God, Reality and Scientific Theory as seen by Prof. Hawking

“Prof. Stephen Hawking’s Philosophical/ epistemological position”

(from “Black holes & baby universes”: Ch.-6, pages – 35 to 41, Originally given as a talk to a Caius College audience in May 1992)

{This is provisional posting - I intend to amalgamate it later on with more of similar material – formulations numberwise and related opinions of Prof. Stephen Hawking are my extractions, re – arrangements and editings without modifying any word but inserting one or two of mine at places within brackets}

Philosophical/ epistemological position #0

“This article is not about whether I believe in God - I will discuss my approach to how one can understand the universe: what is the status and meaning of a Grand Unified Theory, a theory of everything”

Stephen Hawking now berates Philosophers of science

“The people who ought to study and argue such questions, the philosophers, have not had enough mathematical background to keep up with modern developments in theoretical physics”.

“There is a subspecies called, Philosophers of science who ought to be better equipped. But many of them are failed physicists who found it too hard to invent new theories and so took to writing about the philosophy of physics instead. They are still arguing about the scientific theories of the early years of this century, like relativity and quantum mechanics. They are not in touch with the present frontier of physics”.

“I have been variously called nominalist, an instumentalist, a positivist, a realist and several other -ists. The technique seeems to be refutation by denigration”.

Logical self-consistency vs. theory

Philosophical/ epistemological position #1

“I am sure that Einstein, Heisenberg and Dirac didn’t worry about whether they were realists or instrumentalists, they were simply concernend that existing theories didn’t fit together. In theoretical physics, the search for logical self-consistency has always been more important in making advances than experimental results. Otherwise elegant and beautiful theories have been rejected because they don’t agree with observation but I don’t know of any major theory that has been advanced just on the basis of experiment.”

“The theory always came first from the desire to have an elegant and consistent mathematical model. The theory then makes predictions, which can then be tested by observation. If the observations agree with the predictions, that doesn’t prove the theory; but the theory survives to make further predicions, which again are tested against observation”.

About how people defend their challenged theory

“….by questioning the accuracy of the observastions. If that fails, they try to modify the theory in an ad hoc manner. Eventually the theory becomes a creaking and ugly edifice. Then someone suggests a new theory, in which all the awakward observations are explained in an elegant and natural manner.

Example: "Michelson Morley experiment, 1887 >> Showed that the speed of light was always the same, no matter how the source or the observer was moving"

Surely someone moving towards the light ought to measure it travelling at a higher speed than someone moving in the same direction as the light; yet the experiment showed thast both observers would measure exactly the same speed

Hendrik Lorentz and George Fitzerald tried to accommodate this observation within accepted ideas of space and time ……(with) ad-hoc postulates… “Objects got shorter when they moved at high sepeds”.

Then a new theory

1905: Einstein suggested…. “..time was not regarded as completely separate and on its own. Instead it was combined with space in a four-dimensional object called space-time”.

“Einstein was driven to this idea not so much by the experimental results as by the desire to make two parts of the theory fit together in a consistent whole …. (i) laws that govern the electric and magnetic fields and (ii) laws that govern the motion of bodies.

“…. new theory of relativity ….. completely revolutionized our notions of space and time”

Philosophical/ epistemological position #2.1

“This example illustrates well the difficulty of being a realist in the philosophy of science, for what we regard as relity is conditoned by the theory to which we subscribe. I am certain Lorentz and Fitzgerald regarded themselves a realists, interpreting the experiment on the speed of light in terms of Newtonian ideas of absolute space and absolute time. These notions of space and time seemed to coresponed to common sense and reality”.

Philosophical/ epistemological position #2.2

If what we regard as real depends on our theory, how can we make reality the basis of our philosophy?

Philosophical/ epistemological position #2.3

“I am realist in the sense that I think there is universe out there waiting to be investigated and understood. I regard the solipsist position that rverything is the creation of our imaginations as a waste of time …. But we cannot distinguish what is real about the universe withour a theory. I therefore take the view, which has been described as simple – minded and naïve that a theory of physics is just a mathematical model that we use to describe the results of observations. A theory is a good theory,… if it describes a wide class of observations and if it predicts the results of new observations. Beyond that, it makes no sense to ask if it corresponds to reality, because we do not know what reality is independent of a theory.

Philosophers of science vs. Prof. Hawking again

“This (i.e. #2.3) view of scientific theories makes me an instrumentalist or a Positivist”

“The person who called me a positivist went on to add that everyone knew that positivism was out of date – another case of refutation by denigration”

“It may indeed be out out of date in that it was yesterday’s intellectual fad, but the positivist position I have outlined seems the only possible one for some one who is seeking new laws, and new ways, to describe the universe. It is no good appealing to reality because we don’t have a model independent concept of reality".

“The unspoken belief in a model independent reality is the underlying reason for the difficulties philosophers of science have with quantum mechanics and the uncertainty principle”.

“There is a famous thought experiment called Schrodinger’s cat: A cat is placed in as sealed box. There is a gun pointing at it, and it will go off if a redioactive nucleus decays. The probability of this happening is 50 per cent. ……… If one opens the box, one will find thre cat either dead or alive. But before the box is opened, the quantum state of the cat will be a mixture of the dead cat state with a state in which the cat is alive. This some philosophers of science find very hard to accept, the cat can’t be falf shot and half not-shot, they claim, any more than one can be half pregnant. Their difficulty arises because they are implicitly using a classical concept of reality in which an object has a definite single history. … Quantum mechanics … has a different view of reality.”

“An object has not just a single history but all possible histories. In most cases, the probabiltiy of having a particular history will cancel out with the probabillity of having a very slightly different history; but in certain cases, the probabilities of neighbouring histories reinforce each other. It is one of these reinforced histories that we observe as the history of the object”

“... Schrodinger’s cat, … two histories that are reinforced… cat is shot … it remains alive … in quantum theory both possibilities can exist together. Some philosophers … implicitly assume that the cat can have only one history”.

“Nature of time is another example … (where) our theories of physics determine our concept of reality. It used to be consisdered obvious that time flowed on for ever, .. theory of relativity combined time with space and said that both could be warped or distorted, by the matter and energy in the universe”.

“So our perception of the nature of time changed from being independent of the universe to being shaped by it. It then became conceivable that time might simply not be defined before a certain point; as one goes back in time, one might come to an insurmountable barrier, a singularity, beyond which one could not go. If that were the case, it wouldn’t make ssense to ask who, or what, caused or created the big bang. To talk about causation or creation implicitly assumes there was a time befor the big bang singularity”.

“Einstein’s general theory of relativity predicts that time must have had a beginning in a singularity fifteen billion years ago. But the philosophers have not yet caught up with the idea. They are still worrying about the founations of quantum mechanics that were laid down sixty-five years ago. They don’t realize that the frontier of physics has moved on”.

“Even worse is the mathematical concept of imaginary time, in which Jim Hartle and I suggested the universe may not have any beginning or end ….. attacked by a philosopher of science for talking about imaginary time. He said: How can a mathematical trick like imaginary time have anything to do with the real universe? … this Philosopher was confusing the technical mathematical terms real and imaginary nembers with the way that real and imaginary are used in everyday language. This .. illustrates my points how can we know what is real, independent of a theory or model with which to interpret it?

“ … examples from relativity and quantum mechnics to show the problems one faces when one tries to make sense of the universe.

Philosophical/ epistemological position #2.4

“What I hope I have demonstrated is that some sort of positivist approach, in which one regards a theory as model is the only way to understand the universe”

“I am hopeful that we will find a consistent model that describes everything in the universe. If we do that it will be a real triumph for the human race”.

(Ack.: Ms. Dimple Tyagi, in typing out, editing, arranging and formatting, errors are however, my responsibility)