I’m having a little trouble moving on from the Kirk Sundial. I’m still fascinated and, sadly, as you’ll see I’ve been a bit discombobulated, again. Oh, how I wish I’d paid more attention in physics back when I was at High School. They are a long time ago now, those classes when our keen enough teacher attempted to explain to a gaggle of girls how the world works.
What do I remember? The sun streaming through the windows and a, now irrelevant, preoccupation with the number of calories in the yoghurt I’d eaten for lunch. Physics was always immediately after our lunch break – bad, bad timing.
So this week I’ve continued to plague my resident geodesic specialist with questions.
He’ll argue the toss over that “specialist” appellation, when he sees it. Apparently geodesy at Uni had its challenges.
As far as I am concerned he deserves the title “specialist” on account of the plain and simple truth that he knows a lot more about geodesy than I do, or most other people for that matter. And, it is my blog; I get to say what I like. (Rest assured, folks, I do aim for the truth – such as it is.)
Remember, I said I was quite proud of the fact that I’d figured out how to tell the time on the sundial?
The trouble is, that wasn’t enough. Because, you know, I might have been thinking about calories back in the day but nowadays this older me, she wants to know how things work.
So I asked about the gnomon. Does it point at True North, or True South? I thought it must depend on where you are on the planet. In the Northern Hemisphere, I thought it might point to the South and then vice versa down here. I was correct but I was wrong, too. I had it back to front, or should that be upside down?
Apparently, all this is getting a “little hair splitty” which might, or might not, be a direct quote from the resident specialist who back in his day, during physics lessons, probably wasn’t preoccupied with calories; other than wanting more, perhaps.
So, because by now I’d gotten a little obsessive about where exactly that pointer points, I demanded a more specific answer.
His response: Which point exactly are you wondering about?
The gnomon point, I said. (Try getting your tongue around that word when you’re hoping to come across as erudite.)
His brow creased in the way that it does – when he’s exerting patience.
I added: You know, the pointy bit.
For you, my reader, in the interests of transparency I’ll include the photo from my last post.
Folks, I suppose you can see his difficulty with my question? I’ll own up – it took me a while.
The gnomon, as you, no doubt, have observed, well, it’s got two points. That point at the base? The one I assumed was there for aesthetics (go on, admit it, it does make the dial look good); turns out that’s not its sole purpose. Oh, no. One point points to the North and the other to the South.
He said, yet again, What matters the most is the angle of the pointer.
And that, folks, is geodesy.
Because that angle, and I know I’m repeating myself from last time but this time I’ve got it, I really, really do, it needs to be parallel to the earth’s axis. And, this is the bit that’s tricky, the angle changes according to where you are on the planet.
So, if you have a sundial in your pocket like my blogging mate, Dan (see his comments on my earlier post) and that sundial was made for my hometown and you’re somewhere else then you have to do some sums. You have to make adjustments based on the latitude of your present position.
Confused? I don’t blame you.
Apparently, it has to do with the fact that the earth isn’t round.
Wait. Don’t give up on me. I haven’t become a luddite over night, at least not intentionally, or no more than I was unintentionally, before I started all this. You see, our planet is more round than flat. But it’s actually a lump. A rather lumpy lump.
And our orbit of the sun isn’t circular, either, it’s elliptical.
And that’s why geodesy is complicated. And that’s why the angle of the gnomon is important.
About as clear as the bay on a foggy winter’s morning, eh!
Don’t worry, eventually, the sun will come out and there’ll be a shadow to tell the time by.
To bring all this back into the real world; our every day world for ordinary people who, like me, don’t do sums, or not often anyway, here’s a photo of my grandfather and his mates taken at the sundial in question. I don’t know exactly when it was taken. But that plinth and dial are looking decidedly unbattered – as is my grandfather.
None of them look as if they’ve got a headache from trying to understand geodesy. And I’m reasonably sure they could all tell the time from the dial. They look a happy bunch, don’t they.
My grandfather is the chap with the grin – second from the left.
I took this, my final photo in the series, last week.
Nobody here has given themselves a headache trying to work out how the sundial works. They’re having fun. And, they’re trying to puzzle it out. Maybe these girls will pay more attention in physics than I did.
I’m submitting this post to Photo 101 Rehab. Check it out if you’re interested in photography. Or better, yet, join in!
In the meantime, tell me, do you have a sundial near you?
Categories: Off The Beaten Track in Aotearoa