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date 4.Jan.2023

■ Scientific basics: The procession of winter sunsets

Getting kids to appreciate science isn't easy. Most subjects are too complex and obviously "uncool"; how many likes does Newton get on Instagram? Wouldn't you rather watch the Kardashians on TikTok?

This fall I made up my mind to force science upon my 2 (pre-teenage) kids. We measured the exact setting time of the sun, over a period of 3 months, which also involved a short 3 km bike ride to the beach, where the sun sets nicely near the horizon. The project was a good introduction to science involving:

We started our experiment on 21 September, autumn equinox and kept going till winter solstice (21 December), where apparently the day is smallest (or is it? see below). It is a period where days get shorter and colder, both results of the earth's axial tilt. Thanks to Cyprus weather we were able to take observations on more than half of these 90 days. Every day we took a photo of the sunset, and here is a video overlay of the receding sun, moving inexorably to the south as the days go by.

sunsets video

As for the exact sunset times, observed with 1-minute accuracy, were transcribed to an Excel file and plotted over time. During the 3 month period, the sunset time fell more than 1 hour (ignoring daylight saving time change), so overall the day shrunk over 2 hours (we'll do the sunrise experiment another time :)

sunset times

This scientific experiment was as simple as they come, but we came up with a scoop as well. Although we are told that the smallest day is on December 21st, our measurements show a slight error in this popular conjecture. Unfortunately adverse weather and other obligations didn't allow frequent measurements around the solstice time, but the nearest observations are:

04-Dec-22	05:34
05-Dec-22	05:33
09-Dec-22	05:33
20-Dec-22	05:35
21-Dec-22	05:36

The evidence is as clear as the sun, the smallest day this year was around the 15th of December. By the time we reached 21st the sun had already started its reverse course and days were growing. Could it be a measurement error on our part? Theoretically possible, but unlikely, as the combined intellect of 3 scientists young and old powered this experiment :)

What's next? Now we have the observational data, we must come up with a scientific theory to explain their occurrence. Why does the day shrink like that? Could it be that the Sun Ra is getting tired towards the end of the year and is a slow riser? Or is it the underpants gnomes? Let's ask the Kardashians <g>

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