# QuestionIs a black holes event horizon size relative to your distance to it?

#### Greenlight

the closer to a black hole you get the more gravitational time dilation. Since the SoL is constant, and speed = d/t. Since time is dilated by gravity there would a discrepancy between a distant observers SoL and a close one. Wouldn't that make the Event horizon size relative to your distance to the Black hole?

#### stark710

the closer to a black hole you get the more gravitational time dilation. Since the SoL is constant, and speed = d/t. Since time is dilated by gravity there would a discrepancy between a distant observers SoL and a close one. Wouldn't that make the Event horizon size relative to your distance to the Black hole?
@Greenlight The event horizon of a black hole is a series of points beyond which the light cannot escape the attraction of the gravitational pull of the black hole. Schwarzschild radius is one of the commonly used method to calculate this and one of the parameters to calculate the event horizon size is the mass of the black hole. You can refer here to know more about this:

In that sense, the event horizon size of a black hole cannot be relative to the position of the observer. The actual value of this would depend on the parameter values of the black hole!

#### Greenlight

so they would calculate the same size, but is a meter the same for both observers? It is after all based off of the SoL.

#### billslugg

Each observer sees his own meter stick as the correct size. It is the other guy's stick is shorter. Any stick in a gravitational field or moving quickly or in a region of high electric field density will appear shorter to someone outside. In each case it is the local energy density doing the contraction by the way in which the high energy density alters the shape of space.
The event horizon of a black hole is made smaller due to the intense gravitational field but the field also causes the emitted light just outside the event horizon to travel in a curve and to magnify the apparent size of the event horizon so it then appears normal to an outside observer. I am out on a limb here but I think that's how it works.

• Absolute zero

#### Harry Costas

The core mass of a black hole has a property common to all. A dipolar electromagnetic vector force fields. The vortex formed by the dipolar ejects matter out expanding .
The core also attracts and these forces are so great that EMR cannot escape, the position of the EH is dependent on the vector forces going into the core, the core mass determines the position of the EH.

#### Absolute zero

As I understand the op`s question, take two observers A and B. A is well removed from a black hole while B is at R=2Rs. A using their measurements determined Rs to be one light sec. Likewise B determines a value of Rs of approximately .71 light sec. It is not Rs changing but the measurement of the observer. The relative size of a meter is different between the two observers so the relative size of the black hole is proportionally different.