by Andrew Glikson Enrico Fermi, Physicist , 1901-1953 According to Fermi’s Paradox , the failure to date to achieve radio communication between Earth and extraterrestrial civilizations can be attributed to their inevitable short-term self-destruction, a consequence of uncontrolled dispersion of toxic substances, contamination of air, water and land, and construction of deadly weapons. On Earth this includes saturation of the atmosphere by greenhouse gases and production of nuclear weapons. The most extensive mass extinction event in the history of Earth, represented by the Permian-Triassic boundary 251 million years-ago, involved warming, acidification and oxygen depletion of the oceans, with consequent emanations of toxic H₂S and CH₄, leading to a loss of some 57% of biological families, 83% of genera and 81% of marine species . If the history of the 21st century is ever written it would report that, while large parts of the planet were becoming uninhabitable,...