To infinity and beyond

The key to understanding molecules in space lies in the electromagnetic spectrum. The 13th century philosopher and Franciscan friar Roger Bacon, also known as Doctor Mirabilis, was the first scientist to recognise that light, seemingly natural, white light from the Sun produces a rainbow of colours - red, orange, yellow, green, blue, indigo, and violet - through a glass of water. Centuries later, in 1671, Sir Isaac Newton gave this rainbow its modern name - the spectrum - after carrying out sophisticated experiments with sunlight and glass prisms, the basis of the spectrometer.  

A couple of centuries later, physicists began to unravel the secrets of the visible spectrum and beyond. They recognised, for instance, that the spectrum represents a range of energies. (The absorbed energy, ΔE,  is related to its frequency, ν,  by the equation ΔE  = hν, where h is the Planck constant, and the frequency of the absorbed or emitted energy is inversely proportional to its wavelength.) Red light has the least energy (lowest frequency, and longest wavelength) and violet has the most energy (highest frequency and shortest wavelength). 

The visible spectrum, however, is only a very small part of the electromagnetic spectrum, with infrared, microwaves, and radio waves lying beyond the red end of the visible spectrum and have gradually lower energy. Ultraviolet, x-rays and gamma rays lie beyond violet and have increasing energy.