Jack that's interesting you should mention E=mc? - check this out: According to Einstein mass and energy are "different manifestations of the same thing," and "very small amounts of mass may be converted in to a very large amount of energy." Now this all sounds very scientific, but it's very important to note its title: The Theory of *Relativity* -which is dissolutionist- and next and perhaps even more revealing is the spoken equation itself, which is apparently Masonic / Kabalist: E is equal to mc-squared, in which energy is put equal to mass, multiplied by the square of the velocity of light." We've got the Square mentioned repeatedly. Light is given a velocity and is squared.
If you assume that the speed of light is the same in inertial reference frames, then you are forced to conclude that, at least for inertial frames, velocities transform according the the Lorentz transformations. Now, the assumption that the speed of light is the same in all inertial frames is supported by experiment and electromagnetic theory. But you mention c^2, but LIGHT isn't the real key here. SPACE AND TIME are. If you assume light has the same velocity in all inertial frames, you are saying something about
space and
time as much as you are saying something about light, and in turn you are saying something about the universe as a whole.
Anyway, from that, and the assumption that momentum is conserved, it is straight forward mathematically to prove that E = y mc^2, where y is the Lorentz factor, is valid (although it's usually written as E^2).
As far as c being squared... what do you think the physical units of energy ARE in the first place? Kilograms times meters/second squared. Squaring c makes PERFECT sense in an energy relation. Just like KE = (1/2)mv^2, mc^2 is the exact unit of energy.
It's actually fairly easy to derive it from the basic assumptions that the speed of light is constant in inertial frames and that momentum is conserved. I've already done nearly half of it here for you, lol.
http://theflatearthsociety.org/forum/index.php?topic=3152.msg609126#msg609126