Contents
Mea culpa: reality and fantasy blend in my mind. My major source of income is as a scientist and, fortunately for all involved, on my very best behavior I can pass as such. What’s more, it’s fun. Working out problems slowly, carefully, and rigorously gives insight, a sense of solidity, and of a job well done. Often it sheds light in unexpected directions, and opens new doors. But it has limitations. To do it, you must already understand the problem in a detailed way. But many interesting questions are too nebulous and slippery for such Intimacy. My burden is that often I’m insensitive to the difference.
Consider the question of intelligent machines. While the entire idea was once viewed suspiciously by most of the scientific community, the research has, by now, spun off enough practical results to be reasonably tolerated. On my best behavior, for my Ph.D. thesis, I wrote a program that enabled a robot to see well enough to cross a cluttered room, building a map of it along the way [there’s a joke here–it took the robot five hours to make the transit, its million-dollar computer brain churning furiously the whole time]. At the same time I couldn’t help extrapolating that modest reality to very immodest lengths. Why are robots so much worse than animals at the simplest things? When can we expect that to change? Will they ever be as good as humans at most things? Will they be better? Cheaper? Will they be able to carry on their own further improvement without our help? Is there some way we can avoid being left in the dust? What will the world be like after this happens?
By making some tentative assumptions and calculations, I was able to conclude: The computers are too small–insectlike now. Slowly but steadily, 1000-fold every 20 years. Yes, in about 40 years. Yes, rapidly thereafter. Certainly, much. Especially without our help. Only if we join them by rebuilding ourselves in their image. Very different–much bigger and more interesting. While many of my colleagues saw a big difference between the reasoning behind the robot driving program and the futurism, I found little distinction. Maybe it’s the result of reading too much science fiction. In any case, several papers and essays on both subjects were published, with the robot results showing up mainly in technical literature, and the futurism in science fiction outlets. But there was crossover, in both directions.
Which brings us to Harvard. A new editor at Harvard University Press had read several of the futurism articles, and in January of 1985 invited me to submit an outline for a book expanding on the theme. His timing was excellent–I’d just started writing such a book, after ten years of procrastination. It was an opportunity to develop many new ideas, Some were about the evolution of our machines, but others were about surprises in the universe that might await our superintelligent progeny. When my editor read a first draft he explained that the book would have to be passed by an academic review committee, and Harvard, by policy, does not publish science fiction. He felt also that many of the physics and astronautics chapters impeded the theme of the book. So the second draft abandoned several ideas. Fortunately, Jim Baen does publish science fiction, and some of the orphan chapters have found a foster home here.
The first article addresses the possibility of computers so fast they violate apparent physical limits. The secret is exotic materials science.
Computers are usually characterized by their speed (or power) and
their memory capacity. At a next level of detail, the amount of parallelism
is a key measure. Here’s a helpful metaphor: Computing is like a sea voyage
in a motorboat. How fast a given journey can be completed depends on the
power of the boat’s engine, while the maximum length of any journey is
limited by the capacity of its fuel tank. Some computations are like a
trip to a known location on a distant shore; others resemble a mapless
search for a lost island. Parallel computing is like having a fleet of
small boats–it helps in searches, and in reaching multiple goals, but not
very much in problems that require a distant sprint.
The calculation speed of computers has been increasing at a slightly accelerating pace averaging a thousandfold every twenty years. This can be sustained for a considerable time even without great increases in raw switching speed by increasing parallelism–almost all computations have parts that can be sped up somewhat by this strategy. But some destinations cannot be reached in a given time by any number of slow boats.
What is the ultimate speed limit of computer logic? Quantum mechanics demands a minimum energy to localize an event to a given time:
Energy = h' / time
where h is Planck’s constant, the basic scale of quantum mechanics. Higher speeds require greater energy. Above the frequency of light, about 1015 transitions per second, the energy reaches one electron volt–close to the energy of the chemical bonds holding solid matter together. Attempts to switch faster will tear apart the switches. The fastest switches in laboratories today, electronic or optical, operate at a mere 1011 transitions per second, so we can expect a further ten thousandfold speedup before our switches blow up. But things will be increasingly difficult as the limit is approached (by the year 2010, if our projection holds), aggravated by the fact that in 10–15 second, signals can cover a distance of only 30 atoms. Is there any hope of breaching this “light barrier?”
Someday, neutron stars may be the preferred location for monster supercomputers, since they are common and large. For the immediate future they are too far away, the nearest being thousands of light-years from us. Is there any hope for smaller, more immediate, ultraspeed gadgets? After all, we’re going to reach the speed limit of conventional matter in a mere 25 years.
The size of an atom depends on the charge and mass of the electrons orbiting it. If electrons could be made twice as massive, atomic diameters would shrink by half and the density of matter would increase eightfold. Chemical binding energies, which depend on the inverse square law of electric forces, would quadruple, as would the maximum switching speed. Electrons are unlikely to get heavier, but perhaps something could be substituted for them. Heavier particles would bind to nuclei more tightly than electrons, and so would naturally displace them if introduced (just stand back so you’re not fried by the liberated energy?). Protons, found in all atomic nuclei, weigh about 2,000 times as much as electrons, but they have the wrong charge to also serve for electrons. Antiprotons---protons’ mirror images–have the right charge, but combine catastrophically with protons in trillionth-second fireballs of mutual annihilation. Particle physicists long ago discovered heavy cousins of electrons, the mu and (more recently) tau particles, 200 and 3,600 times as massive. Unfortunately, they are unstable and so unsuitable for constructing long-lasting matter. The muon lasts two microseconds before decaying into an electron; the tau much less time. In fact, no particle definitively observed so far will do. Stable charged particles should be very easy to detect in accelerator experiments, and since none have been seen, it’s highly probable that none exist up to the energy range of present accelerators. This is over 50,000 times the electron’s mass, unfortunately. It means the step beyond normal matter is likely to be big and difficult.
Suppose we start with a mass of hydrogen, the simplest atom. In it one electron orbits one proton. Since Higgsinos are heavier than protons, substituting one for the electron will turn the atom inside out; the massive Higgsino will become the nucleus, and the proton will do most of the orbiting, and will set the size of the atom, about 2,000 times smaller in diameter than a normal one. The force between adjacent atoms would be 2,0002 or four million times as great. Only astronomical temperatures would break those bonds–the material would remain a solid under any earthly conditions, and there would be 2,0003 or eight billion times as many atoms per cubic centimeter. Because Higgsinos are heavy, each atom will weigh 75 times as much, so the density would be about 1012 times that of normal matter. But there’s a surprise. Each Higgsino added will itself generate about 20,000 electron volts of energy as it captures a proton–enough to radiate gamma rays. That’s minor. But then the exposed orbiting protons of adjacent resulting “Higgsino Hydrogen” atoms will be in an optimum position to combine with one another in fours to form Helium nuclei in a fusion reaction. Each fusion liberates a whopping 10 million electron volts, and frees the Higgsinos to catalyze more fusions. This will continue until the resulting nuclear explosion blows the material apart. The Higgsinos may cause fusion of heavier elements as well, and perhaps fission of very heavy nuclei. Great opportunities here, but not quite what we had in mind?
Iron nuclei are prone neither to fusion nor fission–it takes energy either to break them down or to build them up–and so can (perhaps) be combined safely with Higgsinos. Each iron nucleus contains 26 protons, and must be neutralized by 26 negative Higgsinos. But it’s unlikely that the Higgsinos can overcome their mutual repulsion to neatly form the right sized nuclei. A different, more condensed arrangement is probable. Suppose we mix small amounts of hydrogen and Higgsinos very slowly and carefully, taking away waste energy (perhaps to help power the Higgsino manufacturing accelerator). The resulting mass will settle down to some lowest energy configuration–probably a crystal of Higgsinos and protons, electrically neutralizing each other, and some neutrons, bound by other electromagnetism and the strong nuclear force. If there are too many neutrons, some will decay radioactively until a stable mix is reached. The protons and neutrons, being the lighter and fuzzier of the particles, will determine the spacing–about that found in neutron stars. The millionfold speedups possible there will apply here also.
The final material (let’s call it Higgsinium) would be 1018 times as dense as water; a thimbleful would have the weight of a mountain. It’ll be a while before that much of it is manufactured. A cubical speck a micron on a side weighs a gram, and should be enough to make thousands of very complex integrated circuits–analogous to a cubic centimeter of silicon. Their speed would be a millionfold greater, as would their power consumption and operating temperature. It may be possible to build the circuits with high energy versions of the optical and particle beam methods used to construct today’s ICs, though the engineering challenges are huge! And in the long run, tiny machines of Higgsinium might be dropped onto neutron stars to seed the construction of immense Neutronium minds.
For over forty years, searches for monopoles all came up empty-handed, and there was great skepticism about their existence. But they may have been fleetingly observed three times in the last decade, though none has yet been caught for extended observation. In 1973 a Berkeley cosmic ray experiment was lofted above most of the scattering atmosphere in a high-altitude balloon. In 1975, after two years of study, a very heavy track bearing the stigmata of a monopole was noted in the lexan sheets that served as three-dimensional detecting film. Calculations suggested it had twice Dirac’s predicted charge, and a mass over 600 times that of a proton. Since monopoles had never been observed before, there was much skepticism. Other, more elaborate but more conventional possibilities were devised, and the incident was shelved.
On Valentine’s Day in 1982, a modest experiment in Blas Cabrera’s Stanford physics lab registered a clean, persistent, steplike jump in the current in a superconducting loop. The size of the step was just what a monopole with Dirac’s quantum of magnetic charge would have caused had it passed through the loop. The only alternative explanation was mechanical failure in the experimental apparatus. Subsequent prodding and banging produced no effect–everything seemed shipshape. The result was so exciting that many groups around the world, including Cabrera’s, built larger detectors, hoping to confirm the observation. For four years there was silence. By then the cumulative experience of the new detectors (collecting area multiplied by time) was over a thousand times that of Cabrera’s original experiment. Once again the possibility of monopoles faded. Then, on May 22, 1986, a detector at Imperial College, London, whose experience was over four hundred times as large as Cabrera’s original, registered another event. Until a monopole is caught and held, its existence will be in question. Yet each additional detection greatly increases the odds that the others were not mistakes.
Magnetism and electricity are right-angle versions of the same thing. A monopole waved up and down will cause a nearby electric charge to move side to side (and vice versa). A current of monopoles flowing in one wire will induce an electric current at right angles to itself. An electric current in a loop of conductor will flow In lock step with a current of monopoles in a monopole conducting loop chain linked with it. Two coils of wire wrapped around a monopole loop make a DC transformer–a current started in one coil will induce a monopole current in the loop, which will produce an electric current in the other coil’s circuit. If good DC transformers had existed in the late nineteenth century, Thomas Edison and George Westinghouse would have had less to fight about, and all our electrical outlets would produce direct current. With monopoles, we might refrain from making electrical connections at the plug at all, and draw power simply by passing the two ends of our power cords through a partially exposed monopole loop.
But let’s get serious. If there are monopoles, they’re not very common, and few will simply be picked out of the air. If they’re very heavy, they will be hard to stop. Perhaps a few can be found already trapped here and there, and can be coaxed out (such a search was conducted worldwide by Kenneth Ford of Brandeis University, armed with a portable electromagnetic solenoid, in the early 1960s). Many things are possible given a few monopoles. Physicists routinely build superconducting solenoids with powerful magnetic fields several hundred thousand times as strong as Earth’s. A monopole accelerates along magnetic field lines (for instance, a “North” monopole is strongly attracted to the south pole of a magnet). A monopole riding the field lines down the center of a powerful solenoid will gain an energy equivalent to the mass of several protons for every centimeter of travel. Ten meters of solenoid will Impart an energy matching that of the most powerful existing accelerators. A few kilometers of solenoids will produce energies equal to millions of proton masses. The fireball resulting from a head-on collision of two monopoles moving thusly is intense enough to produce some number of additional monopoles, in North/South matching pairs. These can be sorted out magnetically, and so monopoles can be harnessed to breed more monopoles.
Detectors of the Cabrera type do not measure the mass of passing monopoles, and the theories are little help. Monopoles can’t be too light or they would have been created in existing accelerators. As mentioned above, the theoretical range of uncertainty is enormous. Things are especially interesting if there are at least two kinds of non-mutually-annihilating stable monopole, analogous to the proton and electron in normal matter (the North/South pairs mentioned above don’t count–the two are antiparticles of each other, and annihilate when brought in contact). Here’s a real leap of ignorance: let’s suppose there are two kinds and that they are near the low end of the possible mass range. Let’s suppose the lighter variety weighs 1,000 protons, and the heavier 1,000,000 protons. If two kinds don’t exist, or if mono- poles turn out to be much heavier, many of the following proposals will become more extreme, or impossible. Others may open in their place.
An atom of Monopolium has a light monopole of one polarity (let’s say North) bound to a heavy monopole of the opposite pole. Its size is set by the fuzzier light monopole. We assumed this has a mass of 1,000 protons (or two million electrons), making the monopole atom about two million times smaller than a normal one. The particle spacing in Monopolium is thus comparable to that in Neutronium or Higgsinium. Its density, however, will be a million times beyond those because of the great mass of the central, heavy monopole. This makes it 1025 times as heavy as normal matter. A thimbleful weighs as much as the Moon. Dirac’s calculation found the magnetic quantum of charge to be 68.5 times as intense as the electric quantum. Two monopoles a certain distance apart would attract or repel each other 68.52 or 4,692 times as strongly as two equally separated electric particles. Combining this with the (inverse square) effects of much closer spacing and the increased density makes Monopolium ten thousand times as strong for its weight as normal matter, though this number changes radically with changes in the assumed masses of the two kinds of monopole. The limiting switching speeds may be a thousand times higher than those we found for Higgsinium.
Macroscopic extents of these substances are possible in very thin fibers or sheets. An (utterly invisible Higgsinium strand one conventional atom (= 106 particles in diameter masses 100 grams per centimeter of length. It may be able to support a 100 million tonnes, being about ten thousand times stronger for its weight than normal materials. Although it would slice through conventional matter as through a cloud (but sometimes the extremely thin cut would heal itself immediately), properly mounted, It would make gargantuan engineering projects such as orbital elevators trivial. A single-particle thick layer of Higgsinium would weigh about ten kilograms per square centimeter. Overlaid on structures of conventional matter, the superconducting version especially would make powerful armor that would shield against essentially all normal projectiles, temperatures into the nuclear range, and all but the highest energy radiation. (But it could be penetrated by even denser Monopolium-tipped bullets. Arms races are relentless!)
The same armor could be used to line the combustion chamber and expansion bell of a matter-antimatter rocket. Normal matter is instantly disintegrated by the violence of the reaction, but Higgsinium would easily bounce the pions, gamma rays and X rays produced when hydrogen meets antihydrogen. Single-particle-thick Monopolium, at a hundred tonnes per square centimeter, may be too heavy to use as a veneer at macroscopic scales. But it might be just the thing for constructing microscopic interstellar ships. A ship with two tiny tanks crammed with ultra-compressed hydrogen and antihydrogen could rapidly propel itself at high acceleration to a few percent of the speed of light. Unaffected by either protons or antiprotons, Monopolium would be better for building the engine and tanks than Higgsinium. The ship’s front end might house a superfast mind, and tiny robot arms. It could probably land on a neutron star and start raising Neutronium crops and children.
Combining electrically conducting matter and Monopolium is interesting.
Our Monopolium is about 10,000 times as strong for its weight as normal
matter. Properly exploited, it can store 10,000 times as much energy in
mechanical or electromagnetic form. Monopolium superconductor plated in
a ring around a copper rod should make a lovely storage battery. To charge
it, pass a current through the rod, thus setting up a monopole supercurrent
in the ring. The magnetic current remains when you break the electrical
connection, and causes the ends of the rod to keep the voltage you had
applied. When you connect a load to the rod ends, a current flows, and
the voltage gradually drops toward zero as the monopole current slowly
converts to electrical power. A kilogram of Monopolium should be able to
store a fantastic one million watt hours. Caution: Do Not Overcharge!
If
the monopole current becomes too large, the electric field it generates
will burst the ring, and all of the stored energy will be released at once
in an explosion equal to a ton of TNT. There are other possibilities, especially
involving intimate mixtures of monopoles and electrically charged matter
(intertwined, like links of a chain), but we’re out far enough on this
limb for now.
The second idea concerns time travel without violating accepted physical laws. The innovations here are mostly psychological and philosophical.
Time travel is a familiar concept in science fiction, and often
brings with it the concept of alternate worlds, The mechanism of time travel
is usually some extrapolation of modern physics–certainly fertile ground,
with special relativity allowing communication to the past if faster-than-light
particles could be found, general relativity allowing spacetime to be warped
and twisted into temporal knots, and quantum mechanics seemingly founded
on the temporary superposition of alternate worlds. Yet, if tachyons really
don’t exist, if Tipler vortex time machines are in principle impossible
to build and black holes lead only to oblivion, if the alternate worlds
in quantum mechanics are a mere mathematical artifact, or are truly inaccessible,
are we stuck, helplessly drifting down the one-way river of time? Is there
some way out, other than exotic physics? Here’s how to do it with
a philosophical leap and a lot of conventional future technology.
The point of view, which I will call the “Body Identity” position, makes a mockery of many of the supposed advantages of being “mind transferred” to a new body. I believe the objection can and should be overcome by intellectual acceptance of an alternate position I will name “Pattern Identity.” Body identity assumes that a person is defined by the stuff of which a human body is made. Only by maintaining continuity of body stuff can we preserve an individual person. Pattern identity, on the other hand, defines the essence of a person, say myself, as the pattern and the process going on in my head and body, not the machinery supporting that process. If the process is preserved, I am preserved. The rest is mere jelly.
If pictures, why not solid objects? A matter transmitter might scan an object and identify, then knock out, its atoms or molecules one at a time. The identity of the atoms would be transmitted to a receiver where a duplicate of the original object would be assembled in the same order from a local supply of atoms. The technical problems are mind-boggling, and well beyond anything foreseeable, but the principle is simple to grasp. If solid objects, why not a person? Just stick him in the transmitter, turn on the scan, and greet him when he walks from the receiver. But is it really the same person? If the system works well, the duplicate will be indistinguishable from the original in any substantial way. Yet, suppose you fail to turn on the receiver during the transmission process. The transmitter will scan and disassemble the victim, and send an unheard message to the inoperative receiver. The original person will be dead. Doesn’t the process, in fact, kill the original per son, whether or not there is an active receiver? Isn’t the duplicate just that–merely a clever imposter? Or suppose two receivers respond to the message from one transmitter. Which, if either, of the two duplicates is the real original?
Consider the message “I am not jelly.” As I type it it goes from my brain, into the keyboard of my computer, through myriads of electronic circuits and over great amounts of wire, and after countless adventures shows up in bunches of books like the one you’re holding. How many messages were there? I claim it is most useful to think there is only one, despite its massive replication. If! repeat it here: “I am not jelly,” there is still only one message. Only if I change it in a significant manner–”I am not peanut butter ‘–do we have a second message. And the message is not destroyed until the last written version is lost, and until it fades sufficiently in everybody’s memory to be unreconstructable. The message is the information conveyed, not the particular encoding.
The “pattern and process” that I claim is the real me has the same properties as the message above. Making a momentary copy of my state, whether on tape or in another functional body, doesn’t make two persons. There is a complication because of the “process aspect; as soon as an instance of a “person message” evolves for a while, it becomes a different person. If two of them are active, they will diverge and become two different people, by my definition. Just how far this differentiation must proceed before you grant the two people unique identities is about as problematical as the question “when does a fetus become a person?” But if you wait zero time, then you don’t have a new person. If, in the dual receiver version of the matter transmitter, you allow the two copies to be made and kill one (either one) instantly on reception, the transmitted person still exists in the other copy. All the things that person might have done, and all the thoughts he or she might have thought, are still possible. If, on the other hand, you allow both copies to live their separate lives for a year, and then kill one, you are the murderer of a unique human being. But, if you wait only a short while, they won’t differ by much, and destruction of one won’t cause too much total loss. This rationale might, for instance, be a comfort in danger if you knew that a tape backup copy of you had been made recently. Because of the divergence, the tape contains not you as you are now, but you as you were: a slightly different person. Still, most of you would be saved should you have a fatal accident, and the loss would be nowhere near as great as without the backup.
Intellectual acceptance that a secure and recent backup of you exists does not necessarily protect you from an instinctive self-preservation overreaction if faced with imminent death. This is an evolutionary hangover from your one-copy past. It is no more a reflection of reality than fear of flying is an appropriate response to present airline accident rates. Inappropriate intuitions are to be expected when the rules of life are suddenly reversed from historical absolutes.
Some supercomputer designs call for myriads of individual computers interconnected by a network that allows free flow of information among them. An operating system for this arrangement might allow individual processes to migrate from one processor to another in mid-computation, in a kind of juggling act that permits more processes than there are processors. If a human mind is installed In a future machine of this variety, functions originally performed by particular cell assemblies might be encoded in individual processes. The juggling action would ensure that operations occurring in fixed areas in the original brain would move rapidly from place to place within the machine. If the computer is running other programs besides the mind simulation, then the simulation might find itself shuffled into entirely different sets of processors from moment to moment. The thinking process would be uninterrupted, even as its location and physical machinery changed continuously, because the immaterial pattern would keep its continuity.
A process that is described as a long sequence of steps can sometimes be transformed mathematically into one that arrives at the same conclusion in far fewer operations. As a young boy the famous mathematician Friedrich Gauss was a school smart-aleck. As a diversion, a teacher once set him the problem of adding up all the numbers between 1 and 100. He returned wit the correct answer in less than a minute. He had noticed that the hundred numbers could be grouped into fifty pairs – 1 + 100, 2 + 99, 3 + 98, 4 + 97, and so on–each pair adding up to 101. Fifty times 101 is 5,050–the answer, found without a lot of tedious addition. Similar speedups are possible in complex processes. So-called optimizing compilers have repertoires of accelerating transformations, some very radical, to streamline programs they translate. The key may be a total reorganization in the order of the computation and the representation of the data. A very powerful class of transformations takes an array of values and combines them in different ways to produce another array. Each final value reflects all the original values, and each original value affects all the results. An operation on a single transformed quantity can substitute for a whole host of operations on the original array, and enormous efficiencies are possible. Analogous transformations in time also work: a sequence of operations is changed into an equivalent one where each new step does a tiny’ fraction of the work of every one of the original steps. The localized is diffused, and the diffused is localized. A program can quickly be altered beyond recognition by a few mathematical rewrites of this power. Run on a multiprocessor, single events in the original formulation may appear only as correlations between events in remote machines at remote times in the transform. Certain operations that don’t matter in the long run may be skipped altogether. Yet the program is fundamentally unchanged. You know what’s coming. If we thus transform a program that simulates a person, the person remains intact. Soul is in the mathematical equivalence, not in any particular detail of the process. It has a very ethereal character.
The superintelligent being has no obligations to model every single detail of the beheld accurately, and may well choose to skip the boring parts, to jump to conclusions that are obvious to it, and to lump together different alternatives it does not choose to distinguish. This looseness in the simulation can also allow some time-reversed action–our superintelligent being may choose a conclusion, then reason backwards, deciding what must have preceded it. Authors of fiction often take such liberties with their characters. The same parsimony of thought applies to the parts of the environment of the contemplated person that are themselves being contemplated. Applied a certain way, this parsimony will effect the evolution of the simulated person and his environment, and may thus be noticeable to him. Note that the subjective feelings of the simulated person are a part of the simulation, and with them the contemplated person feels as real in this implementation as in any other.
It happens that quantum mechanics describes a world where unobserved events happen in all possible ways (another way of saying no decision is made as to which possibility occurs), and the superposition of all these possibilities itself has observable effects. The connection of this observation with those of the previous paragraph leads us into murky philosophical waters. To get even muddier, seriously consider the title of this section. If the subjective feelings of a person are part of the person-message, and if the evolution of the message is implicit in the message itself, then aren’t the future experiences of the person implicit in the message? And wouldn’t this mere mathematical existence feel the same to the person encoded as a more substantial simulation? I don’t think this is mere sophistry, but I’m not prepared to take it any further for now.
In the very long run the ancestral individual is always doomed, as its heritage is nibbled away to meet short- term demands. It slowly mutates into other forms that could have been reached from a range of starting points–the ultimate in convergent evolution. It’s by this reasoning that I conclude that it makes no ultimate difference whether our machines carry forward our heritage on their own, or in partnership with direct transcriptions of ourselves. Assuming long-term survival either way, the end results should be indistinguishable, shaped by the universe and not by ourselves. Since change is inevitable, I think we should embrace rather than retard it. By so doing we improve our day-to-day survival odds, discover interesting surprises sooner, and are more prepared to face any competition. The cost is faster erosion of our present constitution. All development can be interpreted as incremental death and new birth, but some of the fast-lane options make this especially obvious; for instance, the possibility of dropping parts of one’s memory and personality in favor of another’s. Fully exploited, this process results in transient individuals constituted from a communal pool of personality traits. Sexual populations are effective in part because they create new genetic individuals in very much this way. As with sexual reproduction, the memory pool requires dissolution as well as creation to be effective. So personal death is not banished, but it does lose its poignancy because death by submergence into the memory pool is reversible in the short run.
The laws of physics are quite symmetric in time. Simulations can usually be run in reverse as well as forward, and used to “predict” the past, perhaps guided by old measurements or archeological data. As with future predictions, any uncertainty in the initial measurements, or in the rule that evolves the initial state, will allow for a variety of possible outcomes. If the simulation is detailed enough, and is given all available information, then all of its “predictions” are valid–any of the possible pasts may have led to the present situation. This is a strange idea if you are accustomed to looking at the world in a strictly deterministic, Newtonian way. Interestingly, it closely resembles the uncertain world described by quantum mechanics, and perhaps hints at a mechanism underlying our world. Now, imagine an immense simulator that is able to model the whole surface of the earth on an atomic scale, and that can run time forward and back, and produce different plausible outcomes by making different random choices at key points in its calculation. Because of’ the great detail, this simulator models living things, including humans, in their full complexity. By the arguments above, such simulated people would be as real as you or I, though imprisoned in the simulator.
We could join them by linking up with the simulation through a telepresence
interface, that connects a “puppet” deep inside the simulation with a physical
‘helmet” and “gloves” outside, allowing us to experience the puppet’s sensory
environment, and to naturally control its actions. More radically, we could
“download” our minds directly into a body in the simulation, and “upload”
back into the real world when our mission is accomplished. Alternatively,
we could bring people out of the simulation by reversing the process, linking
their minds to an outside robot body, or uploading them directly into it.
In all cases we would have the opportunity to recreate the past, and to
some extent the future, and interact with it in a real and direct way.
Realistically simulating the future is more difficult because archeology
cannot help, and because an advancing culture will produce fundamental
new knowledge not found in the model, by research into new physical arenas
or exploration of new geography. The same techniques, of course, allow
visits to entirely novel situations and universes.
Finally, here’s the core of an idea that, if correct, would put a radically new light on the fundaments of our space and time, incidentally explaining the most bizarre effects of quantum mechanics. Someone should develop it mathematically someday.
Quantum mechanics, a cornerstone of modern physics, has indeterminism
at its heart and soul. Outcome probabilities in quantum mechanics are predicted
by summing up complex valued “amplitude functions” for all the indistinguishable
ways a given event might happen, then squaring the result. The amplitudes
subtract from each other as often as they add, with the strange effect
that some otherwise possible outcomes are ruled out by the existence of
other possibilities. An excellent example is the two slit experiment.
Photons of light radiate from a pinpoint source to a screen broken by two
slits (Figure 1). Those that make it through the
slits encounter an array of photon detectors (often a photographic film,
but the example is clearer if we use individual, immediately responding
sensors). If the light source is so dim that only one photon is released
at a time, the sensors register individually, sometimes this one, sometimes
that one. Each photon lands in exactly one place. But if a count is kept
of how many photons have landed on each detector, an unexpected pattern
emerges. Some detectors see no photons at all, while ones close to them
on either side register many, and a little farther away there is again
a dearth. In the Ion run, a pattern builds that is identical with the banded
interference pattern one would see if two matched waves were being emitted
from sources at the slits.
But waves of what? Each photon starts from one place and lands in one place; isn’t it at just one place on every part of its flight? Doesn’t it go through one slit or the other? If so, how does the mere existence of the other slit prevent it from landing at a certain place on the screen? For indeed, if one slit is blocked, the total number of photons landing on the screen is halved, but the interference pattern vanishes, and some locations that received no photons with both slits open begin to register hits. Quantum mechanics’ answer is that during the flight the position of the photon is unknown, and must be modeled by a complex valued wave describing all its possible locations. This ghostly wave passes through both slits (though it describes the position of only a single photon), and interferes with itself at the screen, cancelling at some points. There the wave makes up its mind, and the photon appears in just one of its possible locations. The undecided wave condition of the photon before it hits the screen is called a mixed state or a superposition of states. The sudden appearance of the photon in only one detector is called the collapse of the wave function.
This explanation profoundly disturbed some of the same physicists who had helped formulate the theory, notably Albert Einstein and Erwin Schrödinger. To formalize their intuitive objections they constructed thought experiments that gave unlikely results according to the theory. In some a measurement made at one site causes the instant collapse of a wave function at a remote location–an effect faster than light. In another, more frivolous example, called Schrödinger’s Cat, a radioactive decay that may or may not take place in a sealed box causes (or fails to cause) the death of a cat also in the box. Schrödinger considered absurd the theory’s description of the unopened box as a mixed state superimposing a live and a dead cat. He suggested that the theory merely expressed ignorance on the part of an observer–in the box, the cat’s fate was unambiguous. This is called a hidden variables theory–the system has a definite state at all times, but some parts of it are temporarily hidden from some observers.
The joke is on the critics. Many of the most "absurd" thought-experiment results have been observed in mind-boggling actuality in a series of clever (and very modern) experiments carried out by Alain Aspect at the University of Paris, and others. These demonstrations rule out the simplest and most natural hidden variables theories, local ones in which, for instance, the hidden information about which slit the photon went through is contained in the photon itself, or in which the state of health of Schrödinger’s cat is part of the feline.
Non-local hidden variables theories, where the unmeasured information is distributed over an extended space, are a possibility. It is easy to construct theories of this kind that give results identical with ordinary quantum mechanics. Most physicists find them uninteresting–why introduce a more complicated explanation with extra variables, when the current, simpler equations suffice? Philosophically, also, global hidden variables theories are only slightly less puzzling than raw quantum mechanics. What does it mean that the "exact position" of a particle is spread out over a large chunk of space? This question was the subject of a lively controversy in the early part of this century among the founders of quantum mechanics. It’s recently become of widespread interest again.
Quantum mechanical interactions have a "spooky" character clearly evident in the two slit experiment, and recently emphasized by physical demonstrations of the Einstein-Podolsky-Rosen paradox by Aspect and others. The ghosts can be exorcised, or at least elucidated, by proposing underlying mechanisms for the basic effects. These mechanisms often suggest radical new possibilities.
The "many worlds" interpretation developed in the 1950s by Hugh Everett and John Wheeler at Princeton, and frequently presented by John Gribbin in these pages (for instance, in the April 1985 issue), may be the most profligate non-local hidden variables explanation of this puzzle. In Everett’s model, the two slit photon does go through both slits, in different universes. At each decision point the entire universe, or at least the immediate portion of it, splits into several, like multiple pages from a copying machine. Until a measurement is made, the different "versions" of the universe lie in close proximity, and interfere with each other (causing banded patterns on screens, for instance). A measurement that can distinguish one possibility from another causes the universes to diverge (alternately, the divergence is the definition of "measurement"). The interference then stops, and in each now-separate universe, a different version of the experimenter can contemplate a different unambiguous result.
Another possibility, outlined in the November 1986 Analog by
John
Cramer, is his "transactional" interpretation, itself based on an old
explanation by Feynman and
Wheeler for the lack of time-reversed waves implicit in Maxwell’s equations.
In it, observer and observed communicate with signals travelling both ways
in time, so the outcome of the experiment is as much part of the initial
condition as the experimental setup. Or perhaps the universe is a computation
in some kind of machine. Quantum effects might be the result of limited
accuracy and parsimony of calculation in its program. The equations of
quantum mechanics implicitly state that the amount of information that
can be extracted from a limited volume of spacetime is finite. Also, with
proper encoding, the undecided state of a system contains less information
than after a measurement. Only during actual measurements must the "universe
computer" bother to choose one outcome from all the possibilities. Here,
for the first time, I offer yet another, in some ways less radical (but
half baked!) mechanism for quantum mechanics. I like it because it derives
the spookiest consequences from a very concrete model.
If the particles in V bump into one another, or interact in some other way (i.e. the gas in nonlinear), then energy can be transferred from one wave mode to another–i.e., one point in F can become stronger at the expense of another. There will be a certain amount of random transference among all wave modes. Besides this there will be a more systematic interaction between "nearby" wave modes– those very similar in frequency and orientation, thus near each other in the F space. Such waves will be in step for large fractions of their length. Because the gas is nonlinear, the periodic bunching of gas particles caused by one mode will influence the bunching ability of a neighboring mode with a similar period.
Now consider the interactions viewed by a hypothetical observer made of F stuff, for whom points in F are simply locations, rather than complicated functions of another space. Keeping as many concepts from the V space as possible, we can deduce some of this observer’s "Laws of Physics" by seasoning about effects in V, and translating back to F. In the following list, such reasoning is in italics:
A few of modern physics’ more exotic theories have possible explanation
in this model. Although energy mainly flows between wave modes very similar
in frequency and direction (i.e., between points adjacent In F),
non-linearities in the V medium should
permit some energy to flow systematically between harmonically related
wave modes; for instance, between one mode and another on the same direction,
but twice as high in frequency. Such modes of energy flow in F
provide "degrees of freedom" in addition to the three provided by nearby
points. They can be interpreted, when viewed on the small scale, as extra
dimensions (energy can move this way, that way, that way, and also that
way, and that way
.
. .). Since a circumnavigation
from harmonic to harmonic will cover the available space in fewer steps
than a move along adjacent wave modes, these extra dimensions will appear
to have a much smaller extent than the basic three. The greater the energy
involved, the more harmonics are activated, and the higher the dimensionality.
Most physical theories these days have tightly looped extra dimensions
to provide a geometric explanation of the basic forces. Ten and eleven
dimensions are popular, and hinted new forces may introduce more. If something
like the F explanation of apparent
higher dimensionality is correct, there is a bonus. Viewed on a large scale,
the harmonic "dimensions" are actual links between distant regions of space,
and properly exploited, could allow instantaneous communication and travel
over enormous distances.
The first microsecond of the big bang might represent eons of subjective time in F–perhaps enough time for intelligence to evolve, realize its situation, and seed smaller but eventually faster life in the V space. Though on the large scale F and V are the same thing, manipulation of one from the other, or even communication, would be extraordinarily difficult. Any local event in either space would be diffused to non-detectability in the other. Only massive, universe-spanning projects with long-range order would work, and these would take huge amounts of time because of the speed limits in either universe, so real-time interaction is ruled out. Such projects, however, could affect many locations in the other space as easily (in many cases more easily) as one, and these could appear as entropy violating "miracles" there. If I lived in F and wanted to visit V, I would engineer such a miracle that would condense a robot surrogate of myself in V, then later another one that would read out the robot’s memories back into an F-accessible form.
The Fourier transform that converts V
into F is identical except for a minus
sign to the inverse transform that converts the other way. Given just the
two descriptions, it wouldn’t be clear which was the "original" world.
In fact, the Fourier transform is but one of an infinite class of "orthogonal
transforms" that have the same basic properties. Each of these is capable
of taking a description of a volume, and operating over it to produce a
different description with the same information, but with each original
point spread to every location in the result. This leads to the possibility
of an ¥ of universes, each a different combination
of the same underlying stuff, each exhibiting quantum mechanical behavior
but otherwise having its own unique physics, each oblivious of the others
sharing its space. I don’t know where to take that idea.
