E=mc2

[Boerseun]

In E=MC2, there's a couple of things I find amazing:

 

Energy is stated to be the result of Mass times the Speed of Light squared.

Energy is measured in Joules.

Mass is measured in Kg.

The speed of light is measured as so many meters per second.

 

So, we have four different units:

Energy (Joules) = (Kg)x(m/s)2

 

This has been proven over the last century in plenty experiments. I'm not doubting the truth of it. But what gave Einstein the insight to square the MC bit? Seeing as light is transmitted spherically in 3D space, I would have thought that the natural intuitive approach would have been to cube the right-hand side of the equation rather than square. Obviously, E=MC3 is wrong, but still - where did the insight come from, and, in actual fact, why is it squared rather than cubed? :) :) :)

[my brain hurts]

In E=MC2, there's a couple of things I find amazing:

 

Energy is stated to be the result of Mass times the Speed of Light squared.

Energy is measured in Joules.

Mass is measured in Kg.

The speed of light is measured as so many meters per second.

 

So, we have four different units:

Energy (Joules) = (Kg)x(m/s)2

 

This has been proven over the last century in plenty experiments. I'm not doubting the truth of it. But what gave Einstein the insight to square the MC bit? Seeing as light is transmitted spherically in 3D space, I would have thought that the natural intuitive approach would have been to cube the right-hand side of the equation rather than square. Obviously, E=MC3 is wrong, but still - where did the insight come from, and, in actual fact, why is it squared rather than cubed? :) :) :)

 

 

For one, the right hand side of the equation isn't squared (as you put it, the "MC bit"). Only the C is squared.

 

True, light is transmitted spherically, but perhaps you've confused volume (a cubic quantity) with the surface area upopn which the radiation is measured. The surface area of a sphere is, of course, 4pir^2.

Think of it as analogous to an inverse square problem-

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html

 

Maybe this helps.

[Tormod]

It is squared because it relates the metric of c to the others (E and m). It is in fact the same thing that happens in Pytagoras theorem a^2+b^2=c^2, which lets you calculate the lengths of sides in a right triangle.

 

It is also squared because it is a force law - much the same way that gravity has an inverse square value related to distance.

 

For a really good explanation of the entire E=mc2 (including why there is a square), I suggest the book David Bodanis, "E=mc2". Excellent read.

 

As for why the letter c was used, I found an interesting article here:

http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/c.html

[Boerseun]

Thanks... I'm starting to see the light now!

[arkain101]

Possibly because he realised that anything that includes motion has energy perportional to its velocity squared?

[Boerseun]

So...

 

Energy equal mass times the square of the speed of light.

 

E = MC2

 

In other words... (turn it around...)

 

The square of the speed of light equals Energy divided by Mass...

 

In other words... (simplifying it..)

 

The speed of light equals the Square Root of (Energy divided by Mass)...

 

C = SQRT(E/M)

 

BUT... C is a constant...(?!?!?!?)

 

SO.... REGARDLESS of what E or M is, C MUST stay the same?!?!?

 

So... E/M MUST ALWAYS give the SAME result.

 

In other words, Energy divided by Mass must give C squared...

 

So, if Mass increases, Energy must increase as well - and vice versa...

 

Because, after all, the answer must ALWAYS equal the square of C...

 

So Mass can't move without influencing Energy, and Energy can't move without Mass being changed...

 

(Yeah - I'm being a bit of a knob... but it's pretty bloody awesome, I'd say!)

 

:)

[arkain101]

http://www.physorg.com/news9248.html

 

pretty cool ^^

[arkain101]

http://www.aip.org/history/einstein/voice1.htm

einstien voice records

 

SR test.

http://www.physorg.com/news8037.html