mirrorshard: (The Book of Rainbows)
[personal profile] mirrorshard
By special request from [livejournal.com profile] midnightmelody.

William Gilberd, a prosperous London physician, president of the College of Surgeons, and physician to Queen Elizabeth I at the end of her life (and, as it turned out, his) is often called the first real scientist. The traditional historical epithet for him is 'the Father of Magnetism', after his most famous, and most complex, project, investigating the Earth's magnetic field through a series of terrella magnets (lit., 'little earth' - a spherical magnet).

In some respects, he was very much a scientist - he worked within a strict experimentalist world-view, and respected the opinions and learning of practical men and craftsmen, rather than working from ideology and reasoning everything out in the Scholastic manner. Educated at Cambridge, he really began to hate the academic traditions of the time, which (as far as natural science went) consisted of reading out chunks of Aristotle and a few others to students and letting them copy it down.

For those of you who don't know the Aristotelian world-view, I'll recap briefly. The history of it gets quite complex, so 'Aristotelian' is really just a handy label for it, and this is a simplification. The entirety of the universe consists of a series of concentric spheres, rotating inside each other, and the planets and stars are attached to those. At the outside, we have Heaven, and in the middle, we have the Earth, an immobile, dead, and basically pointless lump of filth that it's our theological duty to ignore, scorn, and escape as soon as we can. They had a wonderfully evocative Latin term for it: Faeces Mundi, the shit of the world.

Gilberd, though, knew that this wasn't true; the Earth wasn't dead or immobile. He was a Copernican (shush! Whisper who dares!) and believed that the Earth went around the Sun, truly revolutionary for those times. He also knew that something inherent in the Earth made magnets behave oddly, and he had a Theory what it was. He didn't dare state the Theory, of course, didn't even dare breathe a word of it till he was secure at the top of his profession.

Magnetized needles point North. To be precise, they point to magnetic North, and not only that, they don't point parallel to the Earth's surface - if you have a magnetized needle in a three-dimensional bearing, it will adopt a specific angle of inclination, which changes as you move around (for values of "around" that are on the order of miles, or hundreds of miles). It points, in fact, towards the magnetic pole itself, somewhere beneath the surface of the Earth at the physical pole. In the past, Authorities (Pliny is the only one I can recall offhand - I'm doing this without texts handy) had explained this by saying that it had an inherent virtue that made it necessary for it to do this. Yes, that does mean exactly as much as you think it means. The same Authorities also asserted confidently that rubbing garlic on a magnet would harm it, and the needle would deviate from North under the influence of diamonds. (Gilberd actually disproved this, using seventy-five diamonds.)

That's inclination - variation, on the other hand, is even more mysterious. In some places, compass needles deviate from magnetic North, and how much and in what direction changes as you move around.

Elizabethan navigators knew about inclination and variation, and spent a long time compiling charts saying how the compass needle varied in different waters. A prosperous (and sensible) navigator would own three or four compasses made in different places, and calibrated differently (ie. the markings on the compass card) to avoid the risk of losing their way. But they didn't go about making the charts in a very systematic manner, and a number of people spent a lot of time trying to generalize the variation and find a theory to predict how it worked and consequently make fabulous amounts of money. Given the extent of the overseas trade at that time, and the fierce competition between countries, merchant houses, and rival schools of navigation, the amounts involved really were fabulous. But nobody managed it, because it can't be done.

Popular theories about variation involved the motion of the stars and the existence of previously unnoticed magnetic mountains. I'm fairly sure there was also one about a magnetic sea serpent or Great Whale swimming hither and yon. (OK, so I made that one up. But there should have been.) Gilberd's approach was incredibly modern - he took a spherical magnet, a terrella, and moved a compass needle in a three-dimensional bearing across its surface, noting the variation. In modern terms, he modelled the entire Earth, and proved that the Earth was a gigantic magnet. (Insert a 'for all intents and purposes' or an 'as far as they could tell' in there somewhere. Modern science has decided it's More Complicated than that.)

He also reasoned that, if the magnetism of a terrella was implicit in its shape, then changing the shape should have odd effects. So he played around with oval, oblate, and half-spherical magnets, and commissioned a series of terrella magnets with three-dimensional continents and oceans. Moving the caged compass needle across their surfaces, he saw similar variations to those observed and tabulated by navigators all across the (dead, immobile, inert) Earth.

Gilberd's revolutionary Theory was, to his own mind, proved.

The Earth was a stone with a soul, and that soul was magnetism.
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