FEEL THE FORCE!

JD Savage investigates a mysterious, invisible force that rules the universe. Just watch out it doesn't pull you in!

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What makes hospital scanners scan, allows sharks to navigate across miles of featureless open ocean, and creates dazzling light shows in the night sky? The answer is one of the most powerful forces shaping our world – magnetism. You can’t see it, touch it, hear it, smell it or taste it, but you can feel its effects when you play with a magnet. This invisible force only works on certain materials – it doesn’t attract paper, but it will keep your latest artistic masterpiece stuck to the metal fridge.

Humans live on a gigantic magnet, so perhaps it’s no surprise that we’re so attracted by magnets. Our planet throws its own protective forcefield into space, which stops Earth from becoming as barren as Mars. But what exactly is this strange power and where does it come from?

Marvellous magnets

Magnets are objects (these can be metal or rock) that produce an invisible force called magnetism. They exert a force, or pull, on certain types of metal, such as iron. However, not all metals are magnetic – try picking up an aluminium drinks can or a copper coin with a magnet. Nothing happens. But put a magnet near a paperclip or iron filings –instant attraction.

Some rocks containing minerals, such as magnetite, are naturally magnetic. Materials like these are called permanent magnets because they’re always magnetic, without needing to be charged up or powered by electricity. They are used to make your bar magnets, fridge magnets and the small closers that snap tablet covers shut.

The most common permanent magnets today are powerful and hardwearing. They are made of metal alloys (mixtures), such as neodymium and iron mixed with boron. You’ll find them nestled inside your earbuds, in computer hard drives and inside electricity-generating wind turbines. They are also in guitar pickups, where they convert the motion of the string into an electrical signal.