De Magnete, Nothing Less than the First Ever Work of Experimental Physics
As I wrote in my previous post On Little Earths and Little Suns, I am currently reading William Gilbert’s De Magnete (On the Magnet1), first published in 1600. However, before I examine the contents of the six books making up Gilbert’s text, I think it important to underline that this text is not just the first to seriously address magnetism, showing that the earth acts like a giant magnet, but also, arguably, the first to put into practice what we now call the experimental method.
Nevertheless, were one to ask the average person who introduced the experimental method, many, including both lay people and scientists, would automatically answer Galileo, the latter appearing, for example, in each of the Wikipedia entries for Experiment, the History of experiments, and the Scientific method. This is despite the fact that, according to Paolo Galluzzi, an Italian historian of science and director of the Museo Galileo in Florence since 1982, Galileo did not invent the experimental method.
It should be noted that Gilbert’s De Magnete was published ten years before Sidereus Nuncius, Galileo’s first widely read publication, and 23 years before Il Saggiatore (The Assayer), in which Galileo wrote about scientific methodology.
In the preface to De Magnete, Gilbert goes out of his way to highlight the importance of the experimental method, arguing that it is only through the use of simple experiments that unknown aspects of the universe may be uncovered:
Since in the discovery of secret things and in the investigation of hidden causes, stronger reasons are obtained from sure experiments and demonstrated arguments than from probable conjectures and the opinions of philosophical speculators of the common sort; therefore to the end that the noble substance of that great loadstone, our common mother (the earth), still quite unknown, and also the forces extraordinary and exalted of this globe may the better be understood, we have decided first to begin with the common stony and ferruginous matter, and magnetic bodies, and the parts of the earth that we may handle and may perceive with the senses; then to proceed with plain magnetic experiments, and to penetrate to the inner parts of the earth. [p.xlvii]
Gilbert does not mince his words in defending his approach. In the following passage, in language reminiscent of Shakespeare, he shows his utter contempt for those who only wish to look for knowledge in books without undertaking the hard work of examining the real world:
But why should I, in so vast an ocean of books whereby the minds of the studious are bemuddled and vexed; of books of the more stupid sort whereby the common herd and fellows without a spark of talent are made intoxicated, crazy, puffed up; are led to write numerous books and to profess themselves philosophers, physicians, mathematicians, and astrologers, the while ignoring and contemning men of learning: why, I say, should I add aught further to this confused world of writings, or why should I submit this noble and (as comprising many things before unheard of) this new and inadmissible philosophy to the judgment of men who have taken oath to follow the opinions of others, to the most senseless corrupters of the arts, to lettered clowns, grammatists, sophists, spouters, and the wrong-headed rabble, to be denounced, torn to tatters and heaped with contumely. [pp.xlviii-xlix]
Gilbert continues, explaining that it is only through the use of experiments that new knowledge may be gained. He also recounts that these advances were only achieved through incredibly hard work and great expense on his part. According to Stephen Pumfrey and David Tilley2, the cost of Gilbert’s research was around £5000, which at the time was an astronomical sum.
To you alone, true philosophers, ingenuous minds, who not only in books but in things themselves look for knowledge, have I dedicated these foundations of magnetic science — a new style of philosophizing. But if any see fit not to agree with the opinions here expressed and not to accept certain of my paradoxes; still let them note the great multitude of experiments and discoveries — these it is chiefly that cause all philosophy to flourish; and we have dug them up and demonstrated them with such pains and sleepless nights and great money expense. [p.xlix]
Gilbert makes it clear that he understands that for other researchers to be convinced, it is important that experiments be undertaken repeatedly, with a clear focus on ensuring reproducibility of results. That results be reproducible is, of course, a crucial aspect of the experimental method.
Let whosoever would make the same experiments, handle the bodies carefully, skilfully and deftly, not heedlessly and bunglingly; when an experiment fails, let him not in his ignorance condemn our discoveries, for there is naught in these Books that has not been investigated and again and again done and repeated under our eyes. Many things in our reasonings and our hypotheses will perhaps seem hard to accept, being at variance with the general opinion; but I have no doubt that hereafter they will win authoritativeness from the demonstrations themselves. [pp.xlix-l]
If we move from the preface to Book I, Gilbert, in presenting his overall objective of developing a magnetic science, once again insists on the important rôle that experiments play:
But when the nature of the loadstone shall have been in the discourse following disclosed, and shall have been by our labors and experiments tested, then will the hidden and recondite but real causes of this great effect be brought forward, proven, shown, demonstrated; then, too, will all darkness vanish; every smallest root of errors, being plucked up, will be cast away and will be neglected; and the foundations, of a grand magnetic science being laid will appear anew, so that high intellects may no more be deluded by vain opinions. [p.7]
Gilbert’s experiments on magnetism required an ingenious insight or intuition on his part. He created a terrella, i.e., a miniature version of the earth, and undertook detailed experiments thereon. With the results of these experiments, he was able to make predictions about the magnetic properties of the earth. Then the results of detailed observations of the earth were compared to the results of the experiments. Gilbert was making a non-obvious assumption, namely that at different scales of the universe, there are similar structures. This principle of self-similarity at different scales will be studied in future posts.
Here Gilbert discusses the relationship between the earth and the loadstone:
In the heavens, astronomers give to each moving sphere two poles; thus do we find two natural poles of excelling importance even in our terrestrial globe, constant points related to the movement of its daily revolution, to wit, one pole pointing to Arctos (Ursa) and the north; the other looking toward the opposite part of the heavens. In like manner the loadstone has from nature its two poles, a northern and a southern; fixed, definite points in the stone, which are the primary termini of the movements and effects, and the limits and regulators of the several actions and properties. It is to be understood, however, that not from a mathematical point does the force of the stone emanate, but from the parts themselves; and all these parts in the whole — while they belong to the whole — the nearer they are to the poles of the stone the stronger virtues do they acquire and pour out on other bodies. These poles look toward the poles of the earth, and move toward them, and are subject to them. [pp.22-23]
And here he describes how a terrella should be created:
But inasmuch as the spherical form, which, too, is the most perfect, agrees best with the earth, which is a globe, and also is the form best suited for experimental uses, therefore we purpose to give our principal demonstrations with the aid of a globe-shaped loadstone, as being the best and the most fitting. Take then a strong loadstone, solid, of convenient size, uniform, hard, without flaw; on a lathe, such as is used in turning crystals and some precious stones, or on any like instrument (as the nature and toughness of the stone may require, for often it is worked only with difficulty), give the loadstone the form of a ball. The stone thus prepared is a true homogeneous offspring of the earth and is of the same shape, having got from art the orbicular form that nature in the beginning gave to the earth, the common mother; and it is a natural little body endowed with a multitude of properties, hid in deplorable darkness, may be more readily brought the knowledge of mankind. To this round stone we give the name Μιχρόγη [microge] or Terrella (earthkin, little earth). [pp.23-24]
And here is how the poles, meridians and equator of a terrella can be identified:
To find, then, poles answering to the earth's poles, take in your hand the round stone, and lay on it a needle or a piece of iron wire: the ends of the wire move round their middle point, and suddenly come to a standstill. Now, with ochre or with chalk, mark where the wire lies still and sticks. Then move the middle or centre of the wire to another spot, and so to a third and a fourth, always marking the stone along the length of the wire where it stands still: the lines so marked will exhibit meridian circles, or circles like meridians on the stone or terrella; and manifestly they will all come together at the poles of the stone. The circles being continued in this way, the poles appear, both the north and the south, and betwixt these, midway, we may draw a large circle for an equator, as is done by the astronomer in the heavens and on his spheres and by the geographer on the terrestrial globe; for the line so drawn on this our terrella is also of much utility in our demonstrations and our magnetic experiments. [p.24]
When Gilbert’s De Magnete was published, researchers as diverse as Paolo Sarpi, Galileo Galilei and Johannes Kepler had nothing but praise for Gilbert’s work. In 2003, four centuries after Gilbert's death, Stephen Pumfrey and David Tilley wrote that De Magnete “was nothing less than the first ever work of experimental physics.” Nevertheless, today, the rôle that Gilbert played in developing the experimental method and the idea of self-similarity at different scales is little known. Why this is the case is unclear, and merits further study.
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There are two English-language translations of William Gilbert’s De Magnete.
P. Fleury Mottelay’s translation, first published in 1893, is the easiest to read for a modern reader of English and will be the reference I use: W. Gilbert. De Magnete. Dover, New York, 1958.
Silvanus Thompson’s translation, first published in 1900, is closer to the original Latin, so is less accessible to a modern reader. The reference is: W. Gilbert. On the Magnet, Magnetick Bodies also, and on the Great Magnet the Earth; a New Physiology, Demonstrated by Many Arguments & Experiments. Chiswick Press, London, 1900.
Stephen Pumfrey, David Tilley. William Gilbert: forgotten genius. Physics World, 01 Nov 2003. https://physicsworld.com/a/william-gilbert-forgotten-genius.