I’ve never been a big fan of the idea that scientists, because they are so rational, should run the world. First, scientists are often as nutty as the rest of us, or nuttier. Second, leadership requires more than reason. Think Captain Kirk versus Mr. Spock. But recent events make the idea of a Scientist King more appealing. Also, I think of certain scientists as wise, even statesmanlike. They possess a quiet authority that makes you trust their judgment, and not just on scientific matters. Physicists Hans Bethe and Steven Weinberg come to mind, and so does cosmologist Martin Rees. Rees, who is based at the University of Cambridge and is Britain’s Astronomer Royal, has had an illustrious career, which you can read about here. In addition to his decades of contributions to astrophysics and cosmology, he has also spoken out on threats facing humanity. I first met Rees in 1990 at a cosmology conference in Sweden. We have crossed tracks a couple of times since then, most recently at a meeting in Switzerland that Rees attended via cyberspace. After I wrote a column on Rees’s remarks, we had the following email exchange. –John Horgan

Deep down in your gut, do you think we're doomed?

No, I don’t. But we’ll surely have a bumpy ride through this century. The world’s growing and more demanding population puts our natural environment under strain, and could trigger dangerous climate change and mass extinctions if “tipping points” are crossed. But to reduce these risks, we don’t need to put the brakes on technology; on the contrary, we need to enhance our understanding of nature, and deploy appropriate technology (zero-carbon energy, for instance) more urgently.

Novel technologies – bio, cyber and AI – could be transformative. They may offer new solutions; on the other hand, they create new vulnerabilities. It’s hard to be optimistic about a peaceful world if a chasm persists, as deep as it is in today’s geopolitics, between the welfare levels and life-chances in different regions.

Which apocalypse worries you most these days?

I wouldn’t use the word “apocalypse” but I think we have new grounds to be anxious. In the next decade or two what worries me most are issues I highlighted in my book Our Final Century 15 years ago: the empowerment of individuals or small groups by powerful technologies, whose actions, whether errors or intentionally malicious, can cascade globally. Cyberattacks are already high on our radar. And I’d guess that biothreats soon will be too.  Back in the early days of recombinant DNA research, leading biologists met in Asilomar, California,  and agreed guidelines on what  experiments should and shouldn’t be done. But now, 40 years after Asilomar, things are very different:  the research community is far more broadly international, and more influenced by commercial pressures. I’d worry that whatever regulations are imposed, on prudential or ethical grounds, can’t be enforced worldwide  – any more than the drug laws can --- or the tax laws. Whatever can be done will be done by someone, somewhere.

And that’s a nightmare.  An atomic bomb can’t be built without large scale special-purpose facilities. But biotech involves small-scale, dual-use equipment. Indeed, biohacking is burgeoning even as a hobby and competitive game. We  know all too well that being tech-savvy  doesn’t guarantee balanced rationality. The global village will have its village idiots and they’ll have global range. Such threats will pose an intractable challenge to governments and aggravate the tension between freedom, privacy and security.

These threats are of course additional to the risks of nuclear war or of state-level cyber-attacks on national infrastructure.

Should we start a colony on Mars in case things get really bad here?

I disagree strongly with Elon Musk, and with my Cambridge colleague Stephen Hawking, who advocate rapid build-up of  large-scale Martian communities.  It’s a dangerous delusion to think that space offers an escape from Earth's problems. We’ve got to solve these here.  Coping with climate change may seem daunting, but it’s a doddle compared to terraforming Mars. There’s no ‘Planet B’ for ordinary risk-averse people.

However, I think (and hope) that there will be bases on Mars by 2100. But the practical case for sending people gets weaker as robots improve. So the only manned ventures will be high-risk, cut price, and privately sponsored –undertaken by thrill-seekers  prepared to accept one-way tickets. They’re the people who will venture to Mars.

But we (and our progeny here on Earth) should cheer on these brave adventurers. The space environment is inherently hostile for humans, So, precisely because they will be ill-adapted to their new habitat, the pioneer explorers will have a more compelling incentive than those of us on Earth to re-design themselves. They’ll harness the super-powerful genetic and cyborg technologies that will be developed in coming decades. These techniques will, one hopes, be heavily regulated on Earth; but “settlers” on Mars will be far beyond the clutches of the regulators. This might be the first step towards divergence into a new species. So it’s these spacefaring adventurers, not those of us comfortably adapted to life on Earth, who will spearhead the post-human era. So we (or our Earthbound progeny) should cheer them on.

You've been talking about science bumping into limits lately. Is this a new concern?

It’s absolutely not a new concern for me. In fact I said in my very first BBC radio talk, given when I was still a graduate student, that some discoveries might have to await the emergence of “a species more intelligent than ourselves.”

In every subject there will, at every stage, be “unknown unknowns.” (Donald Rumsfeld was famously mocked for saying this in a different context – but of course he was right, and it might have been better for the world had he become a philosopher). But there is a deeper question. Are there things that we’ll never know, because they are beyond the power of human minds to grasp? Are our brains matched to an understanding of all key features of reality?  I’m confident that answers to many current mysteries will come into focus in the coming decades.  But maybe not all:  there may be phenomena, crucial to a full understanding of physical reality, that we are not aware of, any more than a monkey comprehends the nature of stars and galaxies.

So I think we should be open-minded about the possibility that some fundamental truths about nature could be too complex for unaided human brains ever to fully grasp.  Indeed, perhaps we'll never understand the mystery of these brains themselves -- how atoms can assemble into “grey matter” that can become aware of itself and ponder its origins.  Or perhaps any universe complicated enough to have allowed our emergence is for just that reason too complicated for our brains to understand.

The quest for a unified theory of physics seems to have stalled. Could it turn out to be a dead end?

The history of physics of course features successive “leaps” and unifications: Newton, Maxwell, Einstein, quantum mechanics, quantum electrodynamics, and the “standard model.” There are surely deeper regularities that still elude us. But these future unifications are likely to be harder to find than the earlier ones. This is partly because there may not be such direct experimental tests, and partly because they involve an especially big jump in scales. For instance, any unification of gravity and quantum theory is likely to involve the Planck length – twenty powers of ten smaller than an atomic nucleus. That’s the scale on which empty space may have some intricate structure. This may be of the kind envisaged by string theory or loop quantum gravity  -- or it could be something quite different. The optimists hope that some such theory may one day gain credibility by accounting for the unexplained numbers in the standard model, or perhaps by new cosmological observations that probe closer to the Planck scale. We don’t know which, if any, of current ideas may be on the right lines.

I think it’s important that some people should continue to tackle this “Everest problem” – to seek a testable theory from many perspectives..  It’s presumptuous (as some people like Peter Woit have done) to deride the way some manifestly brilliant people choose to dedicate their scientific lives. [See Woit's response to this comment.] But we must be open-minded about the possibility that the true theory may simply be too difficult – but we need to explore far longer and harder before concluding that.   In that sense – and that sense alone – the quest may be deemed a “dead end” by far-future historians.

Is inflation, the theory of cosmic creation, dead?

It’s probably best to think of inflation as a “scenario” rather than a specific theory. In that generic sense it’s very much alive – indeed it remains the best idea we have to account for the scale of the cosmos and the character of the fluctuations. But the trouble is that we have no firm ideas on the physics that prevailed at the huge energies where inflation would have occurred (a trillion times higher than can be reached in a particle accelerator). Measurements of the tilt, the gaussianity and the tensor/scalar ratio of the fluctuations set constrains on that physics and may lead to some new tests or refutations but “inflation” is a great concept and remains a good bet.

Are multiverse theories testable? If not, why does anyone take them seriously?

There are some variants of “inflation” – for instance Andrei Linde’s “eternal inflation”--that lead to many “big bangs” and not just one. But as I’ve just noted, we don’t know whether the actual physics at the relevant ultra-high energies has the specific features that his model requires. Nor do we know whether the separate big bangs (if they occurred) would have cooled down to be governed by the same laws that we observe. There are some theories that allow more than a googol of different vacuum states, in each of which the microphysics would be different.

Could this be true? A challenge for 21st century physics is to answer two questions. First, are there many “big bangs” rather than just one?  Second – and this is even more interesting -- if there are many, are they all governed by the same physics?

Until about 50 years ago we weren’t sure whether there was a big bang at all. Now we have enough evidence to delineate cosmic history back to the ultra-dense first nanosecond – with as much confidence as a geologist inferring the early history of our Earth and with precision better than a few percent.  So in 50 more years, it’s not overoptimistic to hope that we may have a “unified” physical theory, corroborated by experiment and observation in the everyday world, that is broad enough to describe what happened in the first trillionth of a trillionth of a trillionth of a second – where the densities and energies were far higher than the range where current theories apply. If that theory predicts multiple big bangs we should take that prediction seriously even though it can’t be directly verified (just as we give credence to what Einstein’s theory tells us about the unobservable insides of black holes, because the theory has survived many tests in domains we can observe).

It’s sometimes claimed that domains that are in principle unobservable aren’t part of science. But not even the most conservative astronomer would take this line. We’re in an accelerating universe where distant galaxies will disappear over a horizon, and their far future would never be in principle observable. So it’s natural to suppose that there are galaxies that are already beyond the horizon and so forever unobservable. If you’re in the middle of the ocean, you’d be surprised if its boundary lay just beyond your horizon. Likewise, astronomers are confident that the volume of space-time within range of our telescopes -- what astronomers have traditionally called 'the universe' – is only a tiny fraction of the aftermath of our big bang. We'd expect far more galaxies located unobservably beyond the horizon.

If we’re in a multiverse, it would imply a fourth and grandest Copernican revolution; we’ve had the Copernican revolution itself, then the realization that there are billions of planetary systems in our galaxy; then that there are  billions of galaxies in our observable universe.  But now that’s not all. The entire panorama that astronomers can observe could be a tiny part of the aftermath of ‘our’ big bang, which is itself just one bang among a perhaps-infinite ensemble.

It’s highly speculative. But it’s not metaphysics. It’s exciting science. And it may be true -- though whether we’ll ever be sure of this is unclear.

Edward Witten says consciousness might be harder to solve than the origin of the universe. What's your view?

I’m not sure how to answer this question. It’s possible that both these great challenges will be solved in coming decades (or centuries); or that one will be and the other won’t; or that both will have to await posthuman intelligence for a solution. But it’s important to note that only 1 percent of scientists are physicists who work (like Ed Witten) on the frontiers of the very small or of the very large. 99 percent work on the third frontier: the very complex. And the greatest complexity is found in the biological world:  even the simplest living thing has layer upon layer of structure and is perplexingly complicated.

Astronomers can convincingly attribute tiny vibrations in a gravitational wave detector to a “crash” between two black holes more than a billion light years from Earth.  In contrast, our grasp of some familiar matters that interest us all – diet and child-care for instance – is still so meager that “expert” advice changes from year to year. When I was young, milk and eggs were thought to be good; a decade later they were deemed dangerous because of their high cholesterol content; and now they seem again to be deemed harmless. And there is still no cure for many of the commonest diseases and ailments.

But it actually isn’t paradoxical that we’ve achieved confident understanding of arcane and remote cosmic phenomena while being flummoxed by everyday things. It’s because astronomy deals with phenomena   far less complex than the biological and human sciences (even than “local” environmental sciences).

Scientists are nearly all reductionists in the sense that they feel confident that everything, however complex, is a solution of Schrodinger’s equation – unlike the “vitalists” of earlier eras, who thought that living things were infused with some special “essence.” But this reductionism isn’t conceptually useful – it doesn’t offer the best explanation.

Even a phenomenon as un-mysterious as the flow of water in pipes or rivers is understood in terms of “emergent” concepts like viscosity and turbulence. Specialists in fluid mechanics don’t care that water actually made up of H2O molecules; they envisage it as a continuum. Even if they had a hypercomputer that could solve Schrodinger’s equation for the flow, atom by atom, the resultant simulation wouldn’t provide any insight into how waves break, or what makes a flow go turbulent. And new irreducible concepts are even more crucial to our understanding of really complicated phenomena -- for instance, migrating birds or human brains.  Phenomena with different levels of complexity   are understood in terms of different irreducible concepts – turbulence, survival, alertness, and so forth. The brain is an assemblage of cells; a painting is an assemblage of chemical pigment. But what’s important and interesting is the pattern and structure – the emergent complexity.

The entire structure of a building is imperiled by weak foundations. In contrast, the “higher level” sciences dealing with complex systems aren’t vulnerable to an insecure base, as a building is. Each science has its own distinct concepts and modes of explanation. Reductionism is true in a sense.  But it's seldom true in a useful sense. And most of the recent breakthroughs which have rendered the last two decades the most exciting and vibrant period in science have been at these “higher” levels.

Could super-intelligent machines create a new science that transcends the limits of human science?

We are of course already being aided by computational power. In the “virtual world” inside a computer astronomers can mimic galaxy formation; meteorologists can simulate the atmosphere. Just as video games get more elaborate as their consoles get more powerful, so, as computer power grows, these “virtual” experiments become more realistic and useful.

And there indeed seems no reason why computers can’t make discoveries that have eluded unaided human brains.  For example, there is a continuing quest to find the “recipe” for a superconductor that works at ordinary room temperatures (the highest superconducting temperature achieved so far is about -150 degrees centigrade). This quest involves a lot of trial and error, because nobody fully understands what makes the electrical resistance disappear more readily in some materials than in others.  But it’s becoming possible to calculate the properties of materials, and to do this so fast that millions of alternatives can be computed, far more quickly than actual experiments could be done. Suppose that a machine came up with a novel and successful recipe. It would have achieved something that would get a scientist a Nobel Prize. It would have behaved as though it had insight and imagination within its rather specialized universe – just as Deep Mind’s Alpha Go flummoxed and impressed human champions with some of its moves. Likewise, searches for the optimal chemical composition for new drugs will increasingly be done by computers rather than by real experiments, just as for many years aeronautical engineers have simulated air-flow over wings by computer calculations rather than wind-tunnel experiments.

Equally important is the capability to discern small trends or correlations by “crunching” huge data-sets. As an example from genetics, qualities like intelligence and height are determined by combinations of genes. To identify these combinations would require a machine fast enough to scan huge samples of genomes to identify small correlations. Similar procedures are used by financial traders in seeking out market trends, and responding rapidly to them,  so that their investors  can top-slice funds from the rest of us.

You won the Templeton Award in 2011. Does that mean you believe in God? If so, do you think He'll bail us out?

I don’t believe in any religious dogmas, but I share a sense of mystery and wonder with many who do.  If we learn anything from the pursuit of science, it is that even something as basic as an atom is quite hard to understand. This should induce skepticism about any dogma, or any claim to have achieved more than a very incomplete and metaphorical insight into any profound aspect of our existence. As Darwin said, in a letter to the American biologist Asa Gray: "I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton. Let each man hope and believe as he can.”

Hard-line atheists must surely be aware of “religious” people who are manifestly neither unintelligent nor naïve, thought they make minimal attempts to understand them. By attacking mainstream religion, rather than striving for peaceful coexistence with it, they weaken the alliance against fundamentalism and fanaticism. They also weaken science. If a young Muslim or evangelical Christian is told at school that they can’t have their God and accept evolution, they will opt for their God and be lost to science. Adherents of most religions would accord high importance to their communal and ritual aspects. When so much divides us, and change is disturbingly fast, religion offers bonding within a community. And its heritage, linking its adherents with past generations, should strengthen our motivation not to leave a degraded world for generations yet to come.

What's your utopia (assuming we don't destroy ourselves)?

A utopian society would, at the very least, require trust between individuals and their institutions. I worry that we are moving further from this ideal. Two trends are reducing interpersonal trust: firstly, the remoteness and globalization of those we routinely have to deal with; and secondly, the vulnerability of modern life to disruption –-- the realization that “hackers” or dissidents can trigger incidents that cascade globally. Such trends necessitate burgeoning security measures. These are already irritants in our everyday life – security guards, elaborate passwords, airport searches and so forth -- but they are likely to become ever more vexatious. Innovations like blockchain could offer protocols that render the entire Internet more secure. But their current applications – allowing an economy based on crypto-currencies to function independently of traditional financial institutions –seem damaging rather than benign. It’s depressing to realize how much of the economy is dedicated to activities that would be superfluous if we felt we could trust each other. (It would be a worthwhile exercise if some economist could quantify this.)

And the world is so interconnected that no utopia could exist on the scale of one nation-state.  Harmonious geopolitics would require a global distribution of wealth that’s perceived as fair-- with far less inequality between rich and poor nations. And even without being utopian it’s surely a moral imperative (as well as in the self-interest of fortunate nations) to push towards this goal. Sadly, we downplay what’s happening even now in far-away countries and the plight of the “bottom billion.” And we discount too heavily the problems we’ll leave for new generations. Governments need to prioritize projects that are long-term in a political perspective, even if a mere instant in the history of our planet.

Further Reading:

Meta-Post: Horgan Posts on Physics, Cosmology, Etcetera

Is Science Infinite?

Was I Wrong about “The End of Science”?

See also Q&As with Marcelo Gleiser, David DeutschSteven WeinbergGeorge EllisCarlo RovelliEdward WittenScott AaronsonSabine HossenfelderPriyamvada NatarajanGarrett LisiPaul SteinhardtLee SmolinStephen WolframRobin HansonEliezer YudkowskyNaomi OreskesTyler VolkStuart KauffmanChristof KochRupert Sheldrake and Sheldon Solomon.