Torrasque said:
Wyes said:
Black holes are not cosmic vacuum cleaners; they exert a gravitational force in the same way that any other massive object does. If the Sun were to somehow be compressed enough to become a black hole (without losing any of its mass), there would be almost no noticeable effect on the Solar System (in terms of orbits and the like, obviously suddenly there's no light etc.).
Except you would have to ignore several details of physics, and what makes black holes, black holes, for your scenario to work =P
Your super condensed sun would be a neutron star before it became a black hole.
The key factor of black holes, that makes them black holes, is the massive gravitational force they exert on everything around them.
I'm sorry, but no =P
The only reason black holes exert such large gravitational forces is because they tend to have extremely large masses. Now, in a black hole all of this mass is concentrated at a single point, but that does
not make them exert any more force than any other object with the same mass.
Using Gauss' Law, we know that the gravitational force exerted (obviously in this case at distances larger than the radius of the object) by an object with some radius r is the same as a point mass (at the position of the centre of mass of the previous object) with the same mass as our original object.
What makes black holes dangerous is that there is nothing to stop you from getting quite close to this mass, namely you can inside its Roche Limit [http://en.wikipedia.org/wiki/Roche_Limit]. This is why black holes tend to have accretion discs.
However, that does
not mean that overall black holes exert any more force than another object of the same mass. My example with the Sun remains true; if you were to somehow compress the Sun without losing any of its mass (by the power of the Flying Spaghetti Monster or whatever, this is a thought experiment), down to its Schwarzschild Radius [http://en.wikipedia.org/wiki/Schwarzchild_radius], it would form a black hole. And the gravitational force it exerts on the objects in the Solar System would be
no greater than that exerted by the Sun originally. The only other gravitational effect to consider would be certain tidal effects which would disappear, but that's already almost negligible.