View out the hospital widow when I'm walking for exercise.

View out the hospital widow when I’m walking for exercise.

The sun will rise today in Fairbanks at 7:34 in the morning, and set 12 hours 16 minutes later at 7:51 pm. Yes, it’s the equinox today – at 6:29 pm, to be exact. But equinox does not mean 12 hour days

Why?

In the first place, sunset and sunrise are defined by when the top edge of the sun touches the horizon. Twelve hour days would be true if the center of the sun was the defining point.

Second, where you see the sun is not where it is actually located, especially when it is near the horizon. Even seen a road mirage where it looks as if a hot road is covered with water? What you are really seeing is the light of the sky, bent by the strong temperature gradient near the road. The opposite kind of bending occurs when the air near the ground is denser that that higher up, which is the normal case in the atmosphere. In this case, the sun looks higher in the sky than is really the case. The result is that days at the equinox are really a little bit longer than the nights.

It didn’t rain much in Fairbanks between the first few days in September and the last weekend, though we did get a good dollop last Saturday. Anchorage (I’m still in the hospital there) has been making up for it. Well over 4″ so far, and raining most of the time I’ve been in the hospital here.

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