A siphon is -- in a way -- a "free" energy machine. (Not _really_, but in a way.)
The siphon takes a tiny amount of input energy -- sometimes called the suck -- and uses that to induce a gradient into a "system" where that gradient hadn't existed. Once the gradient is in place, the siphon can "generate" power so long as an imbalance exists across the gradient. (Well, a siphon could generate power if a turbine were inserted within the siphon, or if the outflow ran across a waterwheel...)
This is worth posting about because it's entirely possible that so-called "free energy" machines may be built around similar principles.
That is, rather than "generating free energy," such machines may use a small amount of energy to tap into some pre-existing imbalance in potential either in the atmosphere or space-time itself or zero-point quantum flux or shazbot fosdex (i.e., whatever), and then then the "magic machine" just serves the same purpose as a siphon -- it induces a gradient, and then acts as a way to harness the flow across the gradient...
I'd bet that "siphon" is a very good metaphor to keep in mind when evaluating these "free" energy claims. (I bet such machines really exist, but they're not creating free energy, just tapping into naturally occurring imbalances of potential which exist as the quantum equivalent of, say, mountain springs and rivers. )
Mark W.
ROFL!!