This lecture will explore the contribution that physics can make to the understanding of living things. Physicists can play an important part in establishing the essential characteristics of life as demonstrated by the influence that Schoedingers book "What is Life?" (1944) has had on generations of physicists.
To begin with we live in a Universe that has properties that are finely tuned to allow the emergence of life. However that is a necessary but not a sufficient condition for life to arise and our Universe is also governed by thermodynamics, the second law of which maintains that overall the entropy of the Universe will increase. For living things the second law is a sentence of eventual decay, disorder and death and we know that ultimately that is the fate of any organism. However in the context of the second law one might be surprised by the extent to which, locally at least, we have witnessed increasing order and complexity as the Universe has evolved. While such a development is not of course forbidden by thermodynamics its degree is surprising and the lecture will include some idle speculations as to why this might be so. The lecture will also consider the role of quantum mechanics in living systems.