Thursday, December 3, 2020
Dec. 3, 2020

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The astronomical difference a Leap Day makes: We’ll have earliest spring since 1896

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The birds have been chirpier than normal for a February, the snow drops and daffodils are showing no fear, and when was the last time you saw salt brine on a road near you?

People in the U.S. have a 100 percent chance of having their earliest spring in 124 years, arriving officially this year on at 11:50 p.m. EDT on March 19.

Not only do we get a Feb. 29 in this leap year, but spring gets to leap forward on the calendar, and for that we can thank Julius Caesar, who was slightly off the mark (but who was going to correct him?); Pope Gregory XIII, whose calendar we use today; and the relentless eccentricity of Planet Earth.

Why a Feb. 29?

If the earth completed its annual 574,395,530-mile (give or take a few hundred feet) annual journey around the sun in precisely 365 days, calendar-making would be so simple.

Unfortunately, the trip takes 365.2422 days, notes Geoff Chester, an official with the U.S. Naval Observatory who still is enduring “blowback” for his insistence that the ’20s won’t start until next year. Thus the calendar would be out of sync by a day about every four years.

Does 2020 mark the start of a new decade? It’s surprisingly debatable. The glitch was recognized by astronomers in the Roman Empire, and Julius Caesar is credited with being the first to come up with the leap-year fix.

In the 16th century, Pope Gregory XIII determined that Caesar’s solution was an overcorrection. The Gregorian calendar adjusts this by skipping what would normally be a leap year every 400 years at the turns of the centuries. In 2100, February will have 28 days, and again, in 2500.

We do get the extra day this year, but it will add no length to what is and long has been the shortest season of the year.

Winter is the shortest season!?

The distance from winter solstice to spring equinox is just under 90 days, about a day shorter than fall’s trip to the winter solstice. Winter is three days shorter than spring, and four less than summer in the Northern Hemisphere.

The earth’s orbit around the sun isn’t a perfect circle. It actually is closer to the sun in our winter than summer. According to stats from Villanova University astronomy professor Frank Maloney, in 2020, our closest brush with the sun was Jan. 5, at 2:47 am. The planet was just 91.4 million miles away from the heat source, compared with 94.5 million come July 5.

The distance makes a significant difference in seasonal length. On average the earth is hurtling through space at 66,615 mph, says Maloney. But in January, it was booking it at 67,756 mph.

So the speed-up reduces the time it takes to get from the winter solstice, when the sun is directly over the Tropic of Capricorn in the Southern Hemisphere, and the equinox, when it is directly over the Equator. As we all do, the planet slows down in the Northern Hemisphere summer as it gets farther away from the sun, and that lengthens summer — and winter in the Southern.

Who knows what might have happened were the situation reversed. The Northern Hemisphere generally is colder because it has so much land. The south has more ocean, which tends to retain heat.

Over millenia those few extra days of winter might have meant more ice in the Arctic, bulking up the hemisphere’s cold air supply, said Paul Walker, senior meteorologist at AccuWeather Inc.

And Chester says it will indeed reverse some day. The earth’s orbital eccentricity is ever changing, ever so glacially, and some day the Northern Hemisphere will have the longer winter. Just give it 12,000 or 13,000 years.

For now, the snow-plow contractors might be complaining about this year without a winter, but the birds sure aren’t. If you’ve notice them singing more this month, it’s not your imagination. The mild weather, says Audubon bird expert Keith Russell, is “definitely making birds sing and vocalize more as well as migrate on schedule.”

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