58 Please remember to mention OVL when responding to adverts Stelios Mores L oadstone is a ferric ferrite made up of mostly rust (Fe2O3) mixed in with calcites, silicates and quartz plus traces of barium, manganese, nickel and also zinc. At first it is difficult to see why this rusty stone might be considered to be of any special interest, until one realises that it is magnetic. The first references to loadstone and its magnetic properties go all the way back to 600 BC and the ancient Greek province of Magnesia on Asia Minor, when Thales of Miletus first described stones with magnetic properties found in the region. He called these ‘stones of Magnesia’ also known as Magnetite, and the term gave its name to the physical phenomenon of Magnetism. Around the same time, the method of magnetic induction by which magnetic properties can be transferred from a loadstone to an iron object were also discovered. However it seems that very little was made of this knowledge, and despite many of the philosophers of the age mentioning it in their essays, no explanations were ever suggested. The first practical use of magnets was by the Chinese in the 12th century who were making and using crude compasses by magnetising iron needles and floating these on water by placing them on corks. This galvanised natural philosophers in Europe such as the French scholar Peter Peregrinus to conduct experiments which successfully described the behaviour of magnetic forces. This work led to the development of compasses which could be relied on for long-distance navigation. By the late 1500s, the groundbreaking work of the English astronomer and natural philosopher William Gilbert showed that the Earth itself behaved much like a magnet, albeit a very weak one. His published work ‘De Magnete’ confirmed the existence of magnetic polarity and defined the poles of a magnet as North pointing and South pointing, ie. the North and South poles of a magnet. Despite such advances, it was not until the 16th and 17th centuries when protagonists such as Isaac Newton brought about the ‘Age of Enlightenment’ that the understanding of magnetism could progress any further. During the late 1700s, the German Carl Fredrich Gauss considered the theoretical basis of magnetism introducing the notion of a magnetic flux around a magnet. During the same time in France, Charles Coulomb’s experiment with static electricity and magnetism led him to quantify the force of attraction experienced by two magnets, stipulating that this was the result of their magnetic fields affected by the distance between them. Once again the story of magnetism stalled and it took another 200 years and advances in the understanding of electricity before it could be revisited. In 1819 Hans Christian Orsted who was a professor at Copenhagen University planned to demonstrate the heating of a straight length of wire by electricity and to demonstrate magnetism using magnets and a compass. It was to be a home demonstration for family and some close friends. As he was setting up these experiments on the limited space of his small desk, he noticed that his compass moved whenever he connected the wire to his battery. This chance discovery linked magnetism to electricity. Prompted by this, Andre-Marie Ampere in France went on to show how two parallel wires carrying an electric current created a magnetic force, and that this drew them together if the current flowed in the same direction and forced them apart when the current flowed in opposite directions. He determined how this force was affected by the distance between them and the electrical currents flowing in each. At this juncture it had become apparent that the movement of charge and magnetism were inextricably connected. This began Michael Science Ancient Attraction