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.
5,331
questions
2
votes
3
answers
1k
views
Is gravity a tensor?
All other fundamental forces are mediated by vector bosons. The Higgs boson is a scalar boson & the interaction it mediates isn't called as a force. A force is a vector in the usual description. ...
0
votes
1
answer
42
views
Confused about Weinberg's result of gravitational time dilation
I am reading Weinberg's Gravitation and Cosmology. In section 3.5, the author got a result$$\frac{dt}{\Delta t}=(-g_{00})^{-1/2}\tag{3.5.2}.$$Here $dt$ is the time interval of a stationary observer in ...
1
vote
0
answers
32
views
Does gravity accelerate you towards the geodesic of light between you and the mass?
If there's a planet far away, you will accelerate straight towards it due to gravity. If you place a Schwarzschild black hole right in the middle between you and the planet (the distance between the ...
2
votes
0
answers
80
views
Gravitational halos made of neutrinos...?
I have been recently interested in how halos made of standard model particles could be formed and behave.
After asking some questions in this site, I was told about how neutrinos could form such halos....
3
votes
0
answers
42
views
Negative (absolute - not potential) energy of the gravitational field; how to generalize to GR?
Alan Guth gives a thought experiment to show that a gravitational field has negative energy. (See the picture below.) Consider a thin spherical shell of elastic, compressible matter, of radius $R_o$. ...
13
votes
3
answers
3k
views
Why does angular momentum shorten the Schwarzschild Radius of a black hole?
Angular momentum causes the event horizon of a black hole to recede. At maximum angular momentum, $J=GM^2/c$, the Schwarzschild radius is half of what it would be if the black hole wasn't spinning.
...
4
votes
0
answers
91
views
Lorentz force error in the present 2024 version of the gravitoelectromagnetism Wikipedia page? [closed]
I noticed that the Gravitoelectromagnetism (GEM) Wikipedia page has been edited recently. The factor of 4 in the GEM Lorentz force equation is now missing. But the GEM field equations are identical to ...
0
votes
1
answer
97
views
How to derive the surface gravity in terms of redshift factor in static spacetime?
I am following Carroll's book "Spacetime and Geometry" p. 245-247. I have the following expression for the surface gravity of a Killing horizon:
$$\kappa^2=-\frac{1}{2}(\nabla_{\mu}K_{\nu})(\...
0
votes
1
answer
435
views
Mean potential energy per particle of Ideal gas in uniform gravitational field (high temp. limit)
I'm trying to show that for an ideal gas in a uniform gravitational field $\vec{g} = (0, 0, -g)$, confined to a box of height $L$ and base area $A$, the mean potential energy per particle is
$$\langle ...
7
votes
4
answers
963
views
Do you always experience the gravitational influence of other mass as you see them in your frame?
You see a galaxy far away. That galaxy is attracting you with a certain amount of gravity. I'm wondering if the gravity influence of the galaxy on you, as measured by you, always ends up being what ...
-2
votes
0
answers
32
views
What is the energy density of gravitational fields around neutron stars? [closed]
The field strength of gravitational fields around neutron stars is extremely high. This would lead to an extreme negative value for the energy density. But if an absolute negative energy density is ...
2
votes
1
answer
67
views
How to properly combine kinetic and gravitational time dilation effect?
I developed a time dilation calculator that includes both kinetic (Lorentz Factor) and gravitational (Schwarzschild Metric Formula) factors to assess the time difference between Earth and satellites. ...
3
votes
2
answers
84
views
Tug of war between observers in frames with different rate of time
You have a very dense hollow sphere of matter. Observer A is inside the sphere inside a rocket. Observer B is in an identical rocket outside the sphere where the ring's gravity is negligible. They are ...
1
vote
3
answers
71
views
How much time does it take for an object to fall from space? [closed]
Let's say there's an object of mass $m$ in space, $h$ meters away from the surface of the Earth. $h$ is large enough that $g$ cannot be assumed to be constant. The acceleration varies according to ...
7
votes
7
answers
11k
views
Does time dilation cause gravity as explained in this video?
Watch it around 2:00 minutes. https://youtu.be/gcvq1DAM-DE
Do objects move closer to Earth because they experience time at different rates, really? Does it make sense? The video also represents the ...