Human Universe (16 page)

This might seem a bit strong, but it is a view shared at Green Bank by Manhattan Project veteran Philip Morrison. Morrison was intimately involved in the design and development of the first atomic bomb, and he helped load Little Boy onto
Enola Gay
destined for Hiroshima. The fact that human beings had deployed a potentially civilisation-destroying weapon twice, against civilian targets, and that Morrison had personally loaded one of the bombs, must have never left him, and on the eve of the Cuban missile crisis, it must have seemed likely that we would do it again on a much grander scale.

Drake realised this as well, which is certainly one of the reasons why he introduced the time that a technological civilisation can endure into his equation: we can after all only communicate with nearby civilisations if they exist at the same time as us. This is a possible resolution to the Fermi Paradox. Civilisations inevitably blow themselves up soon after acquiring radio technology, and therefore the Milky Way will remain forever silent apart from the briefest, non-overlapping flickers of intelligence. This might seem like a solipsistic conceit; how can we possibly assume that human stupidity is universal? We can’t, of course. But just as for the biological arguments we made against the inevitable emergence of complex life on an otherwise living world, we only have the Earth as a guide, and extrapolating from our own experience is the best we can do. On Earth, Rutherford discovered the atomic nucleus in 1911 and we destroyed two cities and killed over 200,000 of our fellow human beings with nuclear technology 34 years later. About 17 years after that, having seen the devastation nuclear weapons can cause, Khrushchev and Kennedy came close to ending it all, and to this day we don’t know how close we came to eliminating the fruits of almost four billion years of evolution. Here on Earth it appears that sanity, perspective and an appreciation of the rarity and value of civilisation emerges after, and not before, the capability to build big bombs. We have the bombs, but I don’t think enough of us have the rest. Why should other young civilisations be any different? If this is the reason for the Great Silence, then I suppose we might take comfort in the fact that we are not the only idiots to have existed in the Milky Way, but that’s the coldest comfort I can imagine.

The above might be seen as a naïve rant, of course. One could argue that mutually assured destruction, the guiding principle of the Cold War, did act to stabilise our civilisation and is still doing so today. Perhaps no intelligent beings will knowingly destroy their civilisation, which is what global nuclear war on Earth would surely do; after all, Kennedy and Khrushchev ultimately took this view. Similarly, one assumes that the submersion of Miami and Norwich by rising sea levels would silence the so-called climate change sceptics (I’d call them something different) and trigger a change of policy that will avert catastrophic, civilisation-threatening climate change in good time. It seems to me, however, that a small planet such as Earth cannot continue to support an expanding and flourishing civilisation without a major change in the way we view ourselves. The division into hundreds of countries whose borders and interests are defined by imagined local differences and arbitrary religious dogma, both of which are utterly irrelevant and meaningless on a galactic scale, must surely be addressed if we are to confront global problems such as mutually assured destruction, asteroid threats, climate change, pandemic disease and who knows what else, and flourish beyond the twenty-first century. The very fact that the preceding sentence sounds hopelessly utopian might provide a plausible answer to the Great Silence.

What, then, is the range of estimates for the number of civilisations in the Milky Way, given the limited evidence we have at our disposal? During the filming of
Human Universe
, Frank Drake told me that the Green Bank meeting came up with a number of around 10,000, and he sees no reason to change that estimate. This would be wonderful, and makes the search for signals from these civilisations one of the great scientific quests of the twenty-first century. I strongly support SETI, because contact with just one alien civilisation would be the greatest discovery of all time, and it’s worth the investment on that basis alone.

There is, however, one piece of evidence that might suggest a more lonely position for us on our little home world. In 1966 the mathematician and polymath John von Neumann published a series of lectures entitled ‘Theory of Self-Reproducing Automata’ in which he analysed in great detail the possibility of constructing machines capable of building copies of themselves. Such machines exist in nature, of course – all living things do this routinely. In principle, therefore, one might imagine a sufficiently advanced civilisation building a self-replicating Von Neumann space probe and launching it out to explore the galaxy. On reaching a solar system, the probe would mine the planets, moons and asteroids, extracting the materials necessary to build one or more copies of itself. The newly minted probes would launch themselves out to neighbouring solar systems and repeat the process, spreading across the Milky Way. Even given the vast distances between the stars, computer models assuming currently envisioned rocketry technology suggest that such a strategy could result in the exploration of the entire Milky Way galaxy within a million years.

Science fiction? It certainly sounds like it, but if there is no objection in principle to the construction of a Von Neumann probe, then one has to develop an argument as to why we don’t see any. The reason that this is difficult to do is due to timescales. The Milky Way has been capable of supporting life for over ten thousand million years. It is possible to envisage many millions of civilisations rising and falling over such vast expanses of time, and if only one had developed a successful Von Neumann probe, then the galaxy should be filled with its progeny; there should be at least one Von Neumann probe operating in our solar system today. Carl Sagan and the astronomer William Newman noticed a flaw in this line of argument. If the probes multiply exponentially and unchecked, then one can show that they consume the resources of the entire galaxy relatively quickly, and we’d certainly have noticed that! Or more accurately, we wouldn’t be here to notice that. Sagan reasoned that this obvious risk would be sufficient to prevent any civilisation intelligent enough to build Von Neumann probes from actually doing so. They would be doomsday machines. Other astronomers have countered that it wouldn’t be beyond the wit of such an advanced intellect to build in some fail-safe mechanism that guaranteed, for example, only one probe per solar system, or a finite lifetime for each probe. Others have argued that there may indeed be a Von Neumann probe operating in our solar system today, with appropriate fail-safe mechanisms installed to stop it eating everything. If such a probe were relatively small, perhaps sitting amongst the asteroids or even in the Kuiper Belt of icy comets beyond the orbit of Neptune, then we’d almost certainly be unaware of its presence.

Von Neumann probes wouldn’t be the only signatures of ultra-advanced civilisations. Imagine a civilisation many millions of years ahead of us, carrying out engineering projects on a galactic scale. Imagine interstellar starships or great space colonies constructed in otherwise uninhabitable solar systems. Why not? As I said at the start of this chapter, we went from the Wright Brothers to the Moon in a single human lifetime, so, I ask again, how far will we travel, if the laws of physics allow, given another thousand years? Or ten thousand? Or a million? What signature will we leave on the sky if we survive and prosper that long? None of these questions is trivial, because the sheer immensity of the timescales available for life to evolve in the Milky Way galaxy forces us to consider them. Why should we be the most advanced civilisation in the galaxy when we’ve only been building spacecraft for half a century in a 13-billion-year-old universe? I don’t have an answer to this. It bothers me. Perhaps the distances between the stars are indeed too great, or perhaps there are insurmountable difficulties in building self-replicating machines or starships, but I can’t think what they might be.

I am tempted, therefore, to make the following argument for the purposes of debate. I think that advanced, space-faring civilisations are extremely rare, not because of astronomy, but because of biology. I think the fact that it took almost four billion years for a civilisation to appear on Earth is important. This is a third of the age of the universe, which is a very long time. Coupled with the remarkable contingency of the evolution of the eukaryotic cell and oxygenic photosynthesis – not to mention the half a billion years from the Cambrian explosion to the very recent emergence of
Homo sapiens
and civilisation – I think this implies that technological civilisations are stupendously rare, colossally fortuitous accidents that happen on average in much fewer than one in every two hundred billion solar systems. This is my resolution to the Fermi Paradox. We are the first civilisation to emerge in the Milky Way, and we are alone. That is my opinion, and given our cavalier disregard for our own safety, it terrifies me. What do you think?

But why, some say, the moon?

Why choose this as our goal?

And they may well ask why climb the highest mountain?

Why, 35 years ago, fly the Atlantic? …

We choose to go to the moon.

President John F. Kennedy

Astronaut John Young was once asked how he would feel if his epitaph read ‘John Young: The Ultimate Explorer’. Young smiled, and in a test pilot’s drawl replied, ‘I’d feel sorry for the guy who wrote it’. Young was, and still is, a hero of mine. My first vivid memory of live space exploration was watching Space Shuttle Columbia climb on a tower of bright vapour into a blue Cape sky on 12 April 1981. It was midday in Manchester, the Easter holidays, and I was 13 years old. Because of a two-day launch delay, Columbia’s test flight took place precisely 20 years to the day after Yuri Gagarin made his black-and-white voyage into orbit on 12 April 1961, but Young and his co-pilot, Bob Crippen, in their orange spacesuits, were astronauts from the colour age, the future – as distant from the Russian hero as gleaming white-winged Columbia was from
Vostok 1
. Equidistant from both was Apollo, which Young flew to the Moon. Twice. It was the age of optimism, the age of wonder, the golden age when the ape went into space. When unflappable aviator Young, whose pulse rate did not increase during the launch of NASA’s only manned spacecraft ever to have flown without an unmanned test flight, piloted Columbia back for a flawless manual landing at Edwards Air Force Base two days later, he turned to Crippen and said ‘We’re not too far away – the human race isn’t – from going to the stars’.

In 2014 the stars feel further away than they did in 1981; the International Space Station is a wonderful piece of engineering that has allowed us to learn how to live and work in near-Earth orbit, but it is no closer to the stars than Columbia. Its construction is no mean achievement; one of the most important things to realise about engineering at the edge is that the only way to learn is to actually do it. You can’t think your way into space; you have to fly there. But I can’t help but feel, in the words of Billy Bragg, that the space race is over and we’ve all grown up too soon.

It was different in Gagarin’s day. Nobody is born to be a spaceman. We’re apes, honed by natural selection to operate in the Great Rift Valley. Gagarin’s father was a carpenter and his mother was a milkmaid. Both worked on a collective farm. Gagarin’s first job at the age of 16 was in a steel mill, but after showing an aptitude for flight as an air cadet he joined the military when 21 and was posted to the First Chkalovsk Air Force Pilots School in Orenburg. Rising through the ranks, he made a name for himself as a skilled and intelligent aviator, and in early 1960 he was chosen along with 19 other elite pilots for the newly established space programme. Standing just 5 foot 2 inches tall, Gagarin had the right stuff and was perfect for the tiny
Vostok
spacecraft, whose single-seat crew compartment was only 2.3m in external diameter. After a year of training, Nikolai Kamanin, head of the cosmonaut programme, chose Gagarin ahead of his rival, Gherman Titov, just four days before the flight. The history books are filled with the names of great men and women whose presence in the collective memory of humanity was assured by the slimmest of margins. Gagarin, alongside Armstrong, will be remembered for as long as there are humans in the cosmos; the name of the equally brilliant Titov, Russia’s second cosmonaut, has faded away.

Gagarin’s flight was a true journey into the unknown. Strapped on top of the Vostok-K rocket, which flew 13 times and made it into space on 11 occasions, the 27-year-old performed like a true test pilot. Despite a two-hour delay during which every component of the spacecraft hatch was taken apart and rebuilt while Gagarin remained strapped into his seat, his heart rate was recorded at 64 beats per minute just before launch. This is not to say that Gagarin wasn’t fully aware of what he was about to do. Before boarding, Gagarin made one of the great speeches of the age.