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Comment by smanek | Hacker News Reader

This is a really good explanation I saw a while back of the phenomenon. This debunker (a PhD @ Google) originally said it was impossible - and then realized he was wrong.

Initial claim of impossibility: http://scienceblogs.com/goodmath/2008/12/windpowered_perpetu...

Recognition of truth ;-): http://scienceblogs.com/goodmath/2008/12/the_real_bozo_attem...

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I prefer Terry Tao's explanation (http://terrytao.wordpress.com/2009/03/23/sailing-into-the-wi...), carry the result over to land by replacing the "keel" with gears.

As always, Tao's explanation is crystal clear, takes you from the absolute basic layman level to as deep as you want to go.

Thanks! That was far more readable than the original article. I had dismissed the idea for exactly the same reasons as the author, and now understand how I was wrong about it. Glad to have learned something today.

Thank you! That link is much clearer than the article.

One thing wasn't in it that I found cleared this up a lot, though: with a normal sail, wind that gets caught still moves forward relative to the ground, just slower. With this thing, it winds up going backwards. That supplies the extra needed momentum.

What makes me really happy is that when me and my roommate discussed how this worked months ago, we eventually explained it exactly as he did in less-equation-y form.

Moral of the story: I don't fail completely at fluid dynamics.

Thanks. That's the best explanation I've seen.

It took me a long time to persuade myself that it wasn't a hoax, and when I submitted it here I was half expecting someone to point out some flaw.

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