A perpetual motion machine is (as the name implies) a machine that moves perpetually; it never stops. Ever. So if you created one today and set it going, it would keep on going until the Big Freeze.

Perpetual motion—it's fun to say that. For some people, perpetual motion machines hold the secret to everlasting free energy that will save the world. To them, it's a machine that is just beyond our ...

Perhaps the most persistent nonsense in physics: the perpetual motion machine. Bad ideas come and go in physics. But there’s one bit of nonsense that is perhaps more persistent than all others: the ...