SETI Turns 50 - Five Decades of Progress in the Search for Extraterrestrial Intelligence
Jill Tarter (SETI Institute)
The 1959 Nature article by Giuseppe Cocconi and Phil Morrison provided the theoretical underpinnings for SETI, accompanied in 1960 by Project Ozma, the first radio search for signals by Frank Drake at the National Radio Astronomy Observatory (NRAO). Well over 100 search programs have been conducted since that time, primarily at radio and optical wavelengths, (see www.seti.org/searcharchives) without any successful signal detection. Some have suggested that this means humans are alone in the cosmos. But that is far too strong a conclusion to draw from far too small an observational sampling. An appropriate analogy would be to retrieve one glass of water from the ocean, and having found no fish in that sample, to conclude that there were no fish in the ocean. The experiment might have worked – the smallest fish is ~ 1 mm in size and many other species of fish could have fit within the glass and been visible to naked eye inspection – but the sample was far too small to have any significant probability of success.

Instead of concluding that intelligent life on Earth is unique, it is more appropriate to note that in 50 years our ability to search for electromagnetic signals has improved by at least 14 orders of magnitude and that these improvements are still occurring at an exponential rate. In addition, in the past 50 years, the detection of exoplanets, and a growing appreciation of the robustness of extremophiles have given the cosmos at least an appearance of being more biofriendly. If we are looking in the right way, our observational tools will evolve to sample sufficiently large volumes of phase space before SETI turns 100, that evidence for cosmic company can reasonably be expected. If we are not yet looking in the right way, this same exponential growth in our astronomical tools and in new technologies may well uncover evidence of a type we are not wise enough today to predict.

The last sentence of the Cocconi and Morrison paper is as wise today as it was in 1959: “The probability of success is difficult to estimate, but if we never search, the chance of success is zero.”