Skip to content

Equinox Info That's Astronomically Cool


Inspired by Luciana™, we're celebrating the March equinox with a few stellar scientific facts!

On March 20, at 12:15 p.m. EDT, the sun’s center point will cross the Earth’s equator, signaling the start of spring in the northern hemisphere, fall in the southern. In that moment, the sun will shine equally on both hemispheres, and day and night will be nearly equal all over the planet. Different civilizations and cultures have celebrated the equinox since antiquity, but what is so interesting about this cosmic crossroads?

If the Earth’s axis were perpendicular to its path around the sun, then our days and nights would always be of equal length and we’d have no seasons. If that sounds a little monotonous, and you love to see the seasons change, thank Theia: a compelling hypothesis in the scientific community suggests that early Earth collided with another planet-like body, Theia, about 4½ billion years ago, tipping Earth on its axis.

Bonus: Many lunar scientists think the collision produced rocks and debris that eventually became our moon. Fun thing to ponder when moon-gazing during that first warm spring evening!

The equinox is the perfect time to get your bearings: on this day, the sun rises due east and sets due west. And while, these days, our sense of direction relies more on our GPS and less on our ability to observe the position of the sun, it is worth noting that many migrating birds, butterflies, and other animals use cues from the sun as one tool that helps them navigate to the right places at the right time.

And speaking of timing, take the March equinox as your cue to search for interactive animal tracking maps on the web so you and your girl can follow the progress of your favorite migratory animals throughout the seasons, equinox to equinox.

The Earth is not the only planet to experience equinoxes: Mars, Saturn, Uranus, and Neptune all tilt on their axes, so they all experience a spring and fall equinox. Of course, our neighbors’ seasons aren’t quite the same as ours. A single season on Neptune lasts about 41 Earth years due to its long orbit around the sun. And thanks to Mars’ elliptical orbit, where one year is almost two Earth years, the length of each season varies. Spring lasts 7 months—and winter lasts just over half that. Good information to have as the next generation sets their sights on Mars!

© 2018 American Girl. All American Girl marks are trademarks of American Girl.

Related Articles