The egg and the (other) equinox

SkyCaramba weekly astronomy blog for the week ending September 24, 2011

Some people believe the earth and sun align at the equinox in a magical way testable on your kitchen table. Take an egg, they say, and you’ll be able to stand it on its end only twice a year. Some versions of the myth say only during the March equinox. But go ahead and try it now. 

It works because the forces keeping the egg balanced on its end at one equinox are also at work during the other. What escapes people is that the equinox has nothing to do with it. You could stand the egg on its end any day of the year. 

Bad Astronomy author Philip Plait believes the egg rests on its end because of all the tiny bumps on its surface. They act like little legs. Special positioning of the earth and sun is no more necessary for standing an egg than it is for keeping a chair or table upright on its legs. But people have always loved to believe they are tapping into ordinarily uncontrollable powers, so the story goes around. 

It’s hard to balance an egg like that any time. You’ll probably need several tries. You may even give up without success after several attempts. It’s possible some people unwittingly reinforce the myth in their minds by trying repeatedly on the equinox just “knowing” it’s true and finally succeeding but giving up easily the rest of the year. So give it a sincere try no matter what day it is. 

The equinox-egg myth is a great science lesson, especially for kids. Not only can you teach them not to believe everything they hear, you can teach about the scientific method. Even if you demonstrate something once, you have to be able to demonstrate it again for it to be accepted as science. 

If you can get more than one kind of egg, you may be able to prove or disprove Plait’s idea that the little bumps act like legs for the egg to stand on. Some eggs have smoother surfaces than others. If Plait is right, it should be harder to balance those eggs on end. Maybe you can (safely) get eggs from a goose, ostrich, or snake. You might as well try plastic Easter eggs too. I don’t know if it’s possible to take sandpaper or a file to a regular chicken egg to smoothen its surface, but in the interest of science somebody should try. 

At the least, you should be able to prove that the March equinox isn’t the only time the egg balancing trick can be done. But some people are so stuck in their beliefs, they’ll likely just say you proved it can be done only twice a year. Risk an argument or a bet with your friends at your own risk. Sometime, maybe I’ll write about why the way the water goes around in your toilet has nothing to do with which side of the equator you’re on.