What will be the escape velocity on a black hole?

Question

Escpe velocity = root(2GM/R)
so theoritaclly for it to be very high, mass of the black hole should be very high and radius very small
Hows that possible?

theoritically*

Answer 1

The escape velocity of a black hole is, by definition, greater than the speed of light.

Answer 2

A Black Hole can be very dense, hence increasing its mass, without necessarily having a very large radius (think collapsed star such as a dwarf). In fact, many quantum theories hold that there is a point at which celestial bodies cannot get any larger because it wouldn't be able to support its own mass without collapsing.

So, taking the hyper-density of a Black Hole as a reason for a small radius, you'll next need to calculate the Event Horizon for the Black Hole--the point at which nothing can escape because of the gravitational pull. If we wind back the math clock and use relativity, the mass of the object fleeing the Black Hole would have to increase in order to increase the speed to flee the Black Hole, necessarily making it important to know the mass of the fleeing object.

Answer 3

How is it possible to for the mass to be very high and the radius very small?

Mass near the core is compressed by the weight of all the mass 'on top of it'. As the core compresses, the mass further out moves closer to the core, increasing the force of gravity on it. In other words, as the inner core compresses, the weight of the mass further out increases, compressing the core even further, allowing the mass further out to settle even closer, etc. To get the required amount of compression for an object to collapse into a black hole takes a lot of mass (a lot more mass than the Sun has, for instance).

What will be the escape velocity?

As per your equation, that depends entirely on the how far away an object is. It's not hard to escape a black hole's gravity as long as an object is far outside the event horizon.

Answer 4

Unfortunately, the laws of physics that we know currently breaks down inside a Blackhole, so the formula you provided will simply not work. However, there is an answer to your question. The answer is the escape velocity is any velocity greater than the speed of light. This can only happen through Heisenberg's Uncertainty Principle, where a particle-antiparticle pair is created near the event horizon of the blackhole and for a very very brief moment in time, one of the particle pair has velocity greater than 300,000 km persec and thus escapes the blackhole, while the other particle of the pair is sucked into the blackhole and lost forever.

Answer 5

You are right - the Radius or Diameter will be small.

The diameter of a black hole depends on the mass of the original object that becomes a black hole.

If the Earth became a black hole it would have a diameter of about 0.017 meters, about the size of a marble. Our Sun would have a diameter of about 6000 meters, just a little less than 4 miles.

And the mass of a black hole is so dense that nothing can escape it - even light which is the fastest we have found so far.

Perhaps THOUGHT can escape a black hole - no one has measured the speed of thought!

Answer 6

I would imagine that it would involve using the velocity accrued when entering the black hole to then be able to punch through the other side, so it would need to be greater than the speed of light PLUS the extra speed gained when accelerating to the terminal point of the hole.

Answer 7

theoretically: a black hole is a star that collapsed under its own gravity, and eventually became so dense, that the force of gravity exerted by it was so great that any possible escape velocity would have to be greater than the speed of light once a certain distance from it.

Answer 8

The escape velocity of a black hole is the speed of light.

It can never be higher than this. No speed can - its a meaningless concept.

Answer 9

Well, the idea is that black holes have the entire mass of suns compressed into something like the size of a golf ball...
So... take that estimate... and you get something bigger than c... so you are sunk... c is the speed limit there....

Answer 10

I don't think that is knowable. There is really no information on a black hole, its pure speculation. How could you possibly calculate with all unknowns. If you are forced to assume everything-then don't be surprised if every test fails.