This conceptually frustrating wind-powered vehicle claims to move downwind faster than the thing powering it. It’s a concept so counterintuitive that many of the people who have seen its creators’ demonstrations on the subject accuse them of quixotically searching for perpetual motion.

But, as the North American Land Sailing Association put it in 2012 when this vehicle set its land speed records, this is not a perpetual motion machine.

“This is not a joke or an intentional hoax; everyone involved is taking this seriously. The Blackbird is not claiming to be a perpetual motion machine, it is using energy from the wind; if the wind stops so does Blackbird. They just seem to have figured out a way to turn the wind’s energy into forward motion in a way that is more efficient than a parachute, tumbleweed or conventional sail or wing.”

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The reason people are so annoyed by this land yacht is that if the wind is pushing you, once you get up to windspeed, there shouldn’t be any push left. The reason most sailboats have triangular sails that are mounted sideways, though, is because if you go sideways to the wind, the sail acts like a wing, and you can go faster than the wind, albeit not directly downwind.

In fact, Greenbird, another land-yacht, set the wind-power land speed record of 126.1 mph in 2009. That means that if your downwind angle is right, you can still move in the direction of the wind faster than, say, a balloon drifting straight downwind.

This interested the creators of the Blackbird, the vehicle you see here. They reasoned that if the earth were a cylinder, a sailboat could corkscrew downwind faster than the wind. If you put two boats at opposite ends of the cylinder, it would look just like a propeller.

From there, it gets more complicated with the wheels pushing the propeller and the propeller pushing the wheels, which feels a lot like Mitch Hedberg’s joke about his belt holding up his pants and his belt loops holding up his belt and him not knowing who the real hero is.

Regardless, the host of this video, Derek Muller, manages to go faster than the apparent wind. One of its builders was able to go directly downwind 2.8 times faster than the wind speed in 2012, earning himself a record along the way. The vehicle also managed to go upwind at 51.4 mph when in a wind of around 20 mph.

Despite the design that makes late ’60s F1 wings look reasonable and the wobbly nature of the prop, this remains a fascinating and frustrating example of how counterintuitive physics can be sometimes.