# Speed of light, and path of travel, in distorted time-space

1. Dec 16, 2012

### San K

How is the speed of light, and path of travel, effected in time-space distorted (by say, gravity)?

We know that the sun/earth's gravity distorts time-space.

So when a photon travels from sun to earth....as it nears the earth....

how much length would the photon travel?

Would it be slightly more than the "straight line" (or "un-distorted space-time") distance?

Alternatively

lets assume that if there were no gravity (i.e. assume that sun and earth were mass-less or very light).....and that the photon would travel the distance between the sun and earth in say exactly 8 mins

now with gravity (sun and earth factored in with their actual masses) would the distance be slightly more due to space-time distortion? how much time would the photon now take?

2. Dec 16, 2012

### A.T.

Yes, light needs more time to cross an area of the same circumference, if the circumference encloses gravitating bodies. The local speed of light is still constant, because the local clocks are also slowed down by gravity. But globally the average speed of the pulse is slowed down.

3. Dec 16, 2012

### San K

ok. thanks AT

I wonder how (quantum) entangled photons would behave when one of them enters a circumference that encloses gravitating bodies (not sure which forum this should be posted in)

Last edited: Dec 16, 2012