The Beginning of Infinity

by David Deutsch

  These two interpretations of human progress and perfectibility have historically inspired two broad branches of the Enlightenment which, though they share attributes such as their rejection of authority, are so different in important respects in that it is most unfortunate that they share the same name. The utopian ‘Enlightenment’ is sometimes called the Continental (European) Enlightenment to distinguish it from the more fallibilist British Enlightenment, which began a little earlier and took a very different course. (See, for instance, the historian Roy Porter’s book Enlightenment.) In my terminology, the Continental Enlightenment understood that problems are soluble but not that they are inevitable, while the British Enlightenment understood both equally. Note that this is a classification of ideas, not of nations or even individual thinkers: not all Enlightenment thinkers belong wholly to one branch or the other; nor were all thinkers of the respective Enlightenments born in the eponymous part of the world. The mathematician and philosopher Nicholas de Condorcet, for instance, was French yet belonged more to what I am calling the ‘British’ Enlightenment, while Karl Popper, the twentieth century’s foremost proponent of the British Enlightenment, was born in Austria.

  The Continental Enlightenment was impatient for the perfected state – which led to intellectual dogmatism, political violence and new forms of tyranny. The French Revolution of 1789 and the Reign of Terror that followed it are the archetypal examples. The British Enlightenment, which was evolutionary and cognizant of human fallibility, was impatient for institutions that did not stifle gradual, continuing change. It was also enthusiastic for small improvements, unbounded in the future. (See, for instance, the historian Jenny Uglow’s book Lunar Men.) This is, I believe, the movement that was successful in its pursuit of progress, so in this book when I refer to ‘the’ Enlightenment I mean the ‘British’ one.

  To investigate the ultimate reach of humans (or of people, or of progress), we should not be considering places like the Earth and the moon, which are unusually rich in resources. Let us go back to that typical place. While the Earth is inundated with matter, energy and evidence, out there in intergalactic space all three are at their lowest possible supply. There is no rich supply of minerals, no vast nuclear reactor overhead delivering free energy, no lights in the sky or diverse local events to provide evidence of the laws of nature. It is empty, cold and dark.

  Or is it? Actually, that is yet another parochial misconception. Intergalactic space is indeed very empty by human standards. But each of those solar-system-sized cubes still contains over a billion tonnes of matter – mostly in the form of ionized hydrogen. A billion tonnes is more than enough mass to build, say, a space station and a colony of scientists creating an open-ended stream of knowledge – if anyone were present who knew how to do that.

  No human today knows how. For instance, one would first have to transmute some of the hydrogen into other elements. Collecting it from such a diffuse source would be far beyond us at present. And, although some types of transmutation are already routine in the nuclear industry, we do not know how to transmute hydrogen into other elements on an industrial scale. Even a simple nuclear-fusion reactor is currently beyond our technology. But physicists are confident that it is not forbidden by any laws of physics, in which case, as always, it can only be a matter of knowing how.

  No doubt a billion-tonne space station is not large enough to thrive in the very long run. The inhabitants will want to enlarge it. But that presents no problem of principle. As soon as they started to trawl their cube for hydrogen, more would drift in from the surrounding space, supplying the cube with millions of tonnes of hydrogen per year. (There is also believed to be an even greater mass of ‘dark matter’ in the cube, but we do not know how to do anything useful with it, so let us ignore it in this thought experiment.)

  As for the cold, and the lack of available energy – as I said, the transmutation of hydrogen releases the energy of nuclear fusion. That would be a sizeable power supply, orders of magnitude more than the combined power consumption of everyone on Earth today. So the cube is not as lacking in resources as a parochial first glance would suggest.

  How would the space station get its vital supply of evidence? Using the elements created by transmutation, one could construct scientific laboratories, as in the projected moon base. On Earth, when chemistry was in its infancy, making discoveries often depended on travelling all over the planet to find materials to experiment on. But transmutation makes that irrelevant; and chemical laboratories on the space station would be able to synthesize arbitrary compounds of arbitrary elements. The same is true of elementary particle physics: in that field, almost anything will do as a source of evidence, because every atom is potentially a cornucopia of particles just waiting to display themselves if one hits the atom hard enough (using a particle accelerator) and observes with the right instruments. In biology, DNA and all other biochemical molecules could be synthesized and experimented on. And, although biology field trips would be difficult (because the closest natural ecosystem would be millions of light years away), arbitrary life forms could be created and studied in artificial ecosystems, or in virtual-reality simulations of them. As for astronomy – the sky there is pitch black to the human eye, but to an observer with a telescope, even one of present-day design, it would be packed with galaxies. A somewhat bigger telescope could see stars in those galaxies in sufficient detail to test most of our present-day theories of astrophysics and cosmology.

  Even aside from those billion tonnes of matter, the cube is not empty. It is full of faint light, and the amount of evidence in that light is staggering: enough to construct a map of every star, planet and moon in all the nearest galaxies to a resolution of about ten kilometres. To extract that evidence in full, the telescope would need to use something like a mirror of the same width as the cube itself, which would require at least as much matter as building a planet. But even that would not be beyond the bounds of possibility, given the level of technology we are considering. To gather that much matter, those intergalactic scientists would merely have to trawl out to a distance of a few thousand cube-widths – still a piffling distance by intergalactic standards. But even with a mere million-tonne telescope they could do a lot of astronomy. The fact that planets with tilted axes have annual seasons would be plain to see. They could detect life if it was present on any of the planets, via the composition of its atmosphere. With more subtle measurements they could test theories about the nature and history of life – or intelligence – on the planet. At any instant, a typical cube contains evidence, at that level of detail, about more than a trillion stars and their planets, simultaneously.

  And that is only one instant. Additional evidence of all those kinds is pouring into the cube all the time, so astronomers there could track changes in the sky just as we do. And visible light is only one band of the electromagnetic spectrum. The cube is receiving evidence in every other band too – gamma rays, X-rays, all the way down to the microwave background radiation and radio waves, as well as a few cosmic-ray particles. In short, nearly all the channels by which we on Earth currently receive evidence about any of the fundamental sciences are available in intergalactic space too.

  And they carry much the same content: not only is the universe full of evidence, it is full of the same evidence everywhere. All people in the universe, once they have understood enough to free themselves from parochial obstacles, face essentially the same opportunities. This is an underlying unity in the physical world more significant than all the dissimilarities I have described between our environment and a typical one: the fundamental laws of nature are so uniform, and evidence about them so ubiquitous, and the connections between understanding and control so intimate, that, whether we are on our parochial home planet or a hundred million light years away in the intergalactic plasma, we can do the same science and make the same progress.

  So a typical location in the universe is amenable to the open-ended creation of knowledge. And therefore so are alm
ost all other kinds of environment, since they have more matter, more energy and easier access to evidence than intergalactic space. The thought experiment considered almost the worst possible case. Perhaps the laws of physics do not allow knowledge-creation inside, say, the jet of a quasar. Or perhaps they do. But either way, in the universe at large, knowledge-friendliness is the rule, not the exception. That is to say, the rule is person-friendliness to people who have the relevant knowledge. Death is the rule for those who do not. These are the same rules that prevailed in the Great Rift Valley from whence we came, and have prevailed ever since.

  Oddly enough, that quixotic space station in our thought experiment is none other than the ‘generation ship’ in the Spaceship Earth metaphor – except that we have removed the unrealistic assumption that the inhabitants never improve it. Hence presumably they have long since solved the problem of how to avoid dying, and so ‘generations’ are no longer essential to the way their ship works. In any case, with hindsight, a generation ship was a poor choice for dramatizing the claim that the human condition is fragile and dependent on support from an unaltered biosphere, for that claim is contradicted by the very possibility of such a spaceship. If it is possible to live indefinitely in a spaceship in space, then it would be much more possible to use the same technology to live on the surface of the Earth – and to make continuing progress which would make it ever easier. It would make little practical difference whether the biosphere had been ruined or not. Whether or not it could support any other species, it could certainly accommodate people – including humans – if they had the right knowledge.

  Now I can turn to the significance of knowledge – and therefore of people – in the cosmic scheme of things.

  Many things are more obviously significant than people. Space and time are significant because they appear in almost all explanations of other physical phenomena. Similarly, electrons and atoms are significant. Humans seem to have no place in that exalted company. Our history and politics, our science, art and philosophy, our aspirations and moral values – all these are tiny side effects of a supernova explosion a few billion years ago, which could be extinguished tomorrow by another such explosion. Supernovae, too, are moderately significant in the cosmic scheme of things. But it seems that one can explain everything about supernovae, and almost everything else, without ever mentioning people or knowledge at all.

  However, that is merely another parochial error, due to our current, untypical, vantage point in an Enlightenment that is mere centuries old. In the longer run, humans may colonize other solar systems and, by increasing their knowledge, control ever more powerful physical processes. If people ever choose to live near a star that is capable of exploding, they may well wish to prevent such an explosion – probably by removing some of the material from the star. Such a project would use many orders of magnitude more energy than humans currently control, and more advanced technology as well. But it is a fundamentally simple task, not requiring any steps that are even close to limits imposed by the laws of physics. So, with the right knowledge, it could be achieved. Indeed, for all we know, engineers elsewhere in the universe are already achieving it routinely. And consequently it is not true that the attributes of supernovae in general are independent of the presence or absence of people, or of what those people know and intend.

  More generally, if we want to predict what a star will do, we first have to guess whether there are any people near it, and, if so, what knowledge they may have and what they may want to achieve. Outside our parochial perspective, astrophysics is incomplete without a theory of people, just as it is incomplete without a theory of gravity or nuclear reactions. Note that this conclusion does not depend on the assumption that humans, or anyone, will colonize the galaxy and take control of any supernovae: the assumption that they will not is equally a theory about the future behaviour of knowledge. Knowledge is a significant phenomenon in the universe, because to make almost any prediction about astrophysics one must take a position about what types of knowledge will or will not be present near the phenomena in question. So all explanations of what is out there in the physical world mention knowledge and people, if only implicitly.

  But knowledge is more significant even than that. Consider any physical object – for instance, a solar system, or a microscopic chip of silicon – and then consider all the transformations that it is physically possible for it to undergo. For instance, the silicon chip might be melted and solidify in a different shape, or be transformed into a chip with different functionality. The solar system might be devastated when its star becomes a supernova, or life might evolve on one of its planets, or it might be transformed, using transmutation and other futuristic technologies, into microprocessors. In all cases, the class of transformations that could happen spontaneously – in the absence of knowledge – is negligibly small compared with the class that could be effected artificially by intelligent beings who wanted those transformations to happen. So the explanations of almost all physically possible phenomena are about how knowledge would be applied to bring these phenomena about. If you want to explain how an object might possibly reach a temperature of ten degrees or a million, you can refer to spontaneous processes and can avoid mentioning people explicitly (even though most processes at those temperatures can be brought about only by people). But if you want to explain how an object might possibly cool down to a millionth of a degree above absolute zero, you cannot avoid explaining in detail what people would do.

  And that is still only the least of it. In your mind’s eye, continue your journey from that point in intergalactic space to another, at least ten times as far away. Our destination this time is inside one of the jets of a quasar. What would it be like in one of those jets? Language is barely capable of expressing it: it would be rather like facing a supernova explosion at point-blank range, but for millions of years at a time. The survival time for a human body would be measured in picoseconds. As I said, it is unclear whether the laws of physics permit any knowledge to grow there, let alone a life-support system for humans. It is about as different from our ancestral environment as it could possibly be. The laws of physics that explain it bear no resemblance to any rules of thumb that were ever in our ancestors’ genes or in their culture. Yet human brains today know in considerable detail what is happening there.

  Somehow that jet happens in such a way that billions of years later, on the other side of the universe, a chemical scum can know and predict what the jet will do, and can understand why. That means that one physical system – say, an astrophysicist’s brain – contains an accurate working model of the other, the jet. Not just a superficial image (though it contains that as well), but an explanatory theory that embodies the same mathematical relationships and causal structure. That is scientific knowledge. Furthermore, the faithfulness with which the one structure resembles the other is steadily increasing. That constitutes the creation of knowledge. Here we have physical objects very unlike each other, and whose behaviour is dominated by different laws of physics, embodying the same mathematical and causal structures – and doing so ever more accurately over time. Of all the physical processes that can occur in nature, only the creation of knowledge exhibits that underlying unity.

  In Arecibo, Puerto Rico, there is a giant radio telescope, one of whose many uses is in the Search For Extraterrestrial Intelligence (SETI). In an office in a building near the telescope there is a small domestic refrigerator. Inside that refrigerator is a bottle of champagne, sealed by a cork. Consider that cork.

  It is going to be removed from the bottle if and when SETI succeeds in its mission to detect radio signals transmitted by an extraterrestrial intelligence. Hence, if you were to keep a careful watch on the cork, and one day saw it popping from the bottle, you could infer that an extraterrestrial intelligence exists. The configuration of the cork is what experimentalists call a ‘proxy’: a physical variable which can be measured as a way of measuring another variable. (All scientific measurements involve ch
ains of proxies.) Thus we can also regard the entire Arecibo observatory, including its staff and that bottle and its cork, as a scientific instrument to detect distant people.

  The behaviour of that humble cork is therefore extraordinarily difficult to explain or predict. To predict it, you have to know whether there really are people sending radio signals from various solar systems. To explain it, you have to explain how you know about those people and their attributes. Nothing less than that specific knowledge, which depends among other things on subtle properties of the chemistry on the planets of distant stars, can explain or predict with any accuracy whether, and when, that cork will pop.

  The SETI instrument is also remarkably finely tuned to its purpose. Completely insensitive to the presence of several tonnes of people a few metres away, and even to the tens of millions of tonnes of people on the same planet, it detects only people on planets orbiting other stars, and only if they are radio engineers. No other type of phenomenon on Earth, or in the universe, is sensitive to what people are doing at locations hundreds of light years away, let alone with that enormous degree of discrimination.

  This is made possible in part by the corresponding fact that few types of matter are as prominent, at those distances, as that type of scum. Specifically, the only phenomena that our best current instruments can detect at stellar distances are (1) extraordinarily luminous ones such as stars (or, to be precise, only their surfaces); (2) a few objects that obscure our view of those luminous objects; and (3) the effects of certain types of knowledge. We can detect devices such as lasers and radio transmitters that have been designed for the purpose of communication; and we can detect components of planetary atmospheres that could not be present in the absence of life. Thus those types of knowledge are among the most prominent phenomena in the universe.

  Note also that the SETI instrument is exquisitely adapted to detecting something that has never yet been detected. Biological evolution could never produce such an adaptation. Only scientific knowledge can. This illustrates why non-explanatory knowledge cannot be universal. Like all science, the SETI project can conjecture the existence of something, calculate what some of its observable attributes would be, and then construct an instrument to detect it. Non-explanatory systems cannot cross the conceptual gap that an explanatory conjecture crosses, to engage with unexperienced evidence or non-existent phenomena. Nor is that true only of fundamental science: if such-and-such a load were put on the proposed bridge it would collapse, says the engineer, and such statements can be true and immensely valuable even if the bridge is never even built, let alone subjected to such a load.