The Accidental Scientist: Science of Cooking Exploratorium
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activity: Take an Egg for a Spin
Spin an egg and make it stand on end. Amaze your friends!

   
What Do I Need? .
a hard-cooked egg (Click here for instructions on how to hard cook an egg, which is part of our Deviled Eggs recipe.) 
a raw egg (for comparison purposes)  
a kitchen table (or other smooth, hard surface)  
   
What Do I Do?

 

1. Get both eggs spinning on the kitchen table.

   

2. Stop both eggs, then release them. Watch what happens.

 
   

3. The hard-cooked egg will remain stationary, but the raw egg will start spinning again. That’s because the liquid inside didn’t stop moving when you stopped the shell. The moving liquid starts the shell moving again.

   

4. Set the raw egg aside. Spin the hard-cooked egg again. Get it spinning very, very fast. Once it’s going fast enough, the spinning egg will spontaneously rise up on end and spin like a top.

   

5. If you don’t get the egg to stand on end the first time, try again. To stand on end, the egg must be spinning faster than about 10 revolutions per second. It took us a few tries to get the egg spinning fast enough.

   
Whats Going On? .

The short answer is: Friction between the eggshell and the tabletop pushes the spinning egg up.

This trick astounds people because the egg appears to be defying gravity. Rather than lying down comfortably (as many of us prefer), the egg spontaneously stands on end.

Keith Moffatt and Yutaka Shimomura, the mathematicians who spent six months (and many equations) working on this problem, explain that friction destabilizes the egg’s spin and causes it to shift position. Some of the energy of the egg’s spin (kinetic energy) is converted to potential energy, the energy that’s stored in an object that has a distance to fall. When standing on end, the egg has more potential energy and less kinetic energy—at least for a few seconds.

To learn more about spinning eggs, check out some of the articles written on the problem.

 

 
What Else Can I Try? .
• See if you can find other egg-shaped objects that will stand on end when you spin them. To learn about one person’s experiments, check out this letters column from New Scientist magazine.

 

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