Constant speed of light in vaccum?

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SUMMARY

The discussion centers on the behavior of light near a black hole, specifically addressing the constant speed of light and its interaction with gravitational fields. As light approaches the event horizon of a Schwarzschild black hole, its coordinate speed approaches zero due to the warping of spacetime, while an observer falling through the event horizon measures the light's speed as the standard speed of light. The concept of trapped surfaces is introduced, indicating regions where light cannot escape the gravitational pull of the black hole, leading to infinite redshift.

PREREQUISITES
  • Understanding of general relativity and spacetime concepts
  • Familiarity with black hole physics, particularly Schwarzschild black holes
  • Knowledge of coordinate speed versus physical speed in physics
  • Basic grasp of redshift phenomena in astrophysics
NEXT STEPS
  • Research the implications of trapped surfaces in black hole physics
  • Study the concept of redshift and its effects on light near massive objects
  • Explore the differences between coordinate speed and physical speed in relativity
  • Learn about the mathematical framework of general relativity and its applications to black holes
USEFUL FOR

Astronomers, physicists, and students of astrophysics interested in the properties of black holes and the behavior of light in extreme gravitational fields.

violetS
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Just find something very interesting..

If the speed of light is constant, at some distance from the black hole where light can neither escape the attraction of the black hole, nor succumb to its gravitation, what state is the light in? does it have a speed there?

...confused..
 
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As radially infalling light approaches the event horizon of a spherical black hole, the (Schwarzschild) coordinate speed of the light approaches zero. However, an observer who happens to be falling through the event horizon will, at the event horizon, measure the physical speed of the infalling light to be the standard speed of light.

Coordinate speeds and physical speeds are often different.
 
got it

haha thanks a lot:wink:
 
violetS said:
Just find something very interesting..

If the speed of light is constant, at some distance from the black hole where light can neither escape the attraction of the black hole, nor succumb to its gravitation, what state is the light in? does it have a speed there?

...confused..
The speed of light does not change.
What happens is when light approaches the black hole the warping of space-time causes the incoming light rays to converge to a point. In other words they cannot escape anymore, there is no longer a geodesic, they all have to go to that point.
The region were a return is no longer possible is called a trapped surface.
 
Isn't the OP simply asking about escaping light being infinitely redshifted to zero?
 

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