A Word about Magnetism

Remember in grade school or high school science class when you put a magnet under a piece of paper and sprinkled iron filings on the paper to see the lines of force?

Magnetic fields ain’t got lines of force! Magnetism is a field, and fields are smooth. Those lines you saw are a result of smearing the iron particles around, and they’re a handy (and artificial) way to visualize the direction of the magnetism. If you were to draw lines showing equal strength (analogous to contour lines on a topographical map), they’d be perpendicular to those lines everybody mentions. Here are a few examples of someone using both terms interchangeably. He’s being imprecise.

Jets of hot plasma, propelled by a bunch of magnetic field lines, rise from a small sunspot roughly the size of China.

If all goes well, the spacecraft—safe in the shadow of the shield—will beam back a record of the corona’s plasma and the tangled net of magnetic fields that shape it.

Earth’s magnetic field deflects most solar wind particles

Researchers have proposed two mechanisms by which magnetic fields could turn kinetic energy from the sun’s roiling surface into coronal heat

Quotes from an article emailed to me by a friend. The writer is Joshua Sokol, a journalist based in Boston

You’re not likely to write expositorily about magnetism very often, but be sure you get it right when you do.