Einstein's equation

[kwicky]

How did he derive the formula for E=m(c x c).? Also if a general sense how is any formula derived. Newton's equations of motion come to mind but there are others.

I believe they are still testing Einsteins theories long after they were postulated for accuracy. How did he know?.

[honest_joe]

I think this may answer your question about Einstein

http://www.btinternet.com/~j.doyle/SR/Emc2/Der ive.htm

[jake-the-peg]

To be honest special relativity wasn't that big a jump there were a number of people very close to it and E=mc� wasn't even in the paper but in a short follow up paper entitled "Is the inertia of a Body Dependant on it's Energy Content?"

Catchy eh?

It's not even writen in that form Einstein says (In German)

The mass of a body is a measure of it's energy constant: if the energy changes by an amount L then the mass changes in the same sense by L/9x10^20 if the Energy is given in ergs and the mass in grams.

Einstein isn't thinking of getting Energy from mass but mass from Energy!

Now General realtivity! that was the tough one!

It's not so much that they were testing it long after but finding new applications and demonstrations, like flying the atomic clocks around the world - Nobody expected any different result but it was a very catchy (if expensive) demonstration

[mibn2cweus]

The Equivalence of Mass and Energy

[mibn2cweus]

Derivation of Newton's equations of motion