Monday, 23 November 2009


Ok, moving swiftly on (temporal) from Time, or moving up (spatial), I'm now in a minor quandary about the spatial dimension.

We all know where the meridian is - it's that imaginary line that runs through the long room in Flamsteed house (or maybe I got that wrong) and to help tourists - or Greenwich's proud heritage - they've helpfully marked it out on the forecourt, on the pathway immediately below and on the road down to the King William Gate - you can even become at one with this wonderful landmark as you go to the public conveniences.

And yet...and yet...I've got this digital Ordnance survey map and the meridian (for mapping purposes) is not where they tell us it is. Have a shifty at the two red dots in the image below:

(You might need to big it up in a clickety-click kind of way to see the points.) The point over to the left/west is pretty close to where we all know the meridian is. And yet, my digital map tells me that this point is longitude W 0.00180046. And if I tell my OS map to stick a point on 0.0000000 (which should be right to quite a few decimal places!) around the same latitude, it sticks a point 0.08 of a mile to the East - this is the second red point. The old reservoir to the south is west of the heritage meridian and east of the OS meridian. And of course, the Wolfe statue is also sitting somewhere in the middle. (I've only just noticed that the name Wolfe very conveniently has a W at the beginning and an E at the end. Perhaps we should go for a Wolfe meridian....) It's curious really. Greenwich is the one place where you'd expect to be able to find the damn meridian. But it's not that easy. Or is it?

(Any expert who happens to randomly arrive on this page will probably reliably inform us that, due to the vagaries of the Earth's rotation, time is now measured with a series of atomic clocks in Paris, amongst other places, and that the meridian moves around depending on whether the Earth is in a rush or taking the leisurely approach to planetary rotation. However, this complicates things even more - we'd then have a heritage meridian, an Ordnance Survey meridian and a notional meridian that moves about....)

This time and space business really can be confusing!

Though it's not all getting more and more complicated - I was chatting with my clever program-writing mathematically-competent brother the other day when I confided in him that I had no idea what an algorithm was. So, I've just asked a mathematician, there's me expecting a volley of algebraical theorems and....this was his reply:

''OK, it is just a step by step procedure such as "wet hair, shampoo, rinse, repeat until done"

Wow, so it's that easy! He may have skipped a couple of details, of course...but I'm just going to file it as one minor mystery solved.

No comments: