SkepticLance

If we look at the process of evolution, which should apply to all life in our galaxy, a couple of relevent and probable trends appear. 1. Life, universally, should have a tendency to increase its population. 2. Life, universally, should have mechanisms to ensure geographical dispersal. For a species that has evolved a high order of intelligence, these two factors will still apply, and are likely to evolve as behavioural or psychological trends. Of course, intelligence by its nature, is able to overcome and over-ride pure instinct. Thus, technological species should be able to control those two tendencies - at least enough to prevent disaster. However, that does not cause those two drives to disappear. Now, back to my theme. If only a few intelligences exist, possibly they all have may have totally controlled those tendencies and live happily in their own stellar systems at peace. If, however, large numbers of such aliens exist, it is seriously probable that a number of them are still driven by those evolutionary trends. These species would increase their numbers and would be expansionist. If they survive long term, they must develop a partial control, and only increase their numbers when conditions permit. I see this as a very likely outcome.

Sayonara said : This is not true. Because population is expanding, and the rate of expansion increases as the number of populated planets increases, the benefit to be gained from colonising every planet in the available set will drop as vacant planets in the set run out. This is why species that rapidly multiply in finite habitats often follow the "boom and bust" pattern, driving themselves into a population crash. To be frank, I don't actually understand this. Perhaps you can re-word? Or are you equating 'benefit' as meaning benefit to the entire species? If you are, the logic breaks down as individuals make decisions based on their own local short term benefit. Boom/bust patterns are characteristic, as you said, of many populations. However, if enough alien species exist, there will be many that get around that problem through the application of intelligence (as humans are doing). In fact, I suspect that species that survive will all find ways to solve that problem. If small is 10-500 and massive is 500,000-20,000,000, you still have a minimum range of 450,000 species where the colonisation outcomes can only be considered "uncertain". Of course, this is the origin of the argument. How much is 'massive'. I am working with the assertion made by Drs Drake and Sagan, of one million alien technological species. If that number is correct, then it becomes a statistical 'certainty' that a certain number will expand through the galaxy. By the way, when taking data for your calculations, bear in mind that "speeds of up to 0.2c" means the peak velocity during the trip between two points, not the average velocity for the whole trip. Most actually workable methods of reaching these speeds will require extremely long periods of acceleration and deceleration which will significantly affect the time taken for the journey. That depends on the degree of acceleration. If a space vessel accelerates at one Earth gravity, it would reach a very high fraction of light speed in one year, or 0.1c in about 36 days. If we assume an acceleration of 0.01G, then 0.1c would be achieved in 10 years. Add 10 years deceleration, and we add a total of 10 years to our journey time. For Alpha Centauri, at this acceleration/deceleration, and a top cruising speed of 0.1c, that makes a journey time of 53 years. For a space habitat/hotel/city this would be practical and achievable. In fact, if the space structure was big enough, with a large, independently operating population, journeys of much greater time/distances would be practical.

I must be very poor at explaining things, since there seems to be a lot of misunderstanding. Let me try again. First, my whole point is that there cannot be, or have been, more than a few technologically advanced alien species in our galaxy. If the total number is less than (say) 100, over the past 2 billion years, then my logic breaks down. However, if the number is large, then probability requires certain outcomes. For example, some of the species will have expanding populations. Second : arguing by analogy with Earth life. These intelligences must be enormously varied. On earth we have apes, cetaceans, parrots and crows, cephalopods, carnivores, and elephants - all with quite substantial levels of intelligence. They vary enormously in body form. It seems logical to assume equal variability in psychology. This variability must apply to alien intelligences also. This means, if there are very large numbers of such species, we cannot argue on the basis of psychology. Some of the species must, by probability, have the mental attributes for successful expansion. Some will have the mental attributes leading to explosive population growth. Some will have both. Third. Travel through the galaxy. According to my Scientific American article, humans will have the ability to travel between stellar systems within 1000 years, at speeds of up to 0.1 to 0.2 c. Since star systems have existed in the Milky Way for 6 to 8 billion years, and IF large numbers of aliens exist and have existed, then the same probability argument strongly suggests that aliens with exploding populations, with the ability to successfully expand would have spread through the galaxy a long time ago. Four. Yes, I believe the logical place for most of this population will be in space cities. However, if the population pressure is high enough, they will also colonise every planet they can find. And if the number of species is large enough, at least one will suffer that population pressure. Remember that, on Earth, the tendency for every successful species is population growth. Very basic and important principles of biological evolution drive every successful species to gain the ability and tendency to grow its population. Five. Leaving remains. Look at what we already have as fossils. Stromatolite fossils (cyanobacteria) from 3.5 billion years ago. Jellyfish leaving impressions in mud from 700 million years ago. Billions of shells, and bones from all ages of life. Almost anything can form a long lived fossil if conditions are right (such as falling in soft mud). I find it impossible to believe that any alien species could live on Earth and not leave traces. Where is our alien coke bottle? All this logic falls apart if the number of aliens is small. However, if the number is massive, then at least one species must have come to Earth, colonised, and left traces.

Sayonara said : And I will continue to hark back to: a) They don't necessarily have to have visited every planet in the galaxy, and b) If they did they would not necessarily leave any traces that persist for vast time periods. I think it is quite likely that a race capable of interstellar travel might know a thing or two about non-intrusive technology, waste reclamation, and ecologically friendly materials. Why would they not visit every planet? Bear in mind that we are talking about potentially a million species, depending on how it is calculated. Also, it is over 2 billion years. Population growth of even one species would be enough to drive them to colonise every system thay can. As to leaving traces, ask yourself why they would bother to cover up? It is always cheaper and easier to leave a mess. This would apply regardless of how advanced the speices was. If they were here 1 to 2 billion years before human evolution, there would be no logical reason to bother. An advanced technology might clean up all the mess that could harm their society. But to clean up so thoroughly that they leave absolutely nothing for us to detect is a bit beyond credulity. Swansont said : The number you get from the equation depends on the assumptions that go into it, Absolutely correct. I am not arguing the validity of the Drake Equation (though at this point in time it is a singularly variable and useless concept), but simply the idea that numerous technologically advanced alien civilisations exist or have existed in the past. The Drake Equation goes as follows Number of advanced alien species = Rate of formation of suitable stars times Fraction of those stars with planets times Number of planets in the habitable zone per stellar system time Fraction of those planets where life develops times Fraction of life sites where intelligence develops times Fraction of intelligences where technology develops times Lifetime of those technically advanced societies. The major weakness of this is that you can put almost any value into some of the variables. In other words, no-one has the faintest idea! My view is simple. Bearing in mind that aliens have had 2 billion years to colonise/explore Earth before humans evolved, and there is no trace of such activity, then it is likely that the total number of such technologically advanced species is very small. Not necessarily zero. Just a small number.

Whew! After all those postings, where do I begin? Perhaps just a comment or two. First, I was probably wrong at one point in talking of spaceships. It is likely that expansion will be via what we are now calling space cities. Generations in transit matter little for such a structure and such a society. Second, it does not matter too much for space cities, when arriving at another stellar system, whether there are suitable planets or not. They will be able to mine space detritis. There is an enormous amount in our own solar system left over from planet formation, and that is probably true for most stellar systems. Certainly, robot probes sent to Alpha Centauri etc will give us the answer long before any space cities depart. As to aliens doing the same and getting to Earth. I have to keep harping back on the enormous numbers involved. With two billion years to do it, and (according to Sagan and Drake) a million species involved, how is it possible that not one alien species ever got here? It appears beyond belief to me that, if they were here, some time in the past 2 billion years, that they left no traces. Look at the enormous quantity of junk humans have produced. Even the tiniest fraction of that as alien junk would have marked their presense indelibly.

As I understand it, there is nothing to prevent a 'little big bang' occurring any time / any place. Problem is that the result is a new universe, of whatever size. We cannot detect said new universe. Thus it is as if it did not happen.

Lucaspa said : The distance between stars using lightspeed is such that birth control MUST be practiced most of the time. Such ships are going to be generational: several generations living and dying on the ship. So, in order to undertake such a journey in the first place, they must have a brake on reproduction. Otherwise they couldn't maintain a stable population on the ship. Sorry. This is faulty logic. The distance from here to Alpha Centauri is 4.3 light years. At 0.1 c, that journey would take 43 years. If our hypothetical invading alien had a generation time of 25 years (human average), then the population increase would be manageable. It would be easy to design a vessel able to cope with such an increase in numbers. On the other hand, they might use short term population control - just for the ship's journey - and switch to uncontrolled growth after arrival. Either way, we cannot assume that our alien species will not grow dramatically in numbers after arriving at their destination. In fact, assuming numerous species competing, the species that increases fastest has a substantial competitive advantage. The average distance between stars within our galaxy is, in fact, less than 4.3 light years. Thus, a rapidly growing population could easily cross the void, stellar system to stellar system. In fact, such a species is the one most likely to be involved in rapid expansion. Population pressure will pressure the explorer types to get out there. Humans are likely, in the next 50 years, to develop a 'space elevator' which can get us into space cheaply and in large numbers. Assuming our alien species has this technology, they will have no major brakes upon their ability to get into space cities, and from there to expand in all directions.

Sayonara. I think it is important we all accept that this is a speculative discussion, with no proper scientific way of determining who is 'right' and who is 'wrong'. I enjoy this kind of discussion and am happy to engage purely for the pleasure of discourse. Either side may be correct, but let's explore. I do not dispute your ideas on why a particular intelligent species never got to Earth. Perhaps their travelling space city did blow up. The thing is, though, that these possibilities can only apply to a small number of species. If Sagan and Drake were correct, and the galaxy supports a million intelligent species, then suggesting that no-one got to Earth because of this or that individual reason no longer makes sense, because it could not have happened to everyone. At least one alien species would have lived long enough, and been expansionist enough, to make it to Earth. Incidentally, the reason I used the term 'habitat' was because I saw it used that way in a Scientific American article on our future in space. Space 'hotel' does not quite cover it. I suggest we call them space cities.

Sayonara said : It is foolish and arrogant to take the absence of recognisable evidence for alien visits to Earth in the distant past as evidence against intelligent life elsewhere in the galaxy. And there is no getting around that. This is an assertion, not an argument. Present your logic or your evidence, or else it is just a statement to be taken on faith. My statements on space habitats (which is more than just a term of ecology) do not contradict anything I said earlier - just expand on them. Any successful expansionist species moving through the galaxy would be expected to live primarily in space habitats for the reasons given. However, they would also move onto planets. My logic assumes some population pressure. One thing much bigger than the galaxy is the ability of living things to grow in numbers. Unless they had a brake on reproduction, sooner or later, they would be looking for each last bit of habitable acreage. And, if there were many intelligent species, the ones with brakes on reproduction would be overwhelmed by the ones that did not. That is also the reason why the argument that Earth may not have been a hospitable environment is not a good one. A sufficiently advanced technology can produce liveable buildings in any environment. When population pressure is sufficient, even inhospitable Earth would be colonised. The arguments Sayonara etc have put forward are valid, but only if the numbers of intelligent species are small. Let me say one other thing, to avoid looking arrogant. This is all speculation. In science, we know that speculation, theorising, calculating, computer modelling, and other exercises that take place in the human mind or a computer rather than the real world, are ultra prone to error. All my 'logic' may be just so much hot air, and is very likely to be. However, I enjoy speculating, and that is the justification.

Edtharan I seriously doubt that humans will find many planets to our liking once we are travelling interstellar. The vast majority will be too large, have toxic atmospheres, be too cold, too hot, too small etc. This situation would have greeted any alien civilisation that reached Earth. There are two possible solutions. 1. Turn the inhospitable planet into a base for a habitat. That is, build a place to live screened off from the outside environment. This is what we will do if we set up bases on the moon. 2. Change the planet to suit our needs. To change a planet into one similar to Earth is called terraforming. There has already been at least one international conference on terraforming Mars. Those scientists think it is feasible. It is probable that any hypothetical alien civilisation touring the galaxy 2 billion years ago would have to do one of the above for pretty much each and every planet they colonised. An expansionist species would need living space, meaning the need to colonise. (Though I still think most would live in space habitats) Again, I suggest that, if there were numerous intelligences, at least one would have been successfully expansionist, and Earth would have been colonised, with 'fossil' remains left behind. The only explanation I can see that makes sense for the lack of remains is that the number of alien intelligences is very low.

Sayonara I have a personal theory which makes my logic fairly inevitable, if this theory is true. That is : when humans ( and lots of possible hypothetical aliens) have developed sufficiently in terms of space technology, we will also develop large numbers of very substantial and highly advanced space habitats. I am talking about rotating (for gravity) cities in space of a million or more people. After all, once we have made the effort to get into space, what would be more silly than to descend another gravity well (gravity trap) and imprison ourselves on another planet. Human history can be seen as the history of separation from our natural environment, to the point where we now live in air conditioned buildings. The next step is total separation from the surrounding environment, as would happen in a space habitat. Habitats can move freely from place to place simply by strapping on ion drive engines. They can harvest water from asteroids, moons, Saturn's rings etc. They can mine rubble in space for other raw materials. I know this is possible, since I have seen iron extracted from basalt rock which was melted in an electric arc furnace. With sufficient technological development, which is only a matter of time, they can become quite independent. They can use fusion power and lighting to grow their own food, and replenish their own oxygen. Independent cities in space. Once a species reaches that stage in its development, what more simple than for one of these independent cities to simply head for the next star system? If it takes 100 years to get there, what the heck. When there, they can harvest water, rocks etc as before. When the population grows enough, make another habitat. I am sure that humans will terraform and colonise planets. However, I suspect that, in say 20,000 years, there will be more people living in habitats than on planets, and these habitats will freely move from star system to star system. Over a long enough period, they will colonise the entire galaxy. If a large number of intelligent alien species existed 2 billion years ago, they should have gone through this process way back then. A comment about intergalactic travel. This is many orders of magnitude more difficult that interstellar travel. Outside our own little cluster of galaxies (Milky Way, Magellanic Clouds etc), the next galaxy is Andromeda, 2 million light years away. If we assume 0.1c speed of travel, it would take 20 million years to get there. How do you keep a colony of people going 20 million years? This is not totally impossible in theory. We could, for example, with sufficiently advanced computers, get them to travel, carrying frozen embryos. The computers are programmed to thaw out and incubate the embyos, and then raise and teach the new humans. Somewhat risky. To assume nothing going wrong over 20 million years seems a stretch.

A lot of reasons have been put up on this thread as to why no intelligent species ever got to the Earth. (They were stay at homes, died off early etc.) All these are possible, but ONLY if the number of intelligent species that have evolved over the past 6 billion years is small. When Drake and Sagan first published the famous Drake Equation, they put in estimated values and calculated a total of one million intelligent species in our galaxy. That is patently wrong. If we assume they exaggerated by a factor of 1,000, and 10% only came into being during the first 2 billion years our galaxy existed, then we still have 100 intelligent species living 2 billion years before the first mammalian life came into being on Earth. It is somewhat unlikely at every one of these species either died off or were pacifist, stay at home philosophers. Adaptations to multiply in numbers and expand geographically is universal for life on Earth, due to very basic principles of evolution. It is seriously probably that this would apply to extraterrestrial life also. Such adaptations in intelligent species are likely to be behavioural. ie. at least some of their population feel the need to explore and colonise. If only 10% ended up as expansionist survivors, we still have ten intelligent species expanding throughout our galaxy more than 2 billion years ago. If we assume that their population growth is only one doubling per century (much slower than human population growth), they can still fully populate the entire galaxy in 2 million years. Spaceship speeds of only 0.1c is enough to permit this. There are no alien artifacts on Earth. Yet current human technology is such that we are leaving non-biodegradable trash by the millions of tonnes that will still be around in 2 billion years as fossils in rocks. The only viable reason why there are no alien fossils or fossils of alien garbage is that aliens never got here in the first place. And the most likely reason for no early alien visits is that aliens are very, very rare.

Yes. That is an extreme example, and one that few, if any, would claim as not being ecological damage. However, even though the change is dramatically undesirable, the principle still applies. The ecosystem was not destroyed - but morphed into something else. The balance of nature is not lost, just moved to a different, albeit seriously undesirable, balance point. My favourite example is bell frogs in Sydney, Australia. In seeking for venues for the Sydney 2000 Olympics, a team found a polluted pond that 'begged' to be redeveloped. However, ecologists found a thriving population (the world's largest) of a threatened species of bell frog. Turns out that the main cause of their loss of numbers was a fungus from Africa (chytrids) which kills amphibians wholesale. This polluted pond though, was more toxic to the fungus than the frogs. By living there, they 'self-medicated' and stayed healthy where other bell frogs in clean water were killed off. Moral of the story : do not jump to conclusions about which environments are desirable.

Chupacabra. These are good ideas. Any idea how to quantify them?

CanadaAotS said : Thats exactly why, through natural (or artificial depending on how you look at it) selection, as parents have their children later and later in life longevity is increasing Sorry, that's not correct. It is true that longevity is increasing, but this is not genetic - not any form of biological evolution. All that is happening is that we are removing many causes of early death, so that average lifespan grows. We are not living longer. Just less dying young.

Longevity is governed by evolution, and that operates on whatever age is required for successful reproduction, rather than speed of metabolism. An interesting experiment a few years ago looked at longevity in fruit flies as a function of reproductive age. The experimenters bred fruit flies over many generations. As soon as the larvae metamorphosed into adults, they were separated into male and female, preventing mating. They permitted gender mixing, and mating only towards the end of the fruit flies reproductive life. Most were not able to reproduce, which didn't matter since the few that did produced lots of offspring. Each generation, the separation was prolonged a little more. Clearly, we would expect that adaptation would extend reproductive life as a response to this evolutionary pressure. However, in addition, total longevity extended substantially also. The experimenters were breeding long lived fruit flies. Conclusion : longevity is determined by however long the organism has to live to breed successfully, and this is driven by evolution. Humans are long lived because we need a long period to develop into adults. Parents need to be around to care for young, and the presense of grandparents also increases survival of those young. Thus we have evolved as a long lived species in order to have grandparents to help in the care of young.

The fact that Turkey, a very religious muslim nation, is the only one lower than the US on the poll, tells you something.

Sisyphus. I think you just nailed down that defining feature yourself. To wit : "A crackpot is a person who clings to his theories even when presented with hard data that falsifies it."

I think there are two things that make a crackpot. 1. Pure chance. 2. The very human inability to admit they are wrong. In other words, these are people who by pure chance are exposed to silly ideas. Once they adopt those ideas (not having a better alternative) they refuse to change their minds. One of the qualities that makes a good scientist is the ability to say : "I was wrong." That quality is totally absent from the crackpot. Of course, there are lots of other factors. As said earlier, there are as many factors as there are crackpots. For example ; a deep suspicion of authority is one quality that makes crackpots reject conventional wisdom. A lack of good education, especially into critical thinking is another factor. etc. etc. One thing I know for sure is that you cannot change their thinking. Once a crackpot has made a full emotional committment to an idea, that person will not sway from it, no matter how much evidence to the contrary you supply.

Couple of points. 1. People who have been through transplant operations have undergone a major trauma. It is not at all surprising that many will show changes in their approach to life. I had a very minor health hiccough recently, age related, and decided to do a trip to Europe, on the grounds that it is obvious I ain't gonna live forever. Others with greater trauma will experience much greater changes than this. 2. Receiving someone else's organ often results in curiosity about the donor. Once these people find out a little about the donor, some might emulate their benefactor. 3. The media, and ESPECIALLY documentary makers for TV, are not always fond of scientific truth. They frequently select their data to support a predetermined story. This is not science.

A very perceptive observation from bascule. Yes, this is the Fermi Paradox. There was a very interesting article in the February 1999 issue of Scientific American by two NASA scientists, who claimed that the theoretical 'ultimate' speed limit in interstellar travel would be 0.1 to 0.2 c. I used the lower number as my basis for calculations. Swansont, at 0.1 c, it would take about 700,000 years for humans to reach the far side of our galaxy (we are two thirds towards the outer edge of a spiral 100,000 light years across.). This would be most definitely a one way trip, so we need not talk about time to return. Information, on the other hand, would take only 70,000 years to arrive. When I carried out my calculations, I was surprised to see that the most limiting factor time-wise was the average speed. The human reproductive rate was not very limiting, and nor was the suggestion that we would have to spend many generations in one star system before sending out the next manned probe. End result, humans (or hypothetical aliens) could cross and fully colonise the galaxy in 2 to 10 million years. The higher numbers came from the assumption (unproven but possible) that star systems towards the centre would be toxic to human life, and we would have to travel around them. You will appreciate that even 10 million years is a mere eye blink in relation to biological time, since life is probably 3 to 3.8 billion years old. (Some rock structures in Western Australia have been tentatively identified as 3.6 billion year old stromatolite fossils). Thus, if lots of intelligences evolve, then plenty must have been around 2 billion years ago. If even one was expansionist, we can expect the early Earth to have been visited, and even colonised. Thus, if intelligent life in our galaxy is common, we should be finding fossil artifacts.

Swansont, NASA scientists estimate that humans will have begun our journey to visit and colonise other star systems within 1000 years. While some other intelligent species might be 'stay at homes' or else kill themselves off early, if there are large numbers of intelligent species, then it appears probable that at least some would set out to explore the galaxy. At an estimated speed of 0.1c (we assume Einstein was right), and reasonable estimates for speed of population growth etc., we can assume they will fully explore and colonise the entire galaxy withing 2 to 10 million years (depending on which assumptions you use). Do the math yourself. Since 10% of the stars in the Milky Way are about 2 billion years older than our one, then (based on the assumption that lots of intelligences evolve) it is reasonable to deduce that at least one intelligence colonised the galaxy 1 to 2 billion years ago. Thus, the signs I am talking about would be right here on Earth. Hell, humankind produce enough durable garbage. An alien species would be seriously likely to do the same. The result would be a plethora of fossils. Since there are no such signs, it is reasonable to assume that alien intelligences are rare.

Sisyphus said : and if intelligent life is exceptionally rare, that might explain it nicely. I absolutely agree. I have a problem with those who claim (Star Trek et al) that intelligent life is common. If so, where are the traces?

Our star is classified as a third generation star. The first generation contained little more than hydrogen, and some helium impurity. Second generation included larger atoms. Third generation included the full range of atoms currently present. It is very likely that only a solar system with a third generation star could produce life, since earlier models would not have had the right mix of more complex atoms. However, third generation stars have been around for at least 6 to 8 billion years. The Milky Way galaxy has stars (third generation) which are two billion years older than our own. In fact 10% of the galaxy is made up of such stars. Thus life could easily have developed two billion years before Earth life developed. Of course, this is speculation, since we still do not know the specific set of conditions required for biogenesis. The one thing we do know for sure, is that no trace of alien life or alien civilisation has been seen on Earth. Not even a fossil coke bottle! Since it is possible in theory to travel between the stars at one tenth of light speed, crossing the galaxy in a million years, and an advanced civilisation could probably do this, and since the power to reproduce and increase population numbers is unlimited, if evolution had led to a number of intelligent life forms developing two billion years before we did, it is almost certain that they would have visited, and maybe colonised the Earth. Since there is no sign of any such visit, that reduces the probability that intelligent life in our galaxy preceded human life by terribly much, if at all.

Dr. Cloud. Well done. You just put up two very good postings. My view has been that intial conditions in hurricane formation are the result of winds that are, in turn, the result of temperature gradients. I think we agree on that. I appreciate that later development of a hurricane is influenced by many other factors. However, I feel that it is likely that initial conditions must be one factor at least, and those initial conditions are influenced by temperature gradients. Indeed, it appears reasonable that a lowered temperature gradient should reduce the intensity of the winds that lead to hurricanes, and should thus generate fewer hurricanes. That is, of course, deduction, and could well be wrong.