Why do people try to balance eggs upright during the spring equinox?

March 20 is the spring (or vernal) equinox, marking the end of the long winter and the first day of spring.

On the equinox, the sun crosses the right plane of the earth’s equator, making day and night about the same length for everyone all over the world. That’s how we get ‘equinox’ - from the Latin aequi meaning equal and nox meaning night.

Many cultures and communities celebrate the coming of spring with a festival - but there’s another, odder tradition that comes with the spring equinox. It involves eggs.

It’s a recurring folk tale that pops up every year around the equinox. It goes like this:

During the equinox, the sun exerts a peculiar gravitational pull on the planet that makes it much easier to balance things on their ends. Traditionally, the item of choice is an egg, though people have also taken to balancing brooms in recent years.

The practice of egg-balancing originated in China and appears to have been popularized in the U.S. beginning with a 1945 article in Life.

But scientists say there is no truth that you can only balance an egg upright on the equinox. In 1987, astronomer Frank Ghigo published a paper confirming that eggs could be balanced during the equinox, and also at pretty much any other time in the year, reported the Associated Press.

He tested nearly 50 eggs on different days and found that some could balance and some couldn’t. It just depended on the irregularities in the shell - and had nothing to do with gravity or the equinox.

The real key to balancing an egg? Finding one with the yolk nicely centered in the shell.

“We stand upright by keeping our own personal centers of gravity within the bounds of our feet on the ground,” Harry Keller, CEO of Smart Science Education Inc., told Scholastic. “This is why standing on two feet is easier than standing on only one foot.

But just because there is no real science behind sun-based egg balancing doesn’t mean you shouldn’t do it, Ghigo, the astronomer, told the Associated Press.

“I don't wish to spoil people's fun,” he said. “I'm in favor of seasonal celebrations, and if egg balancing ceremonies add to the enjoyment of the festivities, I would encourage people to participate in them.”

This story was originally published March 19, 2018 at 9:19 AM with the headline "Why do people try to balance eggs upright during the spring equinox?."