I cannot live without good coffee, and that means fresh beans ground right before brewing, and either manual drip or French press extraction. Every morning after publishing Centauri Dreams I make a couple of cups and go out on the deck to rest my eyes and ponder the state of things before hitting the books for background research in the afternoon. Various thoughts about what to write next always come to me, but yesterday I mused about Enrico Fermi, the legendary Italian physicist who, among so much else, left us with a great unanswered question: Where are they? If it’s so easy for the universe to make intelligent species, why is SETI coming up so short?
Where are they indeed? The day was gorgeous, the air filled with birdsong, temperatures in the mid-60s and a mild breeze. What better setting to be immersed in, thinking about where life emerges and when? I imagined Fermi sitting across from me with a cup of my Costa Rica Tres Rios in his hand, wondering what he might say about the fuss his question has caused over the years. I can almost hear him saying, “Look, it wasn’t serious. It was just a throw-away comment over lunch. I didn’t even think about it.” And then I imagine him gazing out over the hillside and wrinkling his brow. “But you know, it really is an interesting question, isn’t it? I mean, really!”
Image: Enrico Fermi, with no coffee in sight. Credit: AIP Emilio Segrè Visual Archives.
Alpha Centauri: The Age of Things
Obviously I’m putting words in the man’s mouth, but that’s the thing about the Fermi paradox: It keeps coming around. And in one respect it seems particularly disturbing. If the Sun is in the vicinity of stars that are far older than it is, that would give planets around those stars far more time to produce their own living species and far more time for intelligence and technology to emerge. We can think about these things in terms of Alpha Centauri, the subject of these last few posts, because based on recent studies, these stars are much older than our Sun.
How old? To answer the question, the go-to people are Patrick Eggenberger (Observatoire de Genève) and colleagues, who in 2004 produced a paper on the matter that ran in Astronomy & Astrophysics (citation below). A wide range of ages has been posited for these stars over the years, ranging from as little as 2.71 billion years up to well over 6 billion — the paper runs through the previous analyses — but Eggenberger and team go to work with the latest astrometric, photometric, spectroscopic and especially asteroseismic data to reach a strong conclusion: “The global parameters of the ? Cen system are now ?rmly constrained to an age of t = 6.52 ± 0.30 Gyr.”
6.52 billion years, plus or minus 300 million. Now we can think about the Sun’s age, thought to be about 4.57 billion years, and you can see that Alpha Centauri A and B have a 2 billion year jump on us. So does Proxima Centauri, because as we saw yesterday, Greg Laughlin and Jeremy Wertheimer made a convincing case that Proxima is indeed bound to Centauri A and B, and thus probably originated in the same molecular cloud that produced its companions.
I think I’m going to pour Dr. Fermi another cup of coffee about now, because that 2 billion years provides ample time for interesting things to develop given an astrobiologically friendly planet. Long-time Centauri Dreams readers will also know that Charles Lineweaver (Australian National University) has studied the galactic habitable zone and the distribution of stars in the Milky Way by age, finding that 75 percent of the stars in an annular region between 7 and 9 kiloparsecs from galactic center, where life should be possible, are older than the Sun.
Alpha Centauri, using the age estimates of Eggenberger and colleagues, turns out to be fairly average, for Lineweaver says “…the average age of Earths around Sun-like stars is 6.4 ± 0.9 billion years.” He thus thinks that planets around other stars in the galactic habitable zone should be, on average, 1.8 billion years older than our planet, about the same difference as between our Sun and Alpha Centauri. And this is only an average. Milan ?irkovi? (Astronomical Observatory of Belgrade) notes that there should be inhabited worlds in our galaxy as much as 3 billion years older than our own. So we have on our own doorstep (in astronomical terms) a triple star system that dramatically points to the time frames life has had available to develop civilizations.
Proxima’s Deadly Flares
At this point Dr. Fermi might well take me to task (at least, the imaginary Dr. Fermi who is not only still with us, but completely up to speed on red dwarf studies). I think he would point out that Proxima Centauri is an active flare star with loads of coronal X-ray emission, not exactly a hospitable place for life. We can imagine a calmer, much older Proxima Centauri eventually settling down into a benign middle age, but imagining that also makes us realize that while Alpha Centauri A and B may have provided the opportunity for intelligent life to develop long ago, Proxima may be the most marginal of the Centauri possibilities as of now.
Red dwarfs live, depending on their mass, for trillions of years, so we shouldn’t despair about the future — and we can always ponder whether any kind of adaptive mechanism might rescue astrobiology even in so hostile a place. But as a home for human colonists of the first interstellar mission, any conceivable planet of Proxima Centauri gives way to what we hope to find around Centauri A or B, a rocky world in a habitable zone we might be able to survive within.
Two Charles Lineweaver papers are in play here, the first being “An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect,” Icarus 151 (2001), pp. 307-313 (full-text). The second is “The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way,” Science Vol. 303, No. 5654 (January, 2004), pp. 59-62 (abstract). The Eggenberger paper is “Analysis of alpha Centauri AB including seismic constraints,” Astronomy & Astrophysics Volume 417, Number 1 (April I 2004), pp. 235-246 (abstract).
There is an unhappy way to account for Fermi’s paradox that is pretty easy. Perhaps the length of time a civilization survives its acquisition of technology before dies or some how” transcends to a higher existence ( which I am not convinced) is very short, less than 1 million years. If you add to that the idea that life must start in the early stages of a planets existence or not at all, then all of the nearby stars have either not spawned life, or have not yet reached technological civilization for us to encounter, or the civilization is now extinct ( at least on our plane of existence… if you believe they transcend) . I do not like this explanation because it does not account for the idea of remnants of a civilization moving out among the stars , out distancing the extinction event. I keep asking why are there no aliens in our kuiper belt… or maybe there are(?)
Dear Paul,
I am a suscriber of Centaury Dreams Blog for some time now and whenever I have the chance I read it attentively. Today I dare to comment (well, it is more of a question) for the first time since the issue of finding extraterrestrial life is also very interesting to me.
If we changed places in our galaxy with that “possible” alien life, how would we detect the human activity on the Earth? In other words, what are the signals we are sending (intentional on unintentionally) from the Earth that could be detected by inteligent life forms in the galaxy? Programs as SETI, are looking for the same kind of signals?
I hope this is not a question too naive to be answered. Thanks and all the best.
Science fiction writers suppose civilizations have risen and fallen eons ago…
We’d be part of a galactic civilization if a mature one existed….
An Observer at least….
The Territorial Imperative and all that…
Or you could think Forbidden Planet….
Or rewrite Drake’s Equation….
As The Skeptic author has…
It comes down to at most 3.26 civilizations per galaxy…
Perhaps Earth is to re-start civilization in this galazy…
Or end it all in an Atomic War….
A split second decision can end 10,000 years of growth…
JDS
From Solstation:
“A more recent interior modeling with seismic constraints, however, suggest that Stars A and B could be 5.6 to 5.9 billion years old (Mutlu Yildiz, 2007).”
This agrees with an even more recent study of Proxima using star rotation and brightness as a means to calculate age, which study I don’t have details of at hand.
What we have is a thimbleful of data and a boatload of assumptions, from which we are tempted to make grand sweeping conclusions about life, ETI and the evolution of such beings, their civilizations and their behaviors beyond the point that we have ourselves reached. I expect to see more of these in this post’s comments. I don’t mean to say that speculation is bad, just to recognize it for what it is.
As for the coffee, I am 100% agreed! However I lean to espresso from an Italian machine and varieties of beans imported from Italy. Regrettably most of my family and friends won’t touch the stuff and insist on cappuccino or, more often, something terribly bland.
Chuso writes:
The question is not naive at all — in fact, it’s the kind of question we need to ask as we ponder SETI strategy. The signals most likely to be detectable at interstellar distances from the Earth come from our planetary radars at places like Evpatoria (Crimea) and Arecibo (Puerto Rico). These are strong signals that might be received as a momentary pulse, but the signal would quickly disappear as the radar beam swept past. Our TV shows, which are often mentioned in this regard (see the movie Contact) would be extraordinarily weak, and most of the speculation I’ve seen says that they would be undetectable even from the nearest star without vast antenna installations. We can’t rule out what a truly advanced civilization might be able to do, but a civilization more or less like ours around a nearby star would probably not be able to detect us unless we beamed a powerful signal directly at them, and they happened to be on the right frequency.
Ron S writes:
I love how easy it is to get an espresso when traveling around Europe — even the highway truckstops have a decent espresso in France. And the change in the availability of good beans here in the States over the past years has been wonderful to see. Sorry your friends and family don’t share your passion!
Rather than repeat the tentative thoughts around the implications of what appear to emergent mathmatical features within evolutionary processes I suggested a few days ago in the comments on the post regarding metallicity in other galaxies, I ‘ ll just cross reference to it here…any and all feedback regarding errors / developments appreciated
Since I haven’t seen it mentioned previously on the Centauri Dreams blog, I thought I would put in a plug for the book “If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life” by Stephen Webb (2002). This book is the most thorough treatment of the Fermi Paradox I’ve encountered.
I would like to highlight one factor that is often overlooked. Perhaps we are the lucky planet. All of our mass extinction events seemed to have accelerated evolution; none of them have sent us back to square one.
The latest Nature magazine (19 April) has the cover story ‘Life Force’, about the Great Unconformity, when extraordinary global erosion rates spiked the oceanic calcium concentration and triggered the Cambrian Explosion. Here’s a strong bottleneck to getting intelligence: the rarity of such a gigantic geological event, without which the Earth would still be Ediacaria, the Planet of Sponges & Worms.
Another bottleneck is the Earth’s high oxygen level, due to a previous rare geological event, the Gondwana Supermountains, which had the mass of a thousand Himalayas.
These two bottleneck events (i.e., <1%) were recently added to the list of essentials for intelligent life. We already knew about the Solar System's extraordinary order & stability, the rarity of an L5 companion planet slamming proto-Earth at just the right angle to make the Moon, and the mineralization of the Earth's crust by the Late Heavy Bombardment. Another possibility is that the early Earth had high obliquity, saving it from the Faint Young Sun Paradox. That's six bottlenecks right there, and we haven't even considered the extremely low likelihood of getting intelligence from brainy animal life.
Fermi has been answered by Rare Earth: we've already found enough bottlenecks to depopulate the entire visible Universe.
P.S. I reiterate that habitable planets are an Urban Legend, that spacers will want airless worlds to dismantle.
Marshall T. Savage says look for evidence of blue green algae clouding living distant planetary systems….
Can 50 billion humans live here? 100 billion? 200 billion? What a terrible problem is coming to Earth….
Will the moon’s craters one day be dotted with blue water surrounded by green shores?
Will Mars become a patch-work of blue water and green forests?
The asteroid belt a mess of blue-green worlds as humans learn to adapt…
Coffee? Never heard of it. How about some Diet Coke?
Too salty? Obey your medical Doctor….
JDS
My feeling is that we humans ,as an intelligent toolmaking species , are the product of a statistical equation involving MANY factors who have to be calibrated EXACTLY right . If finally we would be capable of understanding and quantifying all these probability factors and their internal relationships , and then were capable of calculating how many intelligent toolmaking species to expect in our galaxy , the answer would be
N = 1.oo5 !
As an example : perhabs the overwhelming number of lifebearing planets have a gravty much too high to encourage a brainsize big enough to result in intelligence outside the sea , where toolmaking will probably never get anywhere .
Perhabs evolution can take a great number of different paths , all leading to “dead-ends ” , from which it would have to be restarted several times by a very specifik set of circumstances .
The probability of all these rare events have to be multiplied , and the result might be an astronomically small number ..
There is one possible solution to the Fermi equation, “what if” the universe is only now viable for intelligent life to grow, so intelligent life only is now coming into existence “universe wide” due to more conducive factors? ie. less supernovae, more of the higher elements spread out, etc.
Perhaps intelligence is uncommon in the Galaxy, but it is extreme to say that the galaxy is mostly uninhabited.
Trying to examine the factors that lead Earth to develop intelligent life may be helpful in some ways, but I feel that trying to apply what has happened on Earth to the rest of the (potentially) habitable planets in our Galaxy might be disingenuous.
Every habitable planet (including Earth) is bound to be unique in their own way because of different environments, life history, and different planetary composition all of which may very well prove to have either a positive or negative impact on the emergence of complex and intelligent life. Complex and intelligent life could arise from different circumstances than what has occurred on Earth.
Ole Burde:
I of course agree with N=1
first in the entire history of the Galaxy,
but even more so, including every galaxy
within at least 5 billion light years.
Otherwise we would have seen a Type III somewhere,
sprawling over an entire cluster of galaxies.
Unless ‘subluminous galaxies’ are that way
precisely because they are Type III?
Andrew Higgins said on April 25, 2012 at 11:05:
“Since I haven’t seen it mentioned previously on the Centauri Dreams blog, I thought I would put in a plug for the book “If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life” by Stephen Webb (2002). This book is the most thorough treatment of the Fermi Paradox I’ve encountered.”
Webb is thorough, but it becomes obvious soon enough that he is guiding the answer to be just one – us. I think his religious and even political sensibilities need to be checked to see just how much bias is involved.
To give you an example from reality as to how one’s religion can have an adverse effect in regards to how many ETI we think exist, read the book Life Everywhere by David Darling. He found out that one of the guys who came up with the Galactic Habitable Zone idea is a dyed in the wool creationist. Which goes a way in explaining that they “discovered” that in the entire 400 billion star systems of the 100,000 light years wide Milky Way, life can only exist in a very narrow belt – and take a guess who just happens to be there?
This same fellow went on to co-author the book titled The Priviledged Planet, which “proves” that Earth is the only place in the entire Universe which has life. His co-author was a theologian, not a scientist. So much for unbiased and objective science.
As for James D. Stillwell mentioning Marshall T. Savage, he is another one who is convinced that no one else exists in the entire Milky Way galaxy – which automatically gives humanity the right to take and colonize the whole thing ala Manifest Destiny cosmic style.
I get the feeling that, whether there really is anyone out there or not, humanity is going to be in for a big cultural shock when it gets into the wider galaxy and finally learns that it is anything but the most important focal point in existence, despite millennia of convincing itself otherwise.
Interstellar Bill writes
“That’s six bottlenecks right there, and we haven’t even considered the extremely low likelihood of getting intelligence from brainy animal life….
Fermi has been answered by Rare Earth: we’ve already found enough bottlenecks to depopulate the entire visible Universe.”
These kinds of arguments could be used to determine that we should not be here at all. I have seen folks argue that is is impossible for life, or intelligent life, to exist anywhere else in the universe except right here due to a never to be repeated series of virtual miracles. They go on and on adding condition after condition all with such scientific sounding logic. I chalk all these arguments up to what Ron S called a “boatload of assumptions” above.
Chuso said on April 25, 2012 at 9:21:
“If we changed places in our galaxy with that “possible” alien life, how would we detect the human activity on the Earth? In other words, what are the signals we are sending (intentional on unintentionally) from the Earth that could be detected by inteligent life forms in the galaxy? Programs as SETI, are looking for the same kind of signals?”
The Planetary Society blog recently had a post graphically depicting how far our civilization’s electromagnetic leakage has traveled from Earth into the Milky Way galaxy. See here:
http://planetary.org/blog/article/00003390/
And keep this in mind: Not only is this a very small sphere of influence to begin with compared to the size, distances, and numbers of star systems in our galaxy, but most of our signals are both rather weak and scattered aimlessly across space. Only a few are powerful enough to be detected at interstellar distances and even fewer have been both sufficiently powerful and directed at potentially habitable star systems.
So unless there are advanced ETI aiming some very powerful space-based telescopes and other relevant instruments at our planet, it is going to be a long while before humanity expands enough to garner galactic-scale attention.
Another one for Fermi: They are out there but we are hardly big and noisy enough to take notice of. And what do they like to drink in their mornings?
Well, maybe they are coming :) There are suggestions out there that this star http://www.eso.org/public/news/eso1132/ might be actually the deceleration torch of a fusion powered star-ship. There s the inconvenience, though, that it lacks a blue shift… Just a food for thought.
Greg commented previously speculating on galactic habitable zone environmental issues like supernovae. Science popularizer Nigel Calder cites a new paper published by the Royal Astronomical Society in London that links the rate of nearby’ supernovae to cosmic ray flux to cloud cover, asserting the hypothethis that supernova cosmic ray flux and continental drift are directly correlated with Earth’s mass extinctions and sea level changes.
http://calderup.wordpress.com/2012/04/24/a-stellar-revision-of-the-story-of-life/
Well, someone had to be first. Maybe – in this galaxy, at any rate – it’s us?
To add to the speculation, I suspect there may be lots of dolphin or cuttlefish type sophonts out there, with complex societies and symbolic language, and doing just fine – but, being aquatic, unable to smelt metals.
Or perhaps the final stumbling block is not intelligence per se, but evolving the fine motor skills necessary to make such things as microliths, woven baskets or radio telescopes.
Oh, and mine’s chickory-essence, black, no sugar.
Stop laughing.
@Interstellar Bill, regarding bottlenecks: You can always come up with reasonable sounding bottlenecks, for everything. I can easily argue that my own existence, or yours, is due to a long series of unlikely events that makes me (or you) astronomically improbable. This will not do, as obviously, in addition to you and me, there are plenty of other people around. Your “bottleneck” argument, and with it the whole misbegotten Rare Earth argument, is deeply flawed.
There is one event that may be a true bottleneck, and that is abiogenesis. It is where I would put my money with regards to Fermi, if I were a betting man. I am also with fresh ground beans, every morning.
Lineweaver’s Galactic Habitable Zone paper is available on his website (PDF format):
http://www.mso.anu.edu.au/~charley/papers/LineweaverFennerGibson.pdf
http://planetary.org/blog/article/00003390/
Which, coincidentally, is just about the size of Niven’s Known Space.
Somewhere long long ago, I read, perhaps Asimov writing science rather than fiction, that the Earth outshines the Sun in radio frequency. And if some putative alien civilization happened to be close enough, had radio astronomy, and looked, they would see a modest yellow star producing far too much RF to fit within their version of the Hertzberg Russell diagram of Pop 1 stars. If they looked hard, and the solar system wasn’t too oblique, they would note the Doppler shift caused by Earth’s orbit about the Sun.
Is this true, about the RF signal strength, or am I misremembering?
Bob says
“These kinds of arguments could be used to determine that we should not be here at all. ”
Just because an argument can be misused is not a counter-argument.
I’m quite sure we’re not the only intelligent race in the Universe, just the only ones in at least the Local Supercluster, where a Type III would be glaringly obvious. (I laugh at the idea that a space-going race would have any other destiny, because evolution does not produce cowards.)
My argument is that over the 55 years of astrobiology, nearly every pertinent discovery about the Earth’s past came up with a bottleneck. Sorry to be the meanie who’s been studying this for the entire 55 years and thus has to point out the bad news. After all, I was there when the first Mariner photos showed a dead Mars. That was a sad day indeed.
On an optimistic note, it is also obvious that life will leap to its potential once each bottleneck has passed. Evolution is utterly marvelous.
In order of occurrence I’ll rattle off the well-known bottlenecks, but expressed as a series of affirmations:
1. Every time the heaviest protoplanetsplanets don’t migrate but make a stable system instead, then there will be terrestrial planets in the Hab Zone.
2. Every time a right-sized terrestrial planet in a Hab Zone gets hit just right by a co-orbiting planet, it will be endowed with a Stabilizer Moon.
(Otherwise it ends up slowly rotating with an enormous atmosphere.)
3. Every time that Mooned world gets high obliquity, it will survive the Faint Young Sun.
4. Every time such a planet gets the right Late Heavy Bombardment, it will have its surface iron replenished, and life WILL start. Just be sure to have the Goldilocks amount of oceans.
5. Every time such a planet has the proper endowment of core radioactives, it will make continents, which many times get lucky for life.
6. On every planet that does get its oxygen and calcium up enough, there will be vertebrates, and they will conquer the land.
7. Every time their planet offers a timely series of non-excessive mass extinctions, those vertebrates will advance in sophistication.
8. Every time their planet evolves fruit trees, those vertebrates will evolve primates.
9. Every time those primates become river apes eating omega-six food, their brains will grow, and if there is a timely series of glacial cycles then they will become sentient, and then if there is a low-eccentricity interglacial they will originate agriculture.
10. Then as long as they have a good mineral and fossil-fuel endowment and the proper geography, there’s a good chance they’ll eventually get into space
Because of all those factors, I’m optimist that we have at least the Galaxy to ourselves. I shudder at the alternative, and so would Fermi.
Jkittle: Robert Zubrin did an interesting article in the April 2002 issue of Analog in which he modeled the spread of Alien civilizations over time, and his conclusion was that for us to have avoided, repeated and (geologically) recent visitations or colonization, the maximum life span of an alien civilization has to be in the order of 10,000 years.
The arguments here for the Fermi paradox boil down to two possibilities: first there is jkittle’s universal truncator, or there is some factor that makes technological civilizations extraordinarily rare (less than 1 per galaxy).
If civilizations are extraordinarily rare, then if we look extragalactically, we should detect them as being hundreds of millions to billions of years older than our civilization, then will be very powerful (Kardeshev III) civilizations. (It only takes 5000 years at a 2 % growth rate for our civilization to reach Kardeshev III levels.) Gravitational lensing should enable us to view galaxies hundreds of millions of light years away with the necessary sensitivity.
If the universal truncator (that either kills all civilizations or raises them to a higher plane) exists, then no matter how far or how sensitively we look, we won’t find any traces of alien civilizations.
This would be somewhat interesting, had not similar analyses in the past linked the same things to completely different causes. Nemesis, the galactic plane, continental drift, many others I do not know or care to cite. This search for causes by temporal correlation is almost as curious to behold and every bit as fallacious as the Rare Earth arguments.
Some things, like the weather, can change all the time without needing a mysterious cause.
There is one event that may be a true bottleneck, and that is abiogenesis.
Yep.
http://journalofcosmology.com/Abiogenesis107.html
…habitable planets are an Urban Legend
I like that.
Dan Ibekwe, et al.:
We had an interesting conversation about whether tool-using intelligent life could evolve on a water world, and whether that could lead to advanced technological societies a couple months ago.
https://centauri-dreams.org/?p=21818
Some very interesting concepts in the thread there.
I am impressed by the fact that, just as we now have intelligence, we are also facing the accelerating risk of extinction along a number of lines (biotech, self-replicating chemicals, nanotech, seed AI, & maybe physics experiments). I am inclined to believe that all intelligent life would develop each of these threats as well. Given how difficult it is to achieve interstellar colonization, I see universal, complete extinction as something that we should keep as a real possibility.
But also, there are some explanations to Fermi’s Paradox which we can and cannot do something about. Does it matter if we are on an incredibly lucky planet, or that we had this or that event which puts us in our favored position? Do any of these facts change what we should or shouldn’t do from here on? What if the galaxy is well populated with intelligence but we are intentionally being kept in the dark until some Prime Directive criteria is met. Would this fact change what we should or shouldn’t do. They are so smart, there would be no way to detect them unless they wanted us to detect them which, apparently they do not.
BUT, what if all previous intelligence universally killed itself. This would mean that we were very highly likely to do the same to ourselves. Yet, the silence we experience could be positive evidence of universal self-extinction. The silence itself tells us that we ought to try and achieve interstellar colonization AND try to slow whatever causes the universal extinction in order to increase the probability that we will succeed despite the small odds. And, what would be the negative consequences to doing this if the true answer to Fermi’s Paradox is something else? Just an early launch of a “manned” interstellar mission which is passed by a faster-later craft. OK, so some money was spent yet technology was advanced. No big harm.
But, if universal self-extinction is the answer to Fermi, then we would have to imagine that the event will occur even before the colonization of the solar system (unless the cause is an explosion of Earth by a physics experiment). Basically, this give us very little time. Probably less than a century to achieve “manned” interstellar colonization. I believe that only an ESCAPE Mission can be launched in time that early since the propulsion needs are so very much less than anything else.
My opinion is that the Fermi paradox isn’t. I argue this position by analogy with Olbers’ (“dark night sky”) paradox: if the universe is infinite, then any line of sight should intersect a star, so the night sky should be white, not (mostly) black. The stars: “where are they”? The standard solution is that light from any star farther than ~13.5 billion light-years away (at the time it emitted the light) has not had time to reach us. Even though the universe might be infinite in radius, only a small proportion of stars fall within this sphere. Therefore Olbers’ paradox isn’t. Note that this explanation holds, despite the fact that all stars emit light constantly in all directions over their entire lifetime (millions to trillions of years).
My dismissal of Fermi’s as a paradox is similar: consider that spacefaring species ’emits’ spacefaring vehicles. (1) These races are orders of magnitude less common than stars; (2) they ’emit’ spacecraft only for a tiny proportion of their stars’ lifetimes (even if ‘only’ for a million years); and (3) they ’emit’ a limited number of them in only a few directions. Furthermore (4) the craft probably travel at much less than c (barring exotic physics). Conclusion, spacefarers are so rare, so fleeting and so slow that it would be a wonder if any HAD reached us, rather than that they haven’t.
Dispatcher: the more recent paper on solar type star ages is “Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics” by Mamajek & Hillenbrand.
Interstellar Bill: with all due respect, but the whole Rare Earth hypothesis has been repeatedly criticized and demonstrated as being seriously flawed. Primarily because it is biased and detreministic: it takes the typical ‘earth characteristics’ as an exact pinpoint of parameter values and then reasons backward that all these must be present exactly like that and how minute that chance is, instead of deriving general essential criteria for a living planet and from there working toward a more generalized model with margins.
It is like a native on a small lonely island wondering about his amazing environment and concluding that he must be the only one, because the exact combination of conditions on his island must be unique, instead of deriving general conditional parameters and margins for life and then concluding that there must be many places with suitable conditions.
Another flaw is the whole idea of multiplying several small chances, as if they are independent, whereas instead they may and are even likely to be correlated with each other. In other words, a solar type star has certain interrelated characteristics. A terrestrial planet is likely to have certain interrelated characteristics with regard to geology and geophysics. Hence, the occurrenc of certain relevant events, such as terrestrial planet formation, cometary and proto-planetary bombardment, plate tectonics, etc. etc. is not so much a series of very rare and independent chance-events, but rather a bunch of logically related events.
This is like considering the chances for a person to be blond, blue-eyed, light-skinned, and around 6 ft tall as independent chances which can be multiplied and then concluding that such persons must be exceedingly rare indeed, if not unique, instead of realizing that these characteristics are interrelated to a specific type.
While researching our galactic neighborhood, we find that our sun and its environment, though in a minority, is far from unique and the more we discover, the less unique it becomes.
I agree with Eniac that the real bottlenecks, if any, are probably not atronomical nor geological/geophysical, but rather boilogical: the origin of life itself, the higher (Eukaryote) cell, multi-celled life, complex life, intelligence.
With regard to the age of the Alph Cen system, precisely this makes me rather cautious about Alph Cen A: its greater mass (about 1.1 * solar) makes it age faster than our own sun.
Combined with its older age, anywhere from 1 to 2 gy older, that does not bode well: our own sun will be about 10% hotter in another gy and earth will be well on the inside of the HZ, much too hot for any (higher) life, even the oceans may have largely evaporated.
This partly also explains Alph Cen’s much greater luminosity (about 1.56 * solar): its HZ must have been moving outward relatively rapidly during the past 2 gy and any planet within its former (continuous) HZ, where life may have originated, must have left it long time ago already.
In this regard I am much more optimistic about Alph Cen B, which, as a dimmer K0/K1 at about 0.45 times solar luminosity, has a much longer stable lifespan.
Finally, I agree with jkittle and James Stilwell, that an old stellar age itself, though maybe giving stars and their planets plenty of time and opportunity to spawn life, may offer rather little consolation with regard to *present* civilizations, if it appears to be a universal rule that budding intelligences and civilizations tend to be extinguished or extinguish themselves within a short period of time, well before reaching a technological level, let alone interstellar capabilities.
If we ever reach the stars, one of the interesting disciplines might be planetary archeology, the search for former intelligence and civilization.
Denver writes:
I imagine Asimov did have something to say about this. In any case, I’ve run across the statement in numerous sources, most recently this by the SETI League’s Paul Shuch:
There is still controversy over just how large an antenna installation you would need to pick up such extraneous broadcasts as TV signals, but we could assume that a society more advanced than our own would have a shot at detecting them.
Interstellar Bill said on April 25, 2012 at 21:01:
“Because of all those factors, I’m optimist that we have at least the Galaxy to ourselves. I shudder at the alternative, and so would Fermi.”
Why? If ETI are many light years away and interstellar travel is as difficult as we are learning on Centauri Dreams just about every other day per post, it’s not like they are going be on our celestial doorstep with a fleet of ships any time soon, if at all.
Carl Sagan estimated that even if one million technological civilizations exist in the Milky Way galaxy, that would mean on average the nearest one to us is about 200 light years distant, which is outside our current electromagnetic bubble. As we have seen here, most people on this blog would consider that to be a very optimistic number, so the real distances would be much farther, maybe even all the way across the galaxy and right out into intergalactic space.
As I have said elsewhere on this blog, if an aggressive ETI did want to take out humanity, they could do so with relative ease and we would have almost no defenses against it. For me worrying about an alien invasion is like worrying about an earthquake: They seldom happen where I live but if one did occur, there would be darn little I could do about it.
I have come to not let the Fermi Paradox bother me much any more. Why aren’t ETI here? Because with a vast galaxy chock full of star systems, they have plenty of other and better things to do than mess with one world that is already occupied. If most aliens even know that we exist, which I doubt.
This classic paper by Dr. Guillermo A. Lemarchand from 1992 covers a wide range of methods and abilities when it comes to artificial cosmic communications and detection.
http://www.coseti.org/lemarch1.htm
To give just one example from the article, here is a quote on how far nuclear explosions could be deteced in deep space:
Elliot estimated the distance at which the United States “Starfish” nuclear test could be detected by our present technology of X-ray detectors. Assuming that the energy of the explosion is equivalent to 1.4 megatons and that the X-ray pulse was equally intense in all directions, he found that this explosion should be detected from a distance of ~400 Astronomical Units, about ten times the radius of Pluto’s solar orbit.
Supposing that all the terrestrial nuclear powers [3] pooled their nuclear weapons stockpiles to produce a single explosion in space (E~2×10 to the 4 power megatons). Considering that the X-ray pulse could be concentrated into a conical beam of about thirty degrees in angle with no loss of radiation, a typical terrestrial X-ray detector should be able to detect a signal from a distance of ~190 light years.
* In 1989 the United States and the Soviet Union had almost 55,000 nuclear warheads with a combined destructive power of 15,500 megatons (Source: Bulletin of Atomic Scientist, 1990).
And check out this article about detonating nuclear bombs past Pluto as a METI method as envisioned by the father of the Soviet hydrogen bomb, Andrei Sakharov:
http://lnfm1.sai.msu.ru/SETI/eng/articles/sakharov.html
I concurr with Ronald’s comments regarding the need to look at generalised parameters regarding habitability and evolution, rather than assuming specific events that led to humans directly are essential in the wider sense.
Many of the astrophysical and geological criteria are indeed likely to be not strictly independent – and derive from basic physics.
Convergent evolution combined with the tendancy of natural selection to cause speciation to fill avaialble niches may well be very important…it may not rely on a single unique set of events…
Abelard Lindsey: did you read the article by Nick Lane, that you refer to? It definitely does *not* mention abiogenesis as a bottleneck, on the contrary, it states that life is probably very common, but that at the same time complex life is probably very rare.
This great article by a great scientific author should actually be mandatory reading for further discussion.
And no, habitable planets are not an urban legend at all, you probably meant to say ‘inhabited planets’ or ‘colonized planets’. (Potentially) habitable planets are a natural given. What we or any intelligence will decide to do with them is an entirely different matter.
Its interesting to see how scientific thought has evolved over the last couple of hundred years with respect to astronomy; almost daily it seems there is another concept regarding planets and intelligence (or the lack of it). One can only imagine what the next few hundred years will bring to bear on these topics.
@ Ronald: thank you, that sounds like the source I had in mind.
@Ronald: Did you read the Academy Series by Jack McDevitt, which begins with _The Engines of God_? The premise of these SF books is that most alien intelligent races are long gone and that it is easier for find archeological evidence of them than it is to find living intelligent alien species.
“Interstellar Bill: with all due respect, but the whole Rare Earth hypothesis has been repeatedly criticized and demonstrated as being seriously flawed. Primarily because it is biased and detreministic: it takes the typical ‘earth characteristics’ as an exact pinpoint of parameter values and then reasons backward that all these must be present exactly like that and how minute that chance is, instead of deriving general essential criteria for a living planet and from there working toward a more generalized model with margins”
” Has been critiziced” ? And so what ? There are two scools of thought concerning this , and no solid anwer will avaiable until further development of telecopes gives us the anwer .
Un the one hand the ” anti-rare-earth” scool have a point , in that you cant “work backward” in a simplistic way ,
BUT on the other hand the examble of Earth IS the only hard evidence prescent , which means that any other theoretical way to “derive general essential criteria ” will basicly be a filosofical statement until prooven otherwise .
Interstellar Bil defines ten bottlenecks , which are all relevant EVEN if they dont represent the ONLY conditions that could make life and intelligence possible . There could be another LIMITED number of ways in which the same problems could be solved , without that the total sum of all these probabilityes becoming bigger than N=1 toolmaking species.
In this wiev our own “probability of existence” is a result of the combined
probabilities of ALL the subsets of of conditions that could have let to an intelligent toolmaking species . In other words , the “event” of humanity only happened as one arbitrary outcome between many , when the combined probability of all these became big enough .
In this version , there are no logic flaws to the “rare earth” theory , and for each year passing , each new possiblity of comunication crossed out without any ETI beeing found , it becomes more probable that the improoved theory is our best representation of reality .
We can trade articles all we wish, but the absolute truth is that all we have is speculation — and some of that is open to debate. I find all this to be quite important, however, in that some day we will meet someone else and we will know how to think about them. It could be that our geography has given us advantage in facing those not like us: as we explored this planet, we met odd persons. As I have said elsewhere, I’m waiting to meet someone from somewhere else who will play chess with me.
Tea, here. I trust that will not invalidate my comment.
…and somewhere on an Earth analog with a different set of bottlenecks there are thousands of intelligent marmots chittering at each other on the Interburrow about whether there could exist an exoplanet where there are intelligent monkeys rather than marmots, and whether they could possibly evolve past the phase of hurling their droppings at each other…
Hello to you all.
I invite you to read this article, which can feed your interesting debate.
http://www.networkworld.com/community/node/80408
Greetings from Antonio Tavani
A new, interesting discovery …
http://phys.org/news/2012-04-astronomers-extrasolar-planets.html
Greetings from Antonio Tavani
“2. Every time a right-sized terrestrial planet in a Hab Zone gets hit just right by a co-orbiting planet, it will be endowed with a Stabilizer Moon.
(Otherwise it ends up slowly rotating with an enormous atmosphere.)”
Interstellar Bill, just this one “bottleneck” you quote itself is full of assumptions of what can and cannot be. They are based on models which are based on limited data. Models can change over time with new knowledge.
“I have come to not let the Fermi Paradox bother me much any more. Why aren’t ETI here? Because …”
ljk, How do we actually know they aren’t? We think they are not already here. But maybe they are/have been all along and we are just too unaware to notice.
i guess everyone here has seen the hubble deep sky photo where every object in the field is a galaxy. there seems to be a hazy wisp through out that field of galaxies that just quite isn’t resolved. perhaps with longer exposure those objects can be resolved.
our galaxy has been estimated upwards in size and content recently and many times since it was first recognized. carl sagan was fond of saying billions and billions. can humans, even trained scientific humans, grasp the scale of the galaxy? trillions of stars with many times that planets. isnt that close enough to “astronomical” odds? what i am implying is that in such a set of circumstances any can happen and most likely has.
how can we fathom the minds beings a million years advanced of us? after all we are still flinging poo at each other as primates are wont to do. we have trouble sharing great wealth. we practice hegemony and oppression on each other. we never follow through with anything but run willy nilly to the next “big thing”. we are short sighted, especially so when it comes to wealth accumulation. perhaps the wrong choices have been made and there is no going to the stars. will the wall street banksters allow such a vast, almost “astronomical”, sum of money to spent that ain’t going into their pockets?
might some similar scenario happened time and time again on these other
planets? maybe all civilizations fall under the curse of money and capitalism.
the cosmic quarantine holds.
i am very doubtful we can escape our own stupidity.