Are We Alone?
One of the most intriguing questions in astrobiology is whether or not Earth is the only host for life in the universe. Yet, the answer couldnít be more cut and dry; either extraterrestrial life exists or it does not. Both possibilities have profound consequences. The American architect and designer Buckminster Fuller said, "Sometimes I think we're alone. Sometimes I think we're not. In either case, the thought is staggering." The universe is an expansive place. The number of potential sites for life in the universe is enormous, and the chemical constituents of life are ubiquitous. With so many possibilities, it seems unlikely that we are the single occurrence of life. The discovery of intelligent life beyond the solar system will certainly influence our world, for better or worse. At the very least, as anthropologist D.K. Stern has pointed out, the discovery of alien life "would irreversibly destroy our self-image as the pinnacle of creation." The alternative option is equally thought provoking. If we truly are the only manifestations of life in the universe, then it implies a universe of incredible grandeur with us as the only spectators.
Astrobiologists study the possibilities of life beyond Earth as a direct way of questioning our role in the universe. How do we investigate the answer to the question "Are we alone?" Admittedly, discussions of the existence, intelligence, psychology, or appearance of higher alien life forms are almost entirely speculative. However, the fundamental investigations that will allow us to more accurately predict the likelihood of primitive life beyond Earth are already underway.† Astronomers have detected extrasolar planets orbiting other nearby stars in the universe. They have also found complex, carbon-based molecules in interstellar space and in meteorites, telling us that complex chemistry is not a unique result of the formation of our solar system. Chemists have studied the reactions leading to the origins of life.† They have investigated pathways by which replicating molecules and simple life forms can be synthesized from simple constituents.† Evolutionary biologists have also contributed by exploring how complexity can evolve from single-celled organisms.† Physicists have estimated the rates at which interstellar cultures could populate our Milky Way Galaxy.† And, not to be outdone, the philosophers have anticipated the impact of contact with intelligent aliens on human culture.†
As products of a pervasive and persuasive popular culture, many of us have been tainted by optimism of intelligent life beyond Earth.† Movies, television, books, and other media donít challenge us to think about IF we are alone, but rather with what will happen WHEN we finally make contact.† Despite the mediaís optimism, we should practice a healthy amount of skepticism and practice critical thinking skills when considering the true likelihood of discovery or contact with life beyond Earth.† A clear understanding of which questions can be answered by the scientific method, and which cannot, will help us practice realism.† Currently, we know of only one species with the intelligence to understand and explore the universe, ourselves.† Although there has been immense progress in the study of planets beyond our solar system, there is no answer yet to the question: Are we alone?
THE ANTRHOPIC PRINCIPLE
THE ORIGIN OF LIFE ON EARTH
EVOLUTION AND INTELLIGENCE
FROM MOLECULES TO CELLS
THE NATURE OF LIFE