The Eerie Silence: Are we alone in the Universe (2010) by Paul Davies is an engaging, serious look at the question of whether there is likely to be life and intelligence in other parts of the universe and if there is why there is yet to be contact. Davies is a calm, lucid writer who knows his subject well and has a written a dense, interesting book about SETI, METI and alien life in general.
The book starts by looking at the Drake Equation that gives a parameterisation for the number of intelligent life forms in the Universe. Davies goes through each part of the equation and looks at how current science bounds and places the values. Davies discusses the Fermi Paradox which is that given the probability of alien life it is a paradox that alien life has not been encountered.
Davies puts forward the idea that either life is going to be very rare in the universe or that it will be fairly common. The idea that if life is fairly common there could well be a second genesis on earth. Davies thinks that the search for alien life should also include looking this life on earth.
Beyond the earth different possibilities of alien are looked at. The book looks at various forms of exotic travel that could exist given currently allowed physics. The idea of machine intelligence is firmly put forward with the solid idea that travel across star systems is much easier for machines that life. Oddly, the idea that we are in fact the product of a probe that was designed to seed life throughout the universe is not mentioned.
Davis is part of a scientific group for the post detection of life. It’s interesting to learn that governments have not considered the situation and at least until life is not discovered are quite happy to defer these sorts of decisions to the task force.
The book is a fascinating, serious read on the probabilities for alien life and intelligence and a careful consideration of what we should do to search for life. It’s also pleasantly short and concise.