How did Einstein get e=mc2 (squared)? What does it mean too? I can’t remember.
e (energy) = m(mass)x c(the constant aka the speed of light) squared
he got it cause he was really freakin smart I would guess.
Erm, you could look it up almost anywhere on the 'net…go do it.
But, just fur fun,
total Energy of something=Mass of that something * the speed of light ina vacuum © squared.
The energy released if you decomated the object, reduced the matter to energy.
Am I even close? Man, it’s been awhile since I was in Physics.
Are you sure that’s it? I could have sworn it was some really long and drawn out explanation. 
Yep.
Einstein’s book Relativity was written so that someone with a high school education could understand most of it. I highly recommend it. Relativity was completely non-obvious, and Einstein managed to figure it all out just from reading about the inconsistencies (or so they thought) in the experiments of others. He was quite bright.
What were the other experiments?
Michaelson and Morley tried to measure the speed of light relative to the motion of the earth. They figured that it would be different, but it was constant. They figured their device wasn’t accurate enough and floated it on a pool of mercury with the same result.
Who else? Does Millikin’s oil drop experiment come into it?
IIRC, E = mc[sup]2[/sup] is a special case of a more general equation.
Einstein was not influenced by the Michelson-Morley experiment; he later commented that he was not sure he had heard of it at the time of his discoveries. Mostly, he was convinced of the accuracy of Maxwell’s equations, and realized that they implied the equivalence of all reference frames.
If you’re really curious about E=MC[sup]2[/sup] you might try posting your question in GQ, or at the Bad Astronomy bulletin board. There’s plenty of guys with doctorates in physics and astronomy who can lay it out in laymen’s terms for you. That’s where I usually go when I have a question like yours. Oh, and the Bad Astronomer’s a regular here.
I like that Einstein’s time dilation proof can be done with junior-high level geometry once you accept that the speed of light it is a constant.
–John
Gasp! My physics teachers…lied!
This equation was popularized by the atomic bomb, from what I remember in my drunken stupor. It is an equation that came from the basic question: ‘what would light look like if you were travelling at the speed of light?’ (relativity), which einstein proposed at the age of 16. This singular question led him to theorize about many laws of physics, which are now commong place. Some of these are that light bends around objects with large mass, which, in itself, proves that light has mass, as well as the fact that an atom contains enough energy to affect a 3 mile radius, when its effort to hold itself together is disturbed (basically).
Who else? Does Millikin’s oil drop experiment come into it?
I think what you’re referring to, is an experiment, in which a polarized drop of oil is projected in circles upon a magnetic field, in which case, no, it has nothing to do with einstein’s theories.
(In case you’re wondering, I’m really drunk, and don’t feel like posting, nor calculating, any sort of proofs)
From what I remember from college physics:
If light hits an object, it imparts momentum to the object. Since momentum and energy are conserved, the momentum of the individual photons must equal the momentum imparted to the object that the photons are striking. The photons are massless, but they still “appear” to have mass because they impart momentum (momentum = mass*velocity). Thus, it follows, since the photons are obliterated after a collision, using a few equations, that this apparent mass for photons times c[sup]2[/sup] is equal to the energy. This is true for all energy – it appears to have mass, and true for matter as well.
Here is an easy-to-follow description that I found:
http://www.drphysics.com/syllabus/energy/energy.html
I have probably done a poor job at explaining this, but the tutorial does nicely.
::thought Milliken was about determination of the charge of an electron?:: Where’s Doc Matrix when we need him?
I think this could develop into a very informative discussion if it were in GQ. I’m gonna bounce it over there.
Another interesting book is Einstein’s Dreams by Alan Lightman. It speculates on the sort of realities Einstein might have played around with in order to make sense of Maxwell’s equations & derive relativity.
Nitpick: Actually, light particles don’t have any mass - that’s why they can move at the speed of light. Anything with mass moving that fast would acquire infinite mass. The light itself is not affected by the gravity of the large mass, but space around the mass is. The light’s path through that space gets warped and the beam looks like it’s bending. I’m not sure what the 3-mile raduis line is about, should I attribute that to the drinking?
E=mc^2 represents the idea that all mass can be converted to energy and vice-versa. The conversion factor between the rest mass (m) and the amount of energy it could be converted to (E) is c^2.
There is a book by David Bodanis, called “e=mc^2,a history of the world’s most famous equation” that apparently covers the science leading up to the discovery of this equation, and the leaps Einstein made to get to the big a-ha. I haven’t read it yet, but I look forward to learning more about that dimension…
Two (minor) things. Lurker is right: Mulliken’s oil drop experiment determined the charge of the electron (actually, I believe it really only got the ratio of charge to mass, but eh, who cares?). And ultrafilter is also right; the REAL equation, in all it’s glory, is
E[sup]2[/sup] = p[sup]2[/sup]c[sup]2[/sup]+m[sup]2[/sup]c[sup]4[/sup]
where p is the object’s momentum.
Oh, and a nitpick of RGillen’s nitpick. The almost universal convention in physics these days is to think of a mass as being unaffected by velocity; it’s the energy that becomes infinite if the object is moving at the speed of light, unless the object is massless.