Mystery and magic

Solution and notes

The ‘mystery’ in these notes refers to diamagnetism — asubtle magnetic property of materials. The ‘magic’ refers to Pepper’s ghost — atheatrical illusion that uses simple optics. The final section looks back to a time before modern science, to a great thinker — Alcuin — and to alchemy — asubject sometimes dismissed as mystery and magic, but that actually paved the way for modern chemistry and physics

You have probably played with magnets and been fascinated by the forces of attraction and repulsion they exhibit. The magnetic elements we commonly use are iron, cobalt and nickel (and, if you had some below 20°C, gadolinium). Other materials, such as steel and some modern alloys, also show strong magnetic properties. All these materials, which are strongly attracted to external magnetic fields, are known as ferromagnetic materials (Latin ferrum means ‘iron’).

It appears, from simple observation, that other materials are unaffected by magnetic fields, but that is not the case. All materials have some magnetic properties, but their magnetism is generally a thousand to a million times weaker than that of iron.