03. How was it discovered? (A K2S Question)

From The Space Library

From the first time humans looked out into the cosmos under a dark starlit sky, people have speculated about the essence of space. We have moved from the Earth-centered cosmos proposed by Aristotle and Plato, to one that was heliocentric as proposed by Copernicus, to one that now extends beyond our own Milky Way Galaxy to the distant parts of the entire Universe. Once he realized that our galaxy was only one of many galaxies in our Universe, Edwin Hubble provided us with a means of being able to extend our cosmic perspective. And then, Einstein's theory of general relativity showed that space and time are one and that there is essentially no difference between space-time and a gravitation field.

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Answer provided by Jim Zebrowski

Question and Answer extracted from the book Kids to Space - by Lonnie Schorer

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