In The Eerie Silence: Renewing Our Search for Alien Intelligence (Houghton-Mifflin-Harcourt, 2010) Paul Davies reviews the history of the fifty-year-old SETI (Search for Extraterrestrial Life) project. His specific interest is the “eerie silence” of his title. Although SETI has been looking for radio signals from alien civilizations elsewhere in the universe, no signals have been received. What does this mean? That SETI is looking in the wrong places, that there is no alien life out there, that their civilizations are too advanced to use radio signals, that SETI is looking for the wrong kinds of communication? Davies considers all these possibilities. He reviews not only the history of SETI but also the speculation over the last several centuries about whether extraterrestrial life exists and the forms it might take. Davies is a serious scientist who explains that SETI research is a scientific enterprise carried out with scientific methods. Searching for ET he regards as a natural expression of human beings for making connections and for a larger understanding of identity and existence.
Davies suggests that looking for radio signals may be quixotic. The Universe has existed for twelve or more billion years. If there are alien civilizations out there, they may have developed and disappeared millions of years before our present moment. The probability that there is a civilization out there at this precise moment in time that has decided to use radio signals to contact other beings is unlikely. Moreover, such a civilization might be using another form of communication, such as laser beams (which SETI is now looking for).
Davies hypothesizes that an alien civilization further developed than our own might communicate in forms we can’t imagine. To them radio signals would be an ancient, antiquated technology. Perhaps, then, we’re not looking for the kinds of communication aliens might use. Perhaps they wouldn’t be seeking to communicate at all and instead might have left by accident or intention other artifacts of their existence. Davies discusses what these might be and how we could recognize them. He suggests that if an encounter with aliens ever comes, it might be with independent self-replicating robots sent out by their creators to explore and report back on the state of the universe. This aspect of the book is highly speculative.
Davies notes that much speculation about alien civilizations has been anthropomorphic, and that we tend to think of other civilizations as being similar to our own. He speculates as well that life on other planets might well not be carbon-based. He discusses the possibility that life might have begun elsewhere, such as on Mars, and later transferred to earth by meteor impacts.
I was most interested in Davies speculations about the possibility that there is no other life at all out there in the cosmic expanses. As a scientist he expresses his conviction that intelligent life does not exist elsewhere in the universe, that its development on the earth was a highly random and unlikely event. This runs contrary to what many others believe, but Davies makes a persuasive case for his position. He suggests that life may not be as quick to develop as some, such as Carl Sagan, have suggested. At the same time as a human being he wants to believe in the possibility of intelligent life elsewhere in the cosmos.
Davies’ concluding discussion of the consequences of discovering that there is intelligent life elsewhere in the cosmos, or that there isn’t, and his ruminations on what such a discovery would mean to our sense of ourselves as human beings, is fascinating.