It's almost springtime! (You laugh hollowly, as you dig out your car for the fiftieth time this winter.) But this year, as it's been for centuries before, spring is coming just a little bit later.
Spring starts at 1845 Eastern, Friday evening. That's not a random time pulled out of the air by a groundhog — it's the vernal equinox, the moment when the Earth's axis is halfway between the summer and winter solstice. But as LiveScience explains, spring has been losing time to summer in the Northern Hemisphere for millenia, meaning that spring 2015 will be about 30 seconds shorter than 2014.
As the Earth's axis rotates, it also wobbles, very slowly. Over the course of 26,000 years, the axis traces out a cone, and as this gradual progression happens, the seasons lengthen and shorten — spring will be shortest in about 6430. LiveScience has an excellent explanation of the physics behind this.
The change is not enough that most people will notice any change over the course of their lifetime, but taken over thousands of years, it can make quite a difference. In any case, it gives you something to blame when winter rolls around that little bit earlier this year. [LiveScience]
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