Jacques wrote:
Hi everybody,

I have a question which bothers me since long time and maybe with your help
I can find the answer at last. Since I heard the formule E=mc^2 for the
first time it struck me that there seems to be no logical relation between
the energy contained in a mass and the speed of light. I have no
difficulties to understand that the energy contained in a mass is equivalent
to that mass.

My problem is: what the hell has this to do with the speed of something else
(an electromagnetic wave). I cannot see the connection between them. These
two things: mass and energy on one side and the speed of light on the other
side seem too disparate to me to allow a logical link between them.

I wonder, if someone can explain this connection. I wouldn't have been
surprised if the Joule (the unit for energy) had been established in
consequence of this formula, but I think both Joule, kg, m/s were already
existent before E=mc^2.

I learned from Wikipedia that James Joule died in 1889, thus before Einstein
discovered his famous formula, which I think happened in 1905.

It turns out that the speed of light is an important
constant of the spacetime in which we live. That is
why it comes up in the mass/energy formula.

Martin Hogbin