The Earth behaves as if there is a giant bar magnet running through its middle from pole to pole. This affects every magnetic material that comes within its reach. If you hold a magnet so that it can rotate freely, it always ends up with one end pointing to the Earth's North Pole and the other to the South Pole. This is how a compass works- the needle automatically swings to the North. The Earth's magnetism comes from its inner core of iron and nickel. You can use the compass you make here to plot a magnetic field like the Earth's. The Earth's magnetic field is slightly tilted, so compasses do not swing exactly toward the North Pole, but to a point a little little way off from northern canada. This direction is known as magnetic north.

Magnetic Protection

The effects of Earth's magnetism extend 37,000 miles out into space. In fact, there is a vast magnetic force field around the Earth called the magnetosphere. This traps electrically charged charged particles and so protects the Earth from the solar wind - the deadly stream of charged particles hurtling from the Sun.

Place the magnetized needle on the slice of cork. Make sure that it will not spin evenly. Tape the needle into place.


Step 3

Fill the bowl nearly to the brim with water; and float the cork in it. Make sure the cork is exactly in the middle and can turn without rubbing on the edges of the bowl.

The Earth's magnetic field should now swivel the needle on the cork. One end of the needle will always point to the north. That end is its north pole.



Magnetic field

You need :
  1. Large sheet of paper
  2. Bar magnet
  3. Needle compass 
  4. Pencil

Step 1

Lay a large sheet of paper on a table. Put the magnet in the middle of the paper. Set up your needle compass an inch or two away from one end of the magnet.



Step 2

Wait as the compass needle settles in a particular direction as it is swiveled by the magnet. Make a pencil mark on the paper to show which way it is pointing.



Step 3

Move the compass a little way toward the other end of the magnet. Mark a line on the paper to show which way the needle is pointing now.



Step 4

Repeat step 3 for about 25 different positions around the magnet. Try the compass both near the magnet and farther away. You should now have a pattern of marks.

Look at the pattern of marks you have made on the paper. They should form a series of rings around the magnet, like layers of an onion. Earth's magnetic field is shaped like this.