Here's an interesting thing - long after the idea of a "perpetual motion machine" was generally accepted to be an impossible dream, it turns out that not only is someone still chasing it, but they're claiming to have made one, too.

"Orbo" is the mysterious invention of one Sean McCarthy, who has set up the company Steorn to develop and market the device. Although he's understandably cagey about the details (it's something to do with magnetic fields) he's absolutely adamant that the net result of Orbo is free energy - that is, energy created from nothing, with no input required. In other words, a perpetual motion machine, that simply keeps spinning indefinitely under its own steam. This naturally flies in the face of accepted physics, which states that energy is a constant, and cannot be "created" in this way.

McCarthy doesn't attempt to explain how this is possible, only that Orbo works in spite of it, whether physics likes it or not. He hopes that once validated by the scientific community, in a process which is currently underway, it can be marketed as a device for generating free energy inside a host of gadgets, replacing the need for batteries and other power sources. The environmental benefits of this could, of course, be absolutely phenomenal.

There's an interesting article on the BBC here giving the scientific counter-argument to Orbo's claims, from the point of view of Eric Ash, an electrical engineer. It's pretty damningly against the whole idea, but doesn't amount to much more than a repeated shout of "it's impossible!" - which of course it may well be, but it does no harm to dream...