All Questions
44
questions
1
vote
1
answer
188
views
Can photons form a black hole?
Can photons form black holes the same way as other matter? If there happens to be enough of them concentrated in an area of space so that enough energy exists within a radius to form an event horizon, ...
- 113
-3
votes
3
answers
229
views
Why is light not affected by gravity?
If a rocket needs to go to mars, it needs to go through a specific trajectory. But i can see the sun straight where it is, so light does not obey gravity?
- 121
-1
votes
2
answers
190
views
Shapiro time delay
How do we know for sure that the Shapiro time delay effect is as a result of curved space time and not simply the photons slowing down.
- 719
2
votes
2
answers
127
views
Mutual gravitational acceleration (or deflection) of light beams as a function of the angle between them
Given Einstein's famous equivalence between energy and mass, $E=mc^2$, a light beam with power, $P$, has an energy per unit length of $P/c$ and an equivalent mass per unit length of $P/c^3$. A short ...
- 2,403
1
vote
0
answers
27
views
About the gravity field around a lightbeam [duplicate]
Imagine there is an infinitely long beam of light. It has impulse and energy. How it affects the spacetime surrounding it? Will masses be pulled towards it perpendiculary and pulled in the parallel ...
0
votes
0
answers
39
views
What evidence suggests that light exerts a force of gravitational attraction? [duplicate]
I'm aware of other posts outlining the theory of how light generates a force of gravitational attraction, cf. e.g. this Phys.SE post. I'm not so interested in this. I'm interested in what evidence ...
- 1,552
1
vote
1
answer
103
views
Will a massive particle be attracted to an infinitely long beam of light?
I was attended to Bonnor beams. A Bonnor beam is the general relativistic exact solution for the spacetime surrounding an infinitely long straight beam of light (it includes also the spacetime ...
1
vote
1
answer
97
views
How can gravity be describe as a carried on gravitons if light is affected by gravity but no effect on gravity? [duplicate]
if photons are emitting graviton while it going near to mass then this graviton should effect the mass the much as the graviton that object with mass emit, and we know light have no mass so it not ...
- 149
0
votes
1
answer
89
views
Why do people say we need general relativity in order to explain why light is affected by gravity? [duplicate]
I've heard said by many physicists things along the lines of "Since light has no mass, we need general relativity to explain why light is affected by gravity."
But why is this necessary?
We ...
- 101
1
vote
2
answers
189
views
Does it take work to bend light?
We all know that light always travels in a straight line. Would it not then stand to reason that changing the path of light requires energy? If so, would this not violate Newton's laws of motion if ...
- 804
-2
votes
1
answer
109
views
Does light really bends in gravity? [duplicate]
As we know, light travels in straight line in normal circumstances, but when exposed to gravity it bends. But does it actually bend? I actually mean to ask whether if we take light as wave creating ...
- 171
2
votes
1
answer
99
views
That the laser hits the same point on the opposite side of the box implies it is moving faster than $c$?
In Greene's video: https://www.youtube.com/watch?v=2pV20KuDucs
In the video Greene describes a fairly well-known thought experiment. A person is in a rectangular box floating in space with a laser ...
- 2,238
11
votes
3
answers
2k
views
Can light cause gravity? [duplicate]
We know the following:
Two masses are attracted to one another, as represented by Newtonian gravity
$F = \frac{GMm}{R^{2}}$
Light is massless and bends in the curvature of space-time which can be ...
- 540
0
votes
2
answers
541
views
Why there are black holes that have a mass only 6 times the mass of the Sun?
We know that black holes are actually "black" because no light can escape them due to their gravity and that's why they appear black. That means the mass of the black hole most be extremely large even ...
- 117
0
votes
0
answers
85
views
Simplest GR geometrical model for bending of light [duplicate]
How to find orbit of bent light in the simplest gravity model by solving the null geodesic equation either by Newton's physical or by Einstein's GR?
Bent Light
To compare we have the simplest model ...
- 1,032