Derivation of E=MC²

FrCrilly

Hi All,

I’ve developed an interest in Einstein lately and am curious about his derivation of E=MC².

How could a patents clerk devise out such a radical concept on paper with no great experimentation. (ie how could he ponder such a concept without the ability to turn a small amount of mass into a large amount of energy).

Please note I’m not a scientist. If someone out there could give a general summary without going too much into detail, that will be greatly appreciated.

Thanks In Advance

DublinWriter

I asked the exact same question of my LC Hons Physics teacher back in 1988 and "it's because he was a genius" was the reply.

In other words, my teacher didn't know and I've been asking myself the same question ever since.

Have you googled for his original paper?

Son Goku

How could a patents clerk devise out such a radical concept on paper with no great experimentation. (ie how could he ponder such a concept without the ability to turn a small amount of mass into a large amount of energy).

You're question seems to be just how did Einstein arrive at mass energy equivalence.

Basically, around the age of 16 or so he began to think about electromagnetism which carried on until his days in college when he studied and learned Maxwell's Equations. These were the fundamental classical equations for electromagnetic phenomena.

Maxwell's equations carried inside themselves the statement that the velocity of light in a vacuum was a universal constant, but more importantly the contained a hidden symmetry which was at odds with the Galilean conception of space and time.
By taking Maxwell's equations more seriously than Newton's Laws he was lead to Special Relativity.

Even without Einstein somebody was going to find special relativity.


However General Relativity is a completely different story, the answer to how he figured that out is essentially that he was a genius.

FrCrilly

Son Goku wrote:

You're question seems to be just how did Einstein arrive at mass energy equivalence.

Basically, around the age of 16 or so he began to think about electromagnetism which carried on until his days in college when he studied and learned Maxwell's Equations. These were the fundamental classical equations for electromagnetic phenomena.

Maxwell's equations carried inside themselves the statement that the velocity of light in a vacuum was a universal constant, but more importantly the contained a hidden symmetry which was at odds with the Galilean conception of space and time.
By taking Maxwell's equations more seriously than Newton's Laws he was lead to Special Relativity.

Even without Einstein somebody was going to find special relativity.


However General Relativity is a completely different story, the answer to how he figured that out is essentially that he was a genius.

Thanks for your reply.

I think what inspired the idea of General Relatively was Einstein wondering if he was in an elevator that was falling at a very high velocity and he flashed a light from one side to the other, would the light bend as it traveled across the elevator. I think this was a simple starting point that lead to the concept of light bending in space and time.

His work on Special Relativity was apparently inspired by him being on a tram moving away from the town clock in Berne. Apparently he pondered something along the lines of “If I was moving away from that clock at the speed of light, time outside the tram would appear to stop as I would be keeping up with the light omitted from the clock. However, if I looked down at my watch while the tram was moving, time would appear to be ticking away as normal. Hence time must bend while the speed of light remains constant”

These are both simple concepts that have helped my understanding of Einstein’s theories (simple once some genius has thought of them). I wonder is there a similar simple concept behind e=mc²?

kaalgat

Actually a Russian guy who teaches quantum mechanics told me that the E=mc2 equation is a load of rubbish. Apparently it is only a shortened version, and if used correctly basically indicates that light has no energy.

He also said the correct equation that Einstein used is
E=c.sqaure root of p2+m2.c2

I'd love to know whether he was being a pompous ass as would be normal for him, or is this actually correct?

Son Goku

He's correct. Although it isn't "a load of rubbish".
The point of writing it as E=mc^2 is that it shows matter posses energy even when it is stationary, something not known until then. Instead of saying it is a load of rubbish, it's just not valid in a frame where the object is moving. It's the most interesting part of the general equation.

Besides E=mc^2 is used in an objects rest frame, something light doesn't posses, so it doesn't really say much about light. A special case isn't a load of rubbish, it's just a special case.

Time Magazine

kaalgat wrote:

He also said the correct equation that Einstein used is
E=c.sqaure root of p2+m2.c2

E = c x sqrt(m²(c²) + p²)

is easier to my eyes .

Duly edited.

kaalgat

Ok fair enough

No, it's (mxm), as in mass sqaured, and (cxc), as in speed of light sqaured. p is Planck's constant.

Apparently E=mc2 was used to describe the energy of a photon, and as photons have no mass, you are basically multiplying zero and the speed of light. Giving an energy of zero. Which we all know is wrong, as light does have energy.

On the other hand, the guy is a complete wise ass.. (liking to tell us how he was reading up on Newton's laws and building telescopes at the age of 7).

So does his argument carry any weight?

mawk

i was always under the impression that the e=mc^2 deal was just the mathmatical equivilant of the red line going down the page type graph. something that is much more visual and easy to grasp than the complicated mechanics of the situation. and I thought he just picked C on the grounds that it was the speed of light and therefore a big number.

like e= m(fookin loads)

just to help people grasp the concept.

but im not a lawer so dont quote me.

amen

just because your are a patent clerk does not mean you are stupid.
Even today when jobs are advertised in the EU/US paten offices they are often advetised as for patent clerk/patent officer etc with a minumum requirement of a degree in the required subject(physics/egineering) and often a MSc/PhD required.

Patent work often involved looking for prior patents but also proving that the invention actally works and obeys the laws of physics. For instance if you submitted a patent for perpetual motion someone would have to go through the physicis of the machine and ensure it obeyed the standard laws of physics.

As for how he discovered E=mc2 as genuis is "99% perspiration and 1%inspiration"

while not a genius I think everyone has had a moment in work/school/college
where all of sudden you understand something or see the solution to a problem. In the case of Einstein its just bit better!

Of course a lot of thing get discovered by accident such as radiation, penecillin, nylon etc.

And then it often happens that multiple people discover the same thing around the same time period as though if was just the right time to be discovered.

Tar.Aldarion

mawk wrote:

i was always under the impression that the e=mc^2 deal was just the mathmatical equivilant of the red line going down the page type graph. something that is much more visual and easy to grasp than the complicated mechanics of the situation. and I thought he just picked C on the grounds that it was the speed of light and therefore a big number.

like e= m(fookin loads)

just to help people grasp the concept.

but im not a lawer so dont quote me.

Um, lawl?