 How can such a mechanism be tested? To see this, it is illuminating to consider the famous experiment that is said to have enabled a choice between the three DNA replication mechanisms in 1957. Also known as “the most beautiful experiment in biology” (Holmes 2011), this experiment was carried out by Matthew Meselson and Frank Stahl by using an analytic ultracentrifuge (see also the discussion of the Meselson-Stahl experiment in the entry  experiment in physics).