All Questions
46
questions
3
votes
4
answers
3k
views
If everything in the universe doubled in size overnight, would it be noticeable?
By my understanding, if everything doubled in size, such as the Sun and the Earth, and because the space in between them (which is nothing) can't expand, would the gravities greatly change and the ...
- 147
10
votes
2
answers
1k
views
Dark Matter vs Modified Gravity
Why do cosmologists and astrophysicists assume that the reason for the higher velocities of outer stars in galaxies is due to matter at all? The name dark matter seems misleading. Couldn't gravity ...
- 168
4
votes
3
answers
685
views
Is it accurate that light loses energy in the absence of gravity and gains energy in its presence?
I just read an article about the supervoid they found and this is suggested. If so, then I am more and more fascinated with the ties between light and gravity.
Let me emphasize, every article that I ...
- 113
34
votes
6
answers
5k
views
Could gravity be an emergent property of nature?
Sorry if this question is naive. It is just a curiosity that I have.
Are there theoretical or experimental reasons why gravity should not be an emergent property of nature?
Assume a standard model ...
- 13.5k
22
votes
5
answers
28k
views
Stephen Hawking says universe can create itself from nothing, but how exactly?
Stephen Hawking says in his latest book The Grand Design that,
Because there is a law such as gravity, the universe can and will create itself from nothing.
Is it not circular logic? I mean, how ...
- 329
12
votes
1
answer
1k
views
Is there a distance from a gravitational source where the influence of gravity and dark energy are balanced out?
While gravity is a force that attracts
objects with mass, dark energy (or, alternatively, the accelerated expansion of the universe) is not.
However, I have found numerous articles, forums, questions ...
- 2,462
9
votes
5
answers
1k
views
Could the acceleration of universe expansion be caused by gravity itself?
Dark energy is suggested to be a repulsive force in the universe causing an accelerated expansion. If the amount of mass outside our observable universe is greater than inside (higher mass density), ...
- 91
3
votes
2
answers
436
views
Do electromagnetic fields gravitate?
It's well known that electromagnetic fields contains energy but do they gravitate?
When we talk about the composition of the universe it's now accepted that the 74% is dark energy, the 22% is dark ...
- 905
1
vote
0
answers
228
views
Is there a valid solution to Einstein's equations for this cosmological model?
The cosmological model below has been developed in order to explain the flatness problem.
At first it's from Newtonian considerations, then a solution of the Friedman equations is looked for
$$\left(\...
- 13.7k
1
vote
0
answers
96
views
Experimental Test for the cyclic $G_{earth}$ prediction of a Cosmological Model
Can anyone suggest a way to measure or rule out a tiny cyclic variation in the earth’s gravitational constant $G_{earth}$, predicted by an alternative cosmological model? It’s an annual cyclic ...
- 13.7k
12
votes
1
answer
2k
views
Gravitationally bound systems in an expanding universe
This isn't yet a complete question; rather, I'm looking for a qual-level question and answer describing a gravitationally bound system in an expanding universe. Since it's qual level, this needs a ...
- 3,888
7
votes
1
answer
511
views
Does zero point energy really contribute to the cosmological constant?
The zero point energy is usually supposed to contribute to the cosmological constant. And the mismatch between the small cosmological constant compared with the huge zero point energy is deemed as one ...
- 4,452
4
votes
1
answer
3k
views
If the Big Bang theory is true, what caused it to explode?
According to the Big Bang theory, all the matter in the universe was amassed together at one single point. If this was the case, why was it able to explode? The density of the mass would create a ...
- 83
3
votes
1
answer
796
views
What exactly is the cosmological constant? [duplicate]
I know that the cosmological constant was developed as an addition to the Einstein Field Equation as an anti-gravity force: $$R_{\mu \nu} - \frac{1}{2} R g_{\mu \nu} + \Lambda g_{\mu \nu} = \frac{8 \...
- 2,162
3
votes
2
answers
1k
views
How come that an Infinite universe will collapse under gravity?
In this PSE post the issue is about the stability of an infinite universe under Newtonian gravity.
Here I'will drop the Newtonian constraint because we know of the finite speed of interactions and I ...
- 2,657