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Today we begin our annual look at what makes this season special, a time when nature is doing much more than just turning dormant for three months. This is a series we like to call The Science of Winter.
Spring is coming.
Even as winter tightens its grip, the sun’s annual race to our summer all begins today, slow but unstoppable, like a huge freighter pulling away from the dock.
The sun on Thursday is directly overhead for people in São Paulo, Brazil, or anyone else on the Tropic of Capricorn. This line circles the Earth, passing through South Africa, Australia, and Tonga. It marks the most southern points the sun reaches — high summer in the southern hemisphere.
But already the sun is turning its back on the South.
By Friday, the sun will have moved a tiny bit north — less than an hour’s walk in human terms. By New Year’s Eve, as it is speeding up a small amount, it will move less than half a degree north relative to us — about 50 kilometres along Earth’s surface. (Each degree of latitude is about 111 km, give or take a bit, because Earth is not quite round.)
But acceleration is a wonderful thing. One month after winter begins, on Jan. 21, the sun will have moved about four degrees north, or 444 km. It’s still over southern Brazil, but heading our way.
By the end of two months, on Feb. 21, it will have travelled 13 degrees north, or about 1,440 km along Earth’s surface.
And on March 20, when spring arrives, it will be over the equator, having travelled 2,600 km north, relative to Earth’s surface. It’s overhead for people in Ecuador, or Congo, or Singapore (almost — the equator just misses Singapore but it’s close).
From there on it begins to slow down, like a pendulum that has reached the bottom of its swing and is starting to rise up the other side.
So, what’s it all mean to you?
For the moment, it means your days are getting longer even as winter deepens. (Yes, technically every day is 24 hours, but we’re talking about “days” in the sense of “daylight hours.”)
Daylight on Dec. 21 is eight hours, 42 minutes and 53 seconds long. The following day will have three more seconds of daylight. Try to contain your excitement. But again, there’s acceleration.
Daylight stretches out by a total of four minutes by the last day of the month. It will be half an hour longer than the first day of winter by Jan. 18, an hour longer by the last day of January, and that is when things really speed up.
February begins with days fewer than 10 hours long and ends with days more than 11 hours long. And it takes fewer than three weeks of March to reach 12 hours of daylight, the first day of spring.
Even though the days are becoming longer, they will also grow colder until late January because the ground, and ice-covered lakes, form a reservoir of cold.
A point of trivia: Our winter is actually the shortest season of the year, by a day or so. Because the Earth’s orbit around the sun is not exactly a circle, the seasons are not all equal.
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
Spring is coming.
Even as winter tightens its grip, the sun’s annual race to our summer all begins today, slow but unstoppable, like a huge freighter pulling away from the dock.
The sun on Thursday is directly overhead for people in São Paulo, Brazil, or anyone else on the Tropic of Capricorn. This line circles the Earth, passing through South Africa, Australia, and Tonga. It marks the most southern points the sun reaches — high summer in the southern hemisphere.
But already the sun is turning its back on the South.
By Friday, the sun will have moved a tiny bit north — less than an hour’s walk in human terms. By New Year’s Eve, as it is speeding up a small amount, it will move less than half a degree north relative to us — about 50 kilometres along Earth’s surface. (Each degree of latitude is about 111 km, give or take a bit, because Earth is not quite round.)
But acceleration is a wonderful thing. One month after winter begins, on Jan. 21, the sun will have moved about four degrees north, or 444 km. It’s still over southern Brazil, but heading our way.
By the end of two months, on Feb. 21, it will have travelled 13 degrees north, or about 1,440 km along Earth’s surface.
And on March 20, when spring arrives, it will be over the equator, having travelled 2,600 km north, relative to Earth’s surface. It’s overhead for people in Ecuador, or Congo, or Singapore (almost — the equator just misses Singapore but it’s close).
From there on it begins to slow down, like a pendulum that has reached the bottom of its swing and is starting to rise up the other side.
So, what’s it all mean to you?
For the moment, it means your days are getting longer even as winter deepens. (Yes, technically every day is 24 hours, but we’re talking about “days” in the sense of “daylight hours.”)
Daylight on Dec. 21 is eight hours, 42 minutes and 53 seconds long. The following day will have three more seconds of daylight. Try to contain your excitement. But again, there’s acceleration.
Daylight stretches out by a total of four minutes by the last day of the month. It will be half an hour longer than the first day of winter by Jan. 18, an hour longer by the last day of January, and that is when things really speed up.
February begins with days fewer than 10 hours long and ends with days more than 11 hours long. And it takes fewer than three weeks of March to reach 12 hours of daylight, the first day of spring.
Even though the days are becoming longer, they will also grow colder until late January because the ground, and ice-covered lakes, form a reservoir of cold.
A point of trivia: Our winter is actually the shortest season of the year, by a day or so. Because the Earth’s orbit around the sun is not exactly a circle, the seasons are not all equal.
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
