All Astronautical Evolution posts in 2014:
The SpaceShipTwo Crash (Nov.)
To the Rt Hon Greg Clark (Oct.)
A Four-Point Plan for ESA (April)
New in 2015:
Short story The Marchioness
2016: Stragegic goal for manned spaceflight…
2015: The Pluto Controversy, Mars, SETI…
2014: Skylon, the Great Space Debate, exponential growth, the Fermi “paradox”…
2013: Manned spaceflight, sustainability, the Singularity, Voyager 1, philosophy, ET…
2012: Bulgakov vs. Clarke, starships, the Doomsday Argument…
2011: Manned spaceflight, evolution, worldships, battle for the future…
2010: Views on progress, the Great Sociology Dust-Up…
Index to essays – including:
The Great Sociology Debate (2011)
Building Selenopolis (2008)
Down with the Fermi “Paradox”!
Messages to Aliens, the Drake Equation and the Fermi Paradox
Presented at the BIS Space History Conference, Charterhouse, 25 July 2014
In association with the Initiative for Interstellar Studies
Stephen Ashworth, Oxford, UK
The problem of First Contact
Is it a good idea to transmit messages out into the Galaxy to nearby stars in the hope of making first contact with an alien civilisation?
Is it a bad idea to draw attention to ourselves, in case there are dangerous predators out there which have not yet discovered us?
Or is it just a distraction from more urgent concerns, because there’s nobody out there listening anyway?
The subject of this debate is known as METI: Messaging to ExtraTerrestrial Intelligence. If it exists. Which we do not yet know. We would do better to call it Messaging to Hypothetical ExtraTerrestrial Intelligence.
What are people saying about it? Many are opposed to any attempt to make contact.
Professor Stephen Hawking, in a programme for the Discovery Channel, 2010: “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans. We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet” (reported on BBC news).
David Brin, at a Royal Society Conference in 2010, subsequently published in JBIS (Jan. 2014, p.15): “We are the youngest of all technological races in the cosmos, like an orphan child who suddenly finds herself wandering a strange jungle that’s quiet… too quiet. So quiet that the simplest, parsimonious explanations appear rather daunting. Almost as if the creatures and natives know something that we don’t know, and are keeping silent for a reason.”
But others are in favour of attempting to make contact. Seth Shostak, at the same conference: limitations on our transmissions to the skies are “both ineffective and actually detrimental to the long-term well-being of our species” (JBIS, Jan. 2014, p.27).
Alexander Zaitsev: “Civilisations forced to hide and tremble because of farfetched fears are doomed to extinction.” (JBIS, Jan. 2014, p.31).
Zaitsev has already transmitted several messages to selected nearby stars from the 70-metre dish at Yevpatoria in Crimea, including Cosmic Call 1 (1999), the TeenAge Message (2001), Cosmic Call 2 (2003), and A Message From Earth (2008). The last of these was directed at a newly discovered planet orbiting Gliese 581, a red dwarf about 20 light-years away. The message is due to arrive in 2029, and if anyone there receives it and replies immediately, we will receive that reply in 2049.
Paul Davies is chairman of the International Academy of Astronautics SETI Post-Detection Taskgroup. In his recent book celebrating 50 years of SETI he concludes: “I am clear in my own mind that the danger from METI is minuscule. […] In the present context, METI is little more than a harmless stunt.” (The Eerie Silence, 2010, p.198-99).
So a range of opinions. Daring to transmit messages to nearby stars is gambling with terrible risks. Or it is essential for our own survival and growth. Or it is a harmless stunt. How can we decide who is right?
Are there in fact any alien civilisations out there who might receive our messages, or are we alone in the universe?
Fermi’s notorious notion
In order to understand the risks, we must first answer Fermi’s question: “Where are they?” This simple question has grown into a vast body of literature discussing what is now known as the Fermi paradox. The absence of any evidence for intelligent aliens has produced an intellectual climate devoted to highlighting the existential risks faced by human and other civilisations. So let’s start by addressing the Fermi paradox.
I warn you at the outset that I am going to reach some unconventional conclusions. The Fermi paradox and the Drake equation have been two intellectual pillars of established interstellar thought for the past 50 years. If you cannot bear any criticism of them, I suggest you leave now.
I want to approach the Fermi paradox from an oblique direction. Let me first invite you to consider another question: what is the origin of the human species?
Two possible theories offer themselves. According to Charles Darwin, our species evolved by natural selection from other species over millions of years. But according to the revealed word of God, our species was created completely separately from other species by a divine act of will.
It’s a nice, comforting feeling to think that there’s a super-powerful character out there somewhere looking out for us, so let’s believe in the word of God! That settles the scientific question: our species was created by a divine act, not through haphazard evolution by natural selection.
So far, so good. But there is a problem. God is an intelligent being, and so it must be possible to communicate with him, her or it. God in any case needs some infrastructure, or at least must have had in the not-too-distant past: a method of surveillance of life on Earth, a space transport system to get around the Galaxy, and a laboratory in which to develop new species. So we should be able to detect signs of God’s activities on Earth or in near-Earth space; we should be able to locate God’s home base, either in our Solar System or at another star; and we should be able to communicate. Yet none of these investigations has yet thrown up any supporting evidence for God’s existence.
It’s a paradox! On the one hand, we are certain that God exists, but on the other, we are equally certain that we do not yet possess any evidence for that existence. Some think that it’s too early to draw conclusions. So far we’ve searched too small a proportion of the parameter space. Surely at the current rate of technological progress, we can be sure that we will receive a radio message from God, or pick up signs of God’s industrial infrastructure, within the next twenty-five years?
Is this how science works? Do we select a working hypothesis on the basis of what appeals to the emotions, or according to what actually matches the facts?
Now back to Fermi’s question: where are the aliens? Well, we know for certain that we do not yet have any direct evidence for even a single microbe on the planet Mars, let alone for alien civilisations. We also know for certain that alien civilisations do really exist. How do we know that? Because we’ve seen them on Star Trek! So that proves it. But that means we have another paradox. We call it the Fermi paradox: they must have been around long before us, yet we can’t see them.
And so we have to develop special explanations of how they can have existed but not left any obvious traces. Perhaps they all collapsed very quickly, or they’ve deliberately hidden themselves from us, or they’ve all gone away somewhere, or they never got beyond watching cable television, or perhaps there’s some super-predator out there that hates competition and gobbles up any new civilisation that emerges, but then lies low for millions of years waiting for a new target to evolve. Perhaps if we send messages of our own out into space, hoping to get a subscription to the galactic internet, we’ll find instead a fleet of interstellar battleships heading our way, like H.G. Wells’s martians, or Dr Who’s daleks, bent on our extermination. “Shouting into the jungle”, David Brin calls it.
Or perhaps there is after all no great silence in the stars, and the answer is that we’ve not yet searched hard enough. Perhaps we’ll pick up a message from ET within the next twenty-five years? That’s what SETI Institute astronomer Seth Shostak told an audience two years ago at a TEDx talk in California in April 2012.
The reason for Shostak’s confidence was the rapidly increasing sensitivity of our telescopes, and the application of Moore’s law to the electronics that processes their results. But what made him so confident that there was anything out there to be detected? If there are no aliens, then not even an infinitely sensitive radio telescope with infinitely fast software will hear anything.
Why are we obsessed with aliens?
Let us pause here to contemplate the almost religious sense of unshakeable faith that some people bring to the SETI search. On the SETI website, Frank Drake, the father of modern SETI, is quoted as saying: “I know that, at this very moment, there are radio signals from other civilizations passing through this room which we could detect and study if we but pointed our antennas in the right direction and tuned to the right frequency.” How does he know that? Is that a statement that any scientist should be proud of, given our current state of ignorance? Or are we back to the pervasive cultural influence of television space opera?
But do there exist scientifically defensible reasons for believing that alien civilisations must have arisen elsewhere in the Galaxy before now?
Firstly, let’s talk about the principle of mediocrity, or the Copernican principle. This would assert that there must be thousands or millions of other Sun-like stars which possess Earth-like planets on which live Earth-like inhabitants. Earth cannot be special. Unless it actually is special. Since the universe has a finite age, we may be certain of the existence of at least one terrestrial planet with human-like inhabitants which is unique at the time, because it is the first ever to appear.
Is that world ours? Maybe, maybe not. The only way to find out is to get out there and look at what’s actually happening on other terrestrial worlds. Appeals to theoretical statistical arguments get us nowhere because statistics is impersonal: it cannot give us any information about a specific case, only about a population of cases. The Copernican principle does not save us the trouble of making actual observations of other worlds.
And so onto another argument. Let’s assume that Earth life actually began on Earth, or possibly on Mars. Then it must have booted itself up from non-living chemistry within about 500 million years. But if it did so in our Solar System, then it must have done likewise in many similar systems with terrestrial planets much earlier. If the first Earth-like planets capable of supporting life started appearing say 12 billion years ago, then they had 8 billion years start on us.
The majority of those other Earths would have been orbiting the cooler, longer lived stars that are commoner than G2 stars like our Sun. Here, it took us about 3.5 billion years to get from microbes to Moon-landings. Suppose we made that progress unusually quickly, and that our nearest competitors in the race to industrialise took twice as long, so 7 billion years. Even so, they could still have appeared anything up to 5 billion years ago.
Any serious spacefaring civilisation should be able to colonise the entire Galaxy by hopping from each star to its nearest neighbours, establishing colonies and sending out new expeditions to the next nearest neighbours. Say a few hundred years in flight at 2 or 3 per cent of the speed of light, perfectly achievable with a nuclear fusion rocket. Add on another few hundred years to build space colonies at the destination and create the infrastructure necessary for a new round of expansion. At ten light-years per thousand years, the colonisation front advances 100,000 light-years in ten million years. 100,000 light-years is the diameter of the Galaxy. Ten million years is just one part in 500 of the 5 billion year head start that those earlier civilisations should have had. Therefore they should be here by now. Where are they?
The Fermi paradox is a logical consequence of the hypothesis that the genesis of terrestrial life is to be found on Earth or closely nearby in the early Solar System. But is that the only possible hypothesis?
In his book summarising 50 years of SETI, Paul Davies emphasises that we really have no idea how life began. We are therefore completely unable to place any limits at all on the frequency with which Earth-like planets actually have any kind of life.
This fact makes the famous Drake equation completely useless. It contains the factor fl: the proportion of Earth-like worlds which develop life. Given our current ignorance, that factor could be almost unity, or almost zero, or anywhere in between. Perhaps almost all Earth-like planets have life on them, or perhaps only a few of them do, or perhaps only a single one does. There are at present no scientific reasons for preferring any particular figure for this factor. Until evidence is found, the output of the Drake equation, the number of civilisations with which we share the Galaxy, is meaningless.
Davies comments on the remarkable sophistication of even the simplest living cell ever found on Earth. Such a cell cannot have evolved from non-living chemistry in a single step, and therefore there must have been simpler precursors. But no precursor proto-cells have yet been found on Earth. Robert Zubrin made the obvious deduction from this. Maybe the genesis of life simply does not occur on Earth-like planetary surfaces at all, but in some other environment. He does not speculate what environment. But it is clear that the chemistry of complex organic molecules is affected by gravity.
Suppose there is some stage in the genesis of life that requires a microgravity environment. Life would then have to start within an asteroid, perhaps a volatile-rich, carbon-rich comet nucleus. This would have two consequences. The time available for the very first life genesis expands from half a billion years to about 8 billion years. And secondly the pathway from that genesis event to the evolution of ourselves has to go through a low-probability transfer of living cells from the low-gravity environment in which they first evolved to the high-gravity environment of an Earth-like planet.
Suppose alternatively that life does start up on terrestrial planets, but extremely rarely, on average only once every 8 billion years. And that the nearest such life event occurred on a Mars-sized planet which suffered impacts which scattered bacterial cells into interstellar space close to the newly forming Solar System.
In either of these scenarios it is perfectly plausible that Earth is the first planet in the universe to industrialise. The predicted observation is that we do not find any traces of alien civilisations because we are the first.
Which hypothesis matches the observational evidence better: that Earth life began on Earth or Mars, and booted up within half a billion years, or that it began on another long-lived world or in interstellar space, and took 8 billion years to do so?
The Fermi paradox is a product of the assumption that terrestrial life began on Earth or Mars, and took a few hundred million years to do so. But at our current stage of ignorance, it is equally possible that it began somewhere else and took an order of magnitude longer. In the latter case the Fermi paradox never arises.
Given our current lack of knowledge, there is no scientifically meaningful Fermi paradox. Such a paradox cannot arise unless and until hard observational evidence is found of life that existed well before the formation of our Solar System, say prior to 5 billion years ago. Unless and until that evidence comes our way, there is no point in trying to find solutions to the paradox created when an observational fact comes into conflict with a hypothesis: in science, the hypothesis, however attractive, must yield to the evidence, not the other way around!
But what if the SETI Institute receives a message from ET tomorrow? Is that possible? Of course it is!
But consider the circumstances. We know from the study of life on Earth that over evolutionary time species spread until all accessible locations are occupied. Mammals, reptiles and birds have spread to all the continents; billions of years earlier bacteria did the same. If a sustainable form of technological life is possible, then surely it too will spread as far as it finds the material and energy to maintain itself. Suppose the colonisation front travels ten times slower than I suggested earlier: a thousand years to advance each light-year. Even so, that form of life will be present at all stable stars in our Galaxy – especially long-lived ones with orderly planetary systems such as our own Sun – within 100 million years.
To you and me, this is an inconceivably long period of time. But on a geological timescale, it is rather small. The time since animals and plants first colonised Earth’s land surfaces is four times greater; the time since the first known fossils were laid down is 35 times greater. When a new form of life comes into being, it tends to persist.
Therefore, if we want to place effective limits on the prevalence of extraterrestrial life in our Galaxy, we only have to examine one star. Our own Sun.
There does not now exist a large-scale alien colony in our Solar System. We see no ruins of one that was here a long time earlier and then collapsed. Until any such evidence is found, we can state with confidence that no sustainable high-tech civilisation has come into existence in our Galaxy prior to about 10 to 100 million years ago.
Or, to put it the other way around, no spacefaring civilisation emerged during the first 12 billion years of the Galaxy’s history.
Could there still be an ET civilisation out there? Of course there could! Its evolution would have had to coincide closely with our own. But, hey, coincidences happen.
What then are the risks from contact with ET, and are those risks increased if we send signals into space?
A new tool of thought: the parameter matrix
Instead of the discredited Drake equation and Fermi paradox, we need to construct a parameter space. Consider the possibilities.
Was the origin of life early or late? If early, the first civilisations could have appeared billions of years before the present. If late, then they have only begun to appear within the past ten million years or so.
Is technology already close to its ultimate limits in our own society, or might advanced technologies be possible which satisfy Arthur C. Clarke’s concept of magic? Are we stuck with nuclear fusion, the limiting speed of light and stupid computers, or is it possible to develop magical energy sources, faster than light travel and hyper-intelligent conscious machines?
What is the maximum possible physical extent of any civilisation? Is it forever restricted to planet-based life at its star of origin, or can it spread space colonies to nearby stars, and from them gradually across the Galaxy?
What is the maximum possible range of the small-scale probes of any civilisation? Can they never reach beyond a few tens of light-years from the original star, or can they spread around the whole Galaxy, either reproducing automatically, or being constructed by interstellar colonies of the original civilisation?
These broad-brush possibilities produce sixteen permutations which boil down to two general scenarios.
Firstly, it may be that interstellar colonisation is not feasible. Industrial civilisations always remain based on their planet of origin. I don’t myself believe this, because spreading on a galactic scale is clearly technically possible using only technologies which we already understand: nuclear fusion and space colonies. But it’s a logical possibility. Space colonisation has not yet been demonstrated in practice even within our own Solar System, let alone on an interstellar scale.
What are the risks from this scenario? How about long-range contact? Since we ourselves don’t possess tachyon receivers, any such contact has to be at the speed of light. Exchanges of messages will be slow, with decades to centuries between sending a question and receiving a reply. The messages will be hard to interpret and will require years of study, as Paul Davies and Carl Sagan have told us.
Davies draws an analogy with the intellectual revolutions of Copernican astronomy and Darwinian evolution: these created drastic changes in our view of our world and ourselves, but took a long time to sink in. It will be the same with the discovery of ET, he says (The Eerie Silence, p.183-84).
What about short-range contact with a probe? If the probe was talkative, then the process of getting to know one another would certainly be speeded up. But if that probe is here now, why hasn’t it already contacted us?
Or might such a probe have arrived long ago and now be defunct? If civilisations really are incapable of interstellar colonisation, then they could have begun to appear billions of years ago. Their probes could have reached us when there was nothing much to find on Earth but green goo. The likelihood that a functional interstellar probe is watching us from near-Earth space right now is rather small.
The second possible scenario is that life emerged late in the history of the universe so far, that civilisations started to emerge within the last ten million years or so, that interstellar colonisation is feasible, and that the colonisation front of one of these cultures is approaching our position.
If the aliens are aggressive colonisers, then we could be in for trouble. Even if they are friendly, we could still be in for trouble due simply to the great disparity in our levels of development. But note how improbable this scenario is. An alien civilisation that has developed completely independently of our own at some point anywhere in the Galaxy needs to be present now within a few hundred light-years of the Solar System, but has not yet reached us.
I could offer you probability figures, but they would be meaningless. All we can say is that in statistical terms the danger is extremely small, but unknown.
Consider the analogy with human history. European power intruded into the Americas and Australasia from the sixteenth century onwards. It may be that indigenous tribes debated the wisdom of erecting signal flags or fire beacons on their coasts, or of launching a message in a bottle into the ocean. It was certainly well within the laws of physics that these signals might have attracted the attention of a Spanish or English man-o’war. The consequences for the natives might have been dire.
Yet the pre-modern inhabitants lived for over 12,000 years in America and 50,000 years in Australia with no visits from ships bent on establishing global empire. When contact came, it was at a time decided by the pace of European development, not by the more primitive culture.
The time when first contact is possible is tiny compared with the enormous stretches of time before and after. Our best strategy is to continue our own growth, colonising our own Solar System and onwards to the stars. That way we’ll be prepared for anything that may be out there…