Spacetime math issue

[unseen]

So i made up an equation that someone probably thought of years ago can anymore tell me what the mass greater than or less that is ? ST = spacetime, M=mass X= the variable. Y = normal spacetime conditions BH = black hole

ST+M<X=Y

ST+M>X=BH

Thx

or just tell me i am crazy......
SO i guess basically how much mass in what amount of space time does it take to create a BH ?
Hmm what does ST= ? I dont know ?

 

[MeteorWayne]

Since you're just making stuff up, without defining the terms in your equation, since we don'y have a trash can, this is off to The Unexplained.

 

[darkmatter4brains]

So i made up an equation that someone probably thought of years ago can anymore tell me what the mass greater than or less that is ? ST = spacetime, M=mass X= the variable. Y = normal spacetime conditions BH = black hole

ST+M<X=Y

ST+M>X=BH

Thx

or just tell me i am crazy......
SO i guess basically how much mass in what amount of space time does it take to create a BH ?
Hmm what does ST= ? I dont know ?

ST = 5.9875 *10^28.2540 pico-kilo-watt-joules

 

[ramparts]

Well, I'll try to take more of a stab at this question, but there's no easy answer Spacetime and all those things aren't just numbers where you can say "ST>X" or something. The math is a LOT more complicated, and my guess is that the math is going to look completely alien to you if your math background is just algebra, etc.

 

[yevaud]

Read the following, then get back to us when you have a better idea of what you're asking...

http://en.wikipedia.org/wiki/Black_hole

 

[darkmatter4brains]

SO i guess basically how much mass in what amount of space time does it take to create a BH ?

In relation to the above question:

You might also be interested in checking out the Chandresekhar limit, which is the how massive a white dwarf can become, before becming unstable and collapsing:

http://en.wikipedia.org/wiki/Chandrasekhar_limit

There are similar limits for neutron stars, althugh if I remember correctly the details aren't quite as clean cut as for white dwarfs.

Finally, there are fun and VERY rudimentary calculations you can do to see how much mass can be within a certain radius before you would get a black hole. Basically, just shrink the radius of said object, with known mass, until the escape velocity exceeds the speed of light. This can be found in any basics physics text, and here:

http://en.wikipedia.org/wiki/Escape_velocity

This is where the goofy statement, "if you shrunk the earth to the size of a pea, you would have a black hole", comes from. HOWEVER, be wary that really this is incorrect, as it is an extremely crude way of doing things. But, it might get you within an order of magnitude.

P.S. Oh and ignore the idiot that posted the "ST = 5.9875 *10^28.2540 pico-kilo-watt-joules" figure above :lol:

 

[yevaud]

A collapsing mass of 1.4 Solar Masses will result in a nifty Supernova and a Neutron Star; something on the order of 4 Solar Masses will result in a Supernova and resultant Singularity. IIRC, that is, I am probably off by some fractional amount in the second answer. Pretty certain it's three-four solar masses.

 

[darkmatter4brains]

IIRC

Yevaud, what does that mean - IIRC? I keep seeing it alot, but am clueless as to what it stands for ...

 

[yevaud]

Some common Internet shortcuts/abbreviations:

IIRC - If I Remember Correctly
AFAIK - As Far As I Know
BBS - Be Back Soon]
BBL - Be Back Later

Etc...

 

[5hot6un]

This thread is hilarious. :lol:

Since you're just making stuff up, without defining the terms in your equation, since we don'y have a trash can, this is off to The Unexplained.

:lol:

ST = 5.9875 *10^28.2540 pico-kilo-watt-joules

:lol: :lol:

I wonder where those few of you who actually know anything about anything find the patience to keep the rest of us Neanderthals in check.

By the way, everybody knows ST=3.14159265*3E8^2/M

 

[MeteorWayne]

Don't forget, the proper unit is megafurlongs per fortnight

 

[drwayne]

carots per barn yard is a good density unit.

 

[yevaud]

Aether per/Phlogiston is another.

 

[ramparts]

Oh! I didn't notice the question at the end of the OP's post, which was the only legible question he asked Good call, dm4brains.

The precise answer to that question, how much mass in how much space is needed to form a black hole, is that if an object is smaller than its Schwarzschild radius, then it's a black hole. The Schwarzschild radius is the radius from which light can't escape, so if the entire object is compacted into that radius, then by definition you get a black hole. Luckily, the Schwarzschild radius is tiny - for example, the Schwarzschild radius of the Earth is about the radius of a marble, and the Earth obviously is much bigger than that, so you'd need to compress the whole Earth into the size of a marble to make it into a black hole.

The Schwarzschild radius is a length that's dependent on the object's mass and some physical constants. It's given by:

r_s = 2GM/c^2

Where G is Newton's gravitational constant, M is the object's mass, and c is the speed of light. And 2 is two