ...
- 1,289
5
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3
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244
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Current constraints on Dark Matter self-interaction from galactic profiles
The self-interaction of dark matter may be small but it cannot be negligible if it is able to dissipate energy to relax into galactic clumps (necessary to explain galaxy rotation curves).
According ...
- 1,289
0
votes
0
answers
24
views
About the use of Newtonian Relations for the movement of stars in the Galaxy [duplicate]
From a General Relativity point of view Gravity is given as the result of spacetime curvature interacting with energy-mass density. To get to the Newtonian limit one needs to take
a) Non-relativistic ...
- 1,574
9
votes
1
answer
608
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Is it possible to determine whether distant galaxies are gravitationally bound
In a previous question, one issue was related to the potential energy
of cosmic structures. This raised in particular the question of
whether these structures are gravitationally bound.
If you ...
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