Had your spacecraft flown by the Earth a hundred million years ago, in the age of the dinosaurs when there were no humans and no technology, you woul… - Carl Sagan
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Had your spacecraft flown by the Earth a hundred million years ago, in the age of the dinosaurs when there were no humans and no technology, you would still have seen oxygen and ozone, the chlorophyll pigment, and far too much methane. At present, though, your instruments are finding signs not just of life, but of high technology — something that couldn’t possibly have been detected even a hundred years ago: You are detecting a particular kind of radio wave emanating from Earth. Radio waves don’t necessarily signify life and intelligence. Many natural processes generate them. You’ve already found radio emissions from other, apparently uninhabited worlds — generated by electrons trapped in the strong magnetic fields of planets, by chaotic motions at the shock front that separates these magnetic fields from the interplanetary magnetic field, and by lightning.
Carl Edward Sagan (9 November 1934 – 20 December 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages sent into space, the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. Sagan argued the hypothesis, accepted since, that the high surface temperatures of Venus can be attributed to, and calculated using, the greenhouse effect. He testified to the US Congress in 1985 that the greenhouse effect will change the earth's climate system.
Biography information from
Wikiquote·
Portrait adapted from
Wikimedia Commons, NASA/JPL (Public domain / CC0)
Also Known As
Native Name:
Carl Edward Sagan
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Sagan
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Carl E. Sagan
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Carl E Sagan
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C. E. Sagan
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C.E. Sagan
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C E Sagan
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C. Sagan
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C Sagan
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Sagan C
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Sagan C.
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Sagan C. E.
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Sagan CE
By one billion years ago, plants, working cooperatively, had made a stunning change in the environment of the Earth. Green plants generate molecular oxygen. Since the oceans were by now filled with simple green plants, oxygen was becoming a major constituent of the Earth’s atmosphere, altering it irreversibly from its original hydrogen-rich character and ending the epoch of Earth history when the stuff of life was made by nonbiological processes. But oxygen tends to make organic molecules fall to pieces. Despite our fondness for it, it is fundamentally a poison for unprotected organic matter. The transition to an oxidizing atmosphere posed a supreme crisis in the history of life, and a great many organisms, unable to cope with oxygen, perished. A few primitive forms, such as the botulism and tetanus bacilli, manage to survive even today only in oxygen-free environments. The nitrogen in the Earth’s atmosphere is much more chemically inert and therefore much more benign than oxygen. But it, too, is biologically sustained. Thus, 99 percent of the Earth’s atmosphere is of biological origin. The sky is made by life.
Science is a way to call the bluff of those who only pretend to knowledge. It is a bulwark against mysticism, against superstition, against religion misapplied to where it has no business being.
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