PFE002: Perpetual Motion

When deciding how to treat a new paper, there are a number of criteria one uses to determine its crackpot level. That is, there are a lot people out there who try to publish junk under the premise of complicated science. It's the job of actual experts in their field to police this.

An extremely popular crackpot theory that comes up time and again is perpetual motion.

Most of the designs that may seem like perpetual motion rely on energy from the sun, or, more generally, a hidden energy source.

When evaluating a mechanism for perpetual motion (and to figure out where the flaw in the argument must be) I look for a way to get energy out of the system. In the example above, I would likely attach a generator to one of the pulleys to generate electricity. But then something must move the rope to make the pulley move. Clearly, there is a gravitational attraction between the blocks and the earth, and the one on the right has a larger mass, so it moves down causing the system to rotate.

Of course this system is silly, but it demonstrates the process for identifying certain classes of crackpots, an essential part of physics or any hard science.

That's (not really) perpetual motion.