The Compleat McAndrews

What Penrose suggests is that the human brain itself is a kind of quantum device. In particular, the same processes that collapse the quantum mechanical wave function in sub-atomic particles are at work in the brain. When humans are considering many different possibilities, Penrose argues that we are operating in a highly parallel, quantum mechanical mode. Our thinking resolves and “collapses to a thought” at some point when the wave function collapses, and at that time the many millions or billions of possibilities become a single definite idea.

This is certainly a peculiar notion. However, when quantum theory was introduced in the 1920s, most of its ideas seemed no less strange. Now they are accepted by almost all physicists. Who is to say that in another half-century, Penrose will not be equally accepted when he asserts, “there is an essential non-algorithmic ingredient to (conscious) thought processes” and “I believe that (conscious) minds are not algorithmic entities”?

Meanwhile, almost everyone in the AI community (who, it might be argued, are hardly disinterested parties) listens to what Penrose has to say, then dismisses it as just plain wrong. Part of the problem is Penrose’s suggestion as to the mechanism employed within the brain, which seems bizarre indeed.

As he points out in a second book, Shadows of the Mind (Penrose, 1994), he is not the first to suggest that quantum effects are important to human thought. Herbert Fröhlich, in 1968, noted that there was a high-frequency microwave activity in the brain, produced, he said, by a biological quantum resonance. In 1992, John Eccles proposed a brain structure called the presynaptic vesicular grid, which is a kind of crystalline lattice in the brain’s pyramidal cells, as a suitable site for quantum activity.

Penrose himself favors a different location and mechanism. He suggests, though not dogmatically, that the quantum world is evoked in elements of a neuron known as microtubules. A microtubule is a tiny tube, with an outer diameter of about twenty-five nanometers and an i

Penrose’s critics point out that microtubules are also found elsewhere in the body, in everything from livers to lungs. Does this mean that your spleen, big toe, and kidneys are to be credited with intelligence?

My own feeling is that Penrose’s ideas sounded a lot better before he suggested a mechanism. The microtubule idea feels weak and unpersuasive.

Fortunately I don’t have to take sides. In the eighth chronicle, I was deliberately silent on how the AI came into existence. However, as a personal observation, I would be much surprised if in our future we do not have human-level AI’s, through whatever method of development, before humans routinely travel to the satellites of Jupiter and Saturn; and I believe that the latter will surely happen in less than five hundred years.

Compressed matter.

We know that compressed matter exists. In a neutron star, matter has been squeezed together so hard that the individual protons and electrons that normally make up atoms have combined to form neutrons. A neutron star with the mass of the Sun can be as little as twenty kilometers across, and a simple calculation tells us that the average density of such a body is about 475 million tons per cubic centimeter. That is still not at the limit of how far matter can be compressed. If the Sun were to become a black hole, as mentioned earlier, its Schwarzschild radius would be about three kilometers and its mean density twenty billion tons per cubic centimeter. McAndrew’s illustrious but unfortunate father developed an unspecified way of squeezing matter down to something between neutron star and black hole densities.

It is easy to calculate what it would be like if you were unwise enough to take hold of a speck of such compressed matter. And it might well be a speck. An eighteen thousand ton asteroid in normal conditions would be a substantial lump of rock about twenty meters across. Squeeze it to a density of three billion tons per cubic centimeter, and it becomes a tiny ball with radius 0.11 millimeters. Its surface gravity is almost ten thousand gees.

The gravitational force falls off rapidly with distance, so if you were a meter away from the mote of matter you would probably be unaware of its existence. It would pull you toward it with a mere ten-millionth of a gee. But take hold of it, and that’s a different story. Ten thousand gees would suck any known material, no matter how strong, toward and into the ball. That process would continue, until either you sacrificed some skin and broke free, or you were eventually totally absorbed. In practice, I think that McAndrew’s father would have realized what was happening and found a way to free himself. He would have plenty of time, because the absorption process into the compressed matter sphere would be slow. That, however, would not have made as interesting a story.

The way that McAndrew’s father produced compressed matter remains pure science fiction. However, the “strong force” itself is an accepted part of modern physics, one of four basic known forces. The other three are gravity, the electromagnetic force, and the so-called “weak force” responsible for beta decay (emission of an electron or positron) in a nucleus. Although there is an adequate theory of the strong force, embodied in what is known as quantum chromodynamics, there is not the slightest hint in that theory of a method to make such a force either stronger or weaker than it is.

That’s all right. Five hundred years ago, magnetism was a curious property of certain materials, and no one knew what it was or had any way of generating it artificially. That had to wait until another strange phenomenon, electricity, had been explored, and experimenters such as Ampère, Oersted, and Faraday proved a link between electricity and magnetism. After that could come Maxwell, providing a unified theory for the two ideas that led to such practical devices as radios, dynamos, and powerful electromagnets.

It is not unreasonable to model the future on the past. A few hundred years from now, maybe we will be able to play our own games with all the known forces in the context of a unified theory, creating or modifying them as we choose. The weak force and the electromagnetic force have already been unified, work for which Glashow, Weinberg, and Salam were awarded the Nobel prize in physics in 1979.

I ca

Salam also had one endearing but disconcerting habit. He did not drink, but he must have been told that it was a tradition at Cambridge for tutors to serve sherry to their students on holiday occasions. He offered my partner and me sherry, an offer which we readily accepted. He then, unfamiliar with sherry as a drink, poured a large tumbler for each of us. We were too polite to refuse, or not to drink what we had been given, but we emerged from the supervision session much the worse for wear.