Stephen Hawking Quotes

As quoted in "The Science of Second-Guessing", The New York Times (12 December 2004)

Source: A Brief History of Time

Der Spiegel (17 October 1988)

Source: The Grand Design

Source: A Brief History of Time (1988), Ch. 12
Context: Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe? The usual approach of science of constructing a mathematical model cannot answer the questions of why there should be a universe for the model to describe. Why does the universe go to all the bother of existing?

As quoted in Stephen Hawking's Universe http://books.google.com/books?id=lkntNIwunAAC&pg=PA77&dq=hawking+%22my+goal+is+simple%22&ei=q5HtSvCOIoLklQTU_cWhDA#v=onepage&q=hawking%20%22my%20goal%20is%20simple%22&f=false (1985) by John Boslough, Ch. 7 : The Final Question, p. 77

Response upon being questioned as to his IQ, in interview with Deborah Solomon "The Science of Second-Guessing", The New York Times (12 December 2004)

Source: Black Holes and Baby Universes and Other Essays (1993), pp. 133–135.
Context: The ultimate objective test of free will would seem to be: Can one predict the behavior of the organism? If one can, then it clearly doesn't have free will but is predetermined. On the other hand, if one cannot predict the behavior, one could take that as an operational definition that the organism has free will … The real reason why we cannot predict human behavior is that it is just too difficult. We already know the basic physical laws that govern the activity of the brain, and they are comparatively simple. But it is just too hard to solve the equations when there are more than a few particles involved … So although we know the fundamental equations that govern the brain, we are quite unable to use them to predict human behavior. This situation arises in science whenever we deal with the macroscopic system, because the number of particles is always too large for there to be any chance of solving the fundamental equations. What we do instead is use effective theories. These are approximations in which the very large number of particles are replaced by a few quantities. An example is fluid mechanics … I want to suggest that the concept of free will and moral responsibility for our actions are really an effective theory in the sense of fluid mechanics. It may be that everything we do is determined by some grand unified theory. If that theory has determined that we shall die by hanging, then we shall not drown. But you would have to be awfully sure that you were destined for the gallows to put to sea in a small boat during a storm. I have noticed that even people who claim everything is predetermined and that we can do nothing to change it, look before they cross the road. … One cannot base one's conduct on the idea that everything is determined, because one does not know what has been determined. Instead, one has to adopt the effective theory that one has free will and that one is responsible for one's actions. This theory is not very good at predicting human behavior, but we adopt it because there is no chance of solving the equations arising from the fundamental laws. There is also a Darwinian reason that we believe in free will: A society in which the individual feels responsible for his or her actions is more likely to work together and survive to spread its values.

"The Quantum State of the Universe", Nuclear Physics (1984) <!-- B239, p. 258 -->
Context: Many people would claim that the boundary conditions are not part of physics but belong to metaphysics or religion. They would claim that nature had complete freedom to start the universe off any way it wanted. That may be so, but it could also have made it evolve in a completely arbitrary and random manner. Yet all the evidence is that it evolves in a regular way according to certain laws. It would therefore seem reasonable to suppose that there are also laws governing the boundary conditions.

Source: A Brief History of Time (1988), Ch. 1
Context: Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.

Source: A Brief History of Time

Source: A Brief History of Time

Official Trailer
Hawking (2013)

British Telecom advertisement (1993), part of which was used in Pink Floyd's Keep Talking (1994) and Talkin' Hawkin'<nowiki/> (2014)
Context: For millions of years, mankind lived just like the animals. Then something happened which unleashed the power of our imagination. We learned to talk and we learned to listen. Speech has allowed the communication of ideas, enabling human beings to work together to build the impossible. Mankind's greatest achievements have come about by talking, and its greatest failures by not talking. It doesn't have to be like this. Our greatest hopes could become reality in the future. With the technology at our disposal, the possibilities are unbounded. All we need to do is make sure we keep talking.

On voluntary euthanasia as quoted in People's Daily Online (14 June 2006) http://english.people.com.cn/200606/14/eng20060614_273839.html

Speech at Macworld Expo in Boston, as quoted in The Daily News (4 August 1994) http://news.google.com/newspapers?id=bD8PAAAAIBAJ&sjid=IoYDAAAAIBAJ&pg=4837%2C5338590. A nearly identical quote can be found at the end of the second paragraph of his lecture Life in the Universe http://hawking.org.uk/index.php?option=com_content&view=article&id=65 (1996).

British Telecom advertisement (1993), part of which was used in Pink Floyd's Keep Talking (1994) and Talkin' Hawkin'<nowiki/> (2014)
Context: For millions of years, mankind lived just like the animals. Then something happened which unleashed the power of our imagination. We learned to talk and we learned to listen. Speech has allowed the communication of ideas, enabling human beings to work together to build the impossible. Mankind's greatest achievements have come about by talking, and its greatest failures by not talking. It doesn't have to be like this. Our greatest hopes could become reality in the future. With the technology at our disposal, the possibilities are unbounded. All we need to do is make sure we keep talking.

The Universe in a Nutshell (2001), p. 59
Context: One might think this means that imaginary numbers are just a mathematical game having nothing to do with the real world. From the viewpoint of positivist philosophy, however, one cannot determine what is real. All one can do is find which mathematical models describe the universe we live in. It turns out that a mathematical model involving imaginary time predicts not only effects we have already observed but also effects we have not been able to measure yet nevertheless believe in for other reasons. So what is real and what is imaginary? Is the distinction just in our minds?

As quoted in "Stephen Hawking: 'There is no heaven; it's a fairy story'" by Ian Sample, in The Guardian (15 May 2011) http://www.theguardian.com/science/2011/may/15/stephen-hawking-interview-there-is-no-heaven
Context: I have lived with the prospect of an early death for the last 49 years. I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first... I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark.

"Colonies in space may be only hope, says Hawking" by Roger Highfield in Daily Telegraph (16 October 2001).

During the same 1994 exchange with Penrose as the previous quote, transcribed in The Nature of Space and Time (1996) by Stephen Hawking and Roger Penrose, p. 26 http://books.google.com/books?id=LstaQTXP65cC&lpg=PA26&dq=hawking%20%22where%20they%20can't%20be%20seen%22&pg=PA26#v=onepage&q=&f=false and also in "The Nature of Space and Time" (online text) http://arxiv.org/abs/hep-th/9409195
Unsourced variants: Not only does God play dice with the Universe; he sometimes casts them where they can't be seen.
Not only does God play dice, but... he sometimes throws them where they cannot be seen.
Variant: So Einstein was wrong when he said "God does not play dice". Consideration of black holes suggests, not only that God does play dice, but that He sometimes confuses us by throwing them where they can't be seen.

Foreword to The Physics of Star Trek by Lawrence Krauss (2007), p. xiii http://books.google.com/books?id=NEhSpZFWiBMC&lpg=PP1&pg=PR13#v=onepage&q&f=false

Also quoted in "Stephen Hawking warns over making contact with aliens" http://news.bbc.co.uk/2/hi/uk_news/8642558.stm at BBC News (25 April 2010).
Into The Universe with Stephen Hawking (2010)
Context: If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans. … We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet.

From the lecture Life in the Universe http://hawking.org.uk/index.php?option=com_content&view=article&id=65 (1996)

Source: A Brief History of Time

Source: A Brief History of Time

Source: A Brief History of Time (1988), Ch. 1
Context: It has certainly been true in the past that what we call intelligence and scientific discovery have conveyed a survival advantage. It is not so clear that this is still the case: our scientific discoveries may well destroy us all, and even if they don’t, a complete unified theory may not make much difference to our chances of survival. However, provided the universe has evolved in a regular way, we might expect that the reasoning abilities that natural selection has given us would be valid also in our search for a complete unified theory, and so would not lead us to the wrong conclusions.

Science Watch (September 1994)
Context: I don't believe that the ultimate theory will come by steady work along existing lines. We need something new. We can't predict what that will be or when we will find it because if we knew that, we would have found it already! It could come in the next 20 years, but we might never find it.

Source: A Brief History of Time (1988), Ch. 1
Context: Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.

Source: A Brief History of Time (1988), Ch. 11
Context: As I shall describe, the prospects for finding such a theory seem to be much better now because we know so much more about the universe. But we must beware of overconfidence - we have had false dawns before! At the beginning of this century, for example, it was thought that everything could be explained in terms of the properties of continuous matter, such as elasticity and heat conduction. The discovery of atomic structure and the uncertainty principle put an emphatic end to that. Then again, in 1928, physicist and Nobel Prize winner Max Born told a group of visitors to Gottingen University, "Physics, as we know it, will be over in six months." His confidence was based on the recent discovery by Dirac of the equation that governed the electron. It was thought that a similar equation would govern the proton, which was the only other particle known at the time, and that would be the end of theoretical physics. However, the discovery of the neutron and of nuclear forces knocked that one on the head too. Having said this, I still believe there are grounds for cautious optimism that we may now be near the end of the search for the ultimate laws of nature.

"The Quantum State of the Universe", Nuclear Physics (1984) <!-- B239, p. 258 -->
Context: Many people would claim that the boundary conditions are not part of physics but belong to metaphysics or religion. They would claim that nature had complete freedom to start the universe off any way it wanted. That may be so, but it could also have made it evolve in a completely arbitrary and random manner. Yet all the evidence is that it evolves in a regular way according to certain laws. It would therefore seem reasonable to suppose that there are also laws governing the boundary conditions.

As quoted in "The Science of Second-Guessing", The New York Times (12 December 2004)
Unsourced variant: "When one's expectations are reduced to zero, one really appreciates everything one does have."

Into The Universe with Stephen Hawking (2010)

Interview with Diane Sawyer, as quoted in "Stephen Hawking on Religion: 'Science Will Win'" on ABC World News (7 June 2010) http://abcnews.go.com/WN/Technology/stephen-hawking-religion-science-win/story?id=10830164

Source: A Brief History of Time

Source: Sigan Ŭn Hangsang Mirae Ro Hŭrŭnŭnʼga: Hokʻing Paksa Ŭi Chaemi Innŭn Chʻoesin Ujuron

Interview on Israeli television, as quoted in "Happy 65th Birthday to Prof. Stephen Hawking!" at StarTrek.com (8 January 2007) http://www.startrek.com/startrek/view/news/article/37695.html

Source: The Grand Design

Source: Black Holes and Baby Universes

Source: The Grand Design

Source: A Brief History of Time (1988), Ch. 9
Context: Just like a computer, we must remember things in the order in which entropy increases. This makes the second law of thermodynamics almost trivial. Disorder increases with time because we measure time in the direction in which disorder increases. You can’t have a safer bet than that!

Source: A Brief History of Time

Source: A Brief History of Time (1988), Ch. 8

Source: A Briefer History of Time

Source: A Brief History of Time

Response when asked what he thinks about most during the day, "Stephen Hawking at 70: Exclusive interview" http://www.newscientist.com/article/mg21328460.500-stephen-hawking-at-70-exclusive-interview.html in New Scientist (4 January 2012)