Musk’s “flying car” wasn’t flight—it was a five-second stunt. When Musk posted a video of the Tesla Roadster jumping and spinning in midair, claiming “in the future, real flying cars will exist,” many people cheered. I watched the video and thought, “This is just a ridiculous stunt”—and I was right, as Turing Award winner Yann LeCun precisely demonstrated using physics. LeCun’s critique was simple yet devastating. After confirming the propulsion system used high-pressure compressed air, he pointed out that its specific impulse was under 50 seconds. Compared to hydrogen peroxide rockets used in 1970s jetpacks—which had a specific impulse of about 150 seconds—this system is only one-third as efficient. Even assuming the vehicle’s mass is 50% filled with compressed air, the thrust-to-weight ratio exceeds 1 for less than 10 seconds—and realistically, only about 5 seconds. The conclusion: the chassis must be nearly empty, lightweight shell filled with massive high-pressure tanks, and even then, it can only hover briefly. Actual disclosed data supports this analysis. The cold-gas thrusters mounted on the Roadster operate using tanks of roughly 600 liters and about 250 kg of compressed air, with a boost duration of approximately five seconds. Recharging takes several hours. This is nowhere near a “flying car” that can carry a person, drive on roads, and take off when needed. It’s merely a specially modified vehicle performing a short jump and rotation as a demonstration. Musk’s response? A joke: “I just farted at you.” LeCun replied: “A 700-bar, 600-liter, three-second loud fart.” No rebuttal followed regarding the physics calculations. LeCun later clarified: “It’s a great marketing stunt, but it’s not the path to a real flying car.” Though he owns two Teslas and fully acknowledges Musk’s tangible achievements, he draws a clear line against hype—exactly as I do!! Ultimately, the essence of this video isn’t a declaration of future technology—it’s a show that mislabels a brief hop using compressed air as “flight.” LeCun’s precise numerical analysis makes this distinction unmistakable: it looks impressive, but it’s still far from a practical flying car. Tesla fanatics are going insane over this!! @elonmusk @SawyerMerritt @wholemars