A Physics Model for Origin of Life

In this article, we attempt to convince the reader that the origin of life was such an exceptionally unlikely event that it probably has never occurred elsewhere. This involves an explicit calculation using the laws of physics which, while speculative, may encapsulate the essential science without knowledge of biological details. Making only physics, and no biology, assumptions about the origin of the first single celled organism (SCO) on Earth, we adopt methods of quantum tunnelling to make an estimate of the probability ${\cal P}_{SCO}$ for the origin of life. We argue that before the time $t_{SCO}$ laws of physics must suffice and assume a first-order phase transition which nucleates at the first SCO production. In the classical limit where Planck's constant vanishes $h\rightarrow0$, ${\cal P}_{SCO}$ also vanishes and remains extremely small for the correct value of $h$. Thus quantum mechanics plays a central role in permitting life to form. We compare the resultant probability with the expected number of exoplanets in the Milky Way ($\sim10^{12}$) and the Visible Universe ($\sim10^{24}$) and conclude that the probability of extraterrestrial life in the Visible Universe is infinitesimal. This result suggests that the visible universe is a lonely place for humankind because extraterrestrial life will never be encountered.