# The Bizarre Behavior of Rotating Bodies | Summary and Q&A

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September 19, 2019
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Veritasium
The Bizarre Behavior of Rotating Bodies

## TL;DR

The Dzhanibekov Effect, also known as the Intermediate Axis Theorem or the Tennis Racket Theorem, is a counterintuitive phenomenon where an object flips back and forth when rotating around its intermediate axis.

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### Q: What is the Dzhanibekov Effect and how was it discovered?

The Dzhanibekov Effect refers to the phenomenon where an object flips back and forth when rotating around its intermediate axis. It was discovered by cosmonaut Vladimir Dzhanibekov in 1985 while working on the Soviet space station Salyut 7.

### Q: What is the Intermediate Axis Theorem?

The Intermediate Axis Theorem states that when an object with three different moments of inertia rotates around its intermediate axis, it will experience a half-twist motion that is uncontrollable. This theorem explains the Dzhanibekov Effect.

### Q: Can the Dzhanibekov Effect occur with objects other than tennis rackets?

Yes, the Dzhanibekov Effect can occur with various objects that have three different moments of inertia about their three principal axes. It has been observed with objects like cell phones and discs with holes.

### Q: Why was the Dzhanibekov Effect kept secret by the Russians for ten years?

The secrecy surrounding the Dzhanibekov Effect is possibly due to the implications that arose from experiments involving a spinning ball of modeling clay or plasticine. It raised questions about the Earth potentially flipping over, which led to speculation and conspiracy theories.

## Summary & Key Takeaways

• In 1985, cosmonaut Vladimir Dzhanibekov observed the Dzhanibekov Effect while rescuing the Soviet space station Salyut 7. The wing-nut he was working with maintained its orientation for a short time, then flipped 180 degrees and continued flipping back and forth.

• The Dzhanibekov Effect is related to the Intermediate Axis Theorem, which states that when an object with three different moments of inertia rotates around its intermediate axis, it will experience a half-twist motion that is uncontrollable.

• The phenomenon of the Dzhanibekov Effect is not limited to tennis rackets and can occur with other objects, such as cell phones and discs with holes. It requires an object to have three different moments of inertia about its three principal axes.