20 THIN;;
YOU DIDN’T KNOW ABOUT
MAGNETISM
BY REBECCA COFFEY
ILLUSTRATION BY
JONATHON ROSEN
1. Magnetism is familiar to every ;fth grader, but
describing it can confound even the most brilliant
physicist. 2. Take the case of Richard Feynman.
When asked to explain magnetism, he urged his ;;;
interviewer to take it on faith. After seven minutes of
stonewalling, he ;nally said, “I really can’t do a good
job, any job, of explaining magnetic force in terms
of something else that you’re more familiar with
because I don’t understand it in terms of anything
else that you’re more familiar with.” 3. He did break
down and try for a few seconds before abandoning the attempt. ;ose seconds were packed with
oversimpli;cations: “All the electrons [in a magnet]
are spinning in the same direction.” 4. But who
better than Feynman would have known that not all
electrons spin in the same direction? 5. And they
don’t actually spin. “Spin” is just a physicist’s term for
the little magnetic north and south poles baked into
every electron. ;e orientation of those poles de;nes
the direction of the electron’s (somewhat imaginary)
rotation. 6. Why does every electron have those
poles? As soon as someone ;nds out, we’ll get back
to you. 7. Here is what we do know. Within an atom,
each electron is usually paired with an opposite-oriented electron so that their magnetic pulls cancel
each other out. 8. But if some of the electrons are
unpaired, they can be induced to move around so
that their poles line up, creating a net magnetic ;eld.
;e arrangement of the electrons in metals makes
them particularly open to magnetic peer pressure.
9. ;;; refrigerator magnet: Apply an external magnetic ;eld to some hot metal. Cool it so the aligned
electrons get frozen in place. Slap on your local
plumber’s business card, and—voilà! 10. Yin Seeks
Yang for Magnetic Relationship. All magnets have
north and south poles, and opposite poles attract:
North poles seek south poles seek north poles seek
south poles seek . . . 11. You are standing on a magnet right now. ;e earth’s magnetic ;eld is created
by electric currents in an ocean of molten iron at its
core. ;at’s why the north pole of a compass needle
points . . . er . . . why north? Since north poles are
attracted to south poles, the “north” arrow on your
compass actually points toward the earth’s south
magnetic pole, which is the one up north. Got it?
12. And the earth’s magnetic south (aka “north”)
pole isn’t even precisely at the geographic north pole.
Right now it is in the Arctic Ocean, near northern
Canada. 13. Worse still, it is constantly drifting in
response to currents in the earth’s core. It is moving
toward Siberia at a rate of up to ;; miles per year,
according to the U.S. Geological Survey. Hey, shift
happens. 14. Ancient mariners navigated by lodestone,
naturally occurring magnetic rocks. 15. Where lodestones come from is another mystery of magnetism.
Some geologists think they are created when lighting
strikes iron-rich rocks. 16. Microbes, birds, and
some other animals have magnetic crystals inside
their bodies that allow them to orient themselves.
17. ;at is probably why loggerhead turtles can
migrate ;,;;; miles in unfamiliar waters while humans
can get lost looking for the men’s room at Olive Garden.
18. Magnetic Resonance Imaging (;;;) machines
generate a ;eld ;;,;;; times as intense as the
earth’s to vibrate the hydrogen atoms in your body;
in response, the atoms emit radio waves that are
analyzed to produce a map of your insides. 19. Using
a sensor the size of a sugar cube, researchers from the
National Institute of Standards and Technology can
track the magnetic pattern of a human heart. 20. ;e
signal is faint, but the good news is that science has
proved attraction is quanti;able. Word up, Hallmark.
DISCOVER (ISSN 0274-7529, USPS# 555-190) is published monthly, except for combined issues in January/February and July/August. Vol. 32, no. 6. Published by Kalmbach Publishing Co., 21027 Crossroads Circle, P.O. Box 1612, Waukesha, WI 53187-1612.
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