A YouTuber bet a physicist $10,000 that a wind-powered vehicle can travel twice as fast as the wind itself – and won

• A popular YouTuber filmed himself driving a wind-powered vehicle downwind faster than the wind itself.
• A UCLA professor bet $10,000 that the video was wrong, saying it broke the laws of physics.
• Bill Nye and Neil deGrasse Tyson oversaw the bet. In the end, the professor conceded and paid up.
• See more stories on Insider’s business page.

When YouTuber Derek Muller took an experimental land yacht for a spin this spring, he wasn’t aiming to stir up scientific controversy. He certainly wasn’t trying to win $10,000 in a bet.

Muller, creator of the Veritasium channel, likes to break down funky science concepts for his 9.5 million subscribers. So in May, he published a video about a vehicle called Blackbird, which runs on wind power.

Created by Rick Cavallero, a former aerospace engineer, Blackbird is unique because it can move directly downwind faster than the wind itself for a sustained period of time. Any sailor worth their salt can tell you that a boat can do that by cutting zigzag patterns; that’s called tacking. But the idea that a vehicle can beat the breeze traveling straight downwind, no tacking involved, is controversial.

“I knew this was a counterintuitive problem. To be perfectly honest with you, when I went out to pilot the craft, I didn’t understand how it worked,” Muller told Insider.

Blackbird is so counterintuitive, in fact, that less than a week after Muller released his video (below), UCLA physics professor Alexander Kusenko emailed to inform him that the video had to be wrong. A vehicle like that would break the laws of physics, Kusenko said.

“I said, ‘Look if you don’t believe this, let’s put some money on this,'” Muller said. He suggested a wager of $10,000, never imagining Kusenko would take it.

But Kusenko agreed, and in the weeks that followed, the two exchanged data and argued about Blackbird. They even brought in several of science’s biggest names to help decide who was right, including Bill Nye and Neil deGrasse Tyson.

In the end, Muller emerged victorious.

‘I never saw a way I could lose’

Days after he suggested the wager, Muller said, Kusenko sent him a document with the bet’s terms.

“Everything was always super airtight, I never saw a way I could lose,” Muller said.

But Kusenko was equally confident: “Thanks to the laws of physics, I am not risking anything,” Kusenko told Vice last month. He did not respond to Insider’s request for comment.

Kusenko gave Muller an hour-long presentation that explained why he was certain the YouTuber had been taken in by bad science. The professor said Blackbird was most likely taking advantage of intermittent wind gusts that helped the vehicle speed up. He outlined his objections on a page of his UCLA website, though it has since been taken down.

For his part, Muller sent Kusenko data from the driving test in his video, which was filmed in the El Mirage lake bed in Arizona. During that drive, Blackbird accelerated over two minutes – a feat that would be impossible if it relied on intermittent wind gusts.

The vehicle reached a speed of 27.7 mph in a 10-mph tail wind.

-Derek Muller (@veritasium) June 21, 2021

Muller even contracted fellow YouTuber Xyla Foxlin to build a model cart similar to Blackbird that could be tested on a treadmill. And indeed, Foxlin showed that her wind-powered model could go faster than the wind.

Muller documented all of this back-and-forth in a follow-up video (below), which he released in June.

“Kusenko was so sure he was right. He wanted to make it public,” Muller said.

How Blackbird works

In 2010, Google and Joby Energy sponsored Cavallero and a team of collaborators from San Jose State University to build Blackbird. The team demonstrated that the vehicle could travel downwind 2.8 times faster than the wind’s speed, a record confirmed by the North American Land Sailing Association.

The secret to Blackbird, Cavallero explained, is that once the wind gets the vehicle going, its wheels start to turn the propeller blades – they’re connected to the blades by a chain. So as the vehicle speeds up, its wheels turn the propeller faster and faster. Then the propeller blades, in turn, act like a fan, pushing more air behind the land yacht and thrusting it forward.

“I never even imagined a decade later that a physics professor would still be arguing how it’s impossible,” Cavallero said.

After three weeks of back-and-forth debate, Kusenko acknowledged that Blackbird could go slightly faster than the wind, but maintained that it was only for short periods of time. If a gust of wind speeds up the land yacht then quickly dies down, he said, it will appear that Blackbird is traveling faster than the current wind speed.

“The resolution of our bet was not as clean as I’d hoped,” Muller said. “Kusenko coughed up the 10 grand, let’s leave it at that.”

Cavallero, too, wanted more acknowledgement of his vehicle’s capabilities.

“He conceded on a technicality – that the vehicle moves marginally faster than the wind temporarily,” Cavallero said of Kusenko. “I offered him another $10,000 bet, because his technicality is entirely wrong, but I know I won’t be hearing from him.”

Muller’s two videos have garnered at least 6.8 million views and 41,000 comments each, many of them agreeing with Kusenko that it’s impossible for Blackbird to go faster than the wind. Some viewers have even asked the YouTuber if he’d make follow-up wagers.

“It breaks a lot of people’s brains. Clearly it got Kusenko too,” Muller said.