Heinrich Päs, The One (Andrew Crumey, Wall Street Journal)

Looking for "the one" has been a human preoccupation since time immemorial. For Heinrich Päs it is a question of theoretical physics - trying to explain how the universe, in all its apparent variety, is really the manifestation of a single underlying reality. But what kind of reality? "Is ‘the One' material? Is it spirit or information? Is it math? None of the above? There is no easy resolution yet." Rather than any definite answer, what Professor Päs offers is a heady mix of history, philosophy and cutting-edge theory that is fascinating, provocative, and at times infuriating.

The first part of the book sets the problem in the context of quantum physics. In the 1920s Werner Heisenberg famously showed there must be fundamental limits on what can be observed. It's possible to measure the exact speed of an electron, or to know precisely where it is at a given moment, but the two things can't be done simultaneously. Heisenberg initially explained this uncertainty as a consequence of experimental disturbance - much like a thermometer's own warmth affecting what it's placed in. Niels Bohr showed this could not be correct. In Bohr's opinion, there is no actual speed or position waiting to be measured - those are created by measurement itself, with either quantity giving rise to a certain picture of reality. The pictures are not contradictory, since they can never be seen simultaneously, but instead complementary; and Bohr extended this idea of complementarity in what came to be known the Copenhagen interpretation of quantum theory. The fundamental bits of the universe are neither particles nor waves, but can look like either, depending how we view them. An electron is everywhere or nowhere, until the moment its position is determined.

As counter-argument, Erwin Schrodinger thought about a box containing a cat, a canister of cyanide and a radioactive sample emitting fast electrons. Should one of those electrons hit a trigger on the canister, gas will be released, killing the cat. According to the Copenhagen interpretation, every part of the apparatus could be viewed as a quantum wave, collectively constituting a single wave function embracing all possible outcomes. Surely, Schrodinger argued, it would be absurd to say the cat was neither alive nor dead until the box was opened and the wave function "collapsed" to a definite result? As a further twist, imagine someone outside the laboratory, waiting to open the door and see if what stood within was a smiling cat-owner or weeping one.

A solution was proposed by Hugh Everett in the 1950s and came to be known as the many-worlds interpretation. In that view, the wave function never collapses - every possibility is real, the universe constantly bifurcating into parallel realities. But as well as Schrodinger's cat, there was another paradox to confront. Albert Einstein, Boris Podolsky and Nathen Rosen had argued that quantum theory implied that if a particle split, its parts could remain "entangled" in the sense that observing one would seem to instantaneously affect the other across any distance. They thought it proved the theory must be wrong, yet the effect has been experimentally verified, and it underpins another solution to Schrodinger's paradox, pioneered by Heinz-Dieter Zeh in the 1970s. Known as decoherence, the idea is that quantum systems get entangled with their surroundings in a way that quickly smooths out their "waviness", restoring the familiar laws of classical physics. It would take the briefest of instants for nature to decide the cat's fate, without the box being opened.

The theories of Everett and Zeh play a major role in Professor Päs's book; and rather than see them as rivals, he supports both. Imagine Everett's multiverse as a single all-embracing wave function. Decoherence could then explain why we have the impression - or indeed illusion - of a universe made of disconnected bits and pieces, where most possibilities are never realized. Really, all is One.

For Professor Päs, it is scientific vindication of an ancient insight. "We can still observe today that the idea of an all-encompassing unity is common across many indigenous religions in the Americas, Africa, Asia, or Oceania that often embrace a sacred or spiritual concept of nature." The question, then, is why it has taken so long for science to catch up. That is the theme of the book's second part, which explores the search for one-ness through history. "It has inspired Plato's dialogues, Botticelli's painting The Birth of Venus, Mozart's opera The Magic Flute, and a major part of Romantic poetry from Goethe to Coleridge and Wordsworth." What all of these express, according to Professor Päs, is "monism", and what his lengthy historical excursus demonstrates all too well is a complementarity between science and the humanities. As Professor Päs presents it, monism is rather like energy; it comes in many forms, but they're all mutually interchangeable and basically the same thing. Yet rather than see everything as being like everything else in some grand unified soup of ideas, a philosopher, historian or art critic would surely care more about the specific details - intellectual, historical, cultural, linguistic - that make each ingredient unique.

Professor Päs homes in on a particular kind of monism - the idea that God is not separate from nature but an immanent part of it - and uses it as scaffolding for a kind of historical conspiracy theory that sees every form of monism as having been challenged as heresy. This, apparently, is why it took so long for quantum entanglement to be discovered, though the insight existed long before, for instance in the writings of the ninth-century Irish philosopher John Eriugena, who "drew on Platonism to develop a radical reinterpretation of the earthly and divine realities and the Christian notion of heaven, hell, and the Fall of man - and what's more, a monistic philosophy bearing striking similarities to the workings of quantum mechanics." As well as anticipating Heisenberg, the Irishman anticipated Hegel, Schelling and Kierkegaard by a thousand years, though even Eriugena was late to the game. "Accepting ‘love' as a metaphor for entanglement indeed makes it possible to read the biblical Genesis as an allegory for quantum decoherence."

The only way such silliness can be taken remotely seriously is if one accepts the possibility of revelation as a means of acquiring knowledge. And in the multiverse, anything is possible. Professor Päs wonders if hallucinogenic drugs might serve as gateway to experiencing "quantum holism", and has even proposed an experiment to see if drugged subjects can experience a "nonclassical perspective." It's tempting to speculate about the conditions under which he may have come up with that idea. Emerging from the weird trip that fills the middle of his book, we return to safer ground as Professor Päs goes back to what he does best.

For Everett's idea of a universal wave function to be mathematically meaningful, there needs to be a way of incorporating gravity into quantum theory. Einstein never tried combining his equations of general relativity with Schrodinger's wave equation, but an attempt was made in the 1960s by Bryce de Witt, and led to a curious result. There seemed to be no place left for time - it cancelled out like a redundant term. Some have seen this as an indication that time itself is an illusion. What all agree is that quantum gravity remains the biggest unsolved problem in physics.

String theory raised enormous hopes, dampened when it became apparent how many different versions might be possible - an entire new "landscape" of parallel universes. Most promising for Professor Päs is renewed interest in "wormholes", theoretical tunnels connecting different parts of space. They were shown to be theoretically possible by Einstein and Rosen in 1935, soon after they had worked with Podolsky on entanglement. The two phenomena were assumed to be unrelated until 2013, when work on black holes led to a conjecture summarised by the men's initials: "ER=EPR". Gravitational wormholes and quantum entanglement might be the same thing. For Professor Päs, the idea "gains in plausibility once one approaches it from the parallels between Everett's many worlds and the multiverse that is predicted in cosmic inflation and married with the string theory landscape." Though having already seen Professor Päs marry quantum theory with the book of Genesis, we might wish to approach his matchmaking with caution.

What, then, is the One? Some monists say mind, others matter, or something else. It's hard to say exactly which kind Professor Päs is, since he considers them all the same. Yet for all its frustrations, his dizzying tour through the monist multiverse is engrossing and rewarding.

Giorgio Parisi, In A Flight of Starlings (Andrew Crumey, Wall Street Journal)

Why is a flock of starlings like a glass of water? The answer is that both are complex systems with many parts acting together as one. Nobel Prize-winning theoretical physicist Giorgio Parisi has spent decades studying complex systems of a non-biological kind, and his detour into bird behaviour serves as opener to an interesting collection of essays reflecting on his long career in science.

It's not hard to see why starlings should have caught Professor Parisi's attention. Their flocking behaviour – called murmuration on account of the sound of their beating wings – is one of nature's most beautiful spectacles. The swirling patterns seem almost like an orchestrated manouevre – is one bird in charge, or is some kind of hive mind at work? Parisi and his colleagues saw it differently. Just as water molecules tug each other with electrical force, there must be instinctive behavioural forces steering the birds.

Parisi's team filmed starling murmurations from multiple angles and analysed hundreds of images. They found that the swarms were broadly disk-shaped – the patterns we see from the ground come largely from sudden changes of the disk's orientation. Surprisingly, the birds were discovered not to be densest at the centre – as in a galaxy of stars – but at the edges. This was the surest indication of the force driving the flock – an urge to bunch together as protection against avian predators. Yet equally strong is the need to avoid collision, so the resulting motion resembles cars on a freeway, with outer birds flying virtually wingtip to wingtip while maintaining clear space ahead and behind.

It was neither birds nor water molecules that won Professor Parisi the 2021 Nobel Prize, but discoveries stemming from a different kind of complex system. Atoms in a solid can be viewed as miniature magnets, called spins, whose north poles usually point in random directions. Yet like birds influencing each others' flight, the spins of iron atoms have a tendency to copy their nearest neighbours; and if a hot lump of iron is cooled below a certain critical temperature, all the spins come into precise alignment, making the whole lump magnetic. The metal is then said to have undergone a phase transition, similar to water crystallizing as ice.

Substances such as molten glass or wax behave differently as they cool. Rather than having a precise moment of solidification, they gradually become firmer – sometimes very slowly indeed. Professor Parisi describes a curious experiment to see how long a sample of pitch would take to drip through a funnel. It was begun in 1927 and so far only nine drops have fallen. There's a live feed of it at thetenthwatch.com.

The magnetic phase transitions of some metal alloys – known as spin glasses – are similarly gradual, and it is the theory of these substances that earned Professor Parisi the Nobel Prize. The key to their behaviour is that while some of their constituent spins try to align with their neighbours, others strive to do the opposite. Professor Parisi compares it to a group of people who like or dislike one another, and are trying to form stable subgroups. "I want to be friends with Mr White and Mr Green, for example, but unfortunately they happen to detest each other, making it difficult for me to be very close to them both at once." There can be no perfect solution for the group as a whole, but there may be many arrangements that are reasonable compromises. Something like this happens with spin glasses – there are many ways their atoms might configure themselves. Seeing this hidden order amid apparent disorder – the possibility for multiple equilibrium states – was one of Professor Parisi's most significant breakthroughs.

The possible applications of Professor Parisi's theory are far-reaching. He writes, "The elementary agents can be spins, atoms or molecules, neurons, cells in general – but also websites, financial traders, stocks and shares, people, animals, components of ecosystems, and so on." The devil, though, is in the detail. Even ordinary window glass "is not fully understood by physics", because "it is made up not just of silicon but of many impurities, many different types of molecules of different sizes, all mixed up together." If the theory of starling flocking can't predict which way the birds will turn next, what hope is there for a spin-glass theory of economics?

Professor Parisi's initial inspiration came not from everyday reality, but from the rarefied world of elementary particle physics, which he worked on in the 1970s. He describes how the quark model emerged in preference to rival theories, and wistfully recalls how an insight he failed to spot then might have won him a Nobel Prize far sooner.

This leads him to offer wider speculations about intuition and mathematical discovery. Drawing on his own experience, Professor Parisi supports the idea that creativity is a four-stage process of preparation, incubation, illumination and verification. He attributes this idea to the mathematicians Henri Poincare and Jacques Hadamard but could equally have cited Graham Wallas who codified it in 1926, or the plethora of websites that state is as fact. What Professor Parisi doesn't say is whether there is any evidence, beyond personal introspection and anecdote, that the four-stage model is actually true.

He also says that, "Detailed studies have shown how in a Shakespeare tragedy the dramatic tension... is quite low at the beginning of the play, reaches a maximum at around its midpoint, and then decreases toward the end." I can only assume he's never seen Hamlet, and I'm guessing that by "detailed studies" he means a nineteenth-century book by Gustav Freytag whose dubious legacy is the legion of how-to-write-a-screenplay tutorials that nowadays misrepresent it.

Some of the essays in this book arose from articles or public lectures, others from interviews, making the collection as a whole more like a series of snapshots rather than a continuous narrative. While the scientific explanations are admirably lucid, the tone is somewhat dry, and the human side of research gets less attention than one might hope for. In 1968 Professor Parisi was among several hundred students who voted to occupy the physics department of the Sapienza University of Rome. He says he can add little to the "rivers of ink" already devoted to that turbulent year, instead recalling the students' "real sense of cameraderie", the fears of the departmental librarian, and the "respectful silence" the protesters maintained in the reading room. Science has been the professor's lifelong concern, seemingly to the exclusion of just about everything else, though in one candid moment he does admit to an indulgence. Dining with a colleague at a restaurant in the 1970s, he couldn't resist the cakes. "They had six kinds, and I had a slice of each."

Samuel Graydon, Einstein in Time and Space (Andrew Crumey, Literary Review)

"I lack both the natural aptitude and the experience to deal properly with people," Albert Einstein wrote in 1952. Having lived the previous three decades as a global celebrity, he could hardly have lacked experience; yet judging by Samuel Graydon's intriguing, mosaic-like portrait of the great physicist, he was woefully lacking in aptitude.

Graydon says biographers were long hampered by Einstein's secretary Helen Dukas, who in her role as literary executor suppressed "anything that painted Einstein as less than either a mystery or a secular saint." After she and her co-trustee Otto Nathan died in the 1980s, the floodgates opened and a fuller picture emerged. The Einstein sketched here in 99 short chapters is not only the unworldly genius and quotable sage of popular imagination, but also someone who could excuse his own hurtful behaviour as an unavoidable consequence of his essential nature. "I don't believe in free will," he said in 1932, and to his second wife made it known that he "believed that people were not naturally monogamous, and that the concepts of emotional and physical faithfulness were societal constructs, falsities born of decorum and correctitude." So she just had to make herself absent whenever his mistress would be visiting, often departing in tears.

Einstein's flawed reasoning in human affairs contrasts starkly with his intellectual achievements, which Graydon – a science editor for the Times Literary Supplement – summarises clearly and succinctly. It was in the annus mirabilis of 1905 that Einstein, a 26-year-old patent clerk, produced four landmark papers giving the world the principle of relativity, the equivalence of mass and energy, proof of the existence of atoms, and the idea that light waves could act like particles. It was not his article on relativity but rather the one on light quanta that Graydon says was "the most revolutionary paper of his miracle year." It was the slowest to be accepted as valid, and the one for which Einstein was awarded the Nobel Prize in 1922. Before then he had extended relativity to include gravitation, explaining it as the warping of spacetime. Legend has it that a crucial step occurred when Einstein saw a man fall from a building, prompting the sudden idea of an equivalence between gravitation and acceleration. Actually his "happy thought" was no more than that; he never saw anyone fall, but simply offered the image to a New York Times journalist who chose to present it as fact – a modern counterpart to Newton's apple.

Einstein knew he was special, long before anyone else did. "Strenuous intellectual work and looking at God's Nature are the reconciling, fortifying, yet relentlessly strict angels that shall lead me through all of life's troubles," he wrote grandiloquently to his first girlfriend as a way of finishing with her. His next – a "gloomy, ugly girl with a limp" according to disapproving friends – fell pregnant, so he married her, against his parents' wishes. The marriage cooled and Einstein strayed, finding comfort with his cousin Elsa, to whom he described his wife as "an employee I cannot fire." The Einsteins parted in 1914, their two sons going with the mother. One later developed schizophrenia and spent years in care. Einstein didn't write, professing "an inhibition that I am not fully capable of analysing." To fill the vacant post of wife, Elsa was an obvious but not immediate choice, since Einstein had also taken a fancy to her daughter Ilse. Einstein declared he was prepared to marry either, and it was up to them to choose. Elsa gave the choice to Ilse, so Einstein got Elsa. Even by the standards of 1918 this was, as Ilse generously put it, an "odd and certainly also highly comical affair."

Einstein at this point had already completed his greatest works and been recognised by his peers. World fame came in 1919 when his prediction of the gravitational bending of starlight was confirmed by astronomers observing a total eclipse. The rest of his scientific life was mainly taken up with trying to explain electromagnetic force as a warping akin to gravitation. Stubborness and perseverance had previously served him well, but his quest for a unified field theory went nowhere – a dead horse he insisted on flogging right up to his death in 1955. Those years of creative failure were when he was most avidly feted, his every utterance deemed worthy of record. Someone once found him doggedly trying to fix a bent paperclip. "This would make a good anecdote about me," he said.

Einstein's life and theories have been covered in countless books, at every possible level of detail. Samuel Graydon's patchwork of conveniently bite-sized chunks strikes a nice balance, though his admission that two chapters are "lightly fictionalised" set me wondering how much license he might have taken elsewhere. Did Einstein and a friend really "discuss whether light is a wave or a particle" in 1897, as Graydon states? It sounds unlikely. The advantage of Graydon's approach is the way it highlights key incidents and telling comments. Einstein told the novelist C.P. Snow, "the best creative work is never done when one is unhappy." Yet hadn't he cracked the theory of relativity against the backdrop of an unhappy marriage? A solution might lie in a remark Einstein made in his fifties. "I live in that solitude which is painful in youth, but delicious in the years of maturity." People were a convenience for him, not a necessity.

Robert M. Sapolsky, Determined. Kevin J. Mitchell, Free Agents. (Andrew Crumey, Wall Street Journal)

Is any choice we make truly free? You might decide to answer “yes” right now, just to prove the point, but is your supposedly free choice actually an inevitable result of your personality, your background, the kind of day you’re having? If we could rewind history and repeat the moment, would you always do the same thing, as predictably as clockwork?

It’s an ancient philosophical question, lately refreshed by advances in science, and books from a pair of distinguished neuroscientists tackle it from opposing sides. Robert M. Sapolsky’s “Determined” takes the prosecution’s role with a lively and provocative account of consciousness in which free will is only an illusion. In opposition, Kevin J. Mitchell offers an eloquent defense of our common-sense understanding of the mind in “Free Agents: How Evolution Gave Us Free Will.” Both books are excellent: Neither fully convinced me.

The star witness for the case against free will is the 18th-century French mathematician Pierre-Simon Laplace, who maintained that the laws of nature are completely deterministic. If you knew to the finest detail the speed, direction and other conditions of a ball entering a roulette wheel, you could predict exactly where the ball would land. Extend that thinking to the universe itself, and everything that happens—including your own thoughts as you read these words—must be a direct consequence of subatomic motions. Mr. Sapolsky concurs. “The world is deterministic and there’s no free will.” Consciously or unconsciously, we always act for a reason, there’s a reason for that reason, and so on—a chain of causality where chance plays no part.

This is a minority opinion among philosophers and scientists, most of whom prefer compatibilism, the idea that because life is so unpredictable in practice, we can meaningfully speak of human beings as having free will. That isn’t good enough for Mr. Sapolsky, a professor of biology and neurology at Stanford University, who calls his position “hard incompatibilism.”

Mr. Mitchell, a researcher in genetics and neuroscience at Dublin’s Trinity College, also has his doubts about compatibilism, because it cedes too much ground to determinists. He insists that living things act in ways that can’t be reduced to mechanistic causes. Mr. Sapolsky estimates support for compatibilism at “roughly 90 per cent of philosophers,” so he and Mr. Mitchell are intellectual extremists with big cases to prove. Mr. Mitchell has to explain how our minds can be independent of the underlying physics and chemistry of our bodies. Mr. Sapolsky has to explain why life without free will is still worth living.

After Laplace, another key witness is the 20th-century American neuroscientist Benjamin Libet. In the 1980s, Libet asked experimental subjects to push a button at a moment of their own choosing, and to note the time at which they made their choice. Electrodes recording their brain activity revealed a sudden spike just before each moment of conscious choice. Many see his as proof that subconscious processes are the true masters of our actions. Mr. Mitchell thinks otherwise: He discusses the methodology at length and calls the spike “an artifact of the way the data are analyzed.” More surprisingly, Mr. Sapolsky also rejects “Libetian-ish neuroscience,” saying the experiment failed to address the important question, “Where does intent come from?”

One way to address these questions is to invoke the notion of a soul—though its existence wouldn’t necessarily remove the difficulties. Perhaps souls may be the judges of right and wrong, but if God makes all the choices, our fate is predestined. Dualism—the idea that matter and mind are wholly separate—is likewise indecisive on free will, and has little support among neuroscientists. Messrs. Mitchell and Sapolsky stay silent on religion and explicitly reject dualism. Both believe the mind to be a function of neurons and synapses, axons and dendrites. Their books are replete with detailed explanations of what those things are, what they do, and how their flow of neurotransmitters affects the way we think, feel and behave.

Mr. Sapolsky says there is no single “slam dunk” argument that can prove free will to be an illusion. Instead he offers a mass of circumstantial evidence drawn from a range of disciplines including social science, economics and psychology, all of which illustrates how genetics, culture and daily life can steer a person’s choices. The best predictor, for instance, of whether a judge will grant a parole application is how long ago he or she ate a meal. Telling a lie makes you more likely to wash your hands soon afterward. Mr. Sapolsky loquaciously relates his examples in prose that is often humorous, occasionally grating, yet always highly readable.

More sober and conventional in tone, Mr. Mitchell’s book focuses on evolutionary biology, viewing living organisms as self-directing “agents” and charting their development from the earliest single cells to the appearance of human intelligence. Mr. Mitchell’s answer to a rigid chain-of-causes determinism comes in the form of quantum indeterminacy and thermal fluctuation—the fuzziness of events at the subatomic level.

He proposes an updated version of a theory of free will advocated in the late 19th century by the psychologist William James. Quantum-level randomness, Mr. Mitchell suggests, seeds the initial stage of each neural process, and a kind of Darwinian fitness selection among the possible reactions follows, resulting in “one possible action winning the competition and being released while all the others remain inhibited.” Mr. Mitchell says his two-stage model “powerfully breaks the bonds of determinism, incorporating true randomness into our cognitive processes while protecting the causal role of the agent itself in deciding what to do.”

This type of two-step model gets short shrift from Mr. Sapolsky. “Thus, ‘our brains’ generate a suggestion, and ‘we’ then judge it,” he writes. He labels this notion a variety of dualism that “sets our thinking back centuries.” He argues that quantum effects are not likely important in the workings of the brain. Some have suggested that phenomena known as tunneling and entanglement might work to free the brain from rigid causality, but Mr. Sapolsky dismisses these suggestions, citing a further phenomenon called decoherence. There’s no need to explain here what those all mean; it’s sufficient to say that Mr. Sapolsky’s argument misses the mark. Quantum randomness affects us all the time.

To understand why, think of a Geiger counter placed near a sample of radioactive metal. Every so often, an atom in the metal spontaneously decays and the Geiger counter clicks: a macroscopic event dictated by subatomic randomness. Each day we are exposed to low-level background radiation from many natural sources. If we’re unlucky, one of those particles might break a chemical bond in our body and initiate a chain of events that will result in cancer. Can we claim such events were ordained by necessity? Only if we think that quantum behaviors are themselves governed by a hidden determinism— something that Einstein believed, but which physicists now generally dismiss.

Does that spell victory for Mr. Mitchell? I’d say it’s a dead heat. Quantum randomness implies the future is not yet written, but it doesn’t prove the existence of free will. Mr. Mitchell’s model relies on randomness during the initial preconscious stage, but if that is where our choices are really made, then we’re prisoners of chance rather than determinism. If his claim is instead that choice and intention are formed within the second, conscious stage, how that actually happens is yet to be fully explained.

Having made it through the combined 800 pages of these two fine books, I’m left in a position both authors would doubtless deride—a free-will agnostic, sitting on the fence. As to which book I prefer, my vote goes to “Determined,” which is outstanding for its breadth of research, the liveliness of the writing, and the depth of humanity it conveys. As a self-proclaimed hard incompatibilist, Mr. Sapolsky has had to wrestle with the moral implications of his own theory. If there’s no free will, there’s no reason to praise or blame anyone for what they do. Rather than punish criminals, he says, we should quarantine them as sufferers of a condition over which they have no control. That idea is unthinkable in the United States but seriously entertained in Norway—a societal difference that Mr. Sapolsky attributes to genetics and environment. The trouble, as he acknowledges, is that in every culture, “we like to punish wrongdoers. It feels great.” And that’s in our genes too.

Kelly and Zach Weinersmith, A City on Mars. (Andrew Crumey, Literary Review)

Do you fancy living in space? Some people are prepared to pay Virgin Galactic almost half a million dollars for five minutes of weightlessness, so demand is clearly there among the deep-pocketed. And for generations of science fiction fans, life off-planet has been a dream forever just around the corner. If Elon Musk is to be believed, by 2050 there will be a million people living on Mars. Would you want your progeny to be among them? That’s the question posed by the authors of this book. Kelly Weinersmith provides the jokey, fact-filled text, while her husband, Zach, intersperses it with cartoon illustrations. Both are self-confessed space junkies, and after years of researching the issue they’ve become ‘more pessimistic than almost everyone in the space-settlement field’.

The book’s title is slightly misleading, since Mars is only one part of the enormous cosmic ground they seek to cover. The pros and cons of Moon bases, orbiting space stations and long-distance flight are all laid out in detail, not just from a technological and scientific perspective, but also in terms of the social, psychological and legal issues they raise. The only really compelling reason the authors can find for space colonisation is ‘because it’s awesome’ – the greatest possible manifestation of humanity’s instinct for adventure. Other instincts could get in the way, however.

In 1991, eight volunteers and some assorted livestock entered Biosphere 2, a hermetically sealed compound in Arizona. By creating a kind of self-sustaining mini-Earth, the project leaders hoped to show how life could be lived beyond our planet. The two-year mission quickly ran into both practical and personal problems, as the team split into two opposing factions: ‘With more than a year to go, they were no longer on speaking terms. They stopped dining together or even making eye contact.’ One volunteer said afterwards, ‘Perhaps on Mars, with the safety of home at least forty-eight million miles away, we would have been able to pull together. But then again, perhaps not.’

Real astronauts have done a far better job of getting along together, but they can’t be considered average people and the human data from six decades of space flight is skimpy. The total number of man hours spent on the lunar surface to date is just over eighty. The total number of woman hours is zero. The longest continuous time that any person has spent in orbit is 437 days, achieved by Valeri Polyakov aboard the Russian space station Mir. That’s certainly long enough to get to Mars, which could be reached in as little as six months, but the health effects of longer-term weightlessness are unknown. Consider also the basic fact that on Earth things go down the toilet and in space there is no down. In zero gravity, it’s necessary to give bowel movements a helping hand to send them in the desired direction. Get it wrong and your capsule could be host to a floating object that is known in NASA circles as a ‘brown trout’.

At least on the Moon or Mars there will be some gravity, and also less exposure to harmful solar radiation, if home is buried under a thick layer of rock. Whenever the inhabitants venture out, though, one problem they will encounter is dust of a kind quite unlike any on Earth. Called regolith, it consists of fragments shattered by meteoric impacts and statically charged through solar radiation. It’s sharp, sticky and quickly coats anything that comes into contact with it – and colonisers won’t be able to wash it off with soapy water. It will be especially troublesome on Mars, where dust storms are frequent. The authors mention an unmanned Mars lander whose drill tool quickly packed in, not only because it was gummed up with regolith but also because the pesky dust had fouled its solar panels, cutting off its energy supply. On the subject of energy, nuclear power will probably provide the answer for human colonies, so expect large amounts of fuel flying overhead on its way to space. Let’s hope there aren’t any suborbital mishaps.

If there are to be genuine space cities then their continued existence will depend on space sex. Whether it has ever been tried or even simulated is a question that astronauts have been asked many times, and about which they’re naturally reticent. Two who were training together for the Space Shuttle Endeavour, Mark Lee and Jan Davis, fell in love and secretly married before lift-off in 1992, and are the most obvious candidates for the 500-mile-high club. Yet the authors doubt they would have had any opportunity for conjugal activity: ‘A shuttle has about as much living space as a school bus, only with a crew of seven, a sealed atmosphere, and no shower.’ The authors do, however, share their ‘favorite space sex rumor’, which is that NASA’s neutral buoyancy tank was used to investigate the feasibility of weightless copulation, revealing that it worked best if a third person was there to ‘push at the right time in the right place’. Certainly more fun than steering turds.

Many see space as the ultimate destination of a species bound to outlive, outgrow or simply wreck its home planet. What the Weinersmiths emphasise in their informative and entertaining book is that an overheated, overpopulated and totally polluted Earth would still be infinitely better than whatever we might create elsewhere. Colonising space won’t unify humanity or end warfare, they insist, and as places to live, the Moon and Mars are horrible. But they’re awesome, and that’s why we’ll go there.