More black hole calculations

[coinjunky2]

Hello again,

How does one calculate the volume an amount of matter would take up once compresse into a blackhole?

Thanks again!

[tdaly]

Good question, and one that is currently undergoing a lot a investigation.

The short answer is this: to my knowledge (which is a year or two old) scientists don't know.

Here's the long answer: Stephen Hawking suggests that in a black whole matter is compressed to a singulairity, a "point" of an infinetesmally small size with incredible denisty. I do not know for sure, but my understanding is that no one yet has determined how the size of the singulairty and its mass are related.

[coinjunky2]

Thanks for that answer.

I think I asked that question wrong. I meant how do calcualte for example the mass of human into the "size" of a black hole. Like the event horizon or something. I actually found the answer myself so you don't need to check or anything.

It's called the schwarzchild radius: R=2Gm/c^2

G=Gravitational constant m=mass c= speed of light


I was trying to calcualte the exact blackhole radius for a human. It would be like super cramming someone into the space of an electron. Obviously an electron is super small and I don't have enough digits on my calcualtor or the computers calculator to figure this out.


Anyway thanks!

[Louise]

Thanks for that answer.

I think I asked that question wrong. I meant how do calcualte for example the mass of human into the "size" of a black hole. Like the event horizon or something. I actually found the answer myself so you don't need to check or anything.

It's called the schwarzchild radius: R=2Gm/c^2

G=Gravitational constant m=mass c= speed of light


I was trying to calcualte the exact blackhole radius for a human. It would be like super cramming someone into the space of an electron. Obviously an electron is super small and I don't have enough digits on my calcualtor or the computers calculator to figure this out.


Anyway thanks!

What do you mean you don't have enough digits? The radius of an electron seems to be unknown, but is something like 1*10^-13 or smaller. I do calculations with numbers this small (or oppositely large like 6*10^23) on calculators all the time. Use scientific notation like I did above. The answer will be in scientific notation as well. That is the whole point. No one is going to type in a zillion digits. You put in the number to the degree of accuracy you care about, which is probably only a few digits for a caculation like you are doing. (for example, c (speed of light)= 3 *10^10 cm/s or 2.998*10^10 depending on how careful you want to be.)


Louise

[coinjunky2]

Thanks yeah I know. I meant that I need a better calculator. Mine is crap.
I also can't figure out the stupid calcualtor on the computer. I"ve got it all down now though! Thanks!

[coinjunky2]

Oh, but I do have a math question that I'd be forever grateful if someone helps me out with. What does the math symbol "e" used for? Not E as in energy, but e. I've encoutered this symbol with larger numbers. Why can't they just use scientific notation? Why do they have to throw in another symbol to confuse me?

[Louise]

Oh, but I do have a math question that I'd be forever grateful if someone helps me out with. What does the math symbol "e" used for? Not E as in energy, but e. I've encoutered this symbol with larger numbers. Why can't they just use scientific notation? Why do they have to throw in another symbol to confuse me?

Well, e can mean a couple of things. In the number 3e10, it is the same as 3*10^10. I guess it comes from "e"xponent- you should use whatever comes after the e as the exponent of 10. It can also refer to a special number "e", which is used in a lot of formulas. See:
http://en.wikipedia.org/wiki/E_(mathematical_constant)

Some calculators (most?) use e instead of *10^whatever, since it takes up fewer digits on the screen.

Louise

[coinjunky2]

Ohhh that makes alot more sense now! Thank you!