Despite the recent resurgence of winter weather, I can feel how close spring is. Here in New Mexico, the roadrunners are frolicking, trees are budding and I’m sowing lettuce seeds in my raised garden beds. So mark your calendar for March 20: The vernal equinox signals the astronomical start of spring in the Northern Hemisphere.
While equinoxes might not get the same attention as solstices, they’re a lovely way to observe the seasons shifting. Let’s get to know the vernal equinox, what it is and why it happens.
What is the spring equinox?
You’ve no doubt noticed the lengthening of daylight as winter winds down (especially since daylight saving has already begun). Vernal equinox marks the tipping point into longer days.
The word “equinox” comes from the Latin words for equal and night. Daylight and night are roughly equal during the equinox. We experience two each year — the vernal equinox in the spring and the autumnal equinox in the fall. The word “vernal” traces to Latin and references spring.
This National Weather Service graphic shows Earth’s tilt, how it orbits the sun and when the equinoxes and solstices occur in the Northern Hemisphere.
The Earth spins on an axis (think of it like a line running from pole to pole) with a 23.5-degree tilt. Some parts of the planet get more direct sun than others. That’s how we get our seasons, and how it can be summer in the Northern Hemisphere while it’s winter in the Southern Hemisphere.
“The spring equinox is when the Northern Hemisphere transitions from being pointed away from the sun (during winter) to being pointed toward the sun (during summer),” says Emily Rice, associate professor of astrophysics at the Macaulay Honors College of the City University of New York. “The tilt is lined up with Earth’s orbit for just a moment.” That’s when we get nearly equal amounts of daylight and night.
When does the vernal equinox happen?
Spring equinox has a specific time, at 2:01 a.m. PT on March 20. No need to set an alarm. You can celebrate the equinox all day on March 20.
How are equinoxes different from solstices?
Solstices are the extremes for days and nights. Summer solstice is the longest day while winter solstice is the shortest. Summer solstice for the Northern Hemisphere hits on June 20 while winter solstice occurs on Dec. 21 this year.
Solstices get more love than equinoxes.
“The extremes are easier to mark and to visualize than the inflection points, which are more subtle changes, so the solstices get all the attention,” says Rice. All of them are related to the sun and Earth’s tilt, so think of solstices and equinoxes as siblings that each have their own seasonal connection.
What the equinox looks like from space
It can be challenging to visualize the Earth’s tilt and what happens during equinox from down on the ground, so NASA put together a video showing the Earth as seen by a satellite.
It tracks our planet through its seasons. Watch how night and daylight shift over time.
How you can celebrate the spring equinox
Perhaps you’ve heard that the only day you can balance a raw egg on its end is on the equinox. This legend might be accompanied by some vague discussion points about Earth’s gravity and alignment and the sun.
I balanced this egg on its end on a day that wasn’t the equinox.
One of Rice’s annual equinox duties is debunking the egg-balancing myth.
“Astronomers are usually on the internet telling people that no, they can’t actually balance an egg on its end only on an equinox,” she says. You can go ahead and try it, but be sure to also test it out on a day that’s not the equinox. I pulled it off on Feb. 27, in case you’re wondering.
Equinox is a subtle phenomenon. There are no showy celestial events to mark the day. Don’t let that deter you. The vernal equinox is what you make of it.
“Considering that the Earth’s orbit doesn’t have a beginning or an end, a year could really be started any time, and the equinox is more astronomically meaningful than Jan. 1,” says Rice.
You can come up with your own way to celebrate the occasion. Tell your friends and co-workers it’s the start of astronomical spring. Plant some seeds. Clean your house. Spend time outside. Make spring break plans. And take a moment to toast the sun, the Earth’s tilt and our place in space that brings us the vernal equinox.
