Anaximander, a philosopher who lived in Miletus in modern-day Turkey, contributed one key idea. He was the first to propose that Earth is a body floating in an infinite void, held up by nothing. For someone who lived 2,200 years before Isaac Newton, this was a stunning insight. The philosopher Karl Popper called it “one of the boldest, most revolutionary, and most portentous ideas in the whole history of human thought.” Anaximander also thought Earth was a cylinder with the continents arrayed on one flat end, so he wasn’t right about everything. But he did invent the idea of space, a place with no absolute up or down. And just as important, Anaximander’s system was the first to leave open the possibility that there are other worlds like ours. (Though, to be clear, he may not have believed that these worlds existed elsewhere in space. He may have thought they preceded or would succeed Earth in time or perhaps coexisted in some parallel universe.)Wade Roush, “Alien Dreams: The Surprisingly Long History of Speculation About Extraterrestrials” at MIT Reader (August 3, 2021)
One problem is, of course that some want to conclude that there are endless numbers of universes. We have no reason to think so, as a consequence of the existence of other life forms in the universe.
Data analyst offers 15 reasons extraterrestrials aren’t seen. He estimates that there should be 100,000 civilizations in our galaxy. Some of Yung Lin Ma’s suggested reasons are ones we had not considered before, including flow of time and communication differences.