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TmanMrT
2005-Jul-11, 05:31 PM
I have a good idea for a science fair project that has to do with evaporation of black holes. I am still fuzzy on some facts about black holes though... :-?

1) When calculating the mass that escapes a black hole per second, should I be trying to find how much radiation is shooting out of the BH's gamma jets?

2) What is Hawking Radiation, and how does it work?

3) WHAT IS THE GRAVITATIONAL CONSTANT!??! (Everybody seems to have a different value for it)

4) Does anybody know how long it does take for a Black Hole to evaporate? (Any mass is fine, I would just like an example)

01101001
2005-Jul-11, 05:43 PM
4) Does anybody know how long it does take for a Black Hole to evaporate? (Any mass is fine, I would just like an example)

This is fun:

Hawking Radiation Calculator (http://xaonon.dyndns.org/hawking/)

1 million kg -> 84.07 second lifetime

Tobin Dax
2005-Jul-11, 07:53 PM
3) WHAT IS THE GRAVITATIONAL CONSTANT!??! (Everybody seems to have a different value for it)

You probably want G=6.67x10^-11 m^3/(kg*s^2). If you change which units you are using, the value changes as well (i.e. G=6.67x10^-8 cm^3/(g*s^2)).

John Dlugosz
2005-Jul-11, 09:06 PM
This is fun:

Hawking Radiation Calculator (http://xaonon.dyndns.org/hawking/)



Interesting. It points out that any natural stellar-sized black hole will not evaporate at all but grow due to cosmic background radiation. It will take a loooong time for the universe to cool to the point where evaporation dominates.