How Much Gravity Does a Black Hole Need to Contain Light?

[terrabyte]

what's the amount of gravity or exactly how many "Gees" a black hole must exert to be a black hole (strong enough gravity to contain any light it "emits")?

 

[terrabyte]

realizing that in order to do such a calculation we would need a "size" for the thing.

hmm that complicates matters

let's assume the "Black Hole" is the size of the earth. how many "Earth's" do we need to compress to the size of ONE Earth to create a black hole?

 

[chroot]

To become a black hole, all the mass of an object must be within its Schwarzschild radius,

$$r_s = \frac{2 G M}{c^2}$$

That is the only condition.

- Warren

 

[urtalkinstupid]

How can a black hole "emit" any light at all? If I'm not mistaken, light "falls" into a black hole. Once the light get's too close to the black hole, it is affected by the black hole's space-time curvature. The space-time curvature is so inclined that light falls in, but can not get back out. I dunno.

 

[chroot]

realizing that in order to do such a calculation we would need a "size" for the thing.

hmm that complicates matters

let's assume the "Black Hole" is the size of the earth. how many "Earth's" do we need to compress to the size of ONE Earth to create a black hole?

A black hole with the mass of the Earth would have a radius of...

http://www.google.com/search?hl=en&ie=UTF-8&q=2+*+G+*+(mass+of+earth)+/+c^2&btnG=Google+Search

- Warren

 

[chroot]

A black hole with the same radius of the Earth would have to have a mass of...

http://www.google.com/search?num=30...)+*+c^2+/+(2+*+G)+in+earth+masses&btnG=Search

- Warren

 

[terrabyte]

sweet, thanks chroot that's exactly what i was looking for :D

now i just need to acquire 700 million more Earth's...

 

[HallsofIvy]

sweet, thanks chroot that's exactly what i was looking for :D

now i just need to acquire 700 million more Earth's...

"If we had but world enough and time!"