Tagged Questions
2
votes
2answers
105 views
Is Earth's orbit around the sun affected by the ~8 minutes light delay?
Gravitational change occurs at the speed of light. As a consequence, we experience on Earth the gravitational attraction of the sun based on its position relative to us ~8 minutes ago. How does this ...
0
votes
1answer
29 views
If there's a light ray and it's turned to a new location by a certain angle
Imagine that there's a light ray, with source at point A, and it's directed towards point B (which is very far from point A) and it continues for a huge distance.
How will an observer at point B ...
2
votes
3answers
124 views
Why are black holes special?
A black hole is where it's mass is great enough that light can't escape at a radius above the surface of the mass?
I've been told that strange things happen inside the event horizon such as ...
17
votes
3answers
807 views
Does gravity slow the speed that light travels?
Does gravity slow the speed that light travels? Can we actual measure the time it takes light from the sun to reach us? Is that light delayed as it climbs out of the sun's gravity well?
0
votes
0answers
24 views
Why photons can't escape black hole? [duplicate]
Photons do not have (rest) mass. Then why are they attracted by the black hole? And is it possible that a photon crossing a black hole from a little distance could get accelerated due to the force?
10
votes
4answers
345 views
The definition of an inertial reference frame in Einstein's relativity
I'm reading Sean Carroll's book on general relativity, and I have a question about the definition of an inertial reference frame. In the first chapter that's dedicated to special relativity, the ...
2
votes
2answers
199 views
Another faster-than-light question
Imagine we have something very heavy (i.e supermassive black hole) and some object that we can throw with 0.999999 speed of light (i.e proton). We are throwing our particle in the direction of hole. ...
0
votes
0answers
79 views
Are we always going to measure lightspeed at 3*10^8 no matter what? [closed]
We know light from the sun takes about 8 minutes to reach earth. Now let's imagine a reality where light is twice as fast so it takes 4 minutes to reach earth.
What would be our measure of lightspeed ...
8
votes
2answers
628 views
Does the speed of light vary in noninertial frames?
The speed of light is the same in all inertial frames.
Does it change from a non-inertial frame to another? Can it be zero?
If it is not constant in non-inertial frames, is it still bounded from ...
7
votes
3answers
547 views
Why is a black hole black?
In general relativity (ignoring Hawking radiation), why is a black hole black? Why nothing, not even light, can escape from inside a black hole? To make the question simpler, say, why is a ...
1
vote
3answers
479 views
will free-fall object into black hole exceed speed of light before hitting blackhole surface?
imagine if we throw an object in against direction of gravity with speed v and it achieve max. height of h. now if we allow object to fall from that height h, it will eventually attain speed v when it ...
1
vote
6answers
1k views
Does light have acceleration?
Light travels with the largest speed in our universe. Does light have acceleration?
1
vote
4answers
263 views
Is there a universal rest frame of reference?
I am still struggling with C being a constant and what that implies.
So can an experiment be done to find the resting state for the universe?
Take a device with an observer and a light source and two ...
2
votes
4answers
314 views
Reducing General Relativity to Special Relativity in limiting case
I understand that general relativity is applicable to gravitational fields and special relativity is applicable to case when there is no gravity. But is there a derivation on how to reduce General ...
6
votes
3answers
704 views
Alcubierre Drive - Clarification on relativistic effects
On the Wikipedia article on the Alcubierre drive, it says:
Since the ship is not moving within this bubble, but carried along as the region itself moves, conventional relativistic effects such as ...
9
votes
5answers
3k views
Why can't light escape from a black hole?
Photons do not have mass (that's why they can move at speed of "light").
So, my question is how the gravity of black hole can stop light from escaping?
92
votes
13answers
5k views
How does gravity escape a black hole?
My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. It would seem to ...
