Teach Astronomy - Miller-Urey Experiments

http://www.teachastronomy.com/ How did life begin on Earth? In the 1950s, a classic set of experiments were conducted by Miller and Urey. The Miller-Urey experiments tried to make life in a bottle. A flask containing water and the basic chemical ingredients of the oceans and the Earth's atmosphere is given extra energy and left for weeks. After watching this closed experiment for weeks, it turns out that amino acids and complex molecules and other organic material is created. The Miller-Urey experiments give some sense that complexity can emerge from simple ingredients given sufficient time and an energy source. However, in the 1950s we did not know exactly what the early Earth's atmosphere composition was. It turns out that the first Miller-Urey experiments used too much methane and ammonia and not enough carbon dioxide. Using a more appropriate composition for the early Earth's atmosphere yields less organic materials, but later versions of these experiments have nonetheless been able to reproduce and produce almost all the amino acids, sugars, lipids, and the five bases needed by RNA and DNA. This is of course not the same as producing a replicating molecule, which has never been seen in one of these experiments, and in fact other chemical constituents are probably needed in addition to a large amount of time to produce the first replicating molecule. But it is an indication that life must have started by the building of larger pieces from smaller pieces.