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Old 5th May 2007, 02:44 PM   #1
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Default Spectral analysis of sunrise time variation

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. 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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Old 5th May 2007, 02:46 PM   #2
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Cool Edit waveform:
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Old 5th May 2007, 02:47 PM   #3
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Spectral analysis:
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Old 5th May 2007, 05:27 PM   #4
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Last time I looked, sine waves didn't have any harmonics.

So much for THAT idea...

I_F
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Old 5th May 2007, 06:07 PM   #5
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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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Old 5th May 2007, 06:17 PM   #6
Aengus is offline Aengus  Canada
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White.
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Old 6th May 2007, 04:28 AM   #7
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Quote:
Originally posted by I_Forgot
Last time I looked, sine waves didn't have any harmonics.

So much for THAT idea...

I_F
How would you define "first harmonic" then?
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Old 6th May 2007, 08:09 AM   #8
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I think the waveform is related to the analemma.

Tom
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Old 6th May 2007, 05:48 PM   #9
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Quote:
Originally posted by Circlotron


How would you define "first harmonic" then?
There is no such thing as a "first harmonic". Harmonics start at the 2nd. I believe you are thinking of the "fundamental".

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Old 6th May 2007, 05:58 PM   #10
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Me think you have harmonics: 1st, 2nd, and so on

OR

You have overtones: Fundamental, 1st overtone, 2nd overtone, and so on

But not mixed up.

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