Infra-red waves are just below visible red light in the electromagnetic spectrum ("Infra" means "below"). You probably think of Infra-red waves as heat, because they're given off by hot objects, and you can feel them as warmth on your skin. Infra-Red waves are also given off by stars, lamps, flames and anything else that's warm - including you.

Infra-red waves are called "IR" for short. They are used for many tasks, for example, remote controls for TVs and video recorders, and physiotherapists use heat lamps to help heal sports injuries.

Because every object gives off IR waves, we can use them to "see in the dark". Night sights for weapons sometimes use a sensitive IR detector. Remember the film, "Predator"?

Apart from remote controls, one of the most common modern uses for IR is in the field of security. "Passive Infra-Red" (PIR) detectors are used in burglar alarm systems, and to control the security lighting that many people have fitted outside their houses. These detect the Infra-Red emitted by people and animals.

You've probably seen TV programmes in which police helicopters track criminals at night, using cameras which can see in the dark. These cameras use Infra-Red waves instead of "ordinary" light, which is why people look bright in these pictures. Similar cameras are also used by fire crews and other rescue workers, to find people trapped in rubble.

Weather forecasters use satellite pictures to see what's heading our way. Some of the images they use are taken using IR cameras, because they show cloud and rain patterns more clearly.

The danger from too much Infra-Red radiation is very simple - overheating.