What is Reality?

Nick consults his Quantum Reality bible

Quantum mechanics is the most successful theory of the physical world that mankind has ever possessed. Its domain is the entire physical world -- from the tiniest quark to the largest neutron star -- and wherever it can be tested, it has never been wrong.

However the spectacular successes of quantum mechanics comes with a steep philosophical price -- use this theory, give up "reality".

What does it mean: "give up reality"? Certainly the world itself still exists and quantum mechanics excellently predicts the results of all experiments we can imagine doing in this world. This world seems "real enough" and we now have immense control over it. What more could one ask?

What one could ask is a "plausible story" that tells us "what's happening" in the world. One could ask "Behind all the fancy mathematics what's really going on in the quantum world?" And to this "reality question", quantum theory conspicuously fails to give an answer. In graduate school the classic answer our teachers gave to the quantum reality question was effectively "Shut up and calculate."

What better question with which to begin the New Year -- What is Reality? And who better to ask than a conference of physicists gathered together in a former monastery on Lake Traunsee in Austria to discuss "Quantum Physics and the Nature of Reality".

To assay the current opinions among quantum physicists regarding the Nature of Reality, physicist Anton Zeilinger and a few colleagues devised a multiple-choice test whose results they recently published in the physics arXiv.

The major result of this poll was the immense disagreement between these experts about questions having to do with "what's really going on" in the world. Two of the most popular realities were Copenhagen Interpretation (42%) and Many-Worlds Interpretation (18%). But of course Nature is not democratic and her reality is not determined by a popularity contest.

Some time ago I wrote a book about Quantum Reality describing some of the many possible stories that physicists have invented to describe what really might be going on behind the mathematics. Although many subtle and beautiful experiments have since been carried out to probe "reality questions" -- many of them carried out by the authors of this survey -- the question is still very much up in the air. When I wrote that book, physicists were confused about the nature of reality. What this poll shows is that even after many quantum-reality-probing experiments we are still confused, but now our confusion is deeper than before.