- 14 Sep '08 15:18

This is one way of describng a black hole.*Originally posted by dannyUchiha***I saw in a documentary on TV that a blackhole is simply a mass so big that had a gravity so strong that it swallowed itself and eerything about it.**

Is this true?

The "it swallowed itself" part I don't like. Also "everything about it" is a bit vague.

But approximately it is true. - 14 Sep '08 20:23 / 1 edit

it doesnt´t have to be big*Originally posted by dannyUchiha***I saw in a documentary on TV that a blackhole is simply a mass so big that had a gravity so strong that it swallowed itself and eerything about it.**

Is this true?

EDIT: Misread your post. You said mass so big, not physical dimensions. You are correct. - 14 Sep '08 20:45

Actually the mass doesn't have to be big at all. All it takes is a small enough radius. For each mass,*Originally posted by Wheely***it doesnt´t have to be big**

EDIT: Misread your post. You said mass so big, not physical dimensions. You are correct.*m*, there is a radius,*r*, which makes the body become a black hole if the radius is as big or smaller than*r*. Even a spoon can become a black hole...

Ps: For the case of the spoon at some point QM effects would have to be taken into account and things might not be so straightforward, but in the context of GR it is always possible for a body to become a black hole. - 15 Sep '08 00:56

If we take the spoon as example, what criteria must be met in order to become a blackhole?*Originally posted by adam warlock***Actually the mass doesn't have to be big at all. All it takes is a small enough radius. For each mass,***m*, there is a radius,*r*, which makes the body become a black hole if the radius is as big or smaller than*r*. Even a spoon can become a black hole...

Ps: For the case of the spoon at some point QM effects would have to be taken i ...[text shortened]... aightforward, but in the context of GR it is always possible for a body to become a black hole. - 15 Sep '08 09:51

One thing though: I forgot that while calculating the radius QM effects are already taken into account, so this gravitational collapse will be even stronger than the degenerate pressure cause by fermions.*Originally posted by dannyUchiha***If we take the spoon as example, what criteria must be met in order to become a blackhole?**

The radius is called Schwarzschild radius and is calculated by*r=2Gm/c^2*where the letters have their usual meaning. Just for you to have an idea I'll do a calculus having in mind a person. So say that you weigh 90Kg your Schwarzschild radius will be 1.483173*10^-27m. - 15 Sep '08 12:53 / 1 edit

Question: You say that if you press a human body (of 90 kg) to a sphere with only a radius of about 1.5*10^-27 - what do you get?*Originally posted by adam warlock***One thing though: I forgot that while calculating the radius QM effects are already taken into account, so this gravitational collapse will be even stronger than the degenerate pressure cause by fermions.**

The radius is called Schwarzschild radius and is calculated by*r=2Gm/c^2*where the letters have their usual meaning. Just for you to have an mind a person. So say that you weigh 90Kg your Schwarzschild radius will be 1.483173*10^-27m.

Answer: Well, not less that 8 years of prison... - 15 Sep '08 22:22

Thanks for that example, it made the idea clearer to me.*Originally posted by adam warlock***One thing though: I forgot that while calculating the radius QM effects are already taken into account, so this gravitational collapse will be even stronger than the degenerate pressure cause by fermions.**

The radius is called Schwarzschild radius and is calculated by*r=2Gm/c^2*where the letters have their usual meaning. Just for you to have an ...[text shortened]... mind a person. So say that you weigh 90Kg your Schwarzschild radius will be 1.483173*10^-27m.

So, I guess that based on that equation, it is impossible that the blackhole is something traveling at the speed of light... - 17 Sep '08 16:56 / 1 edit

From prsent day knowledge it is important for a black hole to travel at the speed of light because it has mass, not because of the previous equation.*Originally posted by dannyUchiha***Thanks for that example, it made the idea clearer to me.**

So, I guess that based on that equation, it is impossible that the blackhole is something traveling at the speed of light...

If you are interested in superluminal movement I'd reccomend for you to do a google search on tachyons.

And if you like discussing these themes please consider joining Club 39 - 17 Sep '08 17:08

Thanks. I just applied for this club, although where I can really contribute is on chemistry...*Originally posted by adam warlock***From prsent day knowledge it is important for a black hole to travel at the speed of light because it has mass, not because of the previous equation.**

If you are interested in superluminal movement I'd reccomend for you to do a google search on tachyons.

And if you like discussing these themes please consider joining Club 39