Tagged Questions
1
vote
1answer
46 views
How does gravity effects both time and light if they have no mass [duplicate]
I've been reading about how black holes can effect both time and light with gravity. So I was wondering, doesn't something have to have mass to be effected by gravity? And if so, does this mean both ...
2
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1answer
268 views
Gravitational Redshift around a Schwarzschild Black Hole
Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole.
I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
2
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1answer
149 views
What's the difference between the equivalence principle and curvature of spacetime?
Calculating using the equivalence principle only accounts for half the deflection of light, whereas the other half is from curvature of space-time.
But isn't the equivalence principle the same thing ...
2
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1answer
117 views
Calculating a Deflection of Light Integral from Einstein's 1907 paper on Gravity and Light
$\frac{1}{c^2}\int_{\theta=-\pi/2}^{\theta=\pi/2} \frac{kM}{r^2}cos\theta ds=2\frac{kM}{c^2\Delta}$
An observation: $\cos\theta=\frac{\Delta}{r}$
2
votes
1answer
142 views
Can a charged black hole interact via electromagnetism? [duplicate]
Possible Duplicate:
Detection of the Electric Charge of a Black Hole
Light cannot escape from a black hole. However light is also interpreted as the carrier of the electromagnetic force. So ...
9
votes
2answers
609 views
Does a photon exert a gravitational pull?
I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull ...
1
vote
1answer
379 views
If photons are deflected by a strong gravitational field, then how come photons do not have mass? [duplicate]
Possible Duplicate:
Explain how (or if) a box full of photons would weigh more due to massless photons
It has been proved and showed through experiments that light can be bent by the Sun or ...
2
votes
1answer
249 views
how many times have the first photons lapped the universe?
I'm not really interested in the actual number of times, but rather an explanation of a closed Universe. How do we still measure the background radiation of the Big Bang? Those electromagnetic waves ...
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?
