In the seventeenth and eighteenth centuries it became possible to believe in the existence of life on other planets on scientific grounds. Once the Earth was no longer the center of the universe according to Copernicus, once Galileo had aimed his telescope at the Moon and found it a rough globe with mountains and seas, the assumption of life on other planets became much less far-fetched. In general there were no actual differences between Earth and Venus, since both planets orbited the Sun, were of similar size, and possessed mountains and an atmosphere. If there is life on Earth, one may ponder why it could not also exist on Venus. In the extraterrestrial life debate of the seventeenth and eighteenth centuries, the Moon, our closest celestial body, was the prime candidate for life on other worlds, although a number of scientists and scholars also speculated about life on Venus and on other planets, both within our solar system and beyond its frontiers. Venusians: the Planet Venus in the 18th-Century Extraterrestrial Life Debate (PDF), from The Journal of Astronomical Data (JAD) Volume 19, somewhat via NPR and their mention of amateur astronomer Thomas Dick's estimations of the populations of the other planets in our solar system (Archive.org online view of Celestial scenery, or, The Wonders of the planetary system displayed, 1845).
"It was one of those things that was a gift to humanity... We’re all going to lose for sure." Kepler's career is over, but not before answering one of mankind's most profound questions.
The cosmos is also within us, we're made of star-stuff. We are a way for the cosmos, to know itself.
Cosmos: A Personal Voyage is a thirteen-part television series of one hour shows written by Carl Sagan, Ann Druyan, and Steven Soter, that was aired at the tail end of 1980 and was - at the time - the most widely watched series in the history of American public television. It is best introduced by an audio excerpt of one of his books, The Pale Blue Dot. Inside is a complete annotated collection of the series. [more inside]