Creating a black hole. Why don't orbits change?

[linky]

I'm not familiar with how black holes work in the slightest, but I found it interesting when I turned the sun into a black hole in our solar system, nothing happened to any of the orbits. No velocity changes or direction changes at all, yet the sun has more than a billion times the gravity of Earth.

[atomic7732]

Orbits won't change because a black hole with the mass of the sun is (aside from it's radius) the same as the sun. It's radius is just so small that at a short distance from it, light can't escape. It's escape velocity is >c. Someone else can elaborate. That's the basics I guess.

[linky]

So basically mass is a more important determinant of gravitational pull on objects than is density.

[atomic7732]

So basically mass is a more important determinant of gravitational pull on objects than is density.

Yes. Contrary to popular belief, a black hole does NOT have "more gravity" than another object... I'm not sure the term for it, but I think of it as a gravity gradient... The gradient is just strong because unlike less dense objects, you can't get as close to the center of the mass, and it's in a much smaller area. Something like that. lol

[Wifout Teef]

Like the other poster said, when an object turns into a black hole, all it is really doing is reducing it's radius to a very small point. So small that it's escape velocity is greater than the speed of light, therefore it turns black because light cannot travel fast enough to escape.

The gravity at the black hole's surface is greater than the speed of light, which makes it black.

If Jupiter was a black hole, it would be about 10 feet across. If earth was a black hole, it would fit in your pocket. But these objects would still have the same gravity. So the moon would stay in orbit.

[linky]

Makes sense now. Same gravity, but tiny diameters. So they become super dense. The closer you get to a black hole, the escape velocity increases, but not the actual gravity.