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One of Ten Billion EarthsHow we Learn about our Planet's Past and Future from Distant Exoplanets$
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Karel Schrijver

Print publication date: 2018

Print ISBN-13: 9780198799894

Published to Oxford Scholarship Online: July 2018

DOI: 10.1093/oso/9780198799894.001.0001

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One Step Short of Life

One Step Short of Life

(p.41) 2 One Step Short of Life
One of Ten Billion Earths

Karel Schrijver

Oxford University Press

This chapter briefly reviews some the challenges encountered in the search for extraterrestrial life. So far, no signs of extraterrestrial life have been found. The search started with radio telescopes, looking for technology-based civilizations, but new strategies have emerged that take on the primary challenges in this search: the enormous distances to exoplanets and the question of the true nature of life. The author outlines the development of new tools for the search, and why the present focus is on Earth-sized exoplanets with a potential for liquid water on their surfaces. Not having been visited by an alien civilization presents us with a paradox: if life develops as quickly elsewhere as on Earth, then why have we not been contacted? Is the speed of light too slow to cross interstellar distances, is life intrinsically rare, or should we conclude that civilizations are intrinsically short-lived?

Keywords:   life, extraterrestrial intelligence, SETI, biosignatures, Fermi paradox, Drake equation, astrobiology

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