The future of SETI: Finite effort or search without end?

For almost 50 years, astronomers have scanned the skies for evidence of an extraterrestrial civilization that has reached or surpassed our level of technological development. In the course of this search, technology has improved dramatically, and additional developments such as larger and more sensitive telescopes and increased computing power will accelerate the search and extend it into new areas. Speculative search strategies that are more firmly rooted in imagination and wish than present-day science may mature with the practical effect of further extending the search space. The search for extraterrestrial intelligence (SETI), based on passive observation, has been joined by the controversial activity of messaging extraterrestrial intelligence (METI), the use of radio transmissions and space probes to proclaim our place in the universe. Potential “wild cards” that could fundamentally change the nature of the search include government intervention, the fruition of breakthrough technologies, and a confirmed detection. A rigorous search could confirm the existence of extraterrestrial intelligence tomorrow, within the lifetime of many people now alive, or in the distant future. All that is required for its continuation is a small number of scientists who have the skills and equipment to conduct a search that most scientists find credible. Since the search for life beyond Earth is motivated by cultural and psychological as well as scientific considerations, we may expect it to continue into the indefinite future.