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 cannot resist a couple of personal reminiscences regarding the late Abdus Salam. He was my mathematics supervisor when I was a new undergraduate. His personal style of solving the problems that I and my supervision partner brought to him was unique. More often than not, he would look at the result to be derived and say, “Consider the following identity.” He would then write down a mathematical result which was far from obvious and usually new to us. Applying the identity certainly gave the required answer, but it didn’t help us much with our struggles.
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.
There is a throwaway comment in the ninth chronicle, that McAndrew was going off to hear a lecture entitled “Higher-dimensional complex manifolds and a new proof of the Riemann Conjecture.” This is a joke intended for mathematicians. In the nineteenth century, the great German mathematician Bernhard Riemann conjectured, but did not prove, that all the zeroes of a function known as the zeta function lay in a certain region of the complex plane. Riemann could not prove the result, and since then no one has managed to do so. It remains the most important unproven conjecture in mathematics, far more central to the field than the long-unproved but finally disposed-of Fermat Last Theorem.
People will keep chipping away at the Riemann conjecture, precisely because it is unproven. Just as we will keep pushing for better observing instruments, more rapid and sophisticated interplanetary or interstellar probes, quantum computers, artificial intelligence, higher temperature superconductors, faster-than-light travel, treatment for all known diseases, and human life extension.
The future in which McAndrew lives is fiction, but I believe that the science and technology of the real future will be far more surprising. There will indeed be ships, built by humans and their intellectual companions, computers, headed for the stars. They will not be powered by Kerr-Newman black holes, nor employ the McAndrew balanced drive, nor will they tap the resonance modes of the vacuum zero-point energy. They will not be multi-generation arks, nor will they find life-bearing planetoids in the Oort cloud, or rogue planets in the interstellar void. What they will be, and what they will find, will be far stranger and more interesting than that. And they will make today’s boldest science fiction conjectures appear timid, near-sighted, small-scale, and lacking in imagination.
Writing of this I wish, like Benjamin Franklin, that I could be pickled in a barrel for a couple of hundred years, to experience the surprising future that I’m sure lies ahead. If I can’t do that and don’t last that long, here is a message to my descendants two centuries from now: On my behalf, make the most of it.