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Carl Sagan

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Do Civilisations Survive?

“The universe is a pretty big place,” as Carl Sagan once remarked. “If it’s just us, seems like an awful waste of space.”

The Drake Equation is gradually filling out, and it’s looking good for the existence of life, the rise of intelligence, and the likely number of civilisations elsewhere in the universe.

There’s even reason to hope that some high-energy technological civilisations successfully pass through the energy-environment bottleneck that our own planetary civilisation is now entering. But not many make it through the bottleneck without suffering major losses, and quite a lot just collapse.

The Drake Equation was written by American radio astronomer Frank Drake in 1961 to estimate how many high-tech civilisations there were in the galaxy. It had seven factors, but they were all empty.

The first three factors, all uncertain in 1961, were: what is the average rate of star formation in our galaxy; how many of those stars have planets; and what proportion of those planets can potentially support life? We know the answers now, and they are pretty encouraging.

There’s around one new star annually, most stars have planets, and about one star in five hosts one or more planets with liquid water on the surface. That means that there are probably around a hundred billion planets in this galaxy alone that can support life, but that’s just a start.

As Douglas Adams pointed out in ‘The Hitch-Hiker’s Guide to the Galaxy’, “Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is.”

The Hubble telescope has revealed around a hundred billion galaxies in the universe. Total number of potentially life-supporting planets? Around 10,000,000,000,000,000,000,000 (ten billion trillion).

Drake’s remaining factors are still unknown quantities. The only two that matter for Adam Frank – because all he wants to know is how many non-human civilisations have ever existed anywhere in the universe – are what fraction of potentially life-supporting planets actually do develop life; and what proportion of those planets go on to develop intelligent life.

What Adam Frank has done, in his recent book, ‘Light of the Stars: Alien Worlds and the Fate of the Earth’, is to point out that there must therefore have been a lot of ‘exo-civilisations’. Make your assumptions about first life and then intelligence emerging on any given planet as pessimistic as you like, and there will still be a lot.

Maybe not billions or even millions, but even if you assume that only one life-supporting planet in a million trillion ever supported a civilisation, there would have been ten thousand of them. That’s big enough for a statistical sample, and what Frank really wants to do is to crank the numbers and get a handle on how many of those civilisations would have made it through the bottleneck.

He doesn’t need to know anything specific about those unknown exo-civilisations. He only need to know that all civilisations use large amounts of energy, and that there is a strictly limited number of ways that a technologically ‘young’ civilisation like ours can access energy.

There are fossil fuels, if your planet had a Carboniferous Era, or just burning biomaterials if it didn’t. There’s hydro, wind and tides. There’s solar, geothermal and nuclear. That’s it. Using energy always produces waste, but some of these modes produce far less heat, carbon-dioxide, and toxic chemicals than others.

So put different original mixes of these energy sources into your experimental models, put in different planetary conditions as well (some planets closer to their suns, some further away), and run a few thousand of these models through your computer.

It turns out that most of the models see runaway population growth, followed at a distance by growing pressures on the planet’s environment that lowers the ‘population carrying capacity’.

At some point the alarmed population switches to lower-impact energy sources. There is still a steep die-back (up to 70 percent) in the population, but then a steady state emerges and the civilisation survives.

In other models, the planet’s people (creatures? beings?) delay switching the energy sources for too long. They all switch in the end, but the laggards still don’t make it. The population starts to fall, then appears to stabilise for a while, then rushes downward to extinction. Nobody saw that one coming, but it’s what the models are telling us.

There’s still a huge amount of research to be done in this new domain, but it’s time to ask where our own planetary civilisation falls on this spectrum of possible behaviours.

I don’t know, but this just in. Oil production is at an all-time high of 100 million barrels a day, and the Organisation of Petroleum-Exporting Countries predicts that it will reach 112 mbd in the next 20 years. That’s the wrong direction.
To shorten to 700 words, omit paragraphs 1 and 8. (“The universe…space”; and “Drake’s…life”)

Life Everywhere

Only 39 light-years away, astronomers have found seven planets circling a very small “red dwarf” star called Trappist-1. All seven are in or near what we call the “Goldilocks zone”: not too hot, not too cold, but just right for water to remain liquid on the planet. So we all speculate once again, but a little more bravely this time, about whether some of these planets might be home to life.

Not only are three of Trappist-1’s planets dead centre in the Goldilocks zone; the other four are on the fringes of the habitable zone. And they are all big enough – from half Earth’s size to slightly bigger than our home planet – to retain an atmosphere for billions of years.

That’s long enough for life to evolve on one or more of them. It’s probably even long enough for complex life forms to evolve there, as it did on Earth.

If an intelligent life form evolved on even one of these planets, it could have colonised all seven: they are very close together. The journey would be not much more demanding than a trip from the Earth to the Moon.

So think about that: a seven-world interplanetary civilisation. It may not exist at Trappist-1: we cannot yet assume that life crops up everywhere that the circumstances are suitable for it. But it surely must exist in one or many (or most) of the hundreds of millions of similar star systems that exist in this galaxy alone.

It looks like life is as common as dirt in the universe, which for living creatures like us is infinitely more interesting than a dead universe ruled only by physics and chemistry. Whereas the poor scientists, shackled by their duty to go not one millimetre further than the evidence will currently support, are condemned to say cool, restrained things like:

“The discovery of multiple rocky planets with surface temperatures that allow for liquid water make this amazing system an exciting future target in the search for life.” (Dr Chris Copperwheat of Liverpool John Moores University, which provided one of the telescopes used in the study.)

Of course, Dr Copperwheat really knows that this discovery makes it 99 percent certain (it was already 98 percent certain) that life is commonplace throughout the universe. He just must not say so until we actually find hard evidence for life on one of the almost 4,000 “exoplanets” orbiting other stars that astronomers have found in the past 24 years.

But I am a journalist, and I am allowed to speak obvious truths even when the scientific evidence is still falling a bit short. Planets are self-evidently as common as dirt. Life is almost certainly as common as dirt. And even intelligent life must be pretty common in the universe.

Maybe only one planet in a million has intelligent life, you say? Okay, then there are at least a hundred and forty million planets with intelligent life in this galaxy alone. And there are at least a hundred billion galaxies.

I started reading science fiction when I was quite young – maybe ten or eleven – and my parents knew an old guy a few streets away who was an amateur astonomer, so they sent me along to see him. He showed me his telescope, and pictures he had taken, and even an exercise book where he had done sketches of our own solar system and the entire galaxy with coloured pencils.

But he couldn’t tell me whether there were any planets beyond our own system, let alone whether there was life elsewhere in the universe. Nobody knew, and he was being properly scientific in his caution. So I returned to my science fiction, and never went back to see him again.

I am probably now at least as old as that “old guy” was then. We live in a truly marvelous time, when the whole universe is opening up to us, and I wish he could have lived long enough to know what we know now.

And now for the next perplexing question. If life is as common as dirt, and intelligent life only maybe a thousand times less common, then where is everybody? Is intelligence so counter-productive that an intelligent species automatically self-destructs within a few dozen generations of developing a scientific civilisation? Or is there something so terrible out there that everybody who survived is observing radio silence?

Questions for another day. But Trappist-1 is so close that in a few hundred years we could probably get there in a generation ship. Meanwhile, a private consortium led by the BoldlyGo Institute and Mission Centaur is working on an orbital telescope that will look for planets around our closest stellar neighbour, Alpha Centauri, only 4.4 light-years (40 trillion kilometres) away.

It’s called Project Blue, after astronomer Carl Sagan’s famous picture of our own “pale blue dot”. But there are a gazillion other pale blue dots, and maybe Alpha Centauri has one too. Hallelujah!
To shorten to 725 words, omit paragraphs 3 and 8. (“That’s…Earth”; and “Of curse…years”)