A perpetual motion machine is one that can do infinite work
with no energy input. Such a machine is impossible as it
would violate the first or second law of thermodynamics (that
internal groan isn't likely be your last).
The first law of thermodynamics relates to the conservation of
energy, so if you are not adding energy to a system, you cannot
take energy out and expect the system to work indefinitely.
The second law of thermodynamics relates to entropy, defining
that the total entropy of a system will always increase over
time. Some energy is always lost through friction or
otherwise dissipates so that not all of the energy is produced as
work.
Violating a few of the laws of thermodynamics hasn't seemed
to be a problem for countless individuals, even long before there
was any way of protecting their intellectual property, and now that
there is, the good burghers of IP Land have decided that such
machines are unpatentable subject matter.
