Some of the Irish claim to have invented a perpetual motion machine.
As a young child I read this was impossible, but frankly I’ve long been convinced of the contrary. The universe itself seemed like a counterexample. It goes and goes and goes and goes. Lots of stuff happens. Stars explode, galaxies crash, planets get downgraded, etc. Where does a vacuum get its energy from anyway? And isn’t the "cosmological constant" a big free push?
Now perhaps our universe is not truly "perpetual." Or perhaps it involves "no net expenditure of energy." I’ve heard it called "a free lunch," through some kind of quantum effect and subsequent inflation.
But still, the universe, as a perpetual motion machine, seems to me like a good enough version of what people have been looking for. (Imagine your venture capital pitch: "Well, it’s not as Big or as Important as The Universe, but it does operate according to the same physical laws…") The universe was produced by some process, and perhaps a smaller and more local version of the idea is possible. Or does it come only in one size? Well…I’d better stop before I make any more scientific blunders…
I can’t get over the idea there is a free lunch floating around out there. Perhaps I read too much Julian Simon in my formative years.
Addendum: Here are the seven warning signs of bogus science.