HISTORY OF ELECTRICITY

The first records of electricity and magnetism

 The most primitive electrical and magnetic phenomena -- the attraction of dry light material such as chaff to rubbed amber, and the attraction of iron to loadstone -- were no doubt observed before recorded history began. However, as far as I can find, these phenomena were not recorded by the Egyptians or any other pre-Greek civilization. The first definite statement is by Thales of Miletus (about 585B.C.) who said loadstone attracts iron because it has a soul. The prevailing view at the time was that movement of any kind indicated life, or a soul, or a god. In fact, it was advanced thinking on Thales’ part to think that the loadstone’s moving of the iron was caused by itself rather than by the intervention of some god. Actually Miletus was a very multicultural environment -- a flourishing commercial city in Asia Minor (now part of Turkey), trading with Babylon and also Egypt, where Thales travelled. This mixture of cultures meant that there was not a strongly repressive religious orthodoxy, as was often the case in primitive (and not so primitive) societies, so freedom of inquiry was tolerated. Sad to report, this did not lead to a more enlightened political system -- it was a slave based society, with bloody rebellion and repression

An early Greek word for the sun - ηλεχτορ - pronounced "elector" - was also used to describe amber, because of its sunshiny color. Amber is the fossilized resin of a now extinct coniferous tree, almost all of it comes from the Baltic region in Northern Europe. Of course, this is the stuff that preserves insects from millions of years ago. It was greatly prized in the early world as jewelry, and used as such in Greece from the earliest recorded times. Amber came to be called "electron" by the Greek classic writers, but this term also referred to native gold and silver-gold alloys (same color).

First scientific-type explanations

The first discussion that begins to look like a scientific explanation I can find is in Lucretius, On the Nature of Things (De Rerum Natura). Lucretius was born in 98 B.C. and died in 55 B.C. or so, but he was summarizing the views of Epicurus (342 - 270 B.C.), himself a follower of Democritus. They all believed everything to be made up of atoms, Democritus thought the atoms followed natural laws, but Epicurus thought they could be deviated a bit by free will. They all thought the soul too was made of atoms, which fell apart at death so there was no afterlife, and if there were gods, they didn’t concern themselves with us. Anyway, back to magnets. Lucretius states (in describing a loadstone attracting a ring of iron): " ..it must needs be that there stream off this stone very many seeds or an effluence, which, with its blows, parts asunder all the air which has its place between the stone and the iron. When this space is emptied .. atoms of the iron start forward and fall into the void, all joined together .. the ring itself follows .. with its whole body." In other word, tiny particles emanating from the loadstone sweep away the air and the consequent suction draws in the iron.

At least this explanation doesn’t depend on gods, souls, etc. However, it has some obvious defects, which Lucretius immediately addresses. Why doesn’t this mean the loadstone would attract gold -- which it doesn’t? Because, he explains, the gold is too heavy, so it doesn’t move. O.K., what about wood? Well, wood is so light that the effluence goes right through it, so does not bounce back and sweep away the air between the two. A nicer point is made by Galen (130-200 A.D., a famous anatomist and doctor), who says Epicurus claimed the atoms flowing from the stone were related in shape to those flowing from the iron, so easily interlocked, and after bouncing between the stone and the iron become entangled and draw the two together. However, Galen goes on, he doesn’t see why anyone should believe this, because it doesn’t explain why a ring thus attached to a magnet will attract a further ring to itself, and says he’s seen five pieces of iron held magnetically in a chain, only the first one being in contact with the loadstone.

These are genuine attempts to explain in a natural fashion a really discrepant event. To quote Pliny (A.D. 23-79) "What phenomenon is more astonishing? Where has nature shown greater audacity? For iron, the tamer of all substances, is drawn to the magnet, following some intangible attraction, and, as it comes nearer, leaps to meet the magnet." Pliny, by the way, claims the name "magnet" came from a shepherd called Magnes, who found his iron-nailed shoes and staff sticking to the ground. It seems more likely that the name came from the Magnesia region, one place where naturally magnetic ore is to be found.

Pliny also has something to say about amber. Apparently, it was used for the end of the spindle by Syrian women spinners, and they called it the "clutcher". One possibility is that it became electrified as it spun and rubbed against their clothing, so attracting chaff, etc.

(Note: Since the most famous Greek philosophers are Aristotle and Plato, we probably should mention that Plato mumbled something in Timaeus, 80, stating that the motions of amber, the Heraclean stone (loadstone) and falling water all depended on the nonexistence of the vacuum combined with the fact that these substances are forced round and round by composition and divination ... whatever all this meant. Gilbert (see later) didn’t think it meant much.)

St. Augustine’s surprise

 Moving into the Christian era, St. Augustine said he was "thunderstruck" when he first saw the magnet lift a chain of rings, each attached to the next by magnetic attraction. He was even more astonished, he says, when a brother bishop moved a bit of iron around on a silver plate by moving a magnet beneath it. He was puzzled to find the loadstone, unlike amber, would not move straw, making a clear differentiation, therefore, between electricity and magnetism. He also wrote that he had read that diamonds made magnets work less well, but had not seen checked this himself. St. Augustine actually used these magnetic phenomena to defend miracles -- skeptics were always saying claims of miracles were false, because they couldn’t be explained, well, magnetic attraction couldn’t be explained either. Unfortunately, St. Augustine was both good news and bad news for progress in E&M. He also said:

"Nor need we be afraid lest the Christian should be rather ignorant of the force and number of the elements, the motion, order and eclipses of the heavenly bodies, the form of the heavens, the kinds and natures of animals, shrubs and stones ... It is enough for the Christian to believe that the cause of all created things, whether heavenly or earthly, whether visible or invisible, is none other than the goodness of the Creator, who is the one true God."

The Dark Ages

 Over the next thousand years or so, very little progress was made, with the important exception of the discovery of the compass and its use in navigation. Gilbert states that it was brought back from China by Marco Polo (which would have been in 1292), but it was definitely known and used in Europe before that time. Benjamin gives a quote (p 129) from the English monk Neckham (1157-1217) describing its use (there’s a clearer Spanish quote, but from 1263, order of Alfonso X of Castile, on p 111). Benjamin’s own rather romantic theory is that the compass came to Europe with the Finns, who were part of the Mongol peoples who originated in Central Asia, so maybe the same group took the secret to China. The first documented description of the compass in China is in 1297 (p 189) but there are claims that it had been known for centuries there, and that there were "south pointing carts" presumably with built-in compasses, thousands of years earlier. Unfortunately, in 200 B.C. or so the emperor destroyed all books and killed the scholars, so that earlier tales wouldn’t detract from his own greatness

The Dark Ages

 Over the next thousand years or so, very little progress was made, with the important exception of the discovery of the compass and its use in navigation. Gilbert states that it was brought back from China by Marco Polo (which would have been in 1292), but it was definitely known and used in Europe before that time. Benjamin gives a quote (p 129) from the English monk Neckham (1157-1217) describing its use (there’s a clearer Spanish quote, but from 1263, order of Alfonso X of Castile, on p 111). Benjamin’s own rather romantic theory is that the compass came to Europe with the Finns, who were part of the Mongol peoples who originated in Central Asia, so maybe the same group took the secret to China. The first documented description of the compass in China is in 1297 (p 189) but there are claims that it had been known for centuries there, and that there were "south pointing carts" presumably with built-in compasses, thousands of years earlier. Unfortunately, in 200 B.C. or so the emperor destroyed all books and killed the scholars, so that earlier tales wouldn’t detract from his own greatness.

An example of the non-experimental inclination during this period is given by the garlic problem: it was widely believed that garlic weakened magnets. This was first mentioned in Pliny (A.D. 23-79). One theory is that Pliny said no such thing, it was just that someone copying his work wrote "allio" (garlic) for "alio" (other) in a discussion of something affecting magnets, but sailors looking after the compass avoided garlic and onions even into the 1600’s as a result.

William Gilber

t The man who began the science of magnetism in earnest was William Gilbert (1540 - 1603) whose book "De Magnete" was published in 1600. Gilbert studied at St. John’s College, Cambridge, and became England’s leading doctor, President of the Royal College of Physicians, and Queen Elizabeth’s personal physician. At the same time, he worked on magnetism, and after seeing his book Galileo pronounced Gilbert "great to a degree that is enviable", not the sort of thing Galileo said too often. Gilbert was one of the earliest Copernicans, probably because the Italian Giardino Bruno gave lectures at Oxford in the 1580’s. Incidentally, the year De Magnete was published, Bruno was burned at the stake in his native Italy because of his beliefs about the universe. Elizabethan England, fortunately, was a less dogmatic place.

Gilbert was the first to understand really clearly that the earth itself is a giant magnet. He constructed a "little earth", terrella in Latin, a magnetized sphere of loadstone, and showed by placing a small compass at many points on its surface that both the direction the compass pointed when "horizontal" and the angle it dipped through when "vertical" corresponded with what was observed in corresponding points on earth. From this, he also concluded that measuring the dip could give sailors the latitude. This got  him in some trouble, because in fact the earth’s field has enough irregularities to make this fairly inaccurate.

Gilbert’s interest in the Copernican theory was not unrelated to his interest in magnetism. He thought that the fact that the earth rotated about a line almost exactly through the two magnetic poles could hardly be a coincidence. He also noted that the moon, in going around the earth, always has the same face towards the earth. He wondered if the force between the two might be magnetic, and we always saw the pole attracted to the earth.

(Parenthetical historical note: It is interesting to note that another famous person who wrongly thought magnetic forces might play a big role in the solar system was Kepler. He noted that the earth’s orbit around the sun was an ellipse rather than a circle, and, he knew the earth was a magnet, with magnetic poles pretty close to the geographic poles (along the line of spin). He also knew this axis the earth spun around was tilted compared to the earth’s orbit around the sun, so that sometimes the north pole was closer to the sun and sometimes the south. Putting all this together, and assuming the sun itself was a magnet, he conjectured that for half the year the sun’s magnetic force would pull the earth closer to the sun, the other half it would be pushed away, and this would account for the earth’s orbit being elliptical instead of circular. This ingenious theory is, unfortunately, completely wrong, but it took Isaac Newton and the invention of calculus to establish that an elliptical orbit was natural for a simple inverse-square gravitational force.)

Gilbert did many investigations of electrical phenomena, using an electroscope which was a light metal compass-like (but not magnetized) needle, balanced on a pinhead at the midpoint. This was much more sensitive than previous work, and he compiled a huge list of materials that could be electrified by rubbing. He also noted that electrical attraction differed from magnetic in that there were no poles in an electrified object. He also noted that, unlike magnetic force, the electrical could be shielded by a sheet of paper.He argued against the old theory that the attractions were caused by effluvia somehow wafting the air and creating a partial vacuum, because swishing the air around takes time, and the attractions were instant if you suddenly moved one object close to another.

He also noted that both electric and magnetic attractions became more powerful as the objects got closer together

t is remarkable (or is it?) that he failed to find electrical repulsion, and interpreted magnetic repulsion as a sort of preliminary maneuver to get the "right" poles together.

Gilbert’s Approach to Science 

Perhaps the most important contribution among the many Gilbert made was that he showed clearly how science might be fruitfully pursued, and how empty and futile was much of the work published up to that point, by authors who simply read what other people had written, over centuries, about phenomena, and hadn’t bothered to check it. This was part and parcel of the whole attitude of medieval society, a belief in absolute authority, first the church, then including also the old Greek writers, who were very good, but science wasn’t their strong point

THE ONE FLUID THEORY OF ELECTRICITY

1. A person standing on wax, and rubbing a tube, and another person on wax drawing the fire; they will both of them, provided they do not stand so as to touch one another, appear to be electrified to a person standing on the floor; that is, he will perceive a spark on approaching each of them with his knuckle.

2. But if the persons on wax touch one another during the exciting of the tube, neither of them will appear to be electrified.

3. If they touch one another after the exciting of the tube and drawing the fire as aforesaid, there will be a stronger spark between them than there was between either of them and the person on the floor.

4. After such a strong spark neither of them discover any electricity

These appearances we attempt to account for thus: 

We suppose, as aforesaid, that electrical fire is a common element, of which every one of these three persons has his equal share before any operation is begun with the tube. A, who stands upon wax, and rubs the tube, collects the electrical fire from himself into the glass; and his communication with the common stock being cut off by the wax, his body is not again immediately supplied. B, who stands upon wax likewise, passing his knuckle along the tube, receives the fire which was collected from the glass by A; and his communication with the common stock being cut off, he retains the additional quantity received. To C standing on the floor, both appear to be electrified; for he, having only the middle quantity of electrical fire, receives a spark upon approaching B, who has an over quantity, but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger; because the difference between them is greater. After such touch, there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality. If they touch while electrising, the equality is never destroyed, the fire only circulating. Hence have arisen some new terms among us. We say, B (and bodies alike circumstanced) is electrised positively; A, negatively; or rather B is electrised plus, A, minus. And we daily in our experiments electrise plus or minus, as we think proper. To electrise plus or minus, no more needs be known than this; that the parts of the tube or sphere that are rubbed, do in the instant of the friction attract the electrical fire, and therefore take it from the thing rubbing. The same parts immediately, as the friction upon them ceases, are disposed to give the fire, they have received, to any body that has less. 

In fact, the one-fluid theory gives a coherent account of all these experiments in which a spark passes between people or objects. But it does not give a full explanation of electrostatic attraction and repulsion. It is perhaps plausible that a body with an excess of electrical fluid will attract one with a deficiency, as is indeed observed. Furthermore, two bodies, each with an excess of electrical fluid, will repel each other. It is more difficult to understand why two bodies each having a deficiency of the fluid will repel each other. Why should lack of fluid causes a force? This is explained naturally in our present picture, a two "fluid" model, in which ordinary material contains both positive and negative charges, normally in exact balance. The negative charges -- electrons -- are light and mobile, and rubbing together two appropriate materials (such as glass and silk) causes some electrons to transfer from one material to the other, leaving electrical charge out of balance in both materials. Consequently, if either of the two materials comes in contact with a third material, the electrical imbalance will tend to cause a flow of electrons into or out of the third material. However, there are some substances, called insulators, which electrons cannot pass through readily. Wax is one example. Franklin's experiments succeeded because he had everyone standing on blocks of wax, so excess electrons could not escape, and a material deficient in electrons was prevented from capturing any. Thus the charge imbalance generated by the rubbing was preserved for a considerable time. (Eventually, charge escapes through the thin layer of moisture that forms on all surfaces if there is any humidity in the atmosphere. This is why electrostatic effects, like sparks, are so much more noticeable in winter, in a heated room, where the air is very dry.)

In a way, Franklin was right -- there is only one moving fluid, the electrons, in all these experiments. But what he didn’t realize was that half of the electrical charge in a body, the positive charge in his own notation, doesn’t move around at all, it is fixed in the body. (Actually, when electricity flows through a liquid, as it does in a car battery, both positive and negative charges flow, in opposite directions. But batteries came into the world after Franklin's time.)