Stephen Hawking Quotes
I think it quite likely that we are the only civilization within several hundred light years; otherwise we would have heard radio waves.
Citations
Hawking, Stephen. "Life in the Universe." Lecture.
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Stephen William Hawking CH CBE FRS FRSA was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge at the time of his death. He was the Lucasian Professor of Mathematics at the University of Cambridge between 1979 and 2009.