Can you explain Em=2 as if I were retarded..but more importantly, what does light squared mean?

Question

I know energy and mass are supposed to be "equivalent" in this theory..but what is the significance of light having to be squared? I have looked and searched and I see no explanation of this online. I don't know why light must be "squared".

If energy travels at the speed of light.. what is the point of using the word squared?

Answer 1

It's a conversion factor.  Energy is measured in Joules, and a Joule is defined as 'kg*m^2/s^2'.  Since the idea is that mass and energy are the same thing, and mass is measured in kg, we're still missing an 'm^2/s^2'.  Well the speed of light is measured in m/s, so if you square that you get m^2/s^2, then multiply it by mass (kg) and you get kg*m^2/s^2, or Joules.  Now you've converted mass to energy.

It's sort of like how if you want to convert distance (m) to speed (m/s) then you divide the 'm' by 's' to get m/s, except a bit more complicated.

What I'm trying to say is just that the definition of energy is kg*m^2/s^2.  So you do mass (kg) times speed squared (m^2/s^2) to get energy.

The reason we use the speed *of light* for the 'speed' here is when you convert mass to energy, the energy is released in the form of photons, so their speed is the speed of light.

Answer 2

As far as I know there really is no great answer to this that is straight forward. Light being squared is the consequence of working through what are called Maxwell's equations, which Einstein used to come up with his special theory. Frankly I don't understand the math behind it either because I have only had four calculus courses (yeah only) but I can tell you Maxwell came up with this in the mid-19th century:

1/c²=ε(naught)μ(naught) where the crazy Greek letters are magnetic constants you probably don't care about.

Then again I could be totally wrong and there be some simple explanation, if so I'd love to see it so I could understand it better myself.

-M

Answer 3

Jerome Seymour Bruner (born 1 October 1915) is an American psychologist who has contributed to cognitive psychology and cognitive learning theory in educational psychology and to the general philosophy of education. He is sometimes quoted as saying, ' that you can teach anything to anybody at an intellectually honest level!'

I only hope, that the following does not prove him wrong!

The famous equation (E=mc²) was derived by Einstein as part of his 1905 paper 'On the Electrodynamics of Moving Bodies'. This theory is now better known as the ‘Theory of Special Relativity’. Its underlying concepts were that wherever an observer is located he or she must find the laws of physics to be the same and furthermore, whatever the observer’s velocity he or she must find the speed of light to have the same value. The speed of light is a universal upper limit to all velocities. To allow observers with different velocities to transform their results so that they agreed, Einstein provided a transform equation: -

x = x'/sqrt(1 -(v/c)²)

Thus measurement x for one observer, separating from another observer with a constant velocity v, can be transformed into the other observers measurement x’.

The famous equation is derived from the expression for work energy. Work equals force times distance.

dW = F.ds

Since force F equals d(mv)/dt and ds/dt = v we can expand the expression for work into: -

dW =(d(mv)/dt).ds

or, expanding further: -

dW=v²dm+mv.dv

Using the observers transform equation for masses (x = m, x’ = m’) we can obtain

m²c² = m²v² + m'²c²

Differentiating, with c and m' as constants, gives: -

2mc²dm = 2mv²dm + 2m²vdv

When the 2m is divided out, we are left with: -

dW = c²dm

Thus integrating between limits m and m' (the rest mass) with c constant gives:-

W = c²∫dm = c²(m - m')

Or (since the total work is the energy): -

E = mc² + m'c²

This is not Einstein's original derivation but I hope you find it perhaps a bit easier going than his briefer, but for all that, calculus rich approach.

  

Answer 4

Look at my link

Answer 5

i think it has to do with the proof...

proof will always make sense...but im not crazy enough to go read about this ....cz this is the realtivity theory man.... it was all for Einestein !!!

im just a sophomore doing cybernetics.

Answer 6

No darling energy travels by the speed of light multiplied by speed of light. E=m *c* c That's the equation. And you cannot disagree a proved equation.Right?They have made relation of energy with mass and light,the only two thing we see around us .