William Herschel discovered infrared radiation in 1800, while living in Slough. It was an accidental discovery, as at the time he was trying to devise a way of cutting down the glare of looking at the sun through a telescope.

He noticed that when using different coloured filters, some would let through more heat than others. This led him to devise an experiment to measure the heat given out by different colours of light.

He passed sunlight through a prism to create a spectrum, and measured the heat given off at various points of the spectrum using thermometers. He discovered that there was even more heat beyond the red end of the spectrum.

Herschel called his discovery 'calorific rays', and upon further testing he found out that they behaved just like visible light - they were in fact another form of light, beyond red light.

This was the first time that someone had shown that there was light which was not visible to the human eye. This was infrared radiation, which today has many useful applications in the fields of astronomy, medicine, police work and weather monitoring, amongst others.