Light and Balance: The Vernal Equinox Explained

So riddle me this, what happens twice a year? Some say you can balance an egg only on this day and was a big deal back in ancient history.

Give up? It’s the equinox and today we’re celebrating the Vernal equinox and it’s the official kick off to spring in the northern hemisphere.

Now, I know what some of you are thinking, “equi-what now?” Don’t worry, we’ll walk you through it. By “we”, I mean, I called in a little help. UWM Manfred Olsen Planetarium director, Dr. Jean Creighton.

So, what exactly is the equinox?

Dr. Creighton says, “The official definition would be where the celestial equator meets the ecliptic. It is the two times of the year in two places, if you will, in space where the path of the sun intersects with our equator that’s projected onto the sky.”

So It’s all about the Earth’s orbit around the Sun. Since the Earth is tilted about 23.5° right now, we’re neither tilted away nor towards the Sun. We’re kind of at a balance.

“If the Earth was standing upright, then the path of the Sun and that projection onto the sky would be exactly the same. But because we’re tilted, they meet those two lines only twice a year,” explains Dr Creighton.

The word equinox actually comes from the Latin words “Aequi” meaning equal and “Nox” meaning night.

Creighton says, “Everybody on the planet has 12 hours of day and 12 hours of night. Generally speaking, every other day of the year, you either have more night or more day. And that’s true everywhere.”

So then, why does spring start off on different days each year?

“There’s an exact moment when the sun is plotting around along the ecliptic, the path of the sun, and it bumps into the celestial equator at a particular time. And that’s why sometimes it’s the 21st of March But it could be the 20th, it could be the 22nd. So there’s a little bit of give on exactly when that happens,” explains Creighton.

Ancient cultures like the Mayans knew this day was special. They built incredible monuments like Chichen Itza in Mexico, where during the equinox a shadow falls on the pyramid creating the illusion of the feathered serpent Kukulkán descending the steps.

It also marked the time when people would start planting crops, pretty important for those ancient civilizations if you think about it. Even modern science continues to study the equinox, using it as a reference point for understanding the Earth’s orbit and climate patterns.

So, there you have it, folks. The Vernal Equinox, a day of balance, renewal, and the official start of spring. Oh, and that whole balancing an egg only on the equinoxes? Not a thing. There’s no correlation to the Earth’s gravitational pull changing on any spot in its orbit around the sun. Sorry, but hey, we’re getting more light everyday and soon it’ll be summer. So there’s that.