if sun turned into an black hole then..

[Delta1212]

 

In my analogy, there are things that have more mass than the force from the end of the vacuum hose can overcome, such as my couch. We can assume that if the sun became a black hole, nothing that massive would exist to overcome the force of the gravity at the event horizon. Does that make sense?

While no analogy is perfect, mass really has no effect on whether something can escape a black hole, and since mass is intimately related to gravity, assigning it a property in an analogy that is does not have in reality can make things more confusing rather than clearer.

[Didymus]

It's a matter of perspective. How did the sun turn into a black hole? As has been stated the sun's mass stayed the same, but it was compressed to a small enough area, then the gravitational field outside of the area where the surface of the sun currently is would be completely unchanged gravitationally. In that case, no change. Your opponent is right

 

However, that's not the only variable. If, instead, the sun's size remained constant and mass was added to the poi t at which it be ame a black hole the size of the sun... Then you would be right. A black hole the size of the sun will have a -lot- more mass and thus a stronger gravitational field and we would be sucked in very quickly.

 

Here's a way to picture it: X=the distance from the center of the earth to the surface of the earth where you are currently sitting. At the surface, you weigh what you weigh. If you get on a passenger jet, you'll weigh a bit less. At 1x from the surface (2x from the center of the earth), you'll way much less.

 

If the earth were compressed to the size of a pea, it would be dense enough to become a black hole. Objects on the surface of that pea would stand no chance of escaping. But, you could be 1X away from that pea and still experience normal earth gravity as you experience it now. Easy?

Btw, I didn't do the math on the pea thing. I just remember a discovery channel special a long time ago that stated that a pea with the mass of the earth would be dense enough. If that scale is wrong.... Find what the right dimension is, and pretend the pea is exactly that big. Don't mess with my illustration, darn it.