Quote Origin: I Don’t Think the Human Race Will Survive the Next Thousand Years, Unless We Spread Into Space

Stephen Hawking? Alvin Toffler? David Deutsch? Apocryphal? Question for Quote Investigator: Humankind currently inhabits only one small fragile planet, and the perils on Earth continue to grow. A prominent physicist once insisted that humankind must expand into space in order to survive the next thousand years. I am not sure of the exact phrasing. Would …

The Greatest Obstacle to Discovery Is Not Ignorance—It Is the Illusion of Knowledge

Daniel J. Boorstin? Stephen Hawking? Henry Thomas Buckle? Anonymous? Dear Quote Investigator: Widely accepted false beliefs can hinder progress and new discoveries. For example, the mistaken belief that heavier-than-air flying machines were impossible or impractical deterred requisite financing and investigation. This thought has been expressed as follows: The greatest enemy of knowledge is not ignorance; …

The Best Evidence That Time Travel Is Not Possible Is That We Have Not Been Invaded By Hordes of Tourists from the Future

Stephen Hawking? Apocryphal? Quote Investigator: There is an argument against the existence of time travel that can be stated as follows: If time travel were possible, we would have been overrun by tourists from the future by now. Did the famous physicist Stephen Hawking say something like this? Alternatively, was it said by another physicist …