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Meeting ET

Preparing for Contact: When Humans and Extraterrestrials Finally Meet (book cover detail)

In Preparing for Contact George Michael has given us a tour de force exploration of the thinking, issues, and dilemmas surrounding the search for extraterrestrial life in the universe.

Those familiar with Professor Michael’s other books and articles—on a wide variety of critical topics including politics, nuclear proliferation, science, and terrorism—know that he conducts rigorous research and major scholarly inventories before completing a manuscript. Preparing for Contact clearly represents years of thinking and research on the subject. Michael’s approach is meticulous, objective, and fearless in examining every relevant aspect—historical, current, and futuristic—of the alien civilization question. The book dives into fundamental questions. First, what have been the scientific (or otherwise) endeavors to consider if intelligent life might exist elsewhere in the universe? Second, if we do make contact with an alien civilization, how should we respond, and what might be the larger implications for our civilization?

Preparing for Contact has a logical chapter progression. From early speculation about extraterrestrial life, including Egyptian, Roman, Hindu, and Central American civilizations’ speculations to the recent findings of astrobiology and astronomy, to the UFO phenomenon, and the SETI (Search for Extraterrestrial Intelligence) project, Michael proceeds in systematic fashion. Regarding possible life on Mars, for example, the Swiss author Erich von Däniken’s wildly popular book, Chariots of the Gods, became a US television film. However, its assumptions of alien life on Mars were disproven after successive probes of Mars found only natural structures, not artificial ones. Additional space probes make us confident that we are the only intelligent life in this solar system. But what about farther out in the Milky Way galaxy, among the thousands of exoplanets which are being discovered at a rate of about two a week?

Before delving into the implications of a possible extraterrestrial contact from beyond the Earth’s solar system, Michael notes that our own planet’s civilization is still relatively young in one key criterion, viz., namely our ability to harness energy. We are still largely dependent on planetary sources such as coal, oil and gas, and only recently have sought to capture solar energy. Intriguingly, should Earth encounter an alien civilization, it is likely that the aliens could be technologically far superior to us, with an advanced ability to harness energy concomitant with military superiority as well.

To that end, Michael presents the system of classification of civilizations based on how effectively they harness energy, first developed in 1964 by the Russian astrophysicist Nikolai Kardashev: “A Type I civilization can harness all available energy sources on its planet. A Type II civilization harnesses energy directly from the star in its solar system…. Finally, a Type III civilization is able to harness the power not only of its solar star, but also other stars in its galaxy” (p. 52). Based on this classification, the Earth is not yet even a Type I civilization. In Carl Sagan’s calculation we are somewhere around 0.7. Accordingly, from that point of comparative disadvantage, Earth’s signals into outer space looking for an extraterrestrial civilization might be viewed as having the potential for carrying risks as well as rewards.

To the book’s thesis, Dr. Michael then considers the SETI project’s communications and how to detect possible alien civilizations’ signals, and speculates on the implications for us if we, or they, are detected. The central issue involves whether to use passive or active SETI communications (listen v. shout), and if active what we should say (and not say) about our civilization, what technical means of communication to employ, and how to decipher and deal with a possible incoming alien message. Again, assuming that any extraterrestrial civilization we come into contact with could be more technically advanced than we are, it would behoove us to be cautious in the content of outgoing, active, SETI messages.

Since an alien civilization’s contact with us could well have a significant impact on religion, as well as on science, there is concern among some scientists that an extraterrestrial civilization discovering us might not be friendly. As Carl Sagan warned, our relatively young civilization should listen quietly “before shouting into an unknown jungle we don’t understand” (p. 210).

Accordingly, Michael asks, “How should we prepare for the prospect of direct contact with an extraterrestrial civilization?” (p. 210). He outlines some of the risks: If the aliens could warp space or time to get here, possibly bringing enormous energy capabilities with their arrival at Earth, would they also be “well armed or ready for combat” (p. 212), or interested in plunder, or our food supply, or even colonization? Could they also carry with them alien microbes or diseases capable of harming life on Earth? Moreover, such an advanced alien life form might not be organic in nature, but instead might have evolved into a more advanced form of life, possibly a post-biological type, such as artificial intelligence (p. 220).

Dr. Michael concludes his compelling book with what he calls “a race against time.” In short, Earth, with its less than Type I civilization, is vulnerable both from without and from within. For example, we could be hit by a major asteroid as has occurred numerous times in the past. But we also might deplete our planet’s resources with overpopulation, or create a toxic atmosphere, or see worsening religious, resource, or environmental conflicts, even as weapons of mass destruction also spread. In short, the SETI endeavor is mortgaged, and its longevity and possibilities remain dependent on humans finding better ways to get along with each other.

All thinking people—whether scientists or amateurs, secular or religious, policy makers or academics—will find Preparing for Contact to be a highly informative discussion about the possibility of making contact with extraterrestrial life. George Michael’s book is a close encounter of the best kind—thoughtful, serious, and consistently interesting. END

About the author

Lawrence E. Grinter is Professor Emeritus, Air War College, and Adjunct Professor, Auburn University where he teaches Asian politics. He was Editor of the Air War College monograph series, the Maxwell Papers, for 11 years. He is a founding member of the Alabama World Affairs Council and continues on their Board. Dr. Grinter is co-editor or author of five published books on Asian and international security affairs, and is author of over 50 scholarly articles and book chapters on related issues. He has made 33 visits to Asia and was stationed in both South Korea and South Vietnam with, or consulting to, the US government. He earned his B.S. at the University of Florida, and his M.A. and Ph.D. at the University of North Carolina, Chapel Hill.


  1. Jeffrey W. Tenney says:

    The review doesn’t reveal anything new in this book. Perhaps a good summary, though, for those not familiar with this subject.

  2. Randy Weiss says:

    Don’t know if the book leaves the discussion out, but the review fails to mention the most important barrier to contact: the size of the space between stars, and our inability to travel, or believe in travel, faster than light. Seems likely to me that there ARE many intelligent life forms out there, but each is stranded within a solar system (or two), and unable to really travel around the galaxy in a ‘Star Trek’ kind of way. We occupy isolated islands in a very large ocean, and no one has a motor boat.

    • sittingbytheriver says:

      excellent point.

    • Tom Clark says:

      I’ve studied this subject for 50 years now, since in high school in 1966 I first heard about Betty and Barney Hill.

      I think the answer to the Fermi Paradox is that interstellar space travel just can’t be done. We like to think that science will be able to solve all problems if the right geniuses come along. Such a belief puts science into the category of religion, or faith.

      If an organism in suspended animation, or perhaps a robot or some kind of cyborg, sets off on a journey to another solar system, he might not arrive there for thousands of years. To whom will he send back his data? To a society that may no longer be interested?

      If it takes millions of years, the folks who set him off might have evolved into a different species by then!

      It’s hard to work up the motivation for the time, energy and gigantic resources such a project would require when you realize that you’ll get nothing in return for it.

      Also, if some species is so far in advance of us that they actually have found a way to explore the Galaxy in a reasonable time at a reasonable cost, why in the world would they want to visit human beings, who are still in their “let’s fight over religion” stage? It seems to me they’d have a lot to lose and next to nothing to gain, unless they enjoy horror shows.

  3. Joel Carlinsky says:

    There have been countless speculations on what an extraterrestrial culture would be like. Almost all of them have started with the assumption that however different from the cultures of earth, they would follow the same basic trajectory in their history. And there is an assumption that if they are capable of getting here from another planet, they must be farther along that path than we are.

    So, let us examine some aspects of our own history and see where our own culture came from and where it is going.

    The story we were told in school is simple: humans started out as simple hunter-gatherers, living in a state of nature, then, after some millions of years, suddenly changed to peasant-farmers, using metal tools instead of stone, growing food instead of searching for it wherever it migfht be, and living in large dense concentrations under kings and religious rulers. Since then, we are told, it has been a steady march to ever-greater technological mastery over the environment, interupted only by wars and ocassional natural catastrophes

    The story is simple in it’s outlines and most people believe it. In fact, enormous peer presure is exerted upon anyone who expresses any doubt. But the whole story is wrong. Nothing of the kind ever took place.

    This is an essay, not a book. What I am going to say here will be condensed. I will make unsuported statements and not explain why I think they are true. I will not present any evidence, only conclusions.

    As is agreed by almost everyone, humans originated ( however that may have been, and for whatever reasons ) a long time ago. For most of the time since then they lived as hunter-gatherers. They have only begun to use metal implements, organize into large-scale communities, fight organized wars, use most forms of technology, and countless other inovations, within the last 10,000 thousand years. Indeed, mst of the main inovations are as recent as only the last 5,000 years or so.

    If you backtrack the earth and other solar system objects by computer, you find that starting around 12,000 years ago the earth intercepted a swarm of meteors in space. These interceptions have recurred every seven or eight centuries since, though with diminishing intensity each time. And each time they occur, changes take place in human history.

    There were repeated and drastic changes in the global climate. There were mass extinctions, especially of the largest and most important members of most continental ecosystems. There was massive desertification. And humans began to change from hunters and gatherers to farmers and city-dwellers.

    Cities depend on farming. Large organized empires depend on farming. To fight a war, an empore must have both a large enough population and a surplus of food to feed non-productive soldiers. Nothing we would call ciivilization could exist without farming. What does farming depend on?

    You can dig up enough ground with a digging stick to grow a little extra food to suplement gathering wild foods, but you cannot plough a large enough field to feed yourself and several other people that way. Farming had to wait for the invention of the plough. And you cannot plough up much land with a plough made of wood. The plough had to wait for the use of metal.

    In the times before the meteors hit the earth, the earth was much more highly charged than it is today. The meteor storms discharged a lot of that charge and it has never recovered to what it was before that. And the use of metals had to wait for the reduction in charge because until then metals could not be used. It hurt to touch anything made of metal. A touch would cause a painful shock every time.

    So the discharging of a large part of the global charge was the needed pre-condition for development of a civilization that uses metals in it’s technology, gets most of it’s food from farming, and has a large enough population to have urban populations that do other things instead of gathering food for a living. And if there had not been a swarm of meteors in the right orbit to hit the earth, we wopuld all still be hunter-gatherers with a stone-age technology.

    So any extraterrestrials we encounter in space will not have a modern-type technology unless they too have had a similar experience in their history. Civilizations do not happen inevitably. They happen because of a specific set of environmental conditions and while the laws of biology indicate there could be, indeed probably are, many planets with humans more or less like those on earth, even possibly many that are identical to the degree we can detect, they are almost certain to be hunter-gatherers, not urban engineers.

    But there will be other difference also. The same meteor storms that made possible development of metal-using technology also caused certain changes in the behavior of the vast majority of human culutres. Maybe a few rainforest tribes escaped the devastation and environmental changes enough to remain unarmored, but the majority of humans did not.emerge unscathed. Almost all human cultures literally went insane from the trauma and have remained so ever since.

    And the cultures that have developed since the meteor storms are dependent on that insanity. To give only one example, no healthy person, feeling alive and aware of his own body and emotions, would consent to spend his working life deep in a mine,.digging for coal or iron. So in a society of healthy people, coal and iron would not be dug. People brought up free and capable of independent thinking would not join a regimented army. So large empires would not exist. People would not live in large cities unless they were out of contact with their biological instincts. So there would be no large cities.

    So any extraterrestrial civilization that becomes able to make ships able to carry them from there to here will have to suffer from the same mental illness that prevails on earth. If they do not, they will remain hunter-gatherers and not develop a technology able to bring them here.

    This means that any extraterrestrial culture we contact will almost certainly resemble our own. Not in all details, just as there are some minor differences between the cultures of China and Europe, but in the essential matter of being armored.

    There may be some like the Klingons, violent and agressive, and some like the Vulcans, cold and detached, and some like the Bajorans, mystical, and some like the Frengi, aquisitive to an extreme, and some like the Romulans, regimented with rigid disciplne, and some like the Borg, all individuality submerged in a collective mind.

    But there will be none who are emotionally healthy; if they are able to get into space, they will have to an armored race, suffering from the same constellation of emotional illnesses that mankind has suffered from for the past several thousand years. Otherwise, they will not be in space; they will be hunting for food in a vast wilderness on a planet that remains almost entirely in it’s natural condition.

    And all this is true regardless of any minor differences they may exhibit from humans of earth. It is true of all mammals on earth, not just humans. It will be true regardless of if a species is telepathic or not, even to the extent of being a Borg-like collective mind. Unless a species is too different from us for us to be able to comunicate, their basic psychological functions will be the same.

    And since the root cause of human armoring is a cosmic accident, one not likely to have happened anywhere else that human life has arisen, there will be no aliens coming here to contact us. We will have to go to them.

    • Herb Van Fleet says:

      Joel, I generally agree with your assessment, but with some variations. See my rather lengthy comments below.

  4. amoron says:

    This level of speculative clap trap searching for mythical aliens based on the grand assumption that we have the penultimate understanding of history and technology has the same intellectual value as diving into the Bible in search of God.

    Carl Sagan presents an interesting method for transcending the speed of light in “Contact” by using science to make men beings of pure energy (gods). Those that pretend the can see the future (even the weatherman struggles seven days out) are performing a curious intellectual service at the height of arrogant folly. It amazes me that people can make a living being wrong (especially when the message appears to be prophetic, for a time beyond our era).

    Joel C’s contribution is excellent but, as Joel notes, it’s based purely on assumptions/opinions and not facts just like the basis for this article.

    • Richard says:

      Contrary to popular belief, there’s no such thing as “pure energy”. Unfortunately, TV physicists use this term for dramatic purposes without explaining that they are simply referring to photon particles.

  5. Casey says:

    Effective communication requires some common frame of reference, and even with that common frame, we generally talk past each other. Some non-confrontational cultures say “interesting” when they mean “no.” To some, “no” means “maybe.” To others, “poor” means “no family” regardless of monetary wealth. Death, to some, means the beginning; to others, it is the end. Some spend their lives preparing for some post-life journey while others concentrate on the here and now. We have a hard enough time communicating with others of our own species on this planet with such attempts often rapidly devolving into conflict (armed and otherwise). What makes us think that we will be able to communicate at all with alien “visitors.” What makes us think that we will be looked at with anything other than mild amusement. At best, maybe we’ll be viewed the way Cortez looked at the Aztecs or the way Andrew Jackson saw Native Americans. At worst, we won’t be viewed at all. When is the last time we asked the ants in our backyard whether they’d mind if we added a room to our house? How many bee hives, hornets nests, etc. have we removed without a second thought? We share virtually identical DNA with our simian cousins, but we don’t give a second thought to putting them in zoos, experimenting on them, destroying their homes, etc. What makes us think that “visitors” will treat us any differently? Our only hope is to wish they are so advanced so as to have outgrown war and conquest yet not so advanced so as to ignore us completely. “If wishes were dishes, beggars would dine,” but they’re not, and I’m not at all comfortable sitting back with a cardboard sign ready at hand reading, “Welcome to Earth, make yourselves at home.” I hope to Zurg that we find them well before they find us.

  6. J W says:

    Joel, this is the kind of stuff to be skeptical of. You present no evidence because you have none. You appear to not even understand how charge works. If you pick up a chunk of metal, even if it is highly charged, being grounded for the first time by your hand will reduce it to the same potential, and therefore no longer a shocking hazard. Not to mention all the other bullshit that was included, and… I just can’t. It’s so stupid. They say you’re not going to convince anyone like this, but if you’re making wild theories ignoring most of human knowledge about how the world actually works and are unwilling to provide evidence, talk it worthless. We’re starting off at different points and we won’t meet until you start thinking rationally. I hate to be so harsh, but this level of ignorance is deserving.

  7. Herb Van Fleet says:

    Right here in our own Milky Way galaxy, NASA estimates there are about 100 billion stars. As to the number of planets that might be suitable to support life, the current estimate is about 8.8 billion. Of course, searching for “intelligent” life, is another matter.

    The SETI project is using radio telescopes to search for signals from somewhere, anywhere, in the galaxy. That is to say, intelligence is limited to life forms that can produce radio signals. But having come up short after the last 56+ years lends support to “Fermi’s paradox.” The paradox says that there is an apparent contradiction between the lack of evidence and high probability estimates for the existence of extraterrestrial life forms, much less “intelligent” life forms.

    So, SETI starts off with a fundamental problem of being able to detect what we call intelligent life. There may be planets out there that have the equivalent of our whales and elephants and ravens, among other highly intelligent creatures. But we have no way of finding these analogous life forms. That being so, maybe SETI should rename itself “Search for Extraterrestrial Radio Signals” – SETRS.

    Personally, I believe the universe is filled with life. But it is most likely single cell or multi-cell “extremophiles.” Higher order life, especially for those that can create radio signals, would be extremely rare given the hurdles of evolution and mother nature over a few billion years.

    And the Drake Equation is not much help here either. With only 7 variables, the reductionism renders it useless and as a predictive model. There are many, many other factors to be considered. For example, the following conditions must be in place for intelligent life to form on any given planet,:

    1 – Must be in Habitable Zone relative to its sun
    2 – Must not be “Tidally Blocked” (always facing its sun)
    3 – Must be solid rather than gaseous
    4 – Must have magnetic core to protect against radiation
    5 – Must have ozone layer to stop too many of the sun’s UV rays
    6 – Must have a moon or moons to stabilize the tilt of the planet’s rotation
    7 – Must have Tectonic Plates to recycle the planet’s crust
    8 – Must have sufficient gravity to hold atmosphere
    9 – Must have atmosphere with life-sustaining elements10 – Must have liquid water
    11 – Must have enough land surface for plants and animals
    12 – Must have a sufficient mix of recoverable metals and other resources
    13 – Must have stable climate with enough time to allow for evolution
    14 – Must have organic compounds needed for life to form
    15 – Must have nutrients available for life to thrive
    16 – Must have energy source for metabolism

    To the extent such a planet or plants exist, there is evolution to consider. Although there are a multitude of pathways for intelligent life to develop over time, we only know of our own evolution. Therefore, consideration of intelligent life can only be based on our own history — and that is anthropocentric. So, here is the taxonomy needed to get our alien life from a single cell to human like aliens:

    1 – Eucaryote (Characterized by cells that contain a distinct membrane-bound nucleus and by the occurrence of DNA transcription inside the nucleus and protein synthesis in the cytoplasm)
    2 – Protozoans (Single-celled microscopic animal such as an amoeba, flagellate, ciliate, or sporozoan)
    3 – Metazoans (Animals that are multicellular and whose cells are organized into tissues and organs)
    4 – Bilateria (Bilaterally symmetrical animals)
    5 – Vertebrates — fishes; amphibians; reptiles; birds; mammals)
    6 – Gnathostomata (Jawed vertebrates)
    7 – Euteleostomi (Bony vertebrates)
    8 – Sarcopterygii (Terrestrial vertebrates)
    9 – Tetraiodo (Four footed vertebrates)
    10 – Amniotes (Vertebrates having an amnion during embryonic development and including the reptiles, birds, and mammals
    11- Mammals
    12 – Eutheria (Placental mammals)
    13 – Primates
    14 – Haplorrhini (Dry nosed primates)
    15 – Simiiformes (Higher primates: the Old World monkeys and apes)
    16 – Hominis (Modern or extinct bipedal primates of the family Hominidae, including all species of the genera Homo and Australopithecus)
    17 – Homo sapiens (Humans)
    18 – Homo sapiens sapiens (Anatomically modern humans)

    But we’re not done yet. Once our alien homo sapiens sapiens have evolved, there has to be another evolution that gets a human-like alien to the invention of the radio. That sequence might look like this:

    1 – Must be able to use fire
    2 – Must be able to fashion and use tools
    3 – Must create language
    4 – Must invent the wheel
    5 – Must create culture
    6 – Must create agriculture
    7 – Must domesticate animals
    8 – Must invent alphabet and writing
    9 – Must establish a form of Law and Order
    10 – Must build permanent dwellings
    11 – Must establish idea of personal property
    12 – Must invent commerce
    13 – Must make glass
    14 – Must invent mathematics
    15 – Must invent printing
    16 – Must develop physics and chemistry
    17 – Must invent electronic communications (Telegraph & Telephone)
    18 – Must invent radio

    So what are the odds of all these events being present on any given planet? For the purposes here, I would just ignore the 16 planetary requirements and just focus on the evolution from single cell to inventing the radio – a total of 36 events.

    For the calculation, and since there is a certain sequence to be followed, I would use the playing card analogy. If the 52 cards from a well-shuffled deck of cards are spread out, the odds of repeating that exact sequence a second time is calculated as a factorial – 52x51x50 . . . x3x2x1. The answer is 1 in 8.06567^67. That’s a lot of zeros. And for the 36 events needed for human-like alien life to form, the factorial of 36 is 1 in 3.7199333^41.

    Now, the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo estimates there are between 4.2 trillion and 5.3 trillion habitable worlds in the visible universe – that’s 4.2^12 and 5.3^12. But I’ve shown that there would have to be 3.72^41 planets to find one that is like our earth and has beings capable of sending radio signals. In other words, we need 10,000,000,000,000,000,000,000,000,000 more planets!

    To borrow from Pogo, we have met the intelligent extraterrestrial life forms and they are us.

  8. Russell Willmoth says:

    “Intriguingly, should Earth encounter an alien civilization, it is •likely•that the aliens could be technologically far superior to us, with an advanced ability to harness energy concomitant with military superiority as well.”

    The fact that the alien managed to zip across interstellar space, and we cannot, makes it not •likely•, but 100% sure that their technology is at least 100 years (and probably thousands of years) ahead of ours.

  9. Bob Pease says:

    I would like eskeptic to get back to topics which are remotely timely and needing a skeptical viewpoint.

    For all of the reasons mentioned in the replies here and more, OUF contact/interaction with BEMs or humanoid ETs ( even if they probably exist somewhere right now )is as about a productive thing to spend time on as stuff like
    “the heresy problem at Cathoilc Schools in Denver and Recourse we have against Schismatics”


  10. BillG says:

    “We are still largely dependent on planetary sources
    (for energy) such as coal, oil and gas, and only recently have sought to capture solar energy.”

    Electricity wise, we in the US have nuclear fission at 20% and France splitting the atom for about 80% for their energy needs. These percentages are likely to increase.
    Then again, today we have approximately a billion people without any electricity – getting by on caveman technology.

    The dream is to tame nuclear fusion and then perhaps shoot for the stars. Although we are always 5-years away – for last 65 years!
    To expedite matters and not unlike the movie “Contact”, perhaps ET could beam down the blueprints;)

  11. Ron W says:

    I do not agree that we would have anything to fear from visitors from another world. People usually present a picture of the future of limited resources, water and energy. The arch of human history shows just exactly the opposite happening. People today are better fed, better clothed, better housed, better health care, better communications, better transportation and more free. We have evolved a brain that has allowed us to master our environment and now we are on the cusp of pushing out into space where resources and energy are literally unlimited. We are solving the problems of pollution and energy production, in a generation we will be operating almost totally on renewable energy sources. As robotics becomes more intelligent and capable, no one will have to work to be well fed and housed. My belief is that any civilization that developes interstellar space travel will also have the technology to satisfy every want and need of their citizens. They will have mastered conversion of mass into energy and transmutation of elements at will. They will be incredibly curious and also have a deep respect for the wonder of life and intelligence in all its forms. Any civilization that lacks these traits is not likely to survive to the level of interstellar travel it just takes too much cooperation among too many people. They will not disturb but observe us. Perhaps help in an unobtrusive way until we are ready to join them at some level. We will share our primitive art and they knowledge that we can handle. Just as we are learning to protect the lessor species of earth. They will protect us and enjoy our company.

  12. Loren Petrich says:

    Post #3 represents some totally unsupported speculation. Is there any *direct* evidence of those meteor showers? Not that I know of. Is there any evidence that the Earth was electrically charged in its past? There is a big problem: the charge would leak away into space. Would it have made metals too difficult to handle? NO. That’s because the Earth’s surface would have been essentially at the same electric potential everywhere.

    So the traditional story still continues to be well-supported, though it does have some curious issues. For instance, humanity developed agriculture several times in the Holocene, but not in any time before. At least agriculture that has persisted to recent centuries. I’ve seen speculation that the Holocene’s climate was relatively stable compared to the 100,000 years before, thus allowing would-be farmers to get started more easily.

    Another curious issue is writing. It was independently invented only about 2 or 3 times, but it has spread through borrowing and stimulus diffusion. That’s invention provoked by awareness that it was possible to do something. Furthermore, in many societies over the last few centuries, a large fraction of people has learned at least some ability to read and write.

    Abstract science was only invented once, it seems, in ancient Greece. It was redeveloped in early modern Europe and it has been an enormous success. Something like writing.

  13. Loren Petrich says:

    Looking at post #7, it is quite correct that the Drake Equation is very simplified. But what it presents is essentially an expanded version of that equation.

    It must be pointed out that its calculations are done totally wrong. What’s relevant here is not some ordering of events, but the probabilities of events. Furthermore, many of these events are not likely to be independent, and some of them do not seem to be very improbable. Let’s look at them.

    A planet being in its star’s habitable zone — it looks very probable, if the numerous discoveries of exoplanets are any guide.

    Not being tidally locked — that will happen if a planet’s star is more massive than for some spectral type in the range K5 – M0.

    Solid rather than gaseous — common, especially for the closer planets.

    Magnetic core — a result of a planet being large enough and rotating fast enough, like the Earth. I wouldn’t say that that’s very improbable.

    Ozone layer — on the Earth, it developed only after its atmosphere got a lot of molecular oxygen. So was the Earth uninhabitable for most of its history?

    A big moon to stabilize its obliquity — not sure that that’s necessary.

    Plate tectonics — will happen if an Earthlike planet is large enough and has enough water.

    Gravity — sufficient size will mean the ability to hold an atmosphere.

    Life-sustaining elements — H, C, N, and O are very cosmically common.

    Liquid water — the definition of the habitable zone.

    Plenty of land — we don’t know how typical the Earth is. Are Earthlike planets usually much drier? Or usually much wetter? Making a superdeep planetary ocean.

    Metal ores are a result of geological processing, and those are from plate tectonics and other sorts of geological activity.

    Stable climate — a result of a stable obliquity and a long-lived star.

    Organic compounds and nutrients — duplication. These are from very common elements, though they form most easily in hydrogen-rich (chemically reducing environments). However, serpentinization of rock (FeO + (1/2)H2O -> (1/2)Fe2O3 + (1/2)H2) produces plenty of hydrogen on our own planet. It does require both geological activity and water, however.

    Energy sources for metabolism — the first one was likely chemical disequilibrium between hydrogen released from interior rocks and a neutral or oxidizing atmosphere. This made possible the likes of methanogen energy capture:
    CO2 + 4H2 -> CH4 + 2H2O

    The major energy source nowadays is sunlight, and a planet that was close enough to be rocky will be close enough to get plenty of light from its star.

  14. Loren Petrich says:

    As to duplicating the emergence of our species, that seems too much to ask. There are alternate pathways to sentient organisms, like what might have happened with theropod dinosaurs.

    I’ll now make my own nominations for milestones of evolution.

    Persistent hereditary system: in our biota, DNA.
    Use of proteins or something similarly versatile for enzymes.
    Chemoautotrophy ~ lithotrophy: the environment of origin is no longer needed. Organisms can now subsist off of Earth-interior and atmospheric gases.
    Photosynthesis: capture of photons by the energy-metabolism system. Makes for less dependence on H2 / Fe++ / CO2 disequilibrium.
    Oxygen release: organisms can get all the hydrogen they need from water.
    Successful maintenance of large genomes: in our biota, the emergence of eukaryotic cells.
    Multicellularity: evolved numerous times, even a few times in prokaryotes.
    Animal-like multicellularity: apparently evolved only once.
    High-resolution camera eyes: at least twice (vertebrates and cephalopods).
    Rigid internal skeleton (enables large size on land): vertebrates only?
    Land plants: apparently evolved only once.
    Land animals: evolved several times (tetrapods, insects, arachnids, isopod crustaceans, myriapods, land snails, clitellate annelids: earthworms and leeches).
    Manipulative organs: evolved several times.
    Societies: evolved several times.
    Recognition of self in mirror: evolved more than once (great apes, elephants, delphinid cetaceans: dolphins and orcas).
    Full-scale language (meaningful assembly of individual words): only once, and possibly also in dolphins.

    • Herb Van Fleet says:


      Thanks for your comments. I think you might have misunderstood my premise, which is to identify the events necessary for intelligent extraterrestrial life forms to produce radio signals.

      Most of those events are sequential; probability is already built in. In other words, you can’t have Homo Sapiens without first having Haplorrhini, and you can’t have Haplorrhini without Simiiformes, and so forth back through the tree of evolution.

      Likewise, you can’t have writing without language, or Einstein before Newton. Yes, there are an untold number of pathways to the evolution of sentient beings. But I’m looking for beings that can invent and use radio transmitters. And the only pathway we know of that gets to that point is the one human beings have taken. We are trapped by our anthropocentricity and can only project that specific orientation onto the universe. Nothing else makes sense. Fermi’s paradox rules.

      And there are many other conditions to consider as well. Were the ancestors of our human-like aliens able to survive five near extinction events as our ancestors did? Would they have Eastern and Western civilizations like us? Are there racial issues? Are there rich and the poor? How would the intelligent extraterrestrials’ culture play a role in their intellect and their motivation? Were they active, for example, in sports, or games? Were they warlike? Did they have tribes, kingdoms or empires, or multiple civilizations? Did they own slaves, have different races, have political revolutions? Did they have a Plato, a Euclid, a Shakespeare, a Beethoven, a Michelangelo, a Washington, a Hitler?

      Ours is the only civilization in the universe that evolved to become senders of radio signals. And we got there, I argue, through a sequence of events, the interruption of any of which would necessarily lead to an almost infinite number of other pathways. I may not have gotten the exact sequences right, but I make an effort. And I suspect anyone else trying to identify the steps needed in an evolutionary order that leads to a radio signaling human-like extraterrestrials would come up with similar results. The probabilities are extremely low.


  15. Loren Petrich says:

    As to the technological milestones, some of them are very widespread, like permanent dwellings. Others seem only rarely invented, like writing.

    There is a hypothesis about our evolution that suggests that similar species elsewhere may not be very communicative: the social-brain hypothesis. It is that our large brains evolved to maintain social relationships in large societies. This would mean a relative lack of interest in developing technology, including technology needed to communicate or travel across interstellar space.

    But we have a joker in that deck. According to Robert Sapolsky’s schizotypal-shaman hypothesis, a genetic tendency toward schizophrenia is maintained because it’s useful to have some of us with such tendencies. That may be for acquiring types of expertise that most of us find difficult to acquire.

    That may also explain autism and Asperger’s syndrome. We may not need many technical experts, but we do need some.

    So could similar things have happened with sentient species elsewhere?

  16. amoron says:

    I wish I had four pieces of a 1,000,000 piece jig saw puzzle and could speak with certainty about the broad picture solely from those four pieces. I especially wish that sentient life could and would develop exactly in accordance with my notional understanding of evolutionary processes. All life throughout the universe would would also have my exact (egotistical) psychological makeup and intellectual limitations as if the universe is somehow created in my image.

  17. Joel Carlinsky says:

    I am glad somebody read my comments.

    The charge of the earth is in constant fluctuation, so grounding something once does not mean it is therefore at the same potential as the earth forever.

    The recurence of meteor showers throughout the Holocene is well-established. I refer you to the work of British astronomers Clube and Naiper for details.

    The great reduction in the average charge of the earth since 12,000 years ago can be inferred from the finding of warm-water organisms in silt dreged up from the Arctic Basin. If the polar seas were warmer, they would hold less CO2 in solution, so there would have been more CO2 in the atmosphere. If there was more CO2 in the air, plants would have removed it from the air and grown larger due to the extra carbon. But without also adding more nitirogen in ”fixed” form as nitrate compounds plants can use, the larger plants would be deficient in protein and animals eating them would soon starve to death. Since that did not happen, there must have been some source of additional bio-available nitrogen compounds to balance the extra carbon. That could only have been lightning, the main mechanism in nature that produces fixed nitrogen compounds in forms plants can use. There must have been a lot more lightning in prehistoric times to balance out the greater amount of carbon then available to plant life with more nitrogen to prevent mass extinctions from starvation among animal life. That in turn argues for the charge of the earth, which is constantly flowing in from space, movcing through the crust in huge surges of current, and being discharged back into space in the form of lightning strikes upward from the ground, a phenomenon known as the Wilson Circuit, being greater than it is now.

    Regarding extraterrestrial inteligence, Issac Asimov once said that Superman’s greatest weakness isn’t Kryptonite; it is that he isn’t much brighter than we are.

    • W. Corvi says:

      Joel, there are exactly ZERO references to Clube and Naiper on GOOGLE, and I (as an astrophysicist) have never heard of them. There IS one reference to Clube and Napier, but it debunks all their evidence, even though it goes on to say “Just because all the evidence is debunked, that doesn’t mean the conclusions are wrong.” Well, yes it does.

  18. Joel Carlinsky says:

    I found quite a few references to them and their ideas.

    Victor Clube
    From Wikipedia, the free encyclopedia

    Stace Victor Murray Clube (born 22 October 1934 in London) is an English astrophysicist.

    He was educated at St. John’s and Christ Church, Oxford. He played first-class cricket for Oxford University.[1] He appeared seventeen times for the university between 1956 and 1959, but only won a Blue—the awarding of the Oxford “colours” to sportsmen—in his first year there, appearing in the 1956 University match against Cambridge. During that match, which finished as a draw, he took just one wicket with his off break bowling.[2]

    Clube obtained his doctorate in 1959 with a thesis titled Interferometry of the Solar Chemosphere and Photosphere[3] and went on to become a professional astrophysicist and astronomer. He has been Dean of the Astrophysics Department of Oxford University,[4] and has worked at the observatories of Edinburgh, Armagh and Cape Town.[5][unreliable source?] He is known primarily for his work in collaboration with Bill Napier and others on the theory of “coherent catastrophism”[6][non-primary source needed][7]

    The asteroid 6523 Clube is named after him.[8]

    Bill Napier

    William M. Napier (born June 29, 1940 in Perth, Scotland) is a professional astronomer currently an Honorary Professor of Astrobiology at Cardiff University. He has also worked at the Royal Observatory in Edinburgh, the University of Oxford, and Armagh Observatory. His collaboration with fellow astronomer Victor Clube and others on the role of comets in Earth history, is known as “coherent catastrophism”. He is also the author of five novels, and scientific books. He received his Bachelor of Science degree in 1963 and his Doctor of Philosophy degree in 1966, both from the University of Glasgow.

    In their book, The Cosmic Serpent, Clube and Napier write:

    “In this book we bring together hitherto unconnected strands in astronomy, biology and geology, and in the early history and mythology of man.
    “The unifying theme is the comet, currently thought of as a minor actor in the cosmic drama. We shall propose that it grows out of the cold, dense nebulae found in interstellar space; is captured into the solar system during a close encounter; and if not flung out again, is thrown either into the space between Mars and Jupiter where it becomes an asteroid, or into an orbit which will bring it eventually, in the form of an asteroid, into collision with a planet.”[1]

    Geologist Derek Ager writes:

    “Victor Clube suggested (1978) that our galaxy had a violent history and later he and Bill Napier argued for a theory of terrestrial catastrophism which really started the recent interest in asteroid impacts on the Earth (Napier & Clube 1979). Later they produced a remarkable book (1982) which was subtitled A catastrophist view of Earth History presenting a convincing argument for a giant comet that terrorized mankind in prehistoric rinses. They put together a great deal of evidence from a variety of sources that speaks of a violent past and a hazardous future.”[2]

    Clube et al have developed their theory of “coherent catastrophism”. Prof. Trevor Palmer writes:

    “Nevertheless, whilst rejecting almost every aspect of Velikovsky’s hypothesis, astronomers accept that a large cosmic body could pass close to the Earth and cause catastrophes. In particular, the Earth may be under threat from giant comets which, although small in comparison to planets, are very much bigger than the comets that are normally seen. That view has been developed mainly by British astronomers, including Victor Clube together with Bill Napier and Mark Bailey of the Armagh Observatory, Duncan Steel of Salford University (and formerly of Spaceguard Australia) and David Asher of Oxford University and the Communications Research Laboratory, Japan.

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