超光子

Relativistic mass equation \Rel`a*tiv*ist"ic mass e*qua"tion\,
n. (physics)
an equation expressing the mass of an object as a function of
its velocity: as the velocity v of an object increases, its
mass m increases from its rest mass m0 according to the
equation: m = m0/root{1 - v^{2}/c^{2}} where c is the speed
of light in a vacuum. If the speed of an object were to
become equal to that of light, it can be seen that the mass
would be infinite, from which it follows that nothing can
accelerate up to or beyond the speed of light.
[PJC]

Note: The theoretical possibility that there are particles
which always move faster than light cannot at present
be disproved and is not denied by this equation; in
such a case, the relativistic mass equation asserts
that such particles can never decelerate to or below
the speed of light. Such hypothetical particles are
referred to as

{tachyons}.
[PJC]