Spring arrives on Friday, and you might want to make the most of it. The season of flowers and showers actually gets shorter every year by about 30 seconds to a minute, due to astronomical quirks, researchers say.
This year, spring officially starts at 6:45 p.m. EDT on March 20, according to the U.S. National Weather Service (NSW). At that exact moment, which is called the vernal equinox, the Earth’s axis will reach a halfway mark, where it points neither toward the sun (as it does on the summer solstice) nor away from the sun (as it does on the winter solstice), said Gavin Schmidt, the director of the Goddard Institute for Space Studies in New York City.
But for thousands of years, spring has been losing time in the Northern Hemisphere. This year, summer is the longest season, with 93.65 days, followed by spring with 92.76 days, autumn with 89.84 days and winter with 88.99 days, said Larry Gerstman, an amateur astronomer in New York. (Gerstman got his values from “The Astronomical Tables for the Sun, Moon and Planets,” second edition, written by Jean Meeus and published in 1995 by Willmann-Bell, Inc.)
The main reason spring is getting shorter is that the Earth’s axis itself moves, much like a wobbling top, in a type of motion called precession.
Spring ends at the summer solstice, and because of precession, the point along the Earth’s orbit where the planet reaches the summer solstice shifts slightly. Next year, the planet will reach the point in its orbit of the solstice slightly earlier.
Spring will end, and summer will begin, just a little bit earlier in the year.
Over thousands of years, the shift in the time of the vernal equinox becomes more apparent. For instance, spring will be shortest in about the year 8680, measuring about 88.5 days, or about four days shorter than this year’s spring, Gerstman said. (After that point, spring will lengthen again.)
This change in speeds affects the length of the seasons. The Earth moves the fastest along its orbit path between December and March, hence both winter and spring are shorter than summer and autumn, he said.
In the year 1246, Earth reached perihelion on the day of December solstice, said Joe Rao, a New York based meteorologist and astronomer (Rao is also a contributing writer at Live Science.) This year, Earth reached perihelion on Jan. 4.
However, these changes are so minute that most people won’t notice a difference during their lifetimes, Schmidt said. In fact, since most people associate spring with warm weather, he said, they will be more likely to notice that warm weather is beginning earlier in the year, because of climate change, than to be aware of the changing orbit. Read more…