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Stark
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As I understand it, an Event Horizon is a boundary surrounding a black hole where light is held 'still'. If the photons never get beyond this boundary, how can they be observed?
This is a misunderstanding.Stark said:As I understand it, an Event Horizon is a boundary surrounding a black hole where light is held 'still'.
That's wrong. You're descrinbing the photon sphere, not the event horizon.The event horizon of a BH is not a boundary; it is simply a radius that defines a particular phenomenon. In simple terms:
- a light ray passing tangentially, but outside, this radius will be bent sharply around the black hole but will continue off into space.
Chronos said:Photons observed entering a black hole by an observer inside the event horizon will be infinitely blue shifted, as Ich noted.
Chronos said:Photons observed entering a black hole by an observer inside the event horizon will be infinitely blue shifted, as Ich noted.
Chronos said:Photons observed entering a black hole by an observer inside the event horizon will be infinitely blue shifted, as Ich noted.
Nabeshin said:Surely this is not true for a freely falling observer. Which class of observer are you talking about?
Wallace said:As photons fall into a hole, they gain a graviational blueshift (for observers at a smaller radius than the emmitters). This is determined by the difference in radius and the relativistic version of the gravitationl potential, which depends on the black hole mass.
An event horizon is a boundary in space around a black hole, beyond which nothing, including light, can escape its gravitational pull.
We cannot directly see an event horizon because it is completely black. However, we can observe its effects on the surrounding matter and light, such as the bending of light and the emission of X-rays.
Yes, in 2019, the Event Horizon Telescope project successfully captured the first image of a black hole's event horizon, specifically the one at the center of the galaxy M87.
The event horizon is difficult to see because it is a theoretical boundary and does not emit or reflect any light. Additionally, most black holes are surrounded by an accretion disk which can obscure our view of the event horizon.
Seeing an event horizon allows us to confirm the existence of black holes and study their properties, such as their size and mass, which can provide insights into the laws of physics and the nature of space and time.