A new study from Penn State challenges the long-held belief that intelligent life is rare, suggesting instead that it may be more probable than previously assumed.
In 1961, astrophysicist Frank Drake introduced the Drake Equation, a mathematical framework designed to estimate the likelihood of technologically advanced civilizations in the Milky Way and their potential for communication. This equation marked a major shift in how humanity perceives its place in the cosmos.
By 2023, advances in exoplanet science, astrobiology, and SETI research led to refinements of Drake’s original formula. Among these, Canadian astrophysicist Sara Seager introduced an alternative equation focusing not just on intelligent life but also on detecting biosignatures—chemical indicators of biological activity.
Previously, theoretical physicists had approached the question differently. In 1983, physicist Brandon Carter proposed the “hard steps” model, which argued that life is extremely rare due to a series of improbable evolutionary leaps—or “hard steps”—necessary for complex organisms to emerge. Carter suggested that Earth’s sequence of evolutionary milestones was exceptionally unlikely. The new Penn State study revisits this model, offering a fresh perspective on the idea that life may be more common than Carter originally proposed.
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