That Infernal Equinox

06/08/2012 08:23 pm ET | Updated Aug 08, 2012

Is it true, as some people claim, that during the vernal equinox it is possible to stand an egg on end?

Yes, it's true. And during the autumnal equinox, as well. And on Tuesdays in February, and any time during the fourth game of the World Series when the count is three and two on a left-handed batter.

Get the picture? Equinoxes have nothing whatsoever to do with balancing eggs. With patience, you can balance an egg on end any time you feel like it.

But old superstitions never die, especially when perpetuated year after year by kooks who like to perform pixie dances in the meadows on the day of the vernal equinox, which is the first day of spring. This year, it was on March 20, and the autumnal equinox (see below) will occur on Sept. 22.

Take a close look at an egg. It isn't glassy smooth, is it? It has little bumps on it. Go through a dozen and you're sure to find several that are quite bumpy on their wide ends.

Now find a table top or some such surface that is relatively smooth. With a steady hand and some perseverance, you'll be able to accomplish this miraculous astronomical (more appropriately, astrological) feat without any contribution from the "aligned planets" (which they're not), or from Mother Earth, except for supplying the gravity that makes the task challenging. If the balancing surface is even slightly rough, like a textured tablecloth, it's a piece of cake. In fact, an old after-dinner trick was to conceal a wedding ring under the tablecloth and, with feigned difficulty, "balance" the egg on it.

So much for the old egg caper. But what is an equinox, anyway?

Picture Earth, circling the sun at the rate of one revolution per year. The circle made by Earth's orbit around the sun lies in a plane, just as a circle drawn on paper lies in the plane of the paper; it's called the plane of the ecliptic. Now Mother Earth wears another circle around her middle; it's called the Equator, and it also lies in a plane, called the equatorial plane. We can imagine the equatorial plane being extended beyond Earth, way out toward the Sun. Funny thing, though: it misses the Sun. You usually won't find the Sun anywhere in the equatorial plane. That's because Earth is tilted, so its equatorial plane passes above or below the position of the Sun. The equatorial plane is tilted from the plane of the ecliptic by about 23.5 degrees.

As the tilted Earth moves around the Sun, there will be two times in the year when the two planes intersect -- that is, two times when the Sun, in its ecliptic plane, is also in the equatorial plane, meaning that it is directly over the Equator. But for half the year, the Sun is north of the Equator and the northern hemisphere has spring and summer; for the other half of the year the Sun is south of the Equator and the southern hemisphere has spring and summer. The two "crossover" instants, called the vernal (spring) equinox and the autumnal (autumn) equinox, are how we define the beginnings of spring and fall in the northern hemisphere. The word "equinox" comes from the Latin meaning "equal night," because at those instants the periods of daylight (the days) and darkness (the nights) are of equal duration all over the world. Because the sun is directly over the Equator, it favors neither more daylight in the north nor more daylight in the south.

Without knowing all this, primitive people found the equal-light-and-darkness dates to have special significance, ushering in, as they do, seasons of warmth and growth or cold and barrenness. So all sorts of superstitions grew up around these dates. You can see, though, that there is no "alignment of the planets" or any other possible gravitational effects of the equinoxes that would make eggs do anything weird. The only things that are weird are the nuts who claim that these dates have magical powers.

Find much more stuff like this in What Einstein Told His Barber by clicking on the book cover below.