A compass is a valuable tool for outdoor exploration. If you just know the basics of how to use one to find direction, they can be useful for finding your way; if you know how to orient yourself by pairing a map with your compass, you can do a lot more. 

Even when someone does know how to use a compass, however, they don’t always understand how this device actually works.

All magnets have two sides, a north pole and a south pole. Each side emits a magnetic field that pulls at opposing poles. When magnets stick together, it’s because of the attraction between north and south poles. When magnets push away from each other, it’s because two like poles (north to north or south to south) are being forced toward each other. As they say, it’s opposites that attract.

The earth itself is a giant magnet. Think of the North and South Poles. Essentially, any magnet on earth is drawn to align itself with the earth’s magnetic field. Compasses work by taking advantage of the earth’s magnetic field. The problem is, that force is fairly weak. So, a magnet sitting on a table will keep sitting on the table instead of flying through the wall to see Santa.

But, when weak magnets are placed in environments where they aren’t impeded by friction, the force of the earth’s magnetic field is strong enough to move them. And when they do move, they’ll align with the earth’s magnetic poles.

When you look at a compass needle, the part that points north is actually the south pole of the compass’ magnet being attracted to the earth’s North pole, and vice versa.

Once you understand the principles of how compasses work, you’ll understand the principles of how to make your own: create a magnet and place it in a low-friction environment. Creating your own compass is a fun science craft to do with your kids, and a nice way to practice a survival skill. With the basic mechanics down, you can use whatever materials you might have on hand in a pinch; for example, the prisoners who participated in WWII’s “Great Escape” manufactured hundreds of compasses by magnetizing slivers of razor blades and making cases from melted and repurposed phonograph records. If outdoors, a compass can be made by laying a magnetized nail, paperclip, or safety pin on a leaf floating in water.

One classic, simple way to create a DIY compass is by using just an old cork, a sewing needle, and a dish of water; it’s a design that mimics the first compasses used in China during the Song dynasty, over a thousand years ago. Here’s how to do it.

How to Make a Compass

Step 1: Make a Cork Disk

Cut the end off a cork, about 1/4-inch thick, so that you end up with a disk.

Step 2: Magnetize the Needle