What is the event horizon compared to the black hole?

The only size that a black hole has is the size of the event horizon. (Well ... if its spinning, it can two horizons, one is the event horizon, the other is bigger and is called the ergosphere).

So, assuming that your BH is not spinning, when you say it's 1 inch in diameter, that's the size of the event horizon. That would be for a BH about 5.6 times the mass of the Earth. In other words, if you were about 6370 km from this BH, you would feel a gravity force of 5.6 G's. That is, of course, exactly the gravity you would feel on the surface of a dense planet that had a mass 5.6 times the Earth, but the same size as the Earth.

---- Later edit:

quantumclaustrophobe, I disagree. A Earth-mass BH would have a radius of <pulls out calculator, punches buttons ...> ... of about 9 mm. Much much smaller than a golf ball.

Well...

A black hole is ***always*** a dimensionless point. The only indication to how "big" a black hole is - really, how massive - is the size of the event horizon.

If Earth were to form a black hole, it's event horizon would be about 1/2 the size of a golf ball. If the sun were to form one, the event horizon would be about 12 feet in diameter.

Really, the event horizon is that point around the black hole that our universe ends - and the black hole's realm begins. Orbital speed of the black hole *at* the event horizon is the speed of light.

The Event Horizon is the distance from a Black Hole at which the gravity of the Black Hole becomes so strong that inside of that distance nothing (not even light) can escape and is inevitably dragged down to the Black Hole, itself.

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