All Questions
46
questions
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35
views
Energy of the gravitational field within a sphere of radius $R$ in the Schwarzschild metric
The Landau-Lifshitz energy-momentum pseudotensor $t^{μν}$ is defined by
$$16πt^{μν}
= -2G^{μν} - g^{-1} \left[ -g \left( g^{μν}g^{αβ} - g^{μα}g^{νβ} \right) \right]_{,αβ}$$
where $g=\text{det}[g^{μν}]...
- 366
3
votes
0
answers
52
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 $R_o$. ...
- 366
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 ...
- 117
0
votes
2
answers
81
views
Radiative Energy in a Gravity Well
It has been hypothesized that in the very far future, most or all matter will have decayed into radiation.
A planet like Earth is composed of matter, forming a gravity well based upon the total energy ...
- 9,500
2
votes
1
answer
118
views
Does the energy-momentum tensor inside Einstein's field equation include gravitational stress-energy?
The Einstein field equations
$$
R_{\mu\nu} - \dfrac{1}{2}Rg_{\mu\nu} = \kappa T_{\mu\nu}
$$
relate the space-time curvature $R_{\mu\nu}$ to the stress-energy $T_{\mu\nu}$ present in the system. I ...
- 391
9
votes
2
answers
288
views
Is there partial gravitational shielding?
Gravitational waves carry energy. The sticky bead argument shows that this energy can be extracted: https://en.wikipedia.org/wiki/Sticky_bead_argument
But Lee Smolin points out that
"In ...
- 476
0
votes
1
answer
61
views
Is the law of the lever equation the same in classical physics as in relativity ? Why?
In classical mechanics the balancing lever equation (law of the lever) is
$$M_1 a = M_2 b$$
Where $M_1$ is the mass at a distance $a$ from the fulcrum and $M_2$ is the mass at a distance $b$ from the ...
- 926
-1
votes
1
answer
82
views
Does the indeterminacy (uncertainty) of energy and momentum used to calculate mass cause indeterminacy of gravity?
General relativity is considered deterministic. However, the "mass" of an object as defined by modern physics is a calculation based on using measurements of the object's energy and momentum....
- 541
0
votes
0
answers
32
views
What energy in GR? [duplicate]
What is energy in GR. My professor has mentioned several times that GR introduces a manifold in place of Euclidean space. He goes on to say that on a manifold it is not possible to add vectors anymore ...
- 69
1
vote
1
answer
85
views
Does the intrinsic energy of an object vary, if measured at different heights in a gravity field?
The gravitational redshift has different interpretations. Several quantities vary with height (or seem to), by the same equation - time, energy, mass. I wondered if measurements can shed some light on ...
- 85
15
votes
2
answers
3k
views
Has it been experimentally proven that energy causes gravity?
I know that under general relativity energy and mass are equivalent under $E=mc^2$. But has it been experimentally proven that energy alone causes gravity, for example, does a nuclear reaction ...
- 4,783
4
votes
1
answer
277
views
Why does Kip Thorne claim spacetime warping itself contains energy?
Kip Thorne, in this public lecture, says
that a black hole is kept together by the energy of the warping of space.
Quote around 8:00-8:30 :
"in this case, the energy [which keeps a black hole ...
- 53
4
votes
2
answers
492
views
What if I left Earth then turned it into light?
So I asked a question about what would happen in regards to gravitational potential if I left earth and then vaporized it. The answer I got was that the Mass would still remain the same and even if ...
4
votes
1
answer
234
views
Does negative energy in Casimir effect cause repulsive gravity?
In the Casimir effect a negative vacuum energy exists between two plates. Does this cause repulsive gravity?
Can this have consequences for the situation near the big bang, in relation to inflation?
4
votes
1
answer
344
views
Is a vacuum-energy smaller than zero forbidden? Why?
Einstein's Field Equations allow for the derivation of Newton's law and this, together with the velocity profile of the stars within the galaxies and the galaxies within the galaxy clusters, leads to ...
- 255