Real spring arrives this week
Over the last several years, or so, you may have heard your local TV weatherperson declare March 1 as the start of meteorological spring. Personally, I think that term is a big misnomer. Some of the worst winter storms can raise havoc in March and even early April.
The reason meteorological spring occurs on March 1 is mainly for record-keeping. According to the National Centers for Environmental Information, a branch of the National Oceanic and Atmospheric Administration, the year is divided into four seasons of three months each. A few weeks back, we finished meteorological winter, which runs from Dec. 1 to Feb. 28 (or 29 every four years). Meteorological spring continues through May 31.
I can certainly understand how defining seasons this way makes record-keeping easier, but I still prefer the traditional astronomical start of spring, the vernal equinox. That’s a bigger deal, as far as I’m concerned, because that’s when the sun crosses the celestial equator and heads into the northern half of the celestial sphere.
Astronomical seasons are due to Earth’s tilt of 23.5 degrees relative to its orbit around the sun. Because of that, the sun’s path among the backdrop of stars, known as the ecliptic, is inclined to the celestial equator by that same 23.5 degrees. The celestial equator is just a projection of Earth’s terrestrial equator onto our sky and occupies the same mathematical plane as Earth’s terrestrial equator. Because of where we live, the celestial equator runs from the eastern to western horizon, and its highest point is due south about halfway from the horizon to the overhead zenith.
At 10:46 a.m. this Friday morning, the sun will be smack dab on the celestial equator in our sky. That means the sun is shining directly overhead anywhere along Earth’s equator. This also occurs in late September on the day of the autumnal equinox. All parts of Earth experience equal amounts of sunlight and radiation on both vernal and autumnal equinox days.
On summer solstice in late June, the sun’s most direct rays shine over the Earth’s northern hemisphere. That puts the sun high in our sky at its maximum separation north of the celestial equator, making our days much longer than our nights. On winter solstice in late December, the sun’s most direct rays shine over the Earth’s southern hemisphere. That puts the sun very low in our sky at its maximum separation south of the celestial equator, making our nights longer than our days.
There’s a good chance this Friday that if you surf news channels or programs on your cable or satellite system, you’re bound to see a weatherperson or a news anchor attempt to balance an egg on its end. If and when they finally get that egg to stand up on its own, they’ll claim that it’s because of the vernal equinox. That’s absolute malarkey!
The truth of the matter is that you have just as much of a chance to get an egg to stand up vertically on any other day of the year. The equinox has absolutely nothing to do with it. Try this on your own at another time of year if you have a lot of extra time and a lot of patience.
You’ve also been told over the years that on vernal equinox day, everyone worldwide has equal amounts of daylight and nighttime. That’s yet another myth!
Certainly, it’s true that both hemispheres receive equal sunlight, but actually, the days will be longer than the nights. Just check any almanac for Shamokin and you’ll see that by Friday we’ll already have more than 12 hours of daylight. Equal days and nights will be achieved on St. Patrick’s Day, this coming Tuesday, yet another reason to celebrate!
Earth’s atmosphere is responsible for this. The sun’s light, coming from 93 million miles away, is bent by the shell of our atmosphere, a phenomenon known as astronomical refraction. The thicker the atmosphere, the more the sun’s light is bent.
Whenever the sun is rising or setting, at any time of year, its light must cut through a much thicker layer of the atmospheric shell than it does when old Sol is overhead. The bending of the sunlight is so extreme at the horizon that the sun’s disk will appear above the horizon when it’s actually below it, giving us extra daylight.
Believe it or not, up until about 1750, New Year’s Day was not celebrated on Jan. 1 in England and early America. They brought in the new year on the first day of spring because, shortly after that day, nature begins to green up and renew itself. England and the colonies were still using an old calendar with roots dating back to Babylonian times.
Most of the Western world, especially Roman Catholic countries, switched to the Gregorian calendar in the late 1500s. That calendar had Jan. 1 as the first day of the year. England finally decided in 1750 that it was time to align with the rest of the Western world and adopted the Gregorian calendar.
Happy Spring! Eat your eggs — but forget balancing them. It could get a little messy if they roll off the table!
This coming Friday evening, the first evening of spring, there’ll be a nice conjunction between the new crescent moon and the bright planet Venus in the low Western sky during evening twilight. The moon will be shining a little above the cloud-shrouded planet named after the Roman goddess of love.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net. Contact him at mikewlynch@comcast.net.
