My take on the Fermi Paradox – the ET Malthusian solution

7 Mar

This is a repost of a Yahoo group post dating from 2004.

In 1950 Enrico Fermi posed a question. He asked if intelligent extra terrestrial beings exist then why have we not seen them here on earth. His reasoning was that if anywhere in the galaxy an advanced civilisation arose it would spread throughout the galaxy in only a few million years. If, for example, it spread at 2% of the speed of light a civilisation would reach across the galaxy (a distance of 100,000 lightyears) in only 5,000,000 years. And at 1% of c in just 10,000,000 years. He assumed that a) technology would exist to achieve very high velocities, and b) a consolidation period of several hundred years between each hop in reaching his conclusion. And given the large number of stars in the Milky Way (100 billion+) and the age of our galaxy (10 billion+ years) then such civilisations must exist. To work out how many such civilisations there are in the galaxy you can use the Drake Equation.

N = N* fp ne fl fi fc fL. The above link provides a javascript form and an explanation of each variable. You can imput your own values for each variable.

Andrew Lias * summarises the common solutions to the paradox. My own solution would be a combination of the second Stay at Home Hypothesis 2 (SAHH 2) and the Apocalyptic Hypothesis (AH). Briefly SAHH 1 refers to a lack of desire to explore interstellar space and SAHH 3 refers to ETs being too addicted to virtual reality to worry about external reality. SAHH 2 proposes that technology and economics makes the business of interstellar colonisation too unlikely. AH refers to a possible tendency of advanced civilisations to become extinct relatively quickly. Andrew’s site * lists other possible solutions.

Proponents of SAHH 2 claim that there is only so much that technology can do to overcome the problems of colonising other stars and at achieving the high velocities needed to get there, and to do so within realistic economic constraints. A project like colonising a planet in the Alpha Centuri system would require immense amounts of time but deep time poses problems for humans, not the least of which is economics. Added to the time needed for travel is the time needed colony consolidation. How long? It is estimated that the Voyager probes will take 80,000 years to reach the nearest stars travelling about 300,000,000 miles a year. With possible new technologies in the future like ion drives, anti matter and hydrogen this may be cut to few thousand or a few hundred years. A few hundred would be a speed of maybe 1% of c. To add a human cargo to this poses considerable problems in terms of technology and cost. The International Space Station is only a few hundred kilometres above earth and will cost $US100 billion to house a few humans at any time.

Life support systems will be important for both travel and for colony consolidation. The problems of Biosphere 2 show that, for small self contained artificial environments, chaos is the order of the day. Other problems for travellers include micro gravity, cosmic radiation, microscopic dust (dangerous in high speed collusions) and energy supply.

Once at Alpha Centuri a planet will most probably need to be terraformed. That is, made suitable for human habitation. It is thought that Mars may take 100,000 years to terrform. Planetary transformation is a slow process requiring deep time. All this time any bases on Mars would require heavy support from Earth. They would be more dependent than the bases in Antarctica. Colonising Mars will be a very different affair compared to what colonising the new world was for Europeans. The old Europeans did not have to make the new world and the established colonies became viable within years. The expectation, that by 2100, there will be extensive settlements on Mars and various plantary satellites throughout the solar system is, I think, too optimistic. We can use Antarctica as a guide to what will be the pattern of human settlement throughout the solar system. Antarctica has had exploration and scientific bases for 100 years. What is Antarctica today? No permanent population and only a few thousand people occupy the continent 1.5 times the size of Australia on a transitory basis. And Antarctica is a much more friendly environment than Mars. I would expect a few very dependent bases on Mars by 2100 with very small transient numbers.

The problem of colonising other planets, in our solar system or any other, is complexity. Technological complexity will be what allows a Martian colony to be established but such complexity will also be the achilles heel of such a colony. The complexity that will allow a Martian colony to exist will not be the complexity of the colony on Mars but the complexity of society and technology on earth. Mother earth will supply an umbilical cord of everything to neeeded sustain a Mars based colony and the wellspring of that sustenance will be the societical and technological complexity here on earth. Imagine the year is 2050 and Mars has a few bases. Now the apocalyptic balloon goes up on earth resulting in either the extinction of humanity or the collapse of technological civilisation and its’ complexity without human extinction. The outpost of humanity on Mars survives the calamity but succumbs thereafter as the earth fed umbilical cord withers. The colonists die or evacuate back to earth. The Mars colonists are more vulnerable because they do not have the option of surviving with complexity collapse as do earth bound humans. A breakdown in air conditioning on earth with no way of replacing parts or servicing systems as a result of collapsed technology is an inconvienence but on Mars such a collapse would mean death. We saw what a collapse means to anyone off the planet and dependent on earth based complexity when the Soviet Union collapsed in 1991. One cosmonaut was left stranded in orbit but fortunately he was eventually retrieved.

Added to the technological complexity needed for a colony to be independently viable of the home world is the ecology that results from teraforming. With ecological diversity comes stability of ecology and climate, both essential for deep time viability and for a boipheric resource. Ecological diversity means ecological complexity from the micro scale up. Teraforming is more than simply hoping some seeds will grow into small oxygen generating units and hey presto everything else will fall into place. It requires taking a planet through different stages of habitat types; each helping to change the environment into the type usable by the next. Bateria and fungus preparing dust into soil, UV tolerant varieties preparing the way for post ozone varieties of plants. This process is described as ecological succession. It requires vast amounts of time and energy to build an environment into a human friendly eco system that can be self sustaining in equilibrium on a global scale. Probably thousands of years at least, maybe tens or hundreds of thousands of years. In my analysis I assume that such a teraforming process has to be completed before such a colony has a fate that is independent of the fate of the home world.

I will assume that colonising other stars will require a long period of travel of hundreds, or probably thousands, of years followed by long periods of consolidation. Further I will assume that a colony on the frontier will need to be consolidated before moving the frontier on to the next star because of the difficulty in supporting a dependent colony beyond a certain distance. So the home planet (H) could colonise a colony at Frontier colony (F1) at a distance equal to or less than the frontier hop (FH) but not a colony at F2 which is at a distance of 2FHs. F2 could only be colonised by F1 after F1 has been consolidated. The frontier consolidation time (CT) plus travel time (TT) between frontier tiers equals frontier hop time (FHT).


So exspansion velocity (EV) equals FH divided FHT.


Let’s say that that TT equals 10,000 years and CT equals 90,000 years. FHT is then 100,000 years and say that FH is equal to 4 light years.

4ly / 100,000 = 0.00004 of a light year per year. So for a civilisation to spread across the galaxy, a distance of 100,000 light years would take

100,000ly / 0.00004 = 2.5 billion years.

This is a lot slower than the 5 – 10 million years and it gives us a better chance of not having had any contact with ETs. Still the galaxy is not, as far as is known by SETI, full of radio signals from intelligent sources. Should we not still be able to detect signals from colonising civilisations? The chances are that, in 10 billion years, at least some must be rippling through the galaxy.

That brings us to the second part of my solution. The Apocalyptic Hypothesis (AP). The claim is that advanced civilisations tend to become extinct relatively quickly. In the Drake Equation N = N* fp ne fl fi fc fL the last variable fL refers to the longtivity of a civilisation after the discovery of radio communication. If this value is very small than the number of radio communicating civilisations in the galaxy will be very small. That, according to AH, is the solution to Fermi’s Paradox. However critics point out that if there is even only one exception to this rule then the galaxy will be overrun by a civilisation. There is no evidence of one exception and so the paradox still holds.

The implicit assumption is that if a home civilisation holds out until colonial expansion then extinction is unlikely. Another assumption is that each hop will be relatively quick and easy and once enough colonies are conslidated then, like the internet with its’ many independently operating nodes, that such a civilisation would, overall, continue to function in the face of local damage. There is some truth to this because a civilisation that stays at home will meet with extinction at some time. I have assumed that exspansion is slower but when you make this assumption something becomes apparent. The larger the FHT value the more likely is extinction.

Let’s look at Earth in the 20th century. The population increased from 1.5 billion at the start of that century and reached 6 billion by its’ conclusion. 150 million died in wars and millions more by genocide. In addition new forms of pollution and many toxins were invented. Most of the 500,000 derived substances from the petro-chemical industry came during that century. There were also threats from nuclear, chemical and biological warfare. A cold war between 2 super powers kept the world just minutes from nuclear midnight. Much went wrong and much more could have gone wrong. The century provided some people with oppurtunites and denied others any and technological progress helped to increase the differentials between wealthy and poor nations. If we went through the 20th century again would we survive? Maybe. Maybe not. But in the next 100,000 years we will have 1,000 centuries. What are the chances that we can survive 1,000 20th centuries? Too close to zero to call. Each progressive century provides us with more power and more danger. According to the law of averages and given enough time the human race will slip.

We often hear of the danger to the human race of a giant meteorite impact and the need to prepare to defend ourselves in case of a once in 30 million year impact. This overlooks the probability that humans live in a much smaller time frame without the help of a meteorite. We also hear that we must explore space because one day the sun will die. The sun will die but stay at home humans will probably not need the help of our sun to become extinct. The human being is a lethal species with an ape’s brain. What is distinctive about the human brain is the exploded cerebral cortex. This does not make us better animals with better morals but only better able to achieve animalistic aims. Counter intuitively technological progress has increased the odds of extinction even as we have become all powerful over an environment against which our progress was purposed to reduce threats to ourselves from that quarter.

I can see no reason why a colony should be less prone to local extinction than a home planet if we assume long travelling times and long periods of colonial dependence. Thus a civilisation can become a space coloniser and extinct or least very slow at breeding consolidated colonies.

We can, in theory, work out the odds of extinction. If we determine that FHT is 100,000 years and that species extinction (SE) is 0.9 over 100,000 years and that there are 5 colonies at F1 then it looks difficult for a civilisation to flurish. If H holds for 100,000 years then F2 colonies can be established by consolidated F1 worlds independently of the fate of H. If H fails before F1 colonies become consolidated then H and F1 become extinct. If we have 100 space colonising civilisations in the galaxy and if SE is 0.9 then maybe only 10 will survive to the F2 stage. F1 of those 10 civilisations may represent 50 F1 worlds and if F1 worlds seed on average 5 worlds then 25 F2 colonies become consolidated out of 250 established ones. Not sustainable. This is more like a radioactive decay than a critical mass needed for an explosion. We can call the average number of colonies seeded at Fn by Fn-1 consolidated worlds FN.

So if FN < 1/1-SE then the civilisation will not be deep time sustainable.

If FN > 1/1-SE then the civilisation will be deep time sustainable.

SE is measured over the period of FHT.

FN is dependent on factors such as star density and type, suitable planets and moons and so on. SE depends on various other factors such as species biology and the length of time for FHT.

Many cosmologists forget what biologists know full well. That life is a difficult struggle and unlikely. It continues only in diversity and from large selection sample. Selection is a word not heard from cosmologists talking about the possibility of ETs. But it is why only one homo species survives today out of a larger selection in the past. It is assumed that, once in space, species are somehow immune to selection for extinction.

In some ways the question asked by Enrico Fermi has a similarity to one asked by a creationist about life on earth. This creationist went to my high school. A pleasant enough guy who loved his god with his soul but did not have too much of a mind. The question was if the earth is so old how come we do not have so many animals that their numbers stacked them out to Pluto. Another way to look at the same question is to look at flies. A pair to can produce offspring in such numbers that they could replenish the world’s fly population in only weeks if they all survivied. Why are we not walking around waist high in flies amd maggots? Thomas Malthus answers this question. Charles Darwin used Malthus’ insight in populations and biology to help him formulate his theory of evolution. Malthus tells us how an environment will limit animal numbers and Darwin explains how this selective pressure affects the charteristics of a species. Here is a concept called limits; one that is forgotten or dismissed in our hubris. The T shirt that says “There are not limits” is surely one of the more mindless ones. But like animals a space travelling civilisation will meet limits on materials, energy, time and distance and having limits will also face selective pressure. I would call my solution to the Fermi Paradox the ET Malthusian solution.

This solution lacks technological hubris. An invincible belief that we shall overcome all and triumph and expect that other species also would. The main difficulty I believe is an inability to fully appreciate deep time. We are creatures of the nano second in terms of the cosmos. 10,000 years ago we were only just farming. 500 years ago the Earth was the centre of the universe. We call once in 20 year floods “abnormal” when in fact they are quiet normal. We believe naively that in 5 billion years time humans like us will see the death of the sun. This is not much different from animals who do not know they will die.

To summarise my solution to the Fermi Paradox I would say that forces of selection narrow down the sample like the tree of life on Earth. Many branches get pruned and such pruning does not stop simply because a species can space travel. This is more likely if longer periods of time are needed to colonise other star systems than is usually allowed. Between those who say that interstellar travel is too expensive and challenging and therefore it will not happen and those who say the whole galaxy should be colonised in just 5 million years I take a middle position of the business of interstellar travel being not impossible but slow and difficult and that most who start out will fail and that colonisation may, for most space travelling species, be possible but not deep time sustainable.

I have used fairly abritary values for illustration purposes only. It may be that interstellar travel can be faster than I have allowed for. Or that terraforming and consolidating can be speeded up but for this the difference can not be too great since the process involves huge transfers of energy over a long time. I arrived at an abtritary value for SE which in thruth I think is too optimistic. The important aspect of my solution is the ratio of FN to the inverse of 1 – SE.

Finally it allows for an “exception to the rule” moving at a slower rate. Critics may say that a slow moving civilisation is one way to push a square peg into a round hole and make it fit and that it rests on an unproven assumption on limits to what technology can achieve. I would reply that a technology is not known to exist until it is demonstrated to exist and I would repeat the question asked by Fermi. “Where are they?”