prev

next

out of 31

View

44Download

1

Embed Size (px)

Four reasons why you dont existQuantum physics, logic, Buddhism and information theory

James Higgo

2001

Contents

Preface Introduction I 2 3 4 5 6 7 8 Quantum Physics Kolmogorov simplicity The Logic of Liebniz, Kripke and Quine The Buddha's Intuition Consciousness and time Physics, logic, intuition and simplicity Implications: for everyday life Conclusion

ix xi

[Total 60,000 words, approx. 140 pages]

Preface

All we are is our present thought. Four separate bodies of knowledge bring us this one incredible conclusion: there is a thought, but there is no thinker.

The four disciplines converging on this conclusion are quantum physics, the logic of Western philosophy, the intuition of Buddhism, and the simplicity of information theory.

Quantum physics proves - science admits proof - that something in our world-view is amiss. One solution is that everything exists, so that no one person, place or time can be said to exist as an objective feature of reality.

In the 18th century, Liebniz came to a similar conclusion on the basis of logic alone. He has been followed in recent years by Kripke and Quine.

Buddhism takes many forms, but a common theme is 'anatta' - no soul. The self does not exist; to realise this is to achieve enlightenment. But if there is no self, who is it that becomes enlightened? Ah, that question sends the doctor and the priest, in their long coats, running over the fields.

Information theory confirms that far the simplest structure for the universe is one in which everything exists: an infinite ensemble of universes, much as suggested by quantum physics.

The ideas discussed here are neither provable nor disprovable, and are therefore in the realm of metaphysics. Nevertheless, there are good reasons for choosing one idea over another; in general, we should look for the simplest explanation consistent with the facts.

The Summary covers most of the ground of this book in a very dense few pages. It is an unedited version of a paper written in 1999 and published in the Middle Way, the journal of the Buddhist Society, in February 2000.

IntroductionThis introduction first appeared, edited, in the February 2000 issue of The Middle Way, the journal of the Buddhist Society, London

The discovery of the quantum nature of matter left the physics community of the 1920s in a state of profound shock. It was, and is, not possible to reconcile the observed facts with a universe which is remotely Newtonian. All of the competing interpretations still force us to abandon one or more cherished idea: time, locality, identity.

The fundamental problem in quantum physics can be illustrated by a candle. As a candle emits a single photon (a particle of light), a scientist can determine with extraordinary precision its probability of being in any one place. A probability wavefunction (not a physical wave) is said to emanate from the source, and the photon can be anywhere allowed by that wavefunction. The details are computed by the celebrated Schrdinger equation. The problem comes when you observe the photon, and discover where it actually is. At this moment, the wavefunction collapses from a cloud around the candle to a single point. This has led to a large number of metaphysical speculations. How does the wavefunction know it is being looked at? How can quantum mechanics be formulated without recourse to the idea of the conscious observer, outside the system, initiating that collapse? This is the problem.

In 1927, at the Solvay Conference, Niels Bohr succeeded in constructing an orthodoxy the Copenhagen Interpretation which allowed physicists to continue building their armoury of quantum mechanical techniques, while avoiding the frightening questions of what actually happens. He simply said that it was meaningless to give a photon spatial attributes until the wavefunction collapse. This developed into the creed of logical positivism, adherents of which argue it is meaningless to discuss anything that cannot produce concrete experimental results. Positivism is still a major factor in the teaching of physics; students are still told to shut up and calculate rather than inquire after meaning.

The most intuitively accessible description of the problem is the famous Schrdinger cat. In this thought experiment, a cat is placed in a sealed box, along with a radioactive source. The source is set to open a bottle of cyanide if it decays. There is a 50% chance of the source decaying in the minute while the box is closed, so there is a 50% chance of us seeing a live cat when the box is opened. But, according to Bohr, it does not make sense to ask what happens before we make the observation (open the box). The Copenhagen interpretation would have us believe that the cat is in a superposition of the alive and dead states while the box is closed, and only becomes actually dead or alive when we open the box to make our observation.

This, and various other paradoxes, has led wayward physicists to question the orthodoxy and try to develop interpretations that resolve the problems. Because this will not affect how physicists do quantum physics, this endeavour is called metaphysics. Few respectable physicists will lend their name to such a project. Notable exceptions include Fritjof Capras The Tao of Physics (based on David Bohms pilot wave interpretation); Henry Stapps papers deriving consciousness from quantum mechanics (based on Niels Bohrs Copenhagen interpretation), and David Deutschs The Fabric of Reality (based on Hugh Everetts many worlds interpretation).

Nevertheless, the icons of Newtonian physics are crumbling. It is widely acknowledged that time can no longer be considered an objective feature of reality (Barbour, Price, Stenger), or at least its direction of travel is arbitrary. But the Everett many worlds interpretation, or MWI, goes much further. It implies that nothing is objective. Everything exists, and what you see in the plenitude is a function of how far you restrict your view.

Everett simply posited that there is no wavefunction collapse. In other words, the photon is emitted every which way simultaneously; the cat is alive and dead at the same time; a pencil balanced on its point will fall in all directions at once. We only see one result, instead of all of them, because we observe a single path through an ever-branching multitude of infinite universes, and we call that path our universe. The process of splitting is called decoherence.

According to Everetts MWI, the universe is branching off every Planck Time (10-43 seconds) into countless billions of other universes, each an unmoving snapshot in time, and each branching out in turn. So as you turn the page in this universe, you go out for a cup of tea in many others. When you roll a die, all numbers come up. In billions of universes, you roll a six; in billions more, you get a one. In some universes, the die turns into a diamond. None of these events contradicts any known laws of physics. As the probability of anything happening is always one (it will happen), Everett used the term, measure to describe the relative proportions of events. For example, the measure of dice showing one to five is five times the measure of dice showing six, although there are infinitely many universes corresponding to either category. David Deutsch calls the infinite ensemble of snapshot universes the multiverse.

MWI is not the orthodoxy of the physics community, but neither is any competing ontology. It makes precisely the same predictions for the results of experiments as the Copenhagen or any other interpretation. When positivism is accepted as the way to do science, anything that is not even wrong is widely ignored. Nevertheless, various polls of leading physicists have concluded that, when pressed for an answer, more believe MWI than anything else.

There are better reasons for supposing that MWI is true. They centre on the principle of Occams Razor, which states that the simplest theory compatible with the facts is the one we should choose. Superficially, we should choose the MWI because it gives the same results as the Copenhagen Interpretation, without the need for an observer-induced wavefunction collapse. But more profoundly, the MWI makes the world we observe compatible with a universe containing just one bit of information.

This startling idea can be attributed in outline to Max Tegmark, Bruno Marchal and Jrgen Schmidhuber. To an information scientist - and all of physics can be regarded as a subset of information science - the information content of a system (its Kolmogorov complexity) is defined by the length of the computer program required to generate it. The program to generate an MWI system, an infinite multiverse, can be very short. Wei Dai has suggested a counting algorithm. For example, the BASIC program LET A=A+1; GOTO START will generate an enumerably infinite set of natural numbers. These can be mapped onto an infinite physical multiverse - but its information content is almost nil. On the other hand, the program required to generate a single classical universe might be as large as the universe itself.

By analogue, consider the Mandelbrot set, Ford froth, or a fractal pattern. The expression, znew=z2 + c where z and c are complex numbers, can be used to generate infinitely complex, and beautiful landscapes on the screen of a computer (see Figure 1). An inhabitant of a Mandelbrot world would see amazingly rich complexity all around. Mathematicians, outside the Mandelbrot set, can understand that the Kolmogorov complexity of their world is very small - a short equation.

Figure 1 (generated by the University of Utah applet at http://www.hath.utah.edu/~alfeld/math/mandelbrot/mandelbrot.html)

Given that we know that something exists (