Define Red-Shift: Explaining BH Event Horizon

[Aurora-Sky]

Could some one explain what red-shift really means when we're talking about the EH of a BH?

Thank you.

 

[Whovian]

EH of a BH? Remind me what that stands for.

Redshift for moving bodies is caused by the Doppler Effect.

 

[Aurora-Sky]

EH of a BH? Remind me what that stands for.


Event horizon
Black hole

 

[Whovian]

Event horizon
Black hole

Oh! In which case you have to understand that observers under higher gravitation appear time dilated to observers under lower gravitation. So those of us watching an observer falling into a black hole will see that observer slow down (and, in fact, if I understand correctly, never cross the event horizon), and any sort of waves they send back will have more infrequent peaks due to the time dilation. And so we see redshift in light waves.

 

[pmacias]

Red-shift is a phenomenon in which the wavelength of light from an object appears to be longer, or "shifted" towards the red end of the electromagnetic spectrum. This is due to the expansion of space between the object and the observer. In the context of a black hole's event horizon, red-shift refers to the stretching of light as it approaches the event horizon, which is the point of no return for anything entering a black hole. As light gets closer to the event horizon, it becomes increasingly red-shifted, meaning its wavelength becomes longer and its energy decreases. This is because the immense gravitational pull of the black hole causes time and space to warp, causing the light to lose energy as it struggles against the pull. This red-shift effect is one of the key pieces of evidence for the existence of black holes in the universe.