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 grasp. If only we could tweak our design just a little bit, it would work. To others (like me), perpetual motion machines are impossible—they don't fit with our well-tested ideas of the conservation of energy. However, they can still make a fun puzzle, as you see above.