Miller-Urey experiment. Computer illustration showing the apparatus used in the Miller-Urey experiment to study the origin of life. This 1950s experiment attempted to duplicate the conditions that would have existed on the primordial Earth. The apparatus contains a 'sea' of sterile water (H2O, bottom loft) and an 'atmosphere' (top right) of hydrogen (H2), methane (CH4) and ammonia (NH3). The 'sea' is boiled and the water vapour evaporates and enters the 'atmosphere' where electrodes give off sparks within the 'atmosphere' to imitate either lightning or ultra-violet radiation from the Sun. The result is a residue containing amino acids, the basic building blocks of life, which collects in the flask at bottom.