Wednesday, January 7, 2015

Earth is nearest the sun in winter

In fact, it passed perihelion (position nearest the sun) on Jan 4.  

The summer-winter difference of 3 million miles (out of a total average distance of about 93 million miles isn't enough to overwhelm the axial tilt that causes our seasons, but I was surprised to learn that it DOES affect the length of our seasons!  Since Earth gradually speeds up in its orbit, reaching its highest speed at perihelion, the northern hemisphere winter (and southern hemisphere summer) is almost 5 days longer than the opposite seasons.

(Poor southern hemispherians!)

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