= ASTRONAUTICAL EVOLUTION =

What is a Supercivilisation?

Nick Nielsen has another of his long essays on Centauri Dreams, this time under the title “Stagnant Supercivilisations and Interstellar Travel”. He is interested in the question of whether a supercivilisation can reach limits to its growth, and if so, whether it stagnates at a high but zero-growth level of achievement.

As he points out, the concept of a supercivilisation is necessarily vague, but may be generally understood as the product of a civilisation like our own which continues to develop and grow in whichever ways are permitted by its internal dynamics, its environment and the laws of physics for a period of millions to billions of years. Whatever the result, some sort of interplanetary or interstellar range will presumably be a major part of the picture.

Since no such entities have yet made their presence known to us, and since it is fashionable to believe that alien civilisations already exist, the question arises whether even so powerful and knowledgeable a society might come to the end of its material growth before it has absorbed the Solar System into its sphere of influence – thus able to exist, and yet not so far observed by us.

Civilisations on Earth: spatial extent determined by technology

Two factors which characterise a civilisation are closely related: its technology level, and its spatial extent. One thousand years ago, before the adoption of fossil fuels, all human societies were constrained geographically by their pre-industrial communications and transport, whose maximum speed was set, on land, by the horse, and on water, by the sailing ship. The largest empires possible using such systems were continental in scale – thus the Roman, Achaemenid, Chinese, Mongol, Inca and other empires.

Since the total habitable area was greater in size, the result was what we shall call a multiple civilisation. That is, there were multiple centres of civilisation, sharing a common origin (the evolution of Homo sapiens) and a common environment (Earth’s surface), but whose interactions, while sometimes intense (e.g. the Hun and Mongol invasions of Eastern Europe), were more often loose to non-existent (e.g. early medieval Europe, North and South America, and China), with consequently no overall political or economic integration.

The situation on Earth in the present day is clearly different: the transport and communications systems are now easily capable of global unification, with the result that we have in fact a single globalising civilisation, with the prospect of progressively tighter integration on a global scale in centuries to come, provided that centrifugal forces (such as nationalism and religionism) do not come to predominate.

We shall call this an integral civilisation.

But what would happen on interplanetary, and especially interstellar, scales?

Civilisations in space: scenario-building

Since the limits to technological growth are not yet known, we must be content to describe a range of possible future scenarios.

(1) Integral civilisation. In order for this to work on an interstellar scale, faster-than-light (FTL) transport and communications would be essential. This would be the galactic empire setting of innumerable SF epics.

Is faster-than-light travel actually possible? My personal view is that it is not. Maybe this reflects a failure of imagination on my part. The FTL optimists like to point out the huge number of 20th-century inventions which have transformed our lives but which were near-inconceivable around 1900. They like to project the accelerating trend of innovation into the future. My answer is that trends never go on for ever, that we must expect the unexpected, and that innovation is already decelerating as it ploughs into the limits imposed by quantum mechanics and thermodynamics, and the complexity of ecosystems and information processing.

I therefore don’t expect the SF galactic empire ever to become a reality. Maybe I’m wrong. We’ll just have to wait and see.

(2) Semi-integral civilisation. While FTL travel is clearly ruled out by Special Relativity, and the efforts to construct a space-warp drive to get around this by expanding or contracting space itself strike me as highly implausible (disclaimer: I don’t understand the mathematics of General Relativity on which such efforts are based), FTL communication remains a possibility. It would depend upon the experimental discovery of the long-postulated tachyon particle.

It might be thought that FTL communication involved time-paradoxes, but these do in fact have a simple logical solution, derived from the quantum mechanical concept of entanglement.

A semi-integral civilisation would therefore have instant messaging throughout the Galaxy, and indeed the universe if respondents could be identified at intergalactic ranges. But transport of material objects (including the future equivalents of gold reserves, troops to put down a rebellion, etc.) would only be possible at a fraction of the speed of light, with appropriately high energy costs.

I am agnostic on whether tachyon radio will ever be possible.

(3) Multiple civilisation. Without FTL technologies for either transport or communications, a galactic civilisation developing on million-year timescales will inevitably revert to the pattern seen on Earth before around the year 1500. Nearest neighbours will be able to exchange news within decades, and spacecraft visits within centuries, but more distant colonies will be increasingly cut off from their system of origin and from each other to the point where even news is tens of thousands of years old by the time it is passed from one side of the occupied zone of the Galaxy to the other.

Such a scenario is in my view the most plausible long-term result of civilisational growth, given what is known of physics and the universe at present.

How do these scenarios handle growth versus stagnation?

Endless growth versus stagnation

If a supercivilisation is required to be an integral civilisation, then it must of necessity stagnate once it has occupied all the space accessible to it (up to and including the entire known universe), and developed all the technologies physically possible. Of course, it remains possible that these development phases take an infinite period of time to complete.

All we can be certain of for the present is that either there is no integral supercivilisation in our own Galaxy, or else it began its interstellar growth only a fairly short time (say less than a million years) ago.

It may alternatively collapse, in which case it will not collapse everywhere to the same extent. It may then transform itself into a semi-integral or multiple civilisation.

I find these two latter scenarios particularly interesting, as they allow growth to continue forever.

A multiple civilisation is in fact a population of related but largely independent societies. Like a population of animals belonging to one species, there is a continuous process of individual birth, growth, senescence and death. Similarly, on any one planet, moon or asteroid there can be a continuous process of colonisation, economic and population growth, stagnation, decline, and ultimate collapse, subsequently followed by recolonisation. At any given point in space there is change on a historical timescale, but the system overall changes only very slowly, on an evolutionary timescale.

In my view this is the most plausible long-term destination for human civilisation, and for any aliens out there which may currently be embarking on the same processes of growth.

It may be that the introduction of digital intelligence to supplement the original purely biological intelligence may create greater stability at each location in space. This produces a range of possible colony lifetimes without invalidating the key point: so long as each colony is able to reproduce on average at least once during its lifetime, then the population as a whole is secure, even if every single local civilisation is doomed to ultimate collapse.

Speculation taking over from fact

Supercivilisations may or may not exist in reality. We should therefore be wary of statements such as this:

“our previous statement that ET may be millions or billions of years more advanced than us is too weak. Actually, ET is millions or billions of years more advanced than us. We are still in our first century of being capable of sending and receiving interstellar signals. The statistical probability of the ET we might detect also being in its first one hundred years is vanishingly small. We know absolutely nothing about ET’s intentions; however, its ability to do us harm, if it so wished, might be absolute. We are only two thousand years more advanced than Rome, yet the best Roman legion could be annihilated by a modern army in mere minutes. Never mind two thousand years ago, Napoleon’s armies of barely two hundred years ago would face the same fate.”

(John Gertz, “Post-Detection SETI Protocols & METI: The Time Has Come to Regulate Them Both”, JBIS, vol.69 no.8 (Aug. 2016), p.263.)

Clearly, this assertion is not necessarily true at all. Let’s consider some of the questions whose discussion is omitted from Gertz’s editorial:

• Where are the limits to technological progress? Are they close to our present level or still very far off? Could an extraterrestrial civilisation be in practice more advanced than we now are by a factor of 10⁴ to 10⁷ times the difference between us now and the military and other forms of power available in Napoleon’s time (~10² years ago)?
• Suppose ET is confined to their own planet of origin? Maybe expansion into space has turned out to be impractical for some reason. In this scenario, it is impossible for them to be much more advanced technologically than we are now, except in terms of long-term sustainability of their civilisation, because of the sheer physical constraints on planetary life which we are ourselves already running up against. In this scenario, any kind of supercivilisation would be impossible.
• Suppose ET is indeed “millions or billions of years more advanced than us”? In this scenario, they will inevitably have spread throughout the volume of space accessible to them, i.e. the Milky Way Galaxy, if not even further afield. They will have been at work in our own Solar System long ago, and their presence will always have been obvious to us.
• Do one or more ET civilisations exist at all in the Galaxy? It is perfectly possible that Earth is the first planet to industrialise – note that in every possible scenario in a universe which began a finite time ago, this must logically be true of at least one planet. If the pessimists are right that industrial civilisations are inherently unstable and collapse within a millennium or so through pollution, nuclear war or a similar internally generated disaster, then the perception that it is alone in the universe would be true of every civilisation. The existence of aliens capable of receiving our signals and responding to them cannot therefore be proved by merely asserting it as an article of faith!

In other words, the statement “ET is millions or billions of years more advanced than us” may or may not be true in reality. It represents only one of a range of possible scenarios, and needs to be considered alongside other possible scenarios, consistent with our currently extremely limited knowledge, in which it is not true.

Is it possible to reconcile the existence of an extraterrestrial supercivilisation with the fact that no signs of its presence have yet been observed, either in the Solar System or in our galactic vicinity? Many bizarre hypotheses have been proposed, and none have yet been supported by evidence.

The most plausible way to make that reconciliation, so far as I can see, is through a scenario in which the aliens evolved in the Galaxy only very recently, within around the past ten million years, and have not yet reached our neighbourhood. But that timescale is just one thousandth of the age of the Galaxy, making this scenario, while perfectly possible, highly improbable.

It was in order to explore that scenario in more detail that I wrote “Quantifying the Assumptions Behind the METI Debate”, as discussed last month.

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