He studied the Earth’s origin from a chemical viewpoint, deducing its constituents by supposing that final accretion occurred at about 0°C. This would have given it a primitive atmosphere of mainly water vapour, methane, ammonia, and hydrogen. In 1953 his student Stanley Lloyd Miller (1930–2007) subjected a mixture of these gases to an electrical discharge to simulate lightning, in what has come to be called the Miller–Urey experiment. After several days there had formed organic molecules important to life, in particular amino acids. Similar experiments were later carried out by others, including C. E. Sagan. Urey also studied the abundance of elements on the cosmic scale.