Double punch of spring in the sky
After another long winter, we could all use some spring. Yes, winter sports are great, but many of us are ready to turn the page. It’s time for spring of 2023 to begin, at least astronomically, and it will arrive Monday afternoon, March 20, at 5:24 p.m., the exact moment of the vernal equinox.
In 2007, Congress changed the start of daylight saving time to the second Sunday in March. Before 2007, it began in April. The earlier start gives us a preview of spring, in a way.
Admittedly, the beginning of daylight saving time is more noticeable than the vernal equinox because of the dramatic increase in daylight in the early evening, even if the weather outside may be less than spring-like!
Nonetheless, the vernal equinox is a big deal astronomically as the sun crosses the celestial equator heading farther north and higher in our sky.
Earth revolves around the sun with its axis tilted by 23.5 degrees to its orbit around our home star. 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 in our sky of the Earth’s terrestrial equator and occupies the same mathematical plane.
Around the Twin Cities and vicinity, the celestial equator is an imaginary line that runs from the eastern to the western horizon. Its highest point is due south, about halfway from the horizon to the overhead zenith.
At 5:24 p.m. Monday afternoon, the sun will be smack dab on the celestial equator in our sky.
On the day of the vernal equinox in March and the autumnal equinox in September, the sun is shining directly over Earth’s equator. At midday, anywhere along the equator, the sun will be directly overhead. The Northern and Southern Hemispheres experience equal amounts of sunlight.
On the summer solstice in late June, when the sun’s most direct rays shine over Earth’s Northern Hemisphere, the sun reaches its highest point in our sky at midday. The sun is at maximum separation north of the celestial equator, so daylight hours are at a maximum, and nights are the shortest they can be.
On the winter solstice in late December, the sun’s most direct rays are shining over Earth’s Southern Hemisphere, and that puts the sun very low in our sky at its maximum separation south of the celestial equator. Daylight hours are at their shortest, and nights are at their longest.
Almost without fail, on the day of the vernal equinox, you’ll see either a TV weatherman or an anchor attempt to balance an egg on its side. If they get the egg to stand up, they’ll claim it’s because of the vernal equinox. The truth is that the vernal equinox has nothing to do with it. Your chance of getting an egg to stand up is no better or worse than any other day of the year!
No doubt, you have also been told that the days and nights are equal in length on the vernal and autumnal equinoxes. Everyone worldwide experiences twelve hours of daylight and twelve hours of nighttime. Guess what? That’s yet another myth! Indeed, it’s true that both hemispheres receive equal sunlight, but days are already longer than nights. We will have 12 hours and 8 minutes of daylight as of today in Butler. Days and nights were equal this past Friday, March 17, St. Patrick’s Day!
Earth’s atmosphere is responsible for this. The sun’s incoming light from 93 million miles away is bent by Earth’s shell of atmosphere, something called astronomical refraction. The thicker the atmosphere, the more the sun’s light is bent. Whenever the sun rises or sets at any time of the year, its light has to cut through much more of our atmosphere than when it’s shining high in the sky. 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, until about 1750, England and early America didn’t celebrate New Year’s Day on Jan. 1. New Year’s was celebrated on the same day as the vernal equinox. That’s because on the first day of spring, plants and trees slowly begin to green up, and nature begins anew. They were popping champagne corks as flowers were blooming. After this winter jail, believe me, I want to pop open some champagne too!
England and the colonies were still operating under an old calendar with roots that dated back to Babylonian times. Most of the western world, especially Roman Catholic countries, switched to the Gregorian calendar back in the late 1500s. That calendar had Jan. 1 as the first day of the year. In actuality, it was a correction of the Julian calendar that went back to 46 BC, which also had Jan. 1 as the start of the New Year.
England finally decided in 1750 that it was time to get in sync with the rest of the western world and adopted the Gregorian calendar.
Happy spring and Happy New Year!
Celestial Happening this week: The new crescent moon will be passing by the bright planets Jupiter and Venus later this week. On Wednesday evening during twilight about 40 minutes after sunset, look for a very thin crescent moon just above Jupiter in the very low western sky, barely above the horizon. On Thursday early in the evening, a slightly fatter crescent moon will lie just below the very bright planet Venus in western sky. On Friday evening, the moon will be above Venus. With a pair of binoculars or a small telescope, see if you can spot the faint and very distant planet Uranus just off to the low left edge of the moon. It’ll resemble a faint bluish-green star. Uranus is just under 1.9 billion miles from Earth this week!
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of "Stars: a Month by Month Tour of the Constellations," published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at firstname.lastname@example.org.