The Astronomer Royal advances the alarming thesis that the odds on human survival to the end of this century are no better than 50/50. Whilst this could be the critical era in which life on Earth spreads beyond our solar system, it is just as likely that we will endanger the entire universe. Sir Martin carefully decribes how technology could destroy our species, for example by engineered airborne viruses or by rogue nano-machines that replicate catastrophically. Experiments that crash together atomic nuclei could start a chain reaction that erodes all atoms of Earth, or could even affect space.