Black Hole Event Horizon: Is There a Physical Boundary?

In summary, the event horizon in Schwarzschild's metric is a result of coordinate choice and can be resolved by choosing different coordinates. However, the event horizon itself is a well-defined light-like surface and not a physical boundary. A coordinate singularity exists at the horizon but can be removed by a more appropriate choice of coordinates. Therefore, the event horizon is not affected by coordinate choice and remains a significant concept in the study of black holes.
  • #1
ChrisVer
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Is there a physical boundary that is the event horizon? Or is there not?
The reason I'm asking is because texts say that the event horizon that appears in Schwarzschild's metric is a result of the coordinate choice, and it disappears by choosing some other coordinates.
 
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  • #2
ChrisVer said:
The reason I'm asking is because texts say that the event horizon that appears in Schwarzschild's metric is a result of the coordinate choice, and it disappears by choosing some other coordinates.
I think what they say is that the singularity at the EH exists only in some coordinates.
 
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  • #3
ChrisVer said:
Is there a physical boundary that is the event horizon? Or is there not?
The reason I'm asking is because texts say that the event horizon that appears in Schwarzschild's metric is a result of the coordinate choice, and it disappears by choosing some other coordinates.

The singularity at the horizon is a result of coordinate choice (you can make it go away by choosing, for example, Kruskal coordinates) but the physical significance of the event horizon is not. The event horizon is a light-like surface, and "physical boundary" is not an especially natural term for describing it, but it is a well-defined surface in the Schwarzschild spacetime as long as you use coordinates that aren't singular there.
 
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  • #4
ChrisVer said:
The reason I'm asking is because texts say that the event horizon that appears in Schwarzschild's metric is a result of the coordinate choice, and it disappears by choosing some other coordinates.

I have never encountered a text that says this.
 
  • #5
George Jones said:
I have never encountered a text that says this.

That's a coordinate singularity. It exists due to the choice of coordinates, and can be resolved by a more appropriate choice of coords.
 
  • #6
At risk of putting words in George's mouth, I think he's pointing out that a coordinate choice doesn't remove the event horizon, which is a co-ordinate independent surface. You can remove the coordinate singularity at the event horizon by careful choice of coordinates, but the horizon remains.
 

Related to Black Hole Event Horizon: Is There a Physical Boundary?

1. What is a black hole event horizon?

A black hole event horizon is the point of no return for an object that is approaching a black hole. It is the boundary beyond which the gravitational pull of the black hole is so strong that nothing, including light, can escape.

2. How is the black hole event horizon determined?

The black hole event horizon is determined by the mass of the black hole. The more massive the black hole, the larger the event horizon will be. It is typically measured in terms of the Schwarzschild radius, which is directly proportional to the mass of the black hole.

3. Can anything escape from the black hole event horizon?

No, once an object crosses the event horizon, it is trapped within the black hole and cannot escape. This is due to the extreme gravitational pull of the black hole, which is strong enough to trap even light.

4. Is the black hole event horizon a physical boundary?

Yes, the black hole event horizon is a physical boundary. It marks the point where the laws of physics as we know them break down, and the effects of extreme gravity become dominant.

5. Can we observe the black hole event horizon?

While we cannot directly observe the black hole event horizon, we can observe its effects on surrounding matter and light. This allows us to indirectly study and learn more about these mysterious objects.

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