Spectral analysis of sunrise time variation

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Circlotron

Circlotron

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Joined 2002
A couple of days ago I was having a lazy afternoon and I fell asleep on the couch (sofa) and proceeded to dribble on the pillow. :dead: I had a dream and in it I was thinking about how sunrise time varies with the seasons, and whether or not it follows a sinusoidal pattern, and if it doesn't then is there some kind of hidden information in the harmonics?

Tonight I got the sunrise times of Perth, Western Australia, graphed them in a spreadsheet and also imported the data into Cool Edit as an ascii text file to do the harmonic analysis (and listen to the waveform - nothing exciting btw).

This is the spreadsheet graph showing actual time of day:
 

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Christer

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Joined 2002
The main reason for seasons is the angle of the earths rotational axis. However, AFAIk this angles is not perfectly fixed but has a sligth variation (or wobble). Further, earths orbit is elliptical, not circular, even though it is very close to a circle. Without checking the maths, I would presume both of these effects could contribute to the harmonics.
 
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Christer

Member
Joined 2002
Note that the question is in my sig., not in this thread. People have answered in various places already. The question was mainly intended to think about, not to answer, though, since I had no intention of causing the forum to be flooded with answers. But OK, I think the previous post was the seventh answer so far, not counting those I have missed. :)
 
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