from his bestseller book "Cosmos", page 168 in the paperback (mass market) edition.
2011: Cosmos, ISBN 9780307800985, Publisher Random House Publishing Group, Source
Only two things are infinite, the universe and human stupidity and I'm not sure about the former. Albert Einstein
Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying. Arthur C. Clarke
The universe is a pretty big space. It's bigger than anything anyone has ever dreamed of before. So, if it's just us, seems like an awful waste of space, right? Carl Sagan
There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened. Douglas Adams
If you wish to make an apple pie from scratch, you must first invent the universe Carl Sagan