This song deals with Einstein's theory
of special relativity, published in his "miraculous
year" of 1905. (Special relativity deals only with
objects moving at constant velocity. General relativity deals
with accelerating objects, and the interaction between gravity
and spacetime.) The special theory yields many of the most famous
results, including the ideas that moving objects become shorter
("Fitzgerald contraction", mentioned in the third
verse of the song), that moving clocks tick slowly (time dilation),
and that events which appear simultaneous in a "stationary"
reference frame aren't simultaneous if viewed from a "moving"
reference frame. These three effects combine to eliminate all
the apparent paradoxes. (For example, if I see a moving person,
her watch appears to me to tick slowly, but from her point of
view it's my watch that ticks slowly!) If you're feeling
ambitious, you might read my handouts about these effects; you
should be able to understand them if you know basic algebra:
Part 1 .. Part
The special theory of relativity also
yields the most famous equation, E = mc2,
which says that the mass m of an object can equivalently
be thought of as energy E. The factor c is
the speed of light (about 3 x 108 m/s), so that a
modest amount of mass corresponds to an enormous amount of energy.
This equation is given in the first verse of the song, and referred
to in the last verse; in a nuclear fission bomb, a portion of
the relatively innocuous "rest mass" of the uranium
or plutonium is transformed into the much more destructive energy
of a thermonuclear explosion.
One of the most interesting aspects
of this equation is that it tells us that what we normally think
of as energy can behave like mass, in the sense of exerting
a gravitational pull on other objects. This even works for potential
"When the Special Theory of Relativity began to germinate
in me, I was visited by all sorts of nervous conflicts... I
used to go away for weeks in a state of confusion."