Is Anything Real? Have Physicists Lost Their Grip on Reality? Edward L Bosworth, PhD TSYS School of Computer Science Columbus State University Columbus, GA

What is Reality? Reality, also called “ontological reality” may be defined as follows: That which exists independently of our existence and experience, but which gives rise to our experience. This is also called “deep reality”.

What is Knowledge? This is an old question, dating back to Plato. One definition is that it is “what cannot be wrong”. By this definition, it is timeless, universal, necessary, and certain. Another definition is that it is what cannot be reasonably doubted at present. Here it is particular, context-dependent, and probable.

In What Sense is a Theory True? For many it suffices that a theory is “empirically adequate” in that it makes verifiable predictions and has not yet been falsified. Others want a theory to be true because it presents a true picture of reality. Observations cannot prove a theory.

Theories and Truth A theory is of the logical form If A then B. If B is false, then A is false. A theory can be falsified by one result. If B is true, nothing can be said about A. Even an impressively large collection of results cannot show a theory logically true.

Sir Karl Popper on Theory It is too easy to obtain confirmations or verifications for a theory – if we just look. Confirmation counts only if the theory predicts something entirely unexpected. A theory is no good unless it can be refuted. Every genuine test of a theory is an attempt to falsify it.

An Ancient Egyptian Theory If Pharaoh does his job well, the sun will rise in the east every day. The sun rose in the east today. So, Pharaoh must be doing a good job.

Kick Out the Philosophers How many physicists think. Is Newtonian Mechanics true? Yes. Is Einstein's Mechanics true? Yes. They give rise to conflicting predictions. It is not possible for both to be true. So what is your problem?

A Question on Truth The Ptolemaic system was used for centuries. Can one say that it was ever true? Can we say people had knowledge of it. Is it false? Was it ever false?

The Three Great World Systems Galileo named two. There were three views of the planets and the sun at his time. 1. The Ptolemaic model – Not even Ptolemy claimed this was true. It just predicted. 2. The Copernican system – now also this is known to be false. It predicts falsely. 3. Tycho Brahe's system – also false, but not distinguishable at the time from Copernican. Why do some call Copernicus true?

A Matter of Gravity We seek an explanation of the orbits of the planets around the sun. Newton's theory leads to predictions that are very impressively verified. Does it explain gravity? What is gravity? What is the reality behind the name “gravity”? Newton: “I don't know. This just works.” Did Newton discover gravity or invent it?

Neptune: Problem and Solution In the 19 th century, there were problems in analyzing the orbit of Uranus. Either Newton's mechanics were bad, or there was another planet out there. Newton's theory predicted a planet at a specific location. When we looked, it was there! It is hard to say such a theory is not true.

Don't Take the Model Seriously The model is supposed to be an aid to thinking and not represent reality. To take the model seriously is bad physics.

Particles that Spin A classical spinning object can have any value of spin, and all components of that spin may be simultaneously measured. A quantum object has “spin”, but should not be considered to be spinning. This spin is a name for results of experiments. The analogy to a spinning top may be a help to thought, but it will give bad results if taken too literally.

Is Quantum Mechanics True? By this, I mean the latest version of the theory, possibly Quantum Electrodynamics. QED is certainly empirically adequate. It is an extremely accurate predictor of the results of experiments. Some predictions have been verified to twelve decimal digits. To be this good, it must be true.

QM on Reality One clear result of quantum mechanics is the need to distinguish two types of reality. Ontological reality is that which exists independently of our existence. Empirical reality is the set of phenomena that human experience, aided by science, yields access to. NOTE: This is a result of experimental physics.

QM and Pragmatism Some think of the standard view of QM as a pragmatic interpretation. Any QM theory is viewed as a method for generating numbers to be compared with results of experiment. The pragmatist refuses on principle to speculate about deep reality, as it has no direct expression in experiment. No comment on the properties of an unmeasured electron.

Richard Feynman on QM “I think that it is safe to say that nobody understands quantum mechanics.” “Do not keep saying to yourself, if you can possibly avoid it, 'but how can it be like that?' because you will go 'down the drain' into a blind alley from which nobody has yet escaped.” “Nobody knows how it can be like that.”

Heisenberg's Uncertainty Principle Measurements come in pairs, such as position and momentum. Either quantity in a pair can be measured with any desired precision, at the cost of precision in the conjugate quantity. Example:  p  x  h/2  It is reported that Heisenberg came to this after several months of intense work.

The Disturbance Model In the Disturbance Model approach to Heisenberg's Uncertainty Principle, it is the process of measurement itself that gives rise to the uncertainty in the measurement. In this view, an atom's actual position and momentum are always definite, but an accurate position measurement will disturb the momentum. It is the measured position and momentum that cannot be accurately predicted.

Disturbance is False. While the disturbance model is appealing, it is false, in the sense that it gives rise to predictions that contradict experimental results. The key experiments are called “Renninger style measurements” after Mauritius Renninger, who developed them. What can be learned from the absence of a detection event? The photon not seen?

Case Study: Electrons To what extent does an unmeasured electron have attributes? All electrons have the same charge and mass; an unmeasured electron has these. Does an unmeasured electron have a definite position and a definite momentum? Those who believe in hidden variable theories say “Yes”. Bohr says “No”.

Electron Spin The electron is a Fermion; it has spin ½. When measured along any given axis in space, only two values of spin may be measured +1/2 and -1/2 (units of h/2  ). Basic result: An electron cannot have definite values for measurements along two perpendicular axes at the same time. We call these axes X and Z.

Bohr on an Unmeasured Electron A pragmatist would refuse on principle to comment on the existential status of an unmeasured electron's attributes. Bohr claims not that such attributes are meaningless, but that they are nonexistent. Bohr: “It is like asking the color of the number 5. The question is meaningless.”

Hidden Variables The idea of hidden variables is that an unmeasured electron does have definite attributes; they just have not been measured. The hidden variable theory seems to imply that deep (ontological) reality is meaningful, only that we have not yet observed it. Bohr would not agree with that.

Locality The idea of locality is that what happens to a particle depends only on its own variables and its immediate circumstances. The idea of locality is easily expanded to include distant events, if signals from those events could arrive at the particle at the time of the measurement. The theory of relativity speaks to this issue.

Entanglement As a result of an interaction, two particles may exist in an entangled state. In an entangled state, neither particle has a definite quantum state, but the pair does. In entanglement, the pair should be viewed as a single quantum object. This has nothing to do with present distance between the particles.

The EPR Paper This is an outgrowth of work by Einstein, Podolsky, & Rosen, published in 1935 as “Can Quantum Mechanical Description of Physical Reality be Considered Complete”. Einstein called quantum entanglement “spooky action at a distance.” Einstein thought QM to be an incomplete theory and proposed a thought experiment.

The EPR Thought Experiment Consider two electrons in an entangled state with total spin zero. Call them P1 and P2. Before the spin of P1 is measured, neither has a definite spin value. When the spin of P1 is measured along an axis, the spin of P2 instantly gains a value. This happens even if P2 is at a great distance, too far for light to travel quickly.

More on EPR EPR defined reality as follows. “If we can predict something about a system without interacting with that system in any way, that something must be real”. In the paradox, the spin of P2 can be predicted without interacting with it. Thus the spin of P2, not directly measured, must be real. As QM does not allow this, it is an incomplete theory of nature.

Bell's Inequality John Bell took this paradox and developed some of its logical consequences. One was that EPR could be described as entanglement + locality  hidden variables. Quantum entanglement is well established. Bell derived an inequality that any theory based on locality and hidden variables must satisfy. This is “Bell’s inequality”.

Bell’s Result We must either Give up hidden variables (the idea that the result of a quantum measurement is actually predetermined) or Give up on locality and accept that particles can influence each other instantly over great distances (faster than light speed) or both.

Experimental Results Bell's inequality has been the subject of a number of experiments since John Clauser was the first to attempt an experimental verification of Bell's inequality. In 1972, Clauser reported that his data supported Bell's inequality. There were a few problems with his experiment. In 1982 Alain Aspect published the results of a more sophisticated experiment. These also supported Bell's result.

Is Light a Photon Phenomenon Or a Wave Phenomenon Admittedly we may assign a wave length to any variety of electromagnetic radiation and use that to make predictions. The real answer: “Don't ask silly questions.” Do not confuse a convenient model of reality with deep reality. This is a fundamental mistake in physics.

References R_01Quantum Reality: Beyond the New Physics, by Nick Herbert, 1987 Anchor Books, ISBN 0 – 385 – – 3. R_02On Physics and Philosophy, by Bernard d’Espagnat, 2006 Princeton University Press, ISBN 978 – 0 – 691 – – 9. R_03Philosophy of Science, by Jeffrey L. Kasser, Course No. 4100, marketed by The Teaching Company. ( R_04Science Wars: What Scientists Know and How They Know It, by Steven L. Goldman, Course No. 1235, marketed by The Teaching Company. R_05Quantum Mechanics: The Physics of the Microscopic World, by Benjamin Schumacher, Course 1240, marketed by the Teaching Company. R_06The Age of Entanglement: When Quantum Physics Was Reborn Louisa Gilder, published by Alfred A. Knopf, 2009, ISBN 978 – 1 – 4600 – 4417 –7. R_07The Elegant Universe, by Brian Greene, published by W. W. Norton, 2003 ISBN 978 – 0 – 393 – – 1. R_08Quantum: Einstein, Bohn, and the Great Debate About the Nature of Reality, by Manjit Kumar, published by W. W. Norton, 2008, ISBN 978 – 0 – 393 – – 9. R_09The Structure of Scientific Revolutions, by Thomas S. Kuhn, The University of Chicago Press, 1970, ISBN 978 – 0 – 226 – 5808 – 3.