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In Future Issues...

Systems Biology

Nobel Experience for GPP Students

Sigma Xi Survey

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The NIH Catalyst is published bi-monthly for and by the intramural scientists at NIH. Address correspondence to Building 2, Room 2E26, NIH, Bethesda, MD 20892. Ph: (301) 402-1449; fax: (301) 402-4303; e-mail: <catalyst@nih.gov>.

Kids' Catalyst:

Finding Magnetic North

Sometimes it's not so easy to find your way. Whether you live in the city or the country—or have a bike or a new car that talks to a satellite—sometimes you can get a little turned around.

There are many guides to finding your way—maps, stars, street signs, or just asking for directions. But if you really want to know in which way you're pointing, look no further than the earth itself, and a compass.

You can make your own compass at home. You'll need a magnet (refrigerator magnets work, and the magnets typically found in home science kits work even better), a sewing needle, a few inches of office tape (or a cork; see below), a large nonmetallic bowl, and enough water to fill the bowl.

Put the needle on a flat surface, with the eye toward you; then stroke it with the magnet, going from the eye to the tip (always the same direction). How many strokes depends on the strength of your magnet, but about 20 should suffice. Now you have a magnetized needle.

You can place the magnetized needle on a piece of cork or encase it in office tape and then place it in the water and watch how it floats. (Although the needle will float on top of water on its own due to surface tension, it may take longer; making a tape pontoon for the needle is perhaps the most practical approach—it has the added benefit of protecting fingers from the needle's sharpness and making the needle easier to find if it is dropped.)

Once the needle is ensconced and floating on the surface, where do you think the tip will point? If you guessed North, you're right and not just any North, but magnetic North—just the same as any compass.

What if you're in space? Or in the Southern Hemisphere? Or live 100 years in the past or in the future? The fun thing about magnetic North is that it's always changing relative to itself and to where you are, so it's very important to keep up on your declination and inclination toes—but that is for you to look up!

By the way, please note: Our home-made magnetic needle will work only in still water, so its use outdoors is limited. But indoors, it's not only a compass, but can be turned into a game as well. You can make however many tape-encased magnetized needles as you have friends at your house. You can chase the needles around with your magnets—they will go wherever the magnet does—and have races and other rivalries with your friends.

—Jennifer White