Let's start with the basics, and then we will go much deeper into the stuff that magnets are made of. A magnet attracts other magnets, and it also attracts some iron and steel things, such as pins and paper clips. Every magnet has a north pole and a south pole, and opposite poles attract each other while the same poles push each other away. Here is a rule to keep. Magnets are not for mouths or small children. Loose magnets can hurt children if they are swallowed. If a child swallows more than one, the magnets can pull together inside the body and cause serious damage.

In a permanent magnet, the tiny magnetic regions called domains line up in the same direction. The domains in a piece of ferromagnetic material are usually between 0.1 mm and a few mm in size. Domains may be made visible with magnetic colloidal suspensions, which concentrate along the domain boundaries. Ferromagnets tend to stay magnetized to some extent after being subjected to an external magnetic field. A permanent magnet loses its magnetism if it is heated enough, and that is a fact worth knowing about every magnet you meet.

Now let's follow the link between electricity and magnetism, one step at a time, because the two are closely tied. Magnetism is caused by the motion of electric charges, and in 1820 Hans Christian Ørsted's discovery showed that electricity and magnetism are related. The magnetic needle of a compass aligns itself perpendicularly to a current-carrying wire, suggesting a relationship between electricity and magnetism. François Arago found that unmagnetized iron filings orient themselves in a circle around a copper wire carrying current. Iron filings around a current-carrying wire disperse when the current is stopped. Michael Faraday discovered electromagnetically induced currents in 1831.

Now let's look at Earth, and at how its field works. Earth is a really big magnet. Its magnetic field begins in its core, where the motion of electrically conducting iron in the outer core makes electric currents. Those currents generate Earth's magnetic field. Invisible lines of force flow between its magnetic poles. These are not the same as its geographic North and South Poles. That is where the story of the field begins, and it explains much of what comes next.

Now let's see how people have used the field to find their way. A magnetic compass has a magnetized needle that turns to line up with Earth's magnetic field. The needle of a compass lines up with Earth's magnetic poles. A lodestone compass was used in navigation as early as 1086. Magnetic declination is the angle between magnetic north and true north. Edmond Halley carried out the first magnetic declination survey.

Last, let's look at how Earth's field changes over very long spans of time, which is a story of swaps and shifts. During a pole reversal, Earth's magnetic north and south poles swap locations. During a reversal the magnetic field weakens but does not completely disappear. The last time Earth's magnetic field reversed was about 750,000 to 780,000 years ago. Meanwhile, as of November 2026, Earth's magnetic north pole is moving, and this gradual shift must be regularly accounted for in navigation.

Words to know

• domains: tiny magnet regions
• ferromagnetic: strongly magnetic
• filings: tiny iron bits
• reversal: a swap