ET, ARE YOU THERE? A new study investigates theories of intelligent life elsewhere in the galaxy by generating computer models of star formation, planetary formation, and the development of life. One star map from the simulation appears above.
Image: DUNCAN FORGAN/ROYAL OBSERVATORY, EDINBURGH
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One day in 1950, nuclear physicist Enrico Fermi posed a question to a few colleagues he was lunching with at Los Alamos National Laboratory that would become known as the Fermi Paradox: If the Milky Way is indeed teeming with alien civilizations, as many theories suggest, where are they? Shouldn't we see evidence of their existence? Nearly 60 years later, the question remains just as vexing. After all, decades of searching for extraterrestrial radio signals or evidence of alien civilizations have come up empty.
Nevertheless, search for extraterrestrial intelligence (SETI) programs soldier on. And the hunt for any alien life, even in microbial form, is ramping up quickly with instruments probing Mars and other likely nearby candidates in greater detail and with the regular detection of new planets outside our solar system. In the absence of hard evidence for intelligent extraterrestrial life, some researchers have set out to estimate just how much might be out there. The hope is that they can justify the continuation of SETI searches or even refine them and thus up the odds of finding ET, perhaps someday rendering the Fermi Paradox moot.
In a recent paper published online by the International Journal of Astrobiology, graduate student Duncan Forgan of the Royal Observatory, Edinburgh, in Scotland set up a numerical model of the universe under different scenarios of biogenesis. His model relies on current observational knowledge of stars and planetary systems, as well as some assumptions about the viability of life and its ability to evolve into an advanced, intelligent form. If life can only arise under a narrow set of initial conditions, Forgan estimates there should be 361 advanced, stable civilizations in the Milky Way. If life can spread from one planet to another through biological molecules embedded in asteroids, though, the number jumps to nearly 38,000. (Even given a densely populated galaxy, Forgan notes, there is no guarantee of immediate mutual contact.)
Forgan's model makes use of the Monte Carlo method, by which the starting variables in a system are randomized over repeated simulations to allow for uncertainties in their values. By averaging the results from 100 such simulations, Forgan's analysis yields an estimate that accounts for variations in inputs.
But some in the field argue that estimates of the extent of extraterrestrial intelligence cannot carry any degree of accuracy, given the gaps in our knowledge. Such numerical estimates are "still subject to all the other uncertainties and all the other imponderables" regarding the origins of life, says planetary scientist Ian Crawford of Birkbeck College at the University of London. "We have to admit that we're hugely ignorant of many of the pieces of information that we would need to know before we could realistically estimate the prevalence of intelligent life elsewhere in the galaxy."
Mark Burchell, a professor of space sciences at the University of Kent in England, says that astronomically speaking, our knowledge base is fairly refined. "But the biological and social aspects of the equation remain speculative," he said in an e-mail. "As Forgan points out, we are limited to single-event observations (life on Earth) to make sweeping general predictions (life elsewhere)."
Forgan acknowledges that the analysis suffers from some uncertainties, stemming in part from a small and somewhat biased data set on planets outside the solar system. Some 300 planetary systems have been found since 1995, when the first planet orbiting a normal star other than the sun was discovered. But the detection methods employed in this effort tend to find planets that are quite large and hot. The European COROT satellite and NASA's forthcoming Kepler spacecraft, however, should be able to locate more Earth-like worlds in the coming years with dedicated, sensitive monitoring of dips in stellar brightness that occur when a planet passes in front of a star. Forgan says that "Earth-mass, rocky planets are still the best bet for habitability," so such discoveries would significantly affect his conclusions.
He also notes that the numbers, subject as they are to uncertainties, should not be considered the sole outcome of his paper. Simply refining models of where and when life should arise, he says, might improve SETI searches. "Searching for life in the galaxy is the ultimate needle in the haystack," Forgan says, and any guidance as to where and when to search for that needle should be useful.
But Crawford thinks such analyses won't affect the status quo. "We've got no option but to keep looking; there's nothing else we can do," he says. "All the SETI searches can do is what they've been doing for the last 40 years and keep listening."
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32 Comments
Add CommentThe seventh factor of the Drake Equation is the length of time an intelligent planetary civilization releases detectable signals into space. Forgan also makes use of such a variable. What would it take for us to detect, on an extrasolar planet, radiation compatible with the hypothesis that the civilization of that planet has destroyed itself through misuse of atomic power or some other force that should leave detectable and measurable traces?
Reply | Report Abuse | Link to this(That should be "detect from an Earth-based or near-Earth based device", of course.)
Reply | Report Abuse | Link to thisI dunno about that but clearly there is life out there somewhere!
Reply | Report Abuse | Link to thisRT
www.anon-tools.us.tc
Precisely, the fundamental flaw underlying all theoretical hypothesis regarding extra terrestrial life is that they all fail to recognise the one essential factor that is most important, that we as human beings are in fact cylon and as such all of this has already occured and it will all happen again.
Reply | Report Abuse | Link to thisIf you assume that the known universe only contains ONE advanced intelligent form of life (earth), and further assume that the likelihood of a similar intelligent life form in a similar sized area of space is 100 trillion to one, then knowing that space is infinite - there are actually an INFINITE number of planets with advanced life. There is a lot of intelligent life out there. But in the infinity of space, it's like a salt molecule in the pacific finding a similar salt molecule in the Atlantic. it's possible - just not very likely.
Reply | Report Abuse | Link to thisor sublimed off their planets ala Arthur C. Clarke or Ray Kurzweil
Reply | Report Abuse | Link to thisAt Forgan's low estimate of 361 intelligent advanced planets, with an even distribution we are looking at 600 light years between planets. We have only had radio a century, so our signals have not even left the infield yet. For us to be picking up something our closest neighbor's would have had to begun transmitting high strength signals at least 500 years ago but who's to say who the early adopters are. Earth could be the early tech within our local group of intelligent neighbors.
Reply | Report Abuse | Link to thisThe question should not be why we have not heard from them but when we will.
I think intelligent life is extremely rare (even on earth) all the logic used to obtain a figure is still a bad guess, it is quite possible we are the only advanced life form in our galaxy, so we should be looking at ensuring our own future existence, instead of looking for aliens...
Reply | Report Abuse | Link to thisrichieo sure is a stick in the mud intelligent life is not rare this magizine just had an article on it about the gold fish life is not difficult and rare nature does not do things the hard way like humans do
Reply | Report Abuse | Link to thisThere's life, then there's intelligent life. By the lack of any other intelligent species on our own planet despite millions of other complex lifeforms, it's safe to assume that intelligence is a rare accident. And had things not happened just as they did, even we never would have made it out of Africa. I have this funny feeling that in time we'll find plenty of life, and lots of new and exciting complex life-forms. But intelligence may be much more rare than many expect.
Reply | Report Abuse | Link to thisMichael Crichton had a fantastic essay on this subject. Try searching for it on his ste under speeches. A great read.
Reply | Report Abuse | Link to thisyes but don't forget we are only an advanced computer program with A.I created by an anvanced civilization far in the future of our own time.
Reply | Report Abuse | Link to thisWe are like a small child jumping up and down and looking around to see if we have got some attention. We must remember that we are the masters. We must remember that we are the dominant species of the universe and that any aliens we find are to take their lead from us and be subdued for all eternity.
Reply | Report Abuse | Link to thisI find the discussion of the number of intelligent, civilization-forming, extra terrestrial animals to be breathtakingly speculative; rather akin to the debate among medieval scholars, over the number of angels that can fit on the head of a pin.
Reply | Report Abuse | Link to thisOur ideas of what constitutes both intelligence and civilization are not a point of fact, but rather subject individual and cultural interpretation. One measure of civilizations or species’ intelligence should be its longevity. With CO2 at 385 ppm on average in our atmosphere and a global population boom, which is at the heart of the problem, we as species, fail to be intelligent.
It saddens me to see intellectual capitol wasted on such trivia.
While it would appear that the existence of life, intelligent life, is inevitable -- what makes you think they want *anything* to do with us?
Reply | Report Abuse | Link to thisThey may well be hiding from us.
JCARLSFOX : We do not know that the universe is infinite : We can only see as far as the oldest light that has reached us, which can be dated. The rest is pure philosophical speculation.
Reply | Report Abuse | Link to thisMy poor ignorant humans we have been among you observing you for centuries. You aren't ready yet if we exposed you to our civilization and culture yours would be destroyed.
Reply | Report Abuse | Link to thisPardon me I must return to the observation blind.
What is wrong with the Drake-type formulas?
Reply | Report Abuse | Link to thisThe mean star formation rate of the Milky Way.
Assuming that it takes a considerable time span for life to evolve, it is of no interest at all how many stars are formed now - what *is* important is the star formation rate some 2-3-4 billion (1.000.000.000) years ago.
life on earth is everywhere, maybe its the same in the universes and beyond
Reply | Report Abuse | Link to thiswhat is the true meaning of intelligence anyway? we think our intelligence is the only important one .
Reply | Report Abuse | Link to thisI posted this in another thread, but it bears repeating I suppose. First of all, the inverse square law will play havoc with trying to detect any radio signals. To pick up "I Love Lucy" near Alpha Centauri would require instrumentation more sensetive than the Aericeibo Observatory. Also, in this day and age, we are actually leaking less omnidirectional signals than we were 30 years ago. So getting more precise equipment and the weakness of signals, it really makes this sort of stuff a long shot at best (although I personally don't mind looking for the longshot).
Reply | Report Abuse | Link to thisWe are also incredibly earthcentric in our way of thinking about intelligence and life. Granted, we really only have one datapoint for life, so there are just some suppositions that folks need to make. However, too many people are trapped into just this way of thinking and assume it's THE way, as opposed to just one of many ways.
Keep in mind that the reason we're looking is that we don't know. There are so many possibilities out there that it would be a great disservice to not even look. Just because we don't have any data is no reason to stop looking.
This Artical may help The Cosmic Mayfly From deep under the oceans, far from any sunlight, to high up in spewing volcanoes, life-forms have been found on our planet. Even deep in the arctic ice, life-forms have been found to exist. For life is tenacious, if it can exist it will exist, this is the way of nature. Soon, yes very soon, I’m sure we will find life-forms on other planets in our solar system. Indeed I’d be very surprised if the whole universe, were not teaming with some form of primeval life or another. But will we find intelligent, alien life in the cosmos? This is a very different thing. Yes I’m sure intelligent life has existed in the universe at one time or another, but does it exist right now, at this very moment, in our time? Cosmetologists’ and Mathematicians calculating the endless galaxies’ in the universe, with their countless suns, and infinite solar systems with literally, trillions and trillions of planets, will know-doubt say. By the laws of probability there must be many planets, orbiting far-off Suns not unlike our Earth, where intelligent alien life, could well have evolved. It’s even possible some of these solar systems could have two planets, with intelligent life-forms living on them, though not necessarily during the same time period, nothing is entirely impossible. So why haven’t we heard from any of these, alien intelligences? Is it perhaps, simply down to the vastness of space!, the unimaginable distances between the galaxies. Some star systems are Hundreds, even hundreds of thousands of light years from our own galaxy the Milky Way. In this infinite universe, any forms of signals or transmissions may, barely have left their back yards, or indeed in our case, our own back yard! Life forms, bacteria and Algae, first appeared on our Earth approximately 2 Billion year ago. It’s only in the last 100, two 200,000 years that intelligent man has so very, quickly evolved. With mans rapidly developed technology, and nuclear weapons. I fear we are like monkeys playing with grenades, unable to comprehend the science we have so quickly mastered, and here I think could well lie the clue. Perhaps all intelligent life has a built-in obsolescence. Many alien planets could have had highly developed technologies, only to destroy themselves, when they developed nuclear or biological weapons. If MANKIND could only have watched, some KIND of TIME-LAPSE MONITORING DEVICE, from the very beginnings of the universe. The very moment of creation, just what would we have seen? Yes, Millions of galaxies forming over endless trillion of light years. Expanding, dividing, and colliding, at this very birth of the universe. Taking snapshots every million o-so light-year, perhaps the device would have detected Radio or TV signals, or a nuclear explosion, in some far of constellation, indicating intelligent alien life, had reached an advanced stage of technology. Some snapshots would I’m sure, have revealed many planets with intelligent, evolving life-forms. A snapshot a few million light years later, with very few signs of intelligent evolving life. And this may well be the case right now, at this very moment in our own, small corner of the cosmos. We could really truly be, on our own. 200,000 years of mans existence on our small Planet Earth, is a mere day in the history of the universe. Like the Mayfly that soars in the sky, for its one brilliant day in the warm spring Sunshine. Man could well be the cosmic Mayfly, soaring into space for one brilliant day in the cosmos, only finally to fall back to Earth to die. This may well be mans destiny. The chances of other intelligent life-forms nearby, existing right now at this very moment, in our one-day in the universe, must be reasonably remote. I’m sure in later snapshots of the universe, when man has long become extinct. Intelligent life-forms will be detected in outer space, in some far, or not so far of galaxies. Only to eventually go the same way as man, after their one, or perhaps two, brilliant days in the cosmos.
Reply | Report Abuse | Link to thisDavid Sloan
Troubling as the Fermi Paradox is, I would say that it is still early to be convinced no one is getting about out there. It is still very possible that alien artifacts ARE around in our solar system somewhere and we just haven't found them yet. SETI may not have figured out how to listen correctly. Astronomers may not have seen the "Dyson Spheres" even though they are actually there. We haven't even made it back to the moon yet. The apparent lack of suitable aliens is strange, but we are not sufficiently removed from the sand box to really claim that we have studied the surroundings carefully enough. It's puzzling but let's keep looking and not leap to despair quite yet.
Reply | Report Abuse | Link to this@ David Sloan
Reply | Report Abuse | Link to thisTo quote: "Cosmetologists and Mathematicians calculating ...etc"
A cosmetologist is someone who applies make-up & such. I think (hope) you meant 'Cosmologist'. Also, did you just refer to light-years as a measure of time?
The real question is weather Alien Life exists concurrent with human life and then how good is our ability to detect that it every existed? To simply say the Universe is this big and then do some math based on probabilityuseing a bizarre data set coupled with fantastic theories is a farce. One experiment I would like to see is take seeds and other cellular material in bedded in a meteorite and attach it to the exterior of the shuttle for a number of years. Then at the end of the shuttles life bring the meteorite back to earth open it up and see how the cellular material has fared and find out weather it is viable or not.
Reply | Report Abuse | Link to thisPerhaps David Sloan is discounting the possibility of civilisations that could have potentially mastered the limits imposed by time ...
Reply | Report Abuse | Link to thisIf space travel continues to be difficult for advanced civilizations and attempts to make contact cost valuable resources then they are not beaming transmitions at every star but instead listen and waiting. Earths radio transmissions for the twentieth century were continually on the rise, but I would think that WWII was a watershed.
Reply | Report Abuse | Link to thisSo as of now the WWII transmissions would only reach around 60 light years, and the two way transmissions range of only 30 light years. I did some crude calculations and this would mean only 300 could have heard are signal and returned it. Not a large number. However the number grows to the cube, and in a hundred years we would include 3,000 stars.
It’s a young universe. Just compare how older the universe is compared to Earth (around 3 times) and how larger (around several trillion times). Even more so, because the first generation or two of stars were lifeless, due to the absence of varied enough mater.
Reply | Report Abuse | Link to thisWe must be among the earlier technological species (along with the gray and the less aggressive Varginha brown, which seemingly several scientists believe it may not be congenial to have much contact with, nowadays, both in NASA and Royal Society, see below. I personally think they are not a threat if kept at safe distance, but we have little to exchange right now).
Things should be much livelier in a few dozen billion years or so.
We may be the legendary grandparents from the dawn of time, who gardened the galaxy and spread life.
Note the curiously ominous tone. Is this just Hawkings influence? Can the HAARP be a UFO swatter?
NASA
Would Contact with Extraterrestrials Benefit or Harm Humanity? A Scenario Analysis
http://arxiv.org/ftp/arxiv/papers/1104/1104.4462.pdf
ROYAL SOCIETY
The detection of extra-terrestrial life and the consequences for science and society
http://rsta.royalsocietypublishing.org/content/369/1936.toc
This seems like a reasonable, doable 7 relatively inexpensive suggestion. NASA or Spacex take notice.
Reply | Report Abuse | Link to thisOn our dear Earth it took only 5 billion years for intelligent life to develop to a technological level where we could detect extra-terrestrial signals. 50 years divided by five billion represents a rather small probability, nonetheless different from zero - although the window of opportunity will expand linearly. Then one has to factor in the probability of a life form technologically advanced enough, if one considers that the most intelligent non-human life forms on Earth are technologically pretty far from the required level. Then there is the question of synchronicity which is an added requirement. Radio signals are pretty ephemeral. Would really intelligent and powerful aliens not invest in a more permanent poster to proclaim their presence? We might just still be too under-developed to be able to read their posters. Or might they prefer to stay anonymous for security reasons? Even if life were relatively abundant, it could be hard to establish.
Reply | Report Abuse | Link to thisTo find life anywhere else outside of the Earth is an extremely interesting theme. Of course efforts should continue and techniques should be improved. One day we will get in touch. No doubt about it. Excuse me for talking like this in a place in which we like the scientific method at its best. But the existence of a planet like ours really seems to be something miraculous. I can see forces bigger than human in the wings of a butterfly. When in the world did we get all the water that we have in the oceans? I know there are theories, but without water there is no life. My feeling is that the water did not come from outer space, but it was formed by molecules preparing the way for higher forma of life that would come later. There is nothing wrong in expressing our feelings, but we also need to strive for hard facts. Let us continue the search.
Reply | Report Abuse | Link to thisI tend to think that LIFE is likely common in this Galaxy (Universe if you please. Intelligent life does not require technology as their form and environment may preclude it's development. On the other hand consider the dinosaurs who were a very successful life form that might still be around except for one little accident that spelled their doom and eventually made room for us. Consider us. Again except for many accidents we could still be happily hacking ourselves to pieces. In the good old days people who had ideas and made waves tended not to survive. So to sum it up I tend to see a universe teaming with life but without much technology
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