Thursday 1 July 2010

Timey Wimey

No, don't worry - we're not getting all Doctor Who on you. Remember, though that we used to have the Denis N Memorial bay tree in the garden, but it was blocking out the light, so Diamond's John and his trusty chain-saw reduced it to the Denis N Memorial Stump (pictured), onto the top of which will be attached the Denis N Memorial Sundial (picture soon). Well, that's now arrived and Mum and Dad, not satisfied with any old sundial, went for a "proper" one.

They had no idea what this would entail, but chose a shiny brass one and filled in all the details on the form, this just for the design proofs. They had to give latitude and longitude and there is a place for some bigger-script words (we chose "For Denis") and another for a suitable quote or, for example, biblical text. Mum chose "The garden is a lovesome thing, God wot" from a favourite poem.

The dial has now arrived and the setting up is quite a pallaver, especially as John's chain saw cut was not... um.... how shall we put it..... exactly horizontal. The disc of the dial has to sit exactly horizontal (spirit level job) so that meant a bed of putty with suitable sized stones embedded. It then has to be exactly aligned to the meridian.

Amazingly (we learned), the sun's movements relative to earth are not exactly regular - the 24 hours is only an average - in fact the apparent position of the sun at each hour varies by +15 to -15 minutes depending on month (14.20 minutes "slow" by a sundial on 12th Feb, 16.23 mins fast on 3rd November, almost correct on 16th April, 14th June, 2nd Sept and 25th Dec) I kid you not - it's called the "Equation of Time". Neither the sundial nor the clock are "wrong", they are just measuring different versions of time.

The need for latitude (we are 51 degrees, 20 minutes North) is so that the "finger" of the dial (called a "gnomon) can point exactly at the North Star.

And then, of course, there's the fact that the dial is calculated and configured to GMT, so for all the Summer it's an hour wrong.

And then Mum decided she didn't like it just perched on the stump, but would prefer it to have some kind of "table" on which to sit, so a suitable flagstone was bought, the thing dismantled, and the re-assembled with the flag twixt stump and brass.

That's all human stuff - I'm only interested in Breakfast Time, Dinner Time, walk time and bed time


1 comment:

Mr Silverwood said...

The four most important times of the day, who needs all this other time stuff.