light of day

In casual conversation with some guy, I mentioned that the days were getting longer by a minute or so each day – can’t remember the context of our conversation, but rest assured this wasn’t something I said just out-of-the-blue.  It was referenced in support of some other interesting topic.  But right there, the guy interjects that at this time of the year (a few weeks after Winter Solstice) the days get longer by a few seconds each day, and the rate of change accelerates as we approach the Equinox.  I looked back, nodding and non-verbally acknowledging that I understood that.  But I’m sure he could tell by my deer in the headlights gaze that I had no idea that this was in fact the case.  How could I have not noticed this effect before?  And was it actually true?  I asked him to explain. He mentioned the various factors that would go into this calculation; the earth’s elliptical orbit around the sun, the pitched angle of the earth’s rotation on its axis, the tangent line to the latitude for this observation, and the time of year.  And then there’s the question of “Twilight”.  When the sun’s path in the sky is at a low angle, you get to see that little bit of the sun over the horizon for a longer period of time.  You folks up there in Norway know exactly what I’m talking about.  Twilight gets counted as part of the “Day”.  Anyway, I’ve checked this out and the guy knew what he was talking about.  Here’s a Web site that has all the math if you wanted to run the numbers for yourself:  http://www.gandraxa.com/length_of_day.aspx

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