[00:01] Dzhanibekov effect or the tennis racket theorem [music] or the intermediate axis theorem. Now, you may have seen clips like this one before, but in this video, I will provide the best intuitive explanation of how this effect [music]
[00:15] works. So, in 1985, cosmonaut Vladimir Dzhanibekov was tasked with saving the Soviet space station Salyut 7, which had completely shut down. And after rescuing
[00:27] the space station, Dzhanibekov unpacked supplies sent up from Earth, which were supplies sent up from Earth, which were locked down with a wing nut. And as the wing nut spun off the bolt, he noticed something strange. The wing nut
[00:40] maintained its orientation [music] for a short time, and then it flipped 180° and as he kept [music] watching, it flipped back a few seconds later. And it continued flipping back and forth at regular intervals. It was a strange and
[00:55] counterintuitive phenomenon, one that the Russians kept secret for 10 years. Six years later, in 1991, a paper was published in the Journal of Dynamics and Differential Equations called The Twisting Tennis Racquet. And although it
[01:09] was related, it of course makes no mention of the secret Dzhanibekov effect. The paper says, "If you hold a tennis racket facing you and then flip it in the air like this, it not only rotates the way you intend it to, it
[01:22] also makes a half turn around an axis that passes through its handle. So, the side that was originally facing you will be facing away when you catch it."