Questions tagged [gravity]
Gravity is an attractive force that affects and is affected by all mass and - in general relativity - energy, pressure, and stress. Prefer newtonian-gravity or general-relativity if sensible.
5,338
questions
0
votes
2
answers
56
views
Gravitational Constant with ENM Units?
To give some context, there's a conspiracy 'theory' that I saw called Electric Universe that says that gravity is not a fundamental force and instead is a "incoherent dielectric acceleration"...
0
votes
1
answer
85
views
Questions about speed of gravity [duplicate]
If gravity "travels" at $c$, and the sun is travelling "forward", does it mean the planets are actually orbiting various points "behind" the center of the sun? Does it ...
2
votes
0
answers
69
views
Gravitational time dilation near the Earth [closed]
I recently read the statement that near the Earth, in the Newtonian weak gravitational field, gravity is 99.9999% mainly due to "curvature of time" (ie gravitational time dilation), and only ...
2
votes
1
answer
60
views
Acceleration at peak of a gravitational wave
The amplitude of the strongest gravitational wave signal detected by LIGO sofar can maybe be expressed as an acceleration? If so, what would the numerical value be (in m/s^2)? I would like to compare ...
1
vote
0
answers
48
views
How can you use gravity while trying to model gravity? [duplicate]
So consider the usual pop-science spacetime model, a bowling ball on a trampoline. Apparently, the ball should sink into the trampoline, causing a dip in the fabric which causes nearby objects to fall ...
3
votes
2
answers
84
views
How is it that energy of matter yields gravity if the amount of energy in a system is frame dependent while the force caused by gravity is not?
I've been told that the gravitational field arises due to the energy density terms in the stress-energy tensor of matter and therefore that all energy of matter exerts a gravitational field effect, ...
3
votes
0
answers
80
views
Why does the wavelength of gravitational waves increase with larger energy?
Gravitational and electromagnetic waves are quite similar, as both are fundamental force waves that travel at the speed of light and have no limit to their range, but when it comes to electromagnetism,...
1
vote
1
answer
122
views
Which of Kepler's laws would remain true if the force of gravity were proportional to the product of squares of each masses?
I was asked this question recently on which of the Kepler's Three law would remain if we changed the force of gravitation to be proportional to the product of squares of each masses instead of just ...
1
vote
0
answers
42
views
Einstein's equation of gravitation field [duplicate]
I'm looking for the reason why there is the number eight $8$ at the r.h.s. of EI:
$$R_{\mu\nu}-\frac{1}{2}Rg_{\mu\nu}=\frac{8\pi G}{c^2}T_{\mu\nu}.$$
My attempt was to take the limit of this equation ...
2
votes
0
answers
75
views
Variational description of modified Einstein equations
Let us suppose that we have an Einstein equation of the form
$$ R_{(\mu \nu)}-\frac{1}{2} g_{\mu \nu} R=8\pi T_{\mu \nu},$$
where $R$ is an affine connection, which differs from the Levi-Civita ...
2
votes
1
answer
71
views
On the existence of Gravitational energy in GR [duplicate]
I was reading this paper that puts forward the argument that Gravitational energy in GR is unnecessary and doesn't exist and that got me wondering if this is a fringe theory or what exactly is the ...
0
votes
1
answer
128
views
Do we really know the universal gravitational constant?
We've all heard $$F_g=\frac{gm_1m_2}{r^2}.$$ However, since I took physics, we've discovered "dark energy," which if I have any concept of the current thinking is caused by space being ...
1
vote
1
answer
104
views
Does dark matter have mass?
When trying to understand what dark matter is, it is helpful to know that some properties of it can already be derived from various observations, such as, it only interacting via gravity and no other ...
-6
votes
1
answer
52
views
Why sun revolve around the sun ? Why cant it just rotate ? ( gravitas attraction force makes it revolve , how?) [closed]
Why the revolution ?
How General relativity theory explains it
2
votes
0
answers
43
views
Polarization tensor of graviton in $d$ dimensions
Take the following tensor, that is the sum over the two polarizations of a gravitational wave in 3 spatial dimensions:
$$E_{ijkl}(\vec{k})\equiv\sum_{\lambda = +,\times} \epsilon^\lambda_{ij}(\vec{k})\...