What is magnetism?

Science is our understanding of how the world works—and generally the world works fine whether we understand it or not. Take magnetism, for example. People have known about magnets for thousands of years and they’ve been using them practically, as compasses, for almost as long. The ancient Greeks and Romans knew as well as we do that lodestone (an iron-rich mineral) can attract other pieces of iron, while the ancient Chinese were making magnetic compasses set in intricate wooden inlays for their practice of Feng Shui (the art of carefully arranging a room) thousands of years before interior designers came on board. Science can sometimes be slow to catch up: we’ve only really learned how magnetism works in the last century, since the world inside atoms was first discovered and explored.

Photo: A typical horseshoe magnet. See the trace of brown rust on the top of the magnet’s upper “leg”? That happens because the magnet is made of iron, which corrodes (rusts) in damp air.

The attractive magnetic field between two bar magnets shown up with iron filings.

Photo: The magnetic field between the opposite poles of two bar magnets that strongly attract one another. We can’t normally see magnetic fields, but if you sprinkle iron filings (tiny bits shaved off an iron bar with a file) onto a piece of paper and hold it above the magnets you can see the field underneath. Photo by courtesy of Wikimedia Commons (where you’ll find a bigger version of this image).

Playing with magnets is one of the first bits of science most children discover. That’s because magnets are easy to use, safe, and fun. They’re also quite surprising. Remember when you first discovered that two magnets could snap together and stick like glue? Remember the force when you held two magnets close and felt them either attract (pull toward one another) or repel (push away)? One of the most amazing things about magnets is the way they can attract other magnets (or other magnetic materials) “at a distance,” invisibly, through what we call a magnetic field.

To ancient people, magnetism must have seemed like magic. Thousands of years down the line, we understand what happens inside magnetic materials, how their atomic structure causes their magnetic properties, and how electricity and magnetism are really just two sides of the same coin: electromagnetism. Once scientists would have said magnetism was the strange, invisible force of attraction between certain materials; today, we’re more likely to define it as a force created by electric currents (themselves caused by moving electrons).


Post time: Oct-17-2019
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