When you think about recording something, you usually have sound or image in mind, but, contrary to what you might think you can record all sorts of other information. John Francis Campbell felt the need to record sun lightthe Campbell-Stokes sunshine recorder.
It consists of a sphere - with about 10 cm (4 inches) in diameter - which concentrates the rays of light from the sun, burning a material that is sensitive to heat, previously assembled in a support. The genious of this device is also related with the way in which the data is recorded, which avoids overwriting. Such is assured in a natural way, taking into account the variation in the height of the sun, depending on the season of the year. Because the angle of incidence varies throughout the year, the data is not overwritten.
Obviously, this is a rather simplistic explanation of the way this device works, which uses different data cards according to, for instance, the hemisphere and the season of the year.