How humans may populate the universe in the billions of years ahead

I’m old enough to have viewed the grainy TV images of the first Moon landings by Apollo 11 in 1969. I can never look at the Moon without recalling Neil Armstrong’s ‘One small step for a man; one giant leap for mankind’. It seems even more heroic in retrospect, considering how they depended on primitive computing and untested equipment.

Once the race to the Moon was won, there was no motivation for continuing with the space race and the gargantuan costs involved. No human since 1972 has travelled more than a few hundred miles from the Earth. Hundreds have ventured into space, but they have done no more than circle the Earth in low orbit. In the mid-1960s, Nasa absorbed 4 per cent of the US federal budget; today it’s 0.6 per cent. If that momentum had been maintained, there would surely be footprints on Mars by now.

Space technology has, nonetheless, burgeoned in the past four decades. We depend routinely on thousands of orbiting satellites for communication, navigation, environmental monitoring, surveillance and weather forecasting. Space telescopes orbiting far above the Earth’s atmosphere have beamed back images from the remotest cosmos. They have surveyed the sky in infrared, UV, X-ray, and gamma ray bands that don’t penetrate the atmosphere and therefore can’t be observed from the ground. They have revealed evidence for black holes and have probed the ‘afterglow of creation’ – the microwaves pervading all space, whose properties hold clues to the very beginning, when the entire observable cosmos was squeezed to microscopic size.

Of more immediate public appeal are the findings from spacecraft that have journeyed to all the planets of the solar system. Nasa’s New Horizons beamed back amazing pictures from Pluto, 12,000 times farther away than the Moon. The European Space Agency’s Rosetta landed a robot on a comet. These spacecraft took five years to design and build and then nearly ten years journeying to their remote targets. The Cassini probe spent 13 years studying Saturn and its moons and was even more venerable: more than 20 years elapsed between its launch and its final plunge into Saturn in late 2017. These missions used 1990s technology; it’s not too hard to envisage how much more sophisticated today’s follow-ups could be – just think how drastically smartphones have advanced in those decades.

During this century, the entire solar system – planets, moons, and asteroids – will be explored and mapped by fleets of tiny, automated probes, interacting with each other like a flock of birds. Giant robotic fabricators will be able to construct, in space, solar energy collectors and other giant lightweight structures. Just this week, we have seen the first images from the James Webb telescope, which was launched in December – a big advance on the Hubble telescope in deepening our vision of the cosmos. It can probe 98 per cent of cosmic history, the ‘genesis’ of galaxies, and can perhaps find evidence of life on planets orbiting nearby stars. The telescope’s successors, with oversize mirrors assembled in zero gravity, will further expand our vision of exoplanets, stars, galaxies and the wider universe. Future (and still larger) generations of instruments will be assembled by robots, which may also be used for space mining.

If there were a revival of the ‘Apollo spirit’ and a renewed urge to build on its legacy, a permanent lunar base would be a credible next step. It could be built entirely by robots, bringing supplies from Earth and mining some from the Moon. An especially propitious site for human habitation is the Shackleton crater, at the lunar south pole, 21km across and with a rim 4km high. Because of the crater’s location, its rim is always in sunlight and so escapes the extreme monthly temperature contrasts experienced on the rest of the Moon’s surface. Moreover, there may be a lot of ice in the crater’s perpetually dark interior – crucial for sustaining a ‘colony’.

Hopefully, people who are alive today will walk on the Moon, and even on Mars. The future of human spaceflight lies not with governments, but with privately funded adventurers who will be prepared to participate in a cut-price programme far riskier than western nations could. SpaceX, led by Elon Musk, or rival effort Blue Origin, bankrolled by Jeff Bezos, will soon offer orbital flights to paying customers.

These ventures – bringing a Silicon Valley culture into a domain long dominated by Nasa and a few aerospace conglomerates – have shown it’s possible to recover and reuse the launch rocket’s first stage, presaging real cost savings. They have innovated and improved rocketry far faster than Nasa or ESA has done. The future role of the national agencies will become more akin to an airport than to an airline.

More importantly, private enterprises can be less risk-averse than Nasa and find volunteers who are willing to tolerate greater dangers than a western government could impose on publicly funded civilian astronauts. So it’s these cut-price ventures – with private sponsorship – that should be at the forefront of human space travel.

Later this century, courageous thrill-seekers – in the mould of (say) Sir Ranulph Fiennes, or the early polar explorers – may well establish ‘bases’ independent of Earth. Elon Musk himself (now aged 51) says he wants to ‘die on Mars but not on impact’.

But what is the longer-range scenario? Musk and my late colleague Stephen Hawking envisaged that the first ‘settlers’ on Mars would be followed by millions of others aiming to escape the Earth’s problems. But this is a dangerous delusion. Coping with climate change is a doddle compared to terraforming Mars. Nowhere in our solar system offers an environment even as clement as the Antarctic, the top of Everest, or the ocean bed.

Because humans will be ill-adapted to Martian conditions, they will have a more compelling incentive than those of us on Earth to redesign themselves – and this may not remain science fiction. Indeed, it’s surely on the cards that human beings – their mentality and their physique – may become malleable through the deployment of genetic modification.

For this to happen, two advances are needed: first, deep analysis of the human genome to determine which combination of genes optimise specific desired qualities; and second, the ability to synthesise a genome with these properties.

Optimists suspect that by the end of the century ‘designer babies’ will become conceivable (in both senses of that word). One hopes that such techniques will be constrained, because they are risky: the genome is so complicated that attempts to modify it may have unenvisaged downsides that outweigh any benefits.

Another futuristic concept, more familiar from science fiction, is that our descendants could become ‘cyborgs’, their mental capacities being enhanced by linking the brain (or ‘plugging it in’) to electronic attachments. It’s spacefaring adventurers, not those of us comfortably adapted to life on Earth, who will lead the post-human era – evolving within a few centuries into a new species. This evolution, best described as ‘secular intelligent design’, could proceed on the timescale of technological advance, potentially thousands of times faster than Darwinian selection.

Moreover, there may be limits to the capacity of organic brains; perhaps humans are near this limit already. If our descendants make the transition from flesh and blood to fully inorganic intelligences, they won’t need an atmosphere. And they may prefer zero-gravity, especially for constructing massive artefacts. So it’s in deep space – not on Earth, nor even on Mars – that non-biological ‘brains’ may develop powers that humans can’t even imagine.

Billions of years lie ahead. The Sun formed 4.5 billion years ago: it’s taken most of that immense time for life to evolve from its still-mysterious beginnings into the immensely complex biosphere of which we’re a part. Humans are not the culmination – the top of the tree. We may in fact be nearer the beginning than the end of a cosmic process.

The Sun is still less than halfway through its life: it will survive six billion more years before its fuel runs out. And the expanding universe will continue far longer– perhaps for ever. So even if intelligent life had originated only on the Earth, it need not remain a trivial feature of the cosmos: it could initiate a diaspora whereby ever more complex intelligence spreads through the whole galaxy. Interstellar voyages would hold no terrors for near-immortal electronic entities. There’s plenty of time ahead.

Even though we are not the terminal branch of an evolutionary tree, humans could claim truly cosmic significance for jump-starting the transition to electronic entities, spreading their influence far beyond the Earth.

This raises a further question: will our remote progeny be the first intelligences to spread through the galaxy? Or will they encounter ‘aliens’ already out there, which originated from a planet around an older star where evolution had a headstart over us?

Perhaps the galaxy already teems with advanced life, and our descendants will ‘plug in’ to a galactic community as rather ‘junior members’. On the other hand, Earth’s intricate biosphere may be unique and searches for aliens may fail. Our tiny planet – this pale blue dot floating in space – could be the most important place in the entire cosmos.

Either way, our cosmic habitat seems ‘tuned’ to be an abode for life. Even if we are alone in the universe, we may be far from the final destination of this ‘drive’ towards complexity and consciousness.