Although some bouts of spring-like warmth have surfaced at times in recent weeks, the astronomical calendar is still in the winter season. It is not until the arrival of the vernal equinox (first day of spring) that the spring season is officially upon us. The moment that we pass from winter into the spring season is at 11:15am (Central Daylight Time) on March 20th. Let's dig into exactly what that means for planet Earth.
The word equinox comes from the Latin words aequus (equal) and nox (night). It is on the equinox that the earth's axis is neither tilted away nor towards the sun. The result is the length of the day and night are "nearly" equal across the globe on the equinox. The reason we say that the day and night are nearly the same on the equinox is twofold. First off, the earth is not a perfect sphere, which will result in some small disparities in daylight. The second reason is due to the way the sun's rays get bent over the horizon, making the sun appear above the horizon, when it is actually below for a time. Because of this, the actual amount of daylight will vary from 12 hours, six minutes and thirty seconds at the equator, to 12 hours and sixteen minutes for folks living near 60 degrees latitude. On an equinox, residents who live on the equator will see the sun directly overhead at noon. Another interesting tidbit is that on the equinox, the sun will rise due east and then set due west.
For arctic explorers, the equinox had to be quite a joyous event. This is because the North Pole goes into total darkness in early October and doesn't see the sun rise until the vernal equinox. For those of us stationed at lower latitudes, the days have become noticeably longer in recent weeks, as most areas gain a few minutes of daylight every day from late February into the month of March.
On the same day we are celebrating the official arrival of spring, residents in the southern hemisphere are marking the passage of the autumnal equinox as they mark the end of the summer season.
There are certain myths that continue to live on, concerning the equinoxes. One is that you can balance an egg easier on the equinox than on any other day due to some balance in the gravitational pull that day. Egg balancing can actually be done with some skill and the fortune of having a well-balanced egg on any day, and is no easier on the equinox. So, don't spend too much time trying this feat unless you are planning on having scrambled eggs for breakfast!