This is Largely a continuation of this thread from last year. I decided upon a separate thread because I never saw a comprehensive explanation of why certain Drake Equation values had the values they did, of which my calculations are a variant. Furthermore, as alluded to in this post on the same thread, Jared Diamond argues in his book [i]Guns, Germs, and Steel[/url] that a geography heavily influences which sections of a planet develop high technology the quickest. Having bought a copy of this book myself (not to mention possessing a lot of academic background in Geography) I can certainly vouch that Diamond's thesis is compelling, though provoking,and even mostly agreeabe IMO (even if not 100% convincing in all details). From here, it's easy for a geography minor (with considerable graduate level credit in geography as well) to see that the landform patterns of continents can determine how quickly it develops technology - certainly relevant for technically advanced alien life.

Further geographic aspects will be discussed on another thread, to be posted shortly. For now, I want to share my view of the factors influencing how amiable a solar system may be to life. The actual comprehensive calculation estimates will be in the next post

(STARS IN THE GALAXY- Estimates vary, but I will go with the highest figure I heard: 500 Billion ( Royal Greenwich Observatory. I assume that includes everything from M-Class (Red Dwarfs) to Enormous O- Class Stars (very hot, very fast burning, Blue stars). Our sun is Class G.

Stars outside the core of the galaxy - I (?) We (?) could also be wrong, but I heard from an astronomy professor that this is about 2/3 of all stars.

Such Stars that are in the Galactic Habitable Zone - This is the zone of the galaxy where elements heavier than Helium tend to be most abundant. I’m not too sure about this, but arbitrarily, I will say it’s about 10% of the Galactic Radius (i.e. the 10% of stars most likely to have planets that could harbor life given proper conditions)


Stars on the Main Sequence - These stars burn hydrogen for fuel - 85% of all such stars ( Wikipedia). Stars not on the main sequence are old giant stars that swallowed most of their inner solar system. (as our sun will do 5 billion years from now). Once a star leaves the main sequence, it will start burning Helium into Carbon and Oxygen. These reactions may last for any amount of time up to perhaps a few billion years at most, depending on the mass of the star. Our sun is forecast to be in a Helium-burning red giant for about a billion years, after which it will shed its atmosphere and become a white dwarf. For this reason, stars that have left the main sequence are not good candidates for life, even on the moons of its outer planets.

Stars that are Class G or K - The cooler and “redder” the star, the longer it remains on the main sequence (barring the obvious exception of red giants). The previously-mentioned O-Class (very hot blue) stars will likely last only a few dozen million years, barely enough time for star dust to coalesce into planets. Furthermore, hotter stars emit enormous quantities of ionizing radiation (UV or higher). In fact, large stars tend to emit the bulk of their radiation in the UV band. Stars in classes B (a lower level blue-white) and A (white) suffer similarly, though to not to the extreme extent as O-class ones. Nevertheless, these stars will last only a few billion years at most. This may be long enough for simple life and perhaps even the simplest animal life to form, but not likely enough to allow technologically advanced life to arise (unless its evolution is incredibly quick). F-class (white) is likely to last from 4 to 6 billion years, certainly enough to give rise to complex life (perhaps even intelligent life). Unfortunately, in the Earth-term timeline at least, a white sun will start to leave the main sequence just when intelligence does arise. Timing truly is everything. So while it’s certainly possible and even plausible for a white sun to have a technically advanced civilization, I don’t find it particularly likely.

By contrast, the red dwarf (M-class) stars will be around for billions of years, much more than enough time for life to form. Furthermore, they do not emit as much ionizing radiation as even our own sun (G-Class), another factor favoring a life-friendly environment. Unfortunately, the cooler the star, the narrower its life zone. I personally interpret this fact to mean that a red star’s HZ will be less likely to contain a planet of any sort, let alone one with other preconditions necessary for life to have a chance on it. Even if the red sun’s HZ does have a planet with the appropriate gravity, atmospheric and other characteristics, odds are fairly high that the planet will suffer from “rotation lock” (one face always facing the star). This means one side will be in eternal day or close to it (thus rendering it too hot) and one side will be in eternal night (rendering it too cold). However, there is still at least some chance other mitigating factors will come to play on such a planet (the hot spot over the planet may create atmospheric convection that creates winds, thus spreading heat more evenly over the planet). Obviously, a rotationally-locked planet’s twilight zone could offer a happy medium in which life, and even intelligence can flourish in theory. However, as I will discuss later, such a planet will have a much more difficult time developing a sustainable high technology civilization, and even a high-end pre-industrial civilization.

For these reasons, I will cast my votes for G (yellow), K (orange), and low-level white stars as places favorable for advanced civilization to arise. If we include all G and K stars, plus about 1/3 of all F stars, these stars are about 22% of all stars in the galaxy ( Wikipedia). If M-class (red) stars - 78% of all stars - permit HZ planets without a rotation lock, then perhaps another 10 % of all stars (the hotter M-class ones) can be added to (though I admit this number is rather arbitrary). So we can say that as many as 33% of all stars could support a technical civilization, given other necessary planetary conditions listed above.

Such stars that are the appropriate age - If you are content with finding significant life in any form, you will likely find it around planets between two and five billion years old. This is certainly long enough for life to form an Oxygen atmosphere (strong evidence of life), though not necessarily sentient life. While I know of no proof that the following assumption is, in fact, true, for the sake of simplicity, I will assume that stars have formed at more or less equal rates over the course of at least the past 10 billion years. Within this assumption, it is relatively straight forward to calculate the expected proportion of stars that are between X and Y years old. This is done by dividing that star’s present age by its expected life span (i.e. if we want to figure out what percentage of G2 class stars are between 2 and 5 billion years old, and we know such stars will likely last 10 billion years on the main sequence, then we can say that (5-2)/10 of all such stars are between 2 and 5 billion years old - or 30% of all G2 stars.

Such Stars That Are between 4.5 and 5.0 Billion Years Old - On the other hand, if you are interested only in life capable of extensive radio communication, then I believe you can use a variant of the above formula. For the sake of simplicity, allow me to use an Earth-Biased figure of 4.3 to 4.7 billion years old as the age of the stars we expect to find such worlds, regardless of spectral class (if you are dissatisfied with this bias, you can rework the formula using the target age you see fit). In this case (4.7 - 4.3)/10 equals 0.04. This means that within the appropriate target stars (low level F to high level M) we can plausibly claim that about 5% of all sun-like stars are in this age range. Admittedly, this is an earth-biased trait. We have no clue how quickly stars this age will give rise to technically advanced civilizations. We could have evolved ours slower than expected or more quickly. There’s really no way to know at this time. Even so, 4.5 to 5.0 billion years does give us a proven time in which a planet COULD develop such a civilization. However, because the sun gradually swells and brightens as it gets older (I heard by about 1% every 100 million years), a life-bearing planet will likely undergo a “heat death” long before its star reaches the main sequence. Thus, I guesstimate that 5.5 billion years is usually the longest time frame in which a habitable planet could develop a civilization capable of radio communication. Even so, I will be conservative and stick with the 4.3 byo to 4.7 byo timeline and say that 4% of such stars are the optimal age to have a technical civilization, providing it has a continuously habitable planet.

Such stars with planets. Recently, it’s been found that stars whose metal content is at least one-third that of the sun are somewhat likely to develop planets. Of these stars, I calculate that about 8.4% of such stars are actually found to have planets ( exoplanets.org)

Such stars whose planets are in Sufficiently Stable and Circular Orbits -At the time of this post, the Extrasolar Planets Encyclopedia lists 193 surveyed star systems found to have planets as of the date of this post, 60 of them have eccentricities of 0.1 or less known to contain at least one planet. Of these the majority are in orbits that are highly eccentric by Earth standards, reminiscent of what we think of as cometary orbits. Moderate degrees of eccentricity within a habitable zone for a sun-like star (say, from 0.9 to 1.3 AU; 1 AU = Sun-Earth distance) does not necessarily preclude life from forming but it does makes its development more difficult due to a more extreme climatic regime. Therefore, I will say that life will function and prosper much more readily when the orbital eccentricity is 0.1 (i.e. the difference between apehelion and parahelion is only 10%. Earth’s eccentricity is around 0.02).


Such stars with roughly earth-size planets. Here is where we really truly enter the realm of speculation. Thanks to the discovery of Jupiter-like worlds (“gas giants”) in numerous inner portions of planetary systems, this is not as straight forward as it once seemed to be. Here, we have to use our own solar system as a framework, however imperfect a model it may be. Currently, there are two worlds whose mass is between 0.5 and 10 Earth Masses (the current theoretical optimum size, gravity, etc for which life’s development is favorable due to the ability to hold atmospheres, plate tectonics, magnetic fields, etc.): Earth and Venus. Too little mass and the planet won’t be able to keep its atmosphere (and inevitably liquid water) for longer than a few billion years; too much mass and odds are fairly good that it’ll retain hydrogen and helium, thereby adding more mass to the planet that allows it to trap more H and He - thus starting a cycle that transforms the planet into a gas giant. Based roughly on our own solar system, I will be rather liberal allow for 3 such planets out of a total of 9 revolving around such stars mentioned. This means 33% of the planets are estimated to be between 0.5 and 10 Earth Masses.


Stars Within the Continuous Habitable Zone. It’s been found that stars tend to brighten with age, even when they are not on the main sequence. This means the stars Habitable Zone will move outward with time. Many strongly believe that Venus was once within our sun’s HZ until the sun’s increasing brightness rendered the planet too hot to retain liquid water (although the lack of plate tectonics certainly deprived the planet of a carbonate-silicate cycle that could have trapped CO2 in its rocks, as is the case here on Earth). Earth, being further away, was spared this fate (although some say that its early atmosphere of methane, CO2, and other gases kept the planet warm in an otherwise cold place to be in the young sun days). Mars itself might have had liquid water and a fairly thick atmosphere at one time, which would have effectively rendered it in the HZ. As far as I can tell, HZ boundaries seems rather Earth-centric, and so the boundaries can only exist in a semi-arbitrary sense. In this case, I will go out on a limb and say that 1.5 terrestrial planets of appropriate size are likely to be found in the Continuous HZ, or 50% of all planets.

Such Stars whose planets had A Major Collision That Formed A Moon - It seems that collisions between planet sized bodies may be fairly common in the early solar system. Earth moon was almost certainly formed from such a collision, while some say that the moon Charon resulted from a similar collision with Pluto. Neptune’s radical axial tilt may have been the result of such a collision, though I believe this explanation is rather weak. Nevertheless, it seems that at least one solid body in a young solar system will experience such a collision, and thus has a real possibility of gaining at least a small satellite. Therefore, I will say that one of every three terrestrial planets will undergo such a cataclysm.

I believe this factor is important for a number of reasons: (a) it forms a body that stabilizes a planet’s axial tilt over time (b) it thins out the planet’s crust, thus allowing for more active volcanism, plate tectonics, and other geological processes necessary to take much CO2 from the atmosphere AND form a two-tiered land mass of continental and oceanic landmasses. Although Venus almost certainly has volcanism, it seems to have no plate tectonics. It is strongly believed that Venus has a very thick lithosphere (surface) compared to the earth, which makes for a more rigid surface. This in turn severely limits, if not eliminates, the formation of plates. It also renders volcanism in scattered spots throughout the planet, rather than concentrated in certain areas near plate boundaries as on earth. A Space Daily article addressing this issue said that if all the water in Earth’s oceans were deposited on Venus, then these oceans would cover 90% of the planet’s surface. As we will see later, this seriously limits a planet’s ability to develop a technical civilization, though I don’t think it will too badly impede life itself.

5E+11 5E+11
0.666666667 3.33333E+11
0.1 33333333333
0.85 28333333333
0.333333333 9444444444
0.3 2833333333
0.084 238000000
0.552147239 131411042.9
0.333333333 43803680.98
0.5 21901840.49
0.333333333 7,300,613.497 planets containing ANY kind of life, intelligent or not

5E+11 5E+11
0.666666667 3.33333E+11
0.1 33333333333
0.85 28333333333
0.333333333 9444444444
0.04 377777777.8
0.084 31733333.33
0.552147239 17521472.39
0.333333333 5840490.798
0.5 2920245.399
0.333333333 973415.1329 "Jurassic" worlds or any other whose most intelligent species is sub-sentient

5E+11 5E+11
0.666666667 3.33333E+11
0.1 33333333333
0.85 28333333333
0.333333333 9444444444
0.0000005 4722.222222
0.084 396.6666667
0.552147239 219.0184049
0.333333333 73.00613497
0.5 36.50306748
0.333333333 12.16768916 planets whose most intelligent species is within (but not over) 5000 years of current Western World techonolgical development.

I will stop here, since any specuation about odds of survival of nuclear war or other disaster is highly speculative even for human beings themselves, let alone aliens. I only seek to provide an arguably plausible framework within which the alien intelligent life issue can be answered.

Conclusion: While I think life itself is fairly common throughout this galaxy, and is likely common even among fairly nearby stars, I believe that advanced technical civilizations are quite rare, though not unreasonable to believe in.

Last years long thread How Many Intelligent Civilizations are in This Galaxy? provides many previous posts that are relevant.

There are plenty of assumptions you have made which are arguable, and much fun can be had arguing the details; but the conclusion you have reached seems to me to be a non-sequitur.

You have made an estimate of ~ 12 worlds with 'planets whose most intelligent species is within (but not over) 5000 years of current Western World techonolgical development'.
From this you conclude that 'advanced technical civilizations are quite rare, though not unreasonable to believe in'.

Because you have not considered civilisations more than 5000 years old, you have introduced a limitation that may not apply. If the average age of a civilisation is a million years, that increases the number of civilisations to 2400, all other things being equal.

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I grant that it is a non-sequitor on its face, particularly regarding civilizations whose technology is ahead of current Earth-standard; most of all, those who are 1 million years ahead of us.

Perhaps it has to do with the meaning of "rare", which I admit is quite open-ended. Since I didn't bother to define it, I won't quibble too much about whose idea of "rare" ought to be accepted. Assuming you are correct, 2400 civilizations is quite a lot, though by my simplistic calculations still fairly far from Earth (about 941 LY)*.

If "rare" is defined as "not likely to make contact of any sort", then you probably have the stronger case, particularly with a million-year time frame (although I follow Carl Sagan in saying that a civilization a million years ahead of us is likely to be as much beyond us as we are beyond a macaque. Would we even recognize such a civilization. But that's just a minor quibble, and I don't want to pull the rug out from anyone.).

On the other hand if "rare" means "not likely to be spotted among stars that are less than 12th magnitude in Earth's sky", then "rare" could quite possibly still apply.

But at this point, I'm close to breaking my promise not to quibble. So I'll allow you your well-made point

Answering just the question asked in the subject of this thread, the answer is a clear and simple 0.

A planet that is contained in a star is not inhabitable (and will very soon cease to be a planet at all).

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What if one of the intelligent species colonizes 3 planets and 9 moons, that would be 12 worlds just by itself. If we count Russia's Venera, the Mars spacecrafts, and the Huygens mission, we have 3 planets and 2 moons, 5 worlds for Humanity alone!

Open you mind! Our current evolution is a catalyst for interplanetary base establishment. Some day, we will have "base that are belong to us" - hehe. Evolution is a primitive step, with AI, we can invent a faster process which only takes thousands of years. It's a new frontier.

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One of the factors in your calculation which strikes me as a little dubious is the proportion of G class and K class stars. If you accept the high estimate of the number of stars in the galaxy (500 billion) you should realise that the high estimates almost certainly include many more very small red dwarfs. The estimate of the population of red dwarfs is increasing all the time, as more and more tiny dwarfs are found.

If the high estimate of 500 billion stars includes the very small stars which are now being discovered, then the proportion of red dwarfs is likely to be quite a bit higher than 78%, and the proportion of Sun-like stars is therefore likely to be quite a bit lower.

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On the other hand, the concept of the galactic habitable zone is a little flawed, in my opinion. Rather than a fixed zone which contains the most likely stars to have habitable planets, it is more likely to be a moving zone whch changes location over time.

See this simulation of the development of the GHZ over time. The green zone moves outwards, and will continue to do so in the future allowing a much wider habitable region covering much of the galaxy.
http://astronomy.swin.edu.au/GHZ/GHZmovie.html

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This thread I started in "General Science" deals with how a planet's geography man influence its ability to develop high techonolgy Geography and Other Worlds - Speculations (pardon the self-link, but its best to keep this limit this thread to astronomical aspects)

Henrik,
You caught me fair and square - though you quibble too much

kmarinas
What if one of the intelligent species colonizes 3 planets and 9 moons, that would be 12 worlds just by itself. If we count Russia's Venera, the Mars spacecrafts, and the Huygens mission, we have 3 planets and 2 moons, 5 worlds for Humanity alone!

I was actually speaking of planets where life evolved without artificial intervention to the extent our science can know, not any colonized worlds themselves within that solar system. Personally, I find it very unlikely that two planets in a solar system can evolve life independently, which was my point. On other matters, I will not deal with sentient intervention in life's development on other planets in the system because those other planets are unlikely to have evolved life and sustained it to the point where it developed radio technology. However, I grant that even extrasolar worlds might have some colonies, though I think that would be for species far older and far more technologically advanced that we are (which feeds into eburacum's point).

eburacum
The G & K class percentages (plus other stars): It's obvious that adjusting my estimates down from 33% to even an extreme of 8.25% will still mean 600 such worlds based on your description of potential civs of up to 1 million years old (and a "fourth-ing" of every other conclusion, for that matter).

The Galactic HZ: TY for your movie link, cool and quite instructive. Although you are skeptical of the GHZ, allow me to expand it to include "all past and present locations of the GHZ". Multiplying that by 4 will do one of two things

(a) assuming the 33% figure mentioned above, roughly triple the number of planets we describe (triple because the inner regions of the galaxy will have smaller 3-D volume for their 10% circular band around the core. or
(b) assuming the 8.25% figure, it brings us to 3/4 of our original figures for the number of inhabited worlds of some form.

The 500 billion figure: given the math calculations, you can probably predict how assuming even a rather low-ball figure of 200 million would affect our figures.

Bottom Line: No matter how you slice it, if a civilization has a good chance of surviving its raucous warline adolescence and other disasters - it has a good chance of being a million year old civilization. There could well be hundreds or even thousands of such intelligences in this galaxy. On the other hand, as I said, would we even recognize such a civilization so far ahead of us (and likely almost god-like, barring some unforeseen major physics or technological bottleneck barring advancement to almost-god status).

Even so, this is ultimately beside the point. The point is the estimated ACTUAL number of civs, regardless of how easily we would recognize them.

Is it worth considering starless planets in independent "orbits" within and without the galaxy that are from 0.5 to 20 times the mass of Jupiter and have moons the size of Venus including gravitationally driven plate tectonics. Habitable zones may come in many variations and evolution is an engine capable of powering factories with many outputs.

It's quite likely that within 1000 years we will have spread over a 100 light year radius in our section of the MW and will be detectable by sentients 1000 light years away who won't be able to tell whether we are indigenous to the planet on which we were detected or transplanted from somewhere else. The same holds for us detecting a similar spread of other sentients.

Unless the Europans stop us.

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Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

Modern data from a number of planned space science missions should greatly aid in answering the question, "how many stars have habitable planets?" This October the CNES COROT mission will launch, and it will be capable of determining what fraction of stars have very large terrestrial planets. Next in line (2008), assuming it does not fall to the appalling science budget ax, is the Kepler mission. The Kepler mission will tell us what fraction of stars (spectral type M-F), single and mulitple, have terrestrial planets. We should know this stuff by 2015. People have been wondering about this for ages. Exciting times. In the meantime, microlensing planet searches are already telling us the following:

Microlens OGLE-2005-BLG-169 Implies Cool Neptune-Like Planets are Common

B. S. Gaudi1, A. Gould2, A. Udalski3, D. An2, D. Bennett4, A. Zhou5, S. Dong2, N. J. Rattenbury6, P. C. Yock7, I. A. Bond8, G. W. Christie9, K. Horne10, J. Anderson11, K. Z. Stanek2, MicroFUN Collaboration, OGLE Collaboration, RobotNet Collaboration
1Harvard-Smithsonian, CfA, 2Ohio State, 3Warsaw University, Poland, 4Notre Dame, 5Missouri State University, 6Jodrell Bank, United Kingdom, 7University of Auckland, New Zealand, 8Massey, New Zealand, 9Auckland Observatory, New Zealand, 10St. Andrews, United Kingdom, 11Rice.
Presentation Number: 9.03
We report the detection a Neptune mass-ratio (q~8e-5) planetary companion to the lens star in the extremely high-magnification (A~800) microlensing event OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M~0.5 M⊙ implying a planet mass of ~13 M⊕ and projected separation of ~2.7 AU. When intensely monitored over their peak, high-magnification events similar to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass-ratio planets with projected separations of 0.6 to 1.6 Einstein radii, corresponding to 1.6--4.3 AU in the present case. Only two other such events were monitored well enough to detect Neptunes, and so this detection by itself suggests that Neptune mass-ratio planets are common. Moreover, another Neptune was recently discovered at a similar distance from its parent star in a low-magnification event, which are more common but are individually much less sensitive to planets. Combining the two
detections yields 90% upper and lower frequency limits f=0.37+0.30-0.21 over just 0.4 decades of planet-star separation. Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to detect by other methods of planet detection, including radial velocities, transits, or astrometry.

Actually I don't think surviving war like stages is the deciding factor of what civilizations moves onward or not as is the civilization impact on thier own environment.

I'd break it down like this.

Per 100 Industrial/Post Industrial Civilizations.

Wiped out due to planatary or solar catastophy 1
Wiped out due to nulclear or biological wars 5
Wiped out due to contact with bateria from other planets in thier own solar system 10
Wiped out due to natural evolotionary changes 3
Wiped out due to planatary mismanagement of climate changes 35.

Leaving 46 of 100 potentials that could have reached instersteler travel.

Of those

Choose to revert to a simpler life 20 (abandons most technology)
That commit some from of mass suicide because of beliefs 5
Choose to not become space farring outside thier own solar system
10

So around 11 out of 100 would make it to instersellar travel stage.

So where are we?

Just begining on our way to being wiped out due to planatary mismanagement of climate changes, IMHO

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A very intelligent and thought provoking thread. Just my opinion, but I would be surprised if there were more than a couple of dozen technological civilizations at any given time in our galaxy. Thank You for the interesting read.

GOURDHEAD
Is it worth considering starless planets in independent "orbits" within and without the galaxy that are from 0.5 to 20 times the mass of Jupiter and have moons the size of Venus including gravitationally driven plate tectonics. Habitable zones may come in many variations and evolution is an engine capable of powering factories with many outputs.

This certainly is a possibility for sub-sentient life, and perhaps for low to mid complexity multi-cellular self-propelling life (animal by definition, I’d think). I was actually thinking of surface-dwelling life when I drew up this list, but since I didn’t explicitly say so, I’ll have to allow you that point. Everyone’s heard about how Europa is a promising place, so I won’t elaborate on it.

On the other hand, I think that any moon close enough to such a gas giant to induce plate tectnoics would generate enormous ocean tides - to the point where it would really stir up the amino acids and other building blocks to the point that the organic soup can’t concentrate in one spot. Perhaps there’s some spot well inland that could serve as a tidal pool, but it’s difficult for me to see how any self-replicating system can survive for long in such an environment.


dgavin
Per 100 Industrial/Post Industrial Civilizations.

Wiped out due to planatary or solar catastophy 1
Wiped out due to nulclear or biological wars 5
Wiped out due to contact with bateria from other planets in thier own solar system 10
Wiped out due to natural evolotionary changes 3
Wiped out due to planatary mismanagement of climate changes 35.


Planetary Catastrophe: I think this is somewhat measurable, albeit barely so because we have only one solar system of which we have detailed knowledge thereof. Even so, I’d think it possible to construct some probability of wipe-out based on some probable maximum time span between hits from asteroids >1000 meters wide (or whichever other figure you care to use). Still, keep in mind this factor is only relevant for societies with pre 21st century space technology/engineering, and maybe even pre 2050 CE space tech/engineering too (more advanced civs would find it fairly easy to prevent a collision in some way)

On all others, the only one I disagree with is the third one (space bacteria): Firstly, I think any expedition to a sister planet in a solar system will take strong precautions to prevent this (this is beside the fact that the rest of the solar system is likely to be incredibly hostile to life in any conceivable form [Carbon-water, Carbon-ammonia, Silicon-X, or any other combo you can likely think of]).

Even if a “bad bug” is present and does make it back to the home planet and does cause a horrid epidemic, it’s still going to be very hard to wipe out an entire species - although I can see how a particularly virulent bug might wipe out a civilization. We have the Native Americans as an example particularly the Aztecs and Incas. Their civ was wiped out in great part by diseases, yet the ethnic groups themselves survived.

Result: It may be trivial to say so, but I have to go with 55 out of 100. Certainly it’s not enough to substantially alter the calculations.
Leaving 46 of 100 potentials that could have reached instersteler travel.


dgavin

Of those

Choose to revert to a simpler life 20 (abandons most technology)
That commit some from of mass suicide because of beliefs 5
Choose to not become space farring outside thier own solar system
10

So around 11 out of 100 would make it to instersellar travel stage.

My instinct tells me that only 2 or 3 would abandon technology. Even if 1/100 keep that technology, that’s still a pretty substantial core to maintain it (I think a nation of 63 Million people could adequately sustain a technology even without much help from the rest of the world, if only because their technology gives them superiority over other peoples and hence can easily take those important resources that enable space exploration if they wanted them badly enough). Ditto for mass suicides, except I would choose an even lower figure, given that only the most fanatical will choose to commit suicide for their beliefs, or even say their race should cease to exist altogether (remember that 1 out of 1,000 exception). So I would say “practically zero” in this case

However, I grant the cessation of extrasolar exploration is quite plausible, to the point where I say you underestimated this figure (I’d go with 20, given the extraordinary expenses, distances, time and resources to sustain an extrasolar exploration effort - let alone colonization).

dgavin
Based on my figure, I’d say 55-2-0-20= 31 civilizations might get into space
So where are we?

Just begining on our way to being wiped out due to planatary mismanagement of climate changes, IMHO

filrabat
That I do find disturbing plausible, though by no means strikingly high in probability. There's still plenty of hope

To Folkhemmet
Thanks for the information, folk. I’m sure we will be a lot closer to finding out in a little more than 10 years. This will trul