Every year, the University of Arizona’s College of Sciences puts on a public lecture series; this year’s theme is “Life in the Universe”. Given my ability to deliver good entertainment (my ancestors were in vaudeville), I have been asked to present the opening lecture, “What is life?”My background is extraterrestrial geology, not biology. When biologists define life as the chemistry of complex long-chain hydrocarbons, I think of my favourite complex framework silicate mineral crystals, like plagioclase. If life were nothing more than complicated chemistry, then why not offer a seven-part lecture series on Plagioclase in the Universe? Of course, no one would show up.Yes, life is complex chemistry. But to limit one’s view to mere chemistry misses th