The first stanza describe how the universe functions on probabilities and how the creation of mankind is an extraordinary outcome that came out the probabilities and randomness.
The second stanza is intended to describe the scientific process.
The third through sixth stanza describe the major advancements in modern physics. The third is the unification of gravity, weak and strong nuclear force, and electromagnetism. The reference to the string which holds us down is referring to gravity but also hints toward string theory which unifies these four forces. The fourth is quantum theory which is impossible to measure because of the uncertainty principle. The fifth is also quantum theory but it elaborates by describing how observing the universe defines it's position and therefor forces it to manifest what we see on a daily basis. The sixth is a description of time as enthalpy, and also references to the cosmic background radiation which supports this hypothesis.
The last stanza sums up the purpose of many modern physicist which is to find a unified theory of the universe.