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Happy Spring, almost! The vernal equinox occurs tonight at 7:21 p.m. EDT as the sun crosses the plane of the Earth’s equator into the Northern Hemisphere. It’s the traditional start of spring here, and of autumn in the Southern Hemisphere. Many of us still associate the arrival of spring with March 21. But 1979 was the last time that occurred in the Eastern Time Zone. And in 2020 we’ll see the first equinox to fall on March 19. The calendar resets with a Leap Year in 2100.
Comments
No I don't remember when Spring started on march 21, but I do remember when we got about a foot and a half or two feet of snow on the 23rd. The signs at the Westminster Southern States said "Think Spring" at the time.
Posted by: siasds | March 20, 2011 9:07 AM
OK, so this makes me a huge nerd, but technically, 2100 is NOT a leap year.
Years that are evenly divisible by four are leap years, UNLESS they are evenly divisible by 100 but not 400.
In other words, this means that 2000 is a leap year, but not 1900 or 2100.
FR: By golly, the nerds have it. The slippage in the dates of the equinox will be reset in 2100 because it will NOT be a Leap Year, and the date of the equinox will jump forward in time.
Posted by: Ron | March 20, 2011 10:00 AM
The sun doesn't move, the earth does. So the sun doesn't "cross the plane of the Earth's equator." An accurate explanation would be more helpful than simply repeating what is out there on the web.
FR: It is a traditional definition, based on our perspective from here on the Earth's surface. I see no harm in it. We also use the terms sunrise and sunset, constellations, conjunctions and other such terms that may oscure the astronomical reality of things, but which come legitimately from thousands of years of Earth-bound human observations. I don't think anyone is confused by them.
Posted by: K. Taylor | March 21, 2011 7:39 AM
I think it's odd that we say that March 21 is the first day of Spring. To explain, I need to go back to Dec 21, which we say is the first day of Winter. Now, Dec 21 is the shortest day of the year. It has the least daylight. In a perfect world, this would also be the coldest day of the year. Hence, Dec 21 should be the midpoint of winter, being the coldest day and all. Therefore, March 21 should be the midpoint of Spring, etc.
Of course, it isn't a perfect world. We have a saying, "The cold does Strengthen as the days do lengthen". This means that there is a lag from the day with the least daylight to the actual coldest day of the year. This is due to many factors, but I can't imagine that it would lag so much so, that the day with the least daylight should be the very beginning of the coldest time of the year. As the daylight shortens, it does get colder, so days to the right of Dec 21 should still be wintry.
I think we should just use months for the seasons. The first day of winter is Dec 1, first day of Spring is March 1, etc. Easier, and much closer to the truth. (in my humble opinion).
FR: Can't fault your logic. In fact, meteorologists do regard the months of December, January and February as winter; March, April and May as spring, etc. And many of our ancesteors celebrated the winter solstice as middle of winter and the start of the sun's return, and the night of June 21 as Midsummer's Night. They calculated the seasons from what were called "cross-quarter days," which fell halfway between the equinox and the solstice. So winter began around Hallowe'en, and ended around Groundhog Day.
Posted by: John | March 21, 2011 8:59 PM