All Questions
60
questions
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86
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Is the Planck mass the "lower limit" for gravity?
The Planck units are often treated as being the "lower limits" to things: the Planck length for length, the Planck time for time, etc.
But the Planck mass, which is about $2.2\times10^{-5}$ ...
- 413
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 ...
- 413
-1
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3
answers
107
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Suppose a shell of a sphere formed by matter and with large radius, start afterwards to diminish the radius, give $E=mc^2$ the system stops
Thinking in classical mechanics terms but with the knowledge that $E=mc^2$ let's make the below thought:
Suppose you have a shell of a sphere formed by a mass uniformly distributed over the surface of ...
- 125
1
vote
4
answers
201
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Since light has inertia and experiences gravity, what does it mean for photons to be massless?
I've been trying for a long time to figure out what the heck mass even IS. In introductory physics and chemistry, students are told that massive objects are those that are made of matter and take up ...
- 2,327
0
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0
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36
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Gravity Violation of conservation of energy? [duplicate]
If a satellite gains gravitational energy when shot into space but all matter becomes light, what happens to its potential gravitational energy? When matter turns into light, it loses mass, affecting ...
2
votes
1
answer
222
views
Stress-energy-momentum tensor and potential energy
The stress-energy-momentum tensor in General Relativity includes a mass density terms, which is related to energy via $E=mc^2$. How does potential energy figure into this, since potential energy is ...
0
votes
0
answers
53
views
Can we change coordinates to the Schwarzschild metric and interpret the result as the field corresponding to different matter distributions?
The Schwarzschild metric is the simplest solution to Einstein field equations. It describes the gravitational field around a static object with spherical symmetry.
Perhaps a change in space ...
- 391
7
votes
2
answers
1k
views
If I suddenly store a lot of energy in a small space, this induces spacetime curvature. Does that create gravitational potential energy?
Let us presume that I have a capacitor and suddenly charge it. This induces a (miniscule) spacetime curvature. Nearby objects would experience a gravitational attraction and by extension would have ...
9
votes
3
answers
2k
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Does a double star system have more mass than its constituents?
According to Einstein, energy is equal to mass. Consider a planet that is in gravitational attraction to two stars. Normally I would say that the gravitational attraction is proportional to the masses ...
- 793
0
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3
answers
490
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Do massless particles have gravity? [duplicate]
What I know so far is that according to the general theory of relativity, gravity is not the force of attraction between two objects; instead, it is a consequence of the curvature of space-time. And ...
- 293
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votes
2
answers
289
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What is the real world interpretation of $E = mc^2$?
Why I am asking this question:
There appears to be a logical contradiction in the notion that gravity is "one thing"
mass moves in gravity much differently than light (a massless particle)
...
- 361
1
vote
1
answer
187
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In general relativity, assuming a spherical uniform mass distribution, what is the total energy value of the gravitational field inside the sphere?
In Newtonian mechanics, assuming a spherical uniform mass distribution, the total gravitational potential energy (gravitational self-energy) inside the sphere is
$$U_{gs}=-\frac35\frac{GM^2}R.$$
In ...
- 117
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 ...
3
votes
6
answers
663
views
Does a high-speed particle weigh more?
I tried looking in vain (at the LHC site and elsewhere) on the net and could not find out if a $7$-TeV proton weighs more than its rest mass.
Can anyone explain and point me towards experiments that ...
- 691
2
votes
1
answer
113
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Inertial vs gravitational mass at different temperatures
So, I know more energetic objects have more mass according to Einstein. I'm aware that this has been verified by weighing an object at different temperatures where the object weighed more at higher ...
- 319