Zero Kelvin http://en.wikipedia.org/wiki/Absolute_zero
At temperatures near 0 K, nearly all molecular motion ceases
is the energy that an object has due to its motion.
at 0 K there is almost no motion.
thus almost all of the kinetic energy is lost.
Mass-Energy Equivalence http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence
the mass of a body is a measure of its energy content.
if the entire Universe were to approach 0 K then the mass
of the Universe would shrink to the mass that it would
have minus the kinetic energy that it would lose.
so there would be very little kinetic energy left compared to the kinetic energy that there is in today's Universe.
and the mass of the Universe would shrink by that amount of kinetic energy that it has lost.
mass is not finite.
the universe is not finite.
open your box and look around.