Earth science

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Video

Materials

• 1 sewing needle
• 1 magnet
• 1 cork
• 1 bowl
• 1 pair of scissors
• Water

Short explanation

The sewing needle is now magnetic and acts as a compass needle that points towards north.

Long explanation

The sewing needle is made of iron. Iron consists of crystals and each crystal is magnetic, with its own north and south poles. However, the crystals are pointing in different directions and therefore a piece of iron as a whole is not magnetic. However, they can be arranged by moving a magnet along a piece of iron repeatedly. By doing this, you arrange the crystals so that all of them points in the same direction. The piece of iron, for example a sewing needle, now becomes like a large magnet with a north and a south pole.

When one magnet is on top of another magnet, they will point in opposite directions. The north pole of one magnet (which is usually painted red) will lie on top of the south pole of the other magnet (which is often painted white) and vice versa. This is actually why the sewing needle points in a certain direction. It lies on top of a huge magnet - Earth.

Earth's magnetic field is still a bit of a mystery. But it's believed that it mainly originates from electric currents in the molten iron and nickel found in Earth's outer core. Humans don't feel the magnetic field directly, but it's extremely important for life on Earth. It forms a protective shield against the solar wind, which would otherwise blow our atmosphere away.

One end of the sewing needle points to the magnetic north pole, while the other end points to the magnetic south pole - just like a real compass.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What other objects work as a pointer other than the sewing needle?
• What happens if you only "comb" the needle 10 times?

Variation

For the compass to work, the needle needs to be free to rotate as it pleases. Another way to do this is to hang it on a string.

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