inorganic ones by applying a form of energy.
The idea was to simulate hypothetical conditions thought to be present on the early Earth (Hadean or early Archaean).
It was a test of the chemical origins of life. Specially, the experiment tested Alexander Oprains
and J.B.S. Haldan 's hypothesis that conditions on the primitive Earth favoured chemical reactions that synthesised
organic compounds from inorganic precursors. Considered to be the classic experiment on the origin of life, it was
conducted in 1952 and published in 1953 by Stanley Miller and Harold Urey at the University' of Chicago.
After Miller's death in 2007, scientists examined sealed vials preserved from the original experiments. They were able
to show that there were well over 29 different amino acids produced in Miller's original experiments. That is
considerably more than those Miller originally reported, and more than the 20 that naturally occur in the origin of life.
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Moreover, some evidence suggests that earth's original atmosphere might had a different composition than the gas
used in Miller-Urey experiment. There is abundant evidence of major volcanic eruptions 4 billion years ago, which
would have released carbon dioxide, nitrogen, hydrogen sulphide, and sulfur dioxide into the atmosphere.
Experiments using these gases in addition to the ones in the original Miller-Urey experiments have produced more
diverse molecules.
Note that organic compounds, including amino acids, are present in the meteorite dust which rains down on Earth.
Therefore, interest in abiogenesis and the origin of life has shifted to question of how cells and large macromolecules
formed.