Carl Sagan died last Friday at the age of 62. Sagan was the world's most famous astronomer. Among his many activities as a scientist, he contributed to the discovery that the atmosphere of Venus is prohibitively hot and dense, and found evidence that Saturn 's moon Titan contains oceans stocked with the building blocks of life . Sagan was an outspoken proponent of the search for extra-terrestrial life , including sending probes to other planets and listening with large radio telescopes for signals from intelligent aliens. Sagan 's outstanding ability to explain allowed almost a billion people to better understand the cosmos in which they live.
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