The Skeptical Teacher

Musings of a science teacher & skeptic in an age of woo.

Posts Tagged ‘equilibrium’

It’s Equinox Time, So Balance Some Eggs for Science!

Posted by mattusmaximus on September 22, 2011

Tomorrow, September 23rd, is the autumnal equinox in the northern hemisphere, and it is on this occasion that I like to inject a little skeptical and critical thinking fun into my physics classes.  Most of us have heard of the urban legend about balancing an egg on its end during the equinox – the thing is, this is true!  The myth is the implication that one can only do this on the equinox, when – in fact – you can balance an egg on end pretty much any time you want.

Case in point, here’s a couple of photos of me balancing eggs on their ends during the time of year exactly opposite to the equinoxes…

During the summer solstice…

And during the winter solstice…

In addition, here’s a nice Youtube video showing some tips on how to accomplish this trick:

The reason why this trick works boils down to simple physics: it’s called unstable equilibrium.  If you have a flat and level surface on which to perform this trick, and there aren’t a lot of vibrations around, then chances are you can balance a number of eggs in a standard dozen pack.  As long as the eggs are relatively smooth on their ends (look closely and you’ll see some bumps on some of them) and you are very patient, then with some practice pretty much anyone can perform this trick.  The Bad Astronomy blog has a pretty good rundown on the physics as well.

So the next time you hear someone pass along the “eggs can be balanced only on the equinox” myth, whip out some eggs and balance away.  It’s a quick, easy, and fun way to advocate for skepticism and science 🙂

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