In the past, magnets were nothing to fear. The small ceramic type long used on refrigerators were barely strong enough to hold up a piece of paper. The same size magnet today can kill you.

Every electron in a material has a spin that creates a tiny magnetic field around it. Normally these electrons spin in random directions, canceling each other out, but in permanent magnets, some of the electrons are locked into alignment, producing an overall magnetic field. The stronger this lock-in, the stronger the magnet.

Powerful neodymium-iron-boron magnets are used in everything from jewelry to motors. With the development of new alloys and processing methods, they are getting stronger and stronger, to the point that even very small ones can be dangerous. If you swallowed two separately and they were to find each other, they could puncture your intestinal walls and cause a fatal infection.

tomato being crushed
Tomato: Crush Theodore Gray

Larger magnets, like the two-by-two-by-one-inch monsters I used in this demonstration, require careful planning just to carry from one room to another. Let one get too close to a steel door frame, and it can crush your hand. The two I used hug each other with 520 pounds of force.

Neodymium-iron-boron magnets do, however, have one weak spot: Heat them above 175°F, and the electron spins are knocked out of alignment, permanently destroying the magnetism. So if you ever find yourself with two of them clamped down on your finger, you could hold your hand in boiling water for a few minutes.

But try to find a pry bar first.

WARNING! High-strength NdFeB magnets aren’t toys. Even small ones can crush people’s fingers. Do not actually try holding your hand in boiling water to remove the magnets.