Is light pulled toward a black hole blueshifted?

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 2K views
Superposed_Cat
Messages
388
Reaction score
5
Hi all, I was wondering if, when a beam of light is pulled towards a black hole , because it can't accelerate, it is blueshifted? Thanks in advance.
 
Physics news on Phys.org
Hi Superposed_Cat! :smile:

If two people with identical flashlights are stationary at the top and bottom of a mountain, shining the flashlights at each other,

the top person will see the light redshifted, and the bottom person will see the light blueshifted.

It's the same for stationary observers near a black hole …

the gravitational effect of a black hole is (outside the event horizon and outside the surface of the star) exactly the same as that of a star of the same mass.