DAY 21

January 16th, 2013 Comments Off on DAY 21

Wally at Wembley

I had written a lengthy and thoughtful dissertation on this picture (validity of using material from folk art, comparison of Wally with L. S. Lowry,…) Plus, an explanation on latitude. I was scratching my head on longitude, as many have done before me, and paused for a couple of days to return to the page – all gone! WordPress, what are you up to? Are you another part of the infamous technology which the over-70’s are defeated by?

Must I then return?  One point – many of my fans hastened to point out that I’d, like, totally goofed in my definition of ‘returns to education’ in the last  post. As anyone who thinks about it can probably work out for themselves: if your schooling profits you at all, it’s that your screw increases by a certain percentage, not a certain amount, per year you spend getting schooled; and so you need (I’m sure you can see the point) a linear regression of ‘years of schooling’ against the logarithm of earnings so as to define – Oh, forget it.

 My original aim in raising the question of ‘where we are and how we know it’ was not so much to go on about these classical questions as to move briskly to the satnav, the mobile phone, and the drone (you guessed it). However, promises should be kept – see Nietzsche on how many centuries of torture it has taken for humans to get this idea into their thick heads. So.

1. Let’s assume, to make things shorter, that the Earth is a sphere (roughly), and we agree a system of labelling places on it by latitude, from -90 to +90, and by longitude, from 180 East to 180 West. (Idea dating from around the time of Ptolemy, see the Almagest.)

2. This still leaves the question of finding out what your lat and long are. The latitude is relatively easy, at least these days, on a clear night in the northern hemisphere. Find the pole star, and use your sextant or astrolabe to get its elevation (degrees above the horizon). That, near enough, is the latitude.

An astrolabe

3. It’s the longitude that’s the problem. East and West of where? When al-Biruni was writing the crucial Coordinates of Cities (about 1000 C.E.), which I don’t have to hand, it was probably Baghdad; these days it’s Greenwich. It depends who runs the information system, as everyone knows. Al-Biruni claimed that it was essential to know where you were to determine the qibla, or direction of Mecca, so as to face it in prayer. (Others pointed out that when God told the faithful to face Mecca it can’t have been his intention to make employment for mathematicians – a reasonable guess should be enough.)

Well, if you’re east of Baghdad, the sun rises earlier. In fact, (work it out), one hour earlier for each 15 degrees of longitude, travelling due east. Even better, the astronomers have worked out what the time of sunrise should be at each point on the earth, given its latitude and longitude; and you can translate backwards. If you have a good clock.

Which is where – as you’ll find from the international best-seller Longitude  (Like St James’ Piccadilly, I won’t give you the Amazon link for the book till they pay their taxes) – John Harrison, inventor of the marine chronometer, 1765, lone genius, comes in; inventing a clock which would keep perfect time over long sea voyages and so tell you (with the help of the astronomers’ tables, and a sextant/astrolabe, and a good view of the stars, or the sun, or both) what your longitude was.

But wouldn’t it be better to do without these unreliable stars, clocks, and so on – and instead manufacture our own star system, with radio sets built in to tell us where they were and what they thought the time was?

Now there’s an idea.

Today’s (perhaps too familiar) verse from Ezra Pound expresses my feelings today:

Winter is icumen in,
Lhude sing Goddamm,
Raineth drop and staineth slop,
And how the wind doth ramm!
Sing: Goddamm.
Skiddeth bus and sloppeth us,
An ague hath my ham.
Freezeth river, turneth liver,
Damm you; Sing: Goddamm.
Goddamm, Goddamm, ’tis why I am, Goddamm,
So ‘gainst the winter’s balm.
Sing goddamm, damm, sing goddamm,
Sing goddamm, sing goddamm, DAMM.

A more cheerful winter memory: Georges Brassens’ ‘Chanson pour l’Auvergnat‘ is today’s song…

Comments are closed.

What's this?

You are currently reading DAY 21 at Luke Hodgkin.