The Solstice Clock – Part 1

Preamble

My daily routines tend to be vague, imprecise and are subject to the fragilities of my heath, I am no slave to the clock. (The notable exception to this is when it is time to make the dinner; you can set your watch by it.) Over the last year, however, my fascination with the measurement of time, and the history of the same, has been on the increase.

For several years, I have been disenchanted by some of the artificial, arbitrary and often (to me) pointless aspects of modern, 'Western' timekeeping. Take daylight saving, for instance; I have read the various arguments for it, but have yet to see one which does not have a pertinent counter-argument or that justifies upsetting timekeeping around the globe. The changes in various countries and states are not even synchronous. (The USA and Europe are a couple of weeks apart in their change-over dates. In Australia, the state of Queensland does not even have daylight saving – and good for them, I say.)

A more recent annoyance that has come with my entering the age-group that might be termed 'grumpy old man' is the Gregorian calendar. Follow the link if you want to know more about this – I am not going to repeat at length what is recorded in innumerable places. I concede that the Julian calendar had a year that was a little too long and was getting further and further out of whack with the Tropical year. However, what really makes me grit my teeth is the totally arbitrary (in terms of the Tropical year) start point. The Vernal Equinox (Autumnal Equinox for those of us living in the Southern Hemisphere) tends to be the reference point for the Tropical year, but I can see that this would not fit in with the whole 'Rebirth of the Sun' thing, which would make the Winter (or Summer in the Southern Hemisphere) Solstice the reference point. But no, a point some 10 to 11 days after the Winter Solstice is what we've got to put up with.

Calendars

Let's turn our attention now to calendars in the physical sense. Without any further ranting about the artificial and arbitrary length of the weeks and months of the Gregorian calendar, what does this calendar mean to most of us? Generally, a set of 12 printed pages, broken down into grids so that we can see a correspondence between days of the week and days of the month. This grid may have pre-printed information telling us useful-to-know things like "Moon waxing gibbous" or "Sow mangold-wurzels now!". There may even be space to write our own information like "Wedding anniversary next week", "Wedding anniversary tomorrow", "Wedding anniversary", "Doh, missed it again! In dog house."

If we look at a clock, it tells us what time it is. If we look at the calendar described above, does it tell us what date it is? The answer is no. Despite the fact that calendars that tell you what the date is have been around for quite some time (e.g.: Stonehenge), the ubiquitous paper (or other medium) calendar gives us absolutely no idea of what date it is.

The Importance of Calendars: Food

What events of real importance are indicated by calendars? Irrespective of the calendar system used, the most important thing that I can think of that might be indicated by a calendar is the timings involved in agriculture – the sowing and harvesting of crops, the gestation of livestock, etc. Without these, we have no food. (I suspect that the world population is a little too large for a total reversion to a hunter-gatherer system.)

So, calendars can be of importance, in more widespread terms than the occasional murder due to forgetting one anniversary too many. Our graphic calendars, diaries and almanacs still do not help us know where we are in annual cycle. There are many seasonal indicators that can tell the farmer that it is time to start ploughing (like the snow may have melted so that there is actually ground visible to plough) and – of course – there are always the stars for those who know how to read them, and don't live somewhere that has a permanent overcast. The moon is always a good time-reckoner and many calendars are based on it – you still need a clear sky to watch it though and some way of keeping track of how many moons have passed since event X.

A Clock is a Fast Calendar

As I mentioned earlier, a clock can tell us what time it is. If we take a mechanical clock and add a few more gears (a divide-by-24 from the hour hand shaft), we can make it count days. If months were of a regular length, we could reduce further and have a months dial. Months of irregular lenght may also be dealt with, even for leap years – far more complex mechanics would be involved though.

If we were not concerned about displaying hours and minutes (and possibly seconds) on our mechanical clock, we could turn it into a calendar simply by making it tick slower – much slower.

The Slow Tick

If we take the Tropical year as being 365.24219 to 8 significant figures, we can calculate:

ns = 365.242 x 24 x 60 x 60 = 31556925 = seconds in a tropical year, to 8 significant figures.

If we decided that 12 hours on our clock was to represent a tropical year, we can divide the above number of seconds by the number of 1-second ticks of the clock (assuming that it has a 1-second tick) required to rotate the hands by 12 hours:

nt = number of ticks required to rotate hands by 12 hours = 60 x 60 x 12 = 43200

So, to work out the length of the tick that we would need to rotate the hands once in a Tropical year:

t = ns/nt = 730.48438 seconds, to 8 significant figures.

That means that our Slow Tick would occur roughly ever 12 minutes, 10.5 seconds.

A Tricky Escapement

I will leave it to some clever-clogs to work out how to make a mechanical clock escapement that only ticks every 12-and-a-bit minutes (no down-gearing allowed!)

As I am not particularly interested in modifying a traditional, purely mechanical clock for these purposes, I will look at how an electro-mechanical clock may be used instead.

Quartz clock movements may be obtained cheaply from hobby suppliers. However, entire clocks can be obtained even more cheaply from 'cheap' shops. With the latter, you get a face and a case thrown into the bargain, so have little to do in the way of mechanical construction.

My practical research for this article has so far extended to obtaining and dissecting a quartz clock obtained from a local supermarket for $12 AUD. Once the movement is removed, it looks very much like every other cheap quartz movement that I have seen over the last few years. The drive, contrary to what I suspected, does not consist of a solenoid that is simply pulsed every second with some kind of pawl and ratchet mechanism, but of a cylindrical magnet between the poles of a solenoid that would require a reversing field every second. (If a simple pulse train of fixed polarity were applied, the magnet would move possibly once, then just twitch slightly every time a pulse came along.)

Part 2 details some thoughts on the pulse generator which will drive the Solstice Clock and how it can become more than just a Solstice Clock.