- #1

Grasshopper

Gold Member

- 210

- 111

- Summary:
- What does light from outside the black hole look to you as you fall in, along with the light?

I am under the impression that an outside observer would see things redshifted as the person they are observing approaches the event horizon. So, it seems reasonable that someone from inside the black hole would see incoming light blueshifted. Is this inaccurate? Why or why not?

If it is accurate, is there a point where the light is blueshifted so strongly that it kills the person (or gives them cancer or whatever)? But wouldn't this violate logic since the other observer sees the light redshifted (although clearly they can't see into the even horizon), so why would it kill the person? I'm assuming that blueshift and redshit are simply coordinate dependent phenomena, and have no true independent reality (much like what we see on a clock; differential aging is objectively real, but time dilation is coordinate dependent, given that two observers can measure the other observer's clock as slower than their own). But if in your reference fame, ultra-high-energy gamma rays are smacking you in the face, surely that can't be safe.

Another thing to consider, I think, is if the local spacetime around the observer is locally Minkowskian. If the black hole is large enough that tidal forces don't really matter locally, I can't see why not.

So, what happens here? Does the light coming into the black hole at you turn into ultra deadly high energetic rays? Or is it locally business as usual?

Last question: if the black hole is so large that tidal forces are irrelevant, will the blueshift or redshift also be small for the local observer inside the black hole? Why or why not?

Thanks to all!

If it is accurate, is there a point where the light is blueshifted so strongly that it kills the person (or gives them cancer or whatever)? But wouldn't this violate logic since the other observer sees the light redshifted (although clearly they can't see into the even horizon), so why would it kill the person? I'm assuming that blueshift and redshit are simply coordinate dependent phenomena, and have no true independent reality (much like what we see on a clock; differential aging is objectively real, but time dilation is coordinate dependent, given that two observers can measure the other observer's clock as slower than their own). But if in your reference fame, ultra-high-energy gamma rays are smacking you in the face, surely that can't be safe.

Another thing to consider, I think, is if the local spacetime around the observer is locally Minkowskian. If the black hole is large enough that tidal forces don't really matter locally, I can't see why not.

So, what happens here? Does the light coming into the black hole at you turn into ultra deadly high energetic rays? Or is it locally business as usual?

Last question: if the black hole is so large that tidal forces are irrelevant, will the blueshift or redshift also be small for the local observer inside the black hole? Why or why not?

Thanks to all!