- Spring or spring The 2023 equinox occurs on Monday, March 20.
- The equinoxes occur when the Earth’s tilted axis is perpendicular to the sun’s rays.
- During an equinox at Earth’s equator, the sun appears almost directly overhead.
The vernal equinox of the year, also called the March or vernal equinox, falls on Monday at 5:24 p.m. EDT.
For people living in Earth’s northern hemisphere, this astronomical event marks the arrival of spring, the end of winter, and the increasingly warmer and brighter days that come with the pending arrival of summer.
For those in the southern hemisphere, however, fall will arrive: The days are getting shorter, the weather is cooling, and the sunlight is getting dimmer as winter approaches.
What drives this all-important seasonal clock?
Technically, two things: Earth’s tilted axis and the planet’s orbit around the sun.
How does the vernal equinox work?
Earth orbits the sun once every 365 days and six hours. Our planet also rotates once a day on a tilted axis.
This tilt is about 23.5 degrees (currently) and bathes different parts of the world in different intensities of light over the course of a year. Meanwhile, the planet’s rotation keeps the heating uniform, like a 7,917-mile-wide roasting chicken made of rock and some water.
The rotation of the Earth does not cause equinoxes. The vernal equinox occurs when the sun’s heating rays are aligned perpendicular to the Earth’s axial tilt:
If you are standing directly on the equator at noon in the Eastern time zone at noon, the sun will appear more or less directly overhead. Your shadow will also be at an absolute minimum.
The sun also sets and rises about 12 hours apart during the equinox.
But that moment won’t last as Earth makes its way around the sun at about 66,600 mph.
Our planet’s orbit is elliptical and its center of gravity is slightly offset from the sun, so the time it takes to cycle through the seasons is not perfectly spaced.
About 92 days and 19 hours after the vernal equinox, Earth will reach its summer solstice. Another 93 days and six hours later, the fall or fall equinox will occur.
Some satellites fly around the Earth in a geosynchronous orbit, meaning they move fast enough to hover over a point on the planet.
This creates a great opportunity to photograph the planet throughout the year and see how the angle of the sun changes.
NASA’s Goddard Space Flight Center created the following animation using geomodern satellite images taken over Africa that clearly shows the seasonal evolution:
The equinox is the first day of spring, but not for meteorologists
March 20 is officially the first day of spring, but meteorologists have a very different take on our seasons. For them, spring began on March 1st.
This is because the calendar seasons do not align with the astronomical seasons. The coldest three months of the year, which begin in December, usually end in late February in the Northern Hemisphere. so it makes sense for meteorological spring to begin in early March.
Spring forward can mess with your head
While most of us will be looking forward to the warm weather, spring is also associated with the dreaded Daylight Savings Time, which happened on March 12 for the US.
Research has previously shown that heart attacks, strokes and fatal car accidents increase when the hour starts.
It may be because of our sleep patterns, our bodies are shocked by even an hour’s difference in their sleep schedule, and this can make us more prone to fatal mistakes, Insider previously reported.
A recent YouGov survey found that 62% of Americans would prefer to shorten daylight saving time.
What about the egg balancing trick?
You may hear people say that it is possible to balance an egg on its edge at the equinox because of the way it is positioned in relation to the sun.
Spoiler alert: it’s a myth.
You can balance an egg whenever you want, thanks to the very small pores in its shell.
These pores create almost invisible dimples in the shell onto which a (very, very) patient person can lift the egg.
And don’t look for any gravitational interaction between the Earth and the Sun to help you. it is too weak to make a noticeable difference.
This story was originally published at 6:19 p.m. EDT on March 19, 2018. Dave Mosher wrote an earlier version of this article.