All Questions
100
questions
-2
votes
2
answers
71
views
Shouldn't there be a gravitational field without any mass in our 3d space? [closed]
Imagine there is a Neutron star Displaced a small distance from our accessible 3d slice in the direction transverse to that 3d slice. It will bend the space around it. It will also bend the space of ...
1
vote
4
answers
201
views
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
9
votes
3
answers
2k
views
Contradiction in negative mass interactions according to GR
I quote Sabine Hossenfelder:
Gravitation is a spin-2 interaction. It is straightforward to see that this means that like charges attract and unlike charges repel. The charge of gravity is the mass. ...
- 476
1
vote
1
answer
98
views
Inertial Mass = Gravitational Mass. Why? [duplicate]
Okay, so the inertial mass of an object is always equal to the gravitational mass of the object. Conceptually, however, they seem different. Then what makes them identical? Is it because they are ...
- 1,073
1
vote
0
answers
90
views
If positive mass distorts spacetime (spacetime gets curved toward the object) then would a theoretical negative mass make spacetime bulge out?
So lets assume for this question that negative mass exists then will a theoretical planet made of negative mass create an outward bulge in spacetime to create antigravity (repulsive). Also for this ...
0
votes
1
answer
353
views
Has this random youtube crackpot trying to disprove GR inadvertedly stumbled on a genuine prediction of it? [duplicate]
I'm an Astrophysics major. I was watching strange fringe physics crackpots on Youtube to make fun of them, because I'm an acollierastro, planarwalk kinda gal. I came across this guy who thinks Black ...
0
votes
2
answers
119
views
Since when did inertial mass and gravitional mass became equal?
If we think about inertial mass and gravitational mass as independent concepts and develop physics then we would know after a while they are only propotional (by precision we have by now). but it seem ...
- 1,409
1
vote
3
answers
221
views
Is there a frequency limit for the pendulum near a black hole, and is this related to photons and the UV-cutoff?
I imagine a swinging pendulum being held outside a black hole, supported by the normal force of a rocket. The rocket is hovering the swinging pendulum right above the event horizon in the strong ...
- 95
0
votes
1
answer
378
views
How small do you need to compress mass to make a black hole?
I am wondering if there is an equation for how close you need to compress a mass to make a black hole. I have seen claims that if the earth is shrunk to the size of a golf ball, it would create a ...
- 101
-1
votes
3
answers
197
views
How much mass is needed to make the speed of light equal to 1 mile per second?
The speed of light in special relativity is a constant, 186,000 miles per second, but in general relativity, "the speed of a light wave depends on the strength of the gravitational potential ...
- 29
7
votes
2
answers
1k
views
How can the graviton be both massless and self-interacting?
Gravity is non-linear, so if it is mediated by gravitons, gravitons must interact with each other. On the other hand, the effects of gravity moves with the speed of light, so if it is mediated by ...
- 525
0
votes
1
answer
185
views
Rotation affecting how spacetime is warped (according to general relativity)?
According to this excellent ScienceClic video, satellites don't fall straight towards the center of the Earth, but rather, take a curved path, due to the Earth rotating. A similar thing for black ...
- 1,090
1
vote
2
answers
188
views
Is gravitational mass always the same with inertia mass?
I read an article.
When an object is travelling near speed of light, it's mass increase.
The article argues while the inertia increased, that is, the object will be harder to speed up, the ...
- 601
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