There are still the technical problems to overcome. Sure, if you are not looking for a coherent, centrally (or even distributively) controlled 'empire' or some such thing, it is possible that a technological race could send out seeder ships, or even colony ships that may colonize a few planets in the neighborhood...but it still is a huge stretch. Read "Rendevous with Rama" by Clarke for a pretty good treatment on that subject.

Personally, I think any "real" spacefaring intellect will be electronic/artificial intelligence; the biological stage of evolution (with regards to intelligence) will wind up being just one step up the ladder. Even a trip to any nearby stars will be a hugely daunting and time consuming project for a biology-based entity to consider, even assuming we could muster the required economic resources and social stability and maturity needed, neither of which are a given, judging by our current situation.

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"...wait for the ricochet."

I do there are other civilizations in the galaxy, though there aren't many of them, I'll guess that there are between 5 and 20.

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"Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars." -Carl Sagan

Contemporary with us - and within some reasonabe range of equivalance technologically or socially?

Personally, I'd be stunned if that were the case. On what do you base it?

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"...wait for the ricochet."

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All words, phrases, definitions and theories provided in the above post are, unless otherwise stated, the property of Champion Munch © 2005.

Sign up to sue the Sun

That's likely true and I won't disagree, but there are some things needed for the evolution of complex life-like entities that we can define, and then further refine if needed. some are:

Time - evolution of complex structures like life take time - lots of it. getting it to the point of intelligent life takes still more. life on earth spent at least 2 billion years before multicelled life evolved. from there, another 500m years until "complex" life forms evolved such as arthropods and other such creatures...and so on.

Environmental Variation/Complexity - there needs to be something the induce changes and fitness selection pressures to push evolution along. a very simple, unchanging environment will not get one very far. that said, in some cases (at least) the existence of life alone can have a significant effect on some environments creating a feedback loop. But this is not likely true of ALL environments in which some basic form of life could get started (under the oceans of Europa, say); some environments would place severe constraints on the degree of "dynamicity" possible due to temperature, radiation, constituents (water, chemicals (organic and inorganic), gases, other liquids, etc.), etc.

Stability - this tied to time and to some degree offset by the above - you need to have some consistency in the evironment for long enough to allow and keep things going.

About 90 percent of the stars in our galaxy - of whatever class - are located in conditions where the above requirements are not and cannot be met - too close to the galactic core and there is just too much going on to allow life to happen; planetary orbits disrupted by passing stars, lots of sources of radiation, etc. Many stars even in the arms are located in or near highly ionized nebulae or gas clouds - a sterlizers of planets. And so on and so forth - all these things have to be considered before you then calculate how many possible planets could evolve life, and from them, intelligent/technological life.

My guess is that there is currently one intelligent technological species in our galaxy. There could be one more, but I doubt we'll ever meet them. I'd be willing to bet a pretty penny that there may well have been a few tens over the course of our galaxy's history, but likely not the entire farm. And I also think that our galaxy could go long periods without any technological species active within it at all (though I'll still wager that 'life' in all it's various forms/levels is quite common throughout it at all times). I'd also go so far as to say that I'd think our galaxy, while possibly typical of its type in this way, still is possibly one of the more life-friendly galaxies (perhaps top 20 percent?) in the universe. How do I know? Just a hunch...I'd also be willing to bet I'm not far off, though, either.

Wanna bet? ;o)

Of course, there could be the electronic/AI-based heirs of some of these civilizations floating around - and if anything, I'd bet that's what we'd run into.


bidi-bidi-beep

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"...wait for the ricochet."

Speaking as the thread-starter,

You're perfectly correct about this. This is more of an intellectual exercise, even if tempered with reasonable scientific data.

On the other hand, "earth-bias" is a matter of degree. I decisively agree that a humanoid civilization is so unlikely that it barely deserves discussion. On the other hand focusing on "Carbon-water based" is not quite as Earth-centric -- MANY possibilities come from this broad life-type alone. I implicitly stuck with this type because carbon forms much longer chains than other atoms (even silicon), and because water is an extremely common solvent. Carbon-ammonia, IMO the most likely alternate biochemistry, is quite speculative even if it does turn out to be a common life-type. Therefore, bringing in Carbon-ammonia would bring in another tangent that would muddy the issue. That kind of life needs another set of calculations entirely.

Having said that, I pretty much impled that my calculations were Earth-bias on a number of points. It's only because I believe in sticking closely to what we know rather than stacking hypothesis on top of hypothesis. Yes, there is plenty of room for alternatives, but without setting SOME limits you open the possibility of effectively asking your audience to believe in magic.

I agree that 'earth bias' or 'anthropocentrism' needs to be kept in check; that said, we shouldn't stray further from it than necessary. there are perhaps some good lessons to be drawn from how life here evolved, too...

for example, one of the things to be considered is the development of technology. Despite a FAR longer history, and - arguably - diversity, life in the sea has never developed very far up the intelligence chain (whales moved BACK into the water; their anscestors didn't evolve in it), and apart from some minimal tool-making behavious on the part of octopuses, there's never been any indication that any technology could get going in the sea.

I think it's not unreasonable, therefore, to consider the environment and what impact that would have on the development of higher technology. it seems to me that many of the more exotic chemistries proposed for life would also involve pretty volatile environments; how far could technology be taken in them?

and further, what impact does the ability to develop technology have on the impact of a species survival fitness and later evolution? in our case, admittedly a fairly limited sample (but a sample nonetheless), it's been a significant boost; our evolution has been fairly rapid since australopithecines began whacking their prey - and each other - with sticks, and their descendents began using fire...

So, while earth-bias IS something to avoid, our evolution and development is also something to perhaps draw lessons from, as well.

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"...wait for the ricochet."

It has been suggested that radiation makes much of the galaxy uninhabitable. This seems quite odd as in some areas on earth people are naturally exposed to over 100 times normal background radiation without significant health effects. Also bacteria and animal experiments show life has a signifcant ability to adapt to higher radiation levels. On top of all that radiation from space is greatly affected by the strength of a planet's magnetic field and the thickness of its atmosphere (or ice crust).

Well, 'normal' background radiation on earth is significantly lower on earth than what it would be if we were located close to the galactic core or within a nebula; i'm not sure HOW much of that a magnetic field would stop, but i'm pretty sure it wouldn't be enough. The make-up of our atmosphere also has an effect on reducing the amount of radiation that reaches the surface. even a supernova explosion within a few hundred ly from earth can have a significant effect (the impending impact of the Eta Carinae explosion will at least cause damage to space-borne electronics, and if it had been oriented so that it was 'aimed' at earth a bit more directly, our ozone layer could have been removed, allowing enough radiation to reach earth to seriously affect life on the surface - and that's 8000 ly away. of course, it is also an unusually large SN; but even much more modest explosions closer would have (and have had) an effect).

Any while it's true that some bacteria are radiation-tolerant to some degree, the issue of greatly increased mutation rates would play hell with evolution; by far most mutations are NOT beneficial - most are either have no real effect and many are outright fatal to the organism expressing mutated genes. very few actually improve an organism's fitness, and this effect is further multiplied as you increase the structural complexity of the organism involved. i supposed it is possible that complex creatures in such an environment could evolve some degree radiation tolerance, but i think there are probably upper limits even to that and those are likely not really far beyond ours in absolute terms.

We've evolved in a relatively quiet environment around a relatively stable star. We've been lucky. That said, life on earth is thought to have been negatively affected by such things as distant supernova explosions and transits through gaseous nebula, with some extinction events attributed to, or at least 'enhanced' by, them.

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"...wait for the ricochet."

Well humans in Ramsar in Iran seem to be able to handle background radiation a hundred times higher than normal so it appears likely that we could also handle much higher amounts of radiation from space without difficulty. Very roughly, the lack of ill effects on people living in high radiation areas on earth suggests we could take at least 200 times as much radiation from space as we currently receive.


Mutation rates aren't caused by radiation, although radiation can certainly cause mutations. DNA is not very stable room temperature is enough to cause mutations and is under constant repair. Mutation rates are basically determined by how much effort is put into preventing mutations.

Then we have to consider that we don't know what sort of planets are suitable for technologically advanced life to develop on. Perhaps life is common on earth sized Europa type planets under ice crusts many kilometers thick. And we can be certain that alien life won't use DNA identical to our own, so it's not really possible to discuss how radiation will affect their mutation rates.

Well, i will need to check studies, if any are available, before accepting such a statement at face value; i do know that 'normal' background radiation levels on earth, however, is very low, so 100x increase may not be all that significant and what you're saying could be true. i'd also like check to be sure that negligible 'ill effects' from that (to include increased birth defects, cancer rates, etc.) degree of radiation is also a valid claim. one case in point where background radiation IS a significant cause of mutations is Chernobyl. I don't have handy the radiation levels, however, so i can't make many statements there except that that radiation is from only one small fission reactor; i'd expect radiation from cosmic sources to be orders of magnitude more intense in certain environments/locations in the galaxy.

i also believe that the levels of radiation being described in other environments (galactic core region (say inner 1/3 to 1/2) and nebula is on the order of several hundreds to many thousands (or millions) of times higher. if it were 'around 100 times earth's' then perhaps things would be fine. again, a relative measure vs earth's vs. absolute values in the amount of radiation are different things. while it may seem that 100 times earth's rate is 'high', if earth's rate is VERY low, then even 100 or 1000 times may not really mean much in absolute terms.


Radiation can cause mutations, but doesn't affect mutation rates? i'd think anything that causes mutations is a part of the 'cause' of the mutation rate, and an increase in mutations from a given cause would be considered as to causing an increase in that mutuation rate, no?


Well, i agree with you that life could be common on europa - and i hope it is...it would be exciting! but i also am a bit doubtful, for various reasons. but even if it is there, how diverse can it be, and how advanced? the two are related and the environment will place limits on both. and even if - somehow - intelligent life were to evolve in an environment similar to europa, what sort of technology could it possibly produce? would it even be aware of the rest of the universe? would it be even equipped to gain that knowledge? without fire, how could such technologies such as metallurgy or electronics be developed very far?

sure, it is possible to fall back on the 'we cannot know' argument, and for some things, i would have to say you'd be right; nature has a way of being very ingenious and life being very adaptive. that said, there are some things we can take fairly far with logic/reason alone, and we shouldn't let our ignorance of some things block such reasoning provided it's based on empirical evidence, understanding of nature, and logic, but rather should only temper it through being aware of the nature/implications of possibly unanticipated issues.

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"...wait for the ricochet."

I said radiation does not determine mutation rates. I didn't say it does not affect mutation rates. For one thing radiation from space is a very minor cause of mutation on earth. Also when mutation rates increase for whatever reason this promotes the spread of allele sets that can faithfully replicate so there is negative feedback occuring. Going downhill can certainly affect the speed of your car, but the rate at which your car travels is determined by your foot on the accelerator/brake.

Just how radiation will affect the mutation rate of aliens, we can't say.

My basic point is that life on earth, including us, can survive a lot more radiation from space than we currently do so we shouldn't dismiss the possibility of earthlike life in areas with only a few hundred times more radiation than in our area.

I'll give you that, however very relucantly; i think that it's unlikely that schemes that bypass the laws of physics and the effects of radiation on complex molecules could be evolved that would allow a sufficient balance of stability AND variation to allow for evolution of complex organisms, however i'll admit it's possible i could be in error here.

in any case, i think that the radiation levels of any planet of stars in the inhospitiable areas - such as the galactic core region (where the majority of stars are) and nebular regions (where another good batch of them are) - are much higher than a few hundred times that of earth. i'd need to double-check that, however that's my recollection.

the main thrust of my argument is that i think estimates of there being numerous contempory technological/intelligent races extant in a given galaxy at one time are highly optimistic; there could be some galaxies here or there where that is the case; the universe is a big place and there are a LOT of galaxies, so there is bound to be some degree of variation, but i would be willing to bet that, on average, 1 per given galaxy at any one time would still be a fortunate, but possible and reasonable, estimate. that's not to say that life is NOT much more common - I'd also bet in favor of that being the case - but life has many gradients, and i suspect the more complex the life you're looking for, the rarer it will be at an almost exponential rate going up the scale of complexity.

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"...wait for the ricochet."

No one is suggesting a bypass of the laws of physics and the effects of radiation on complex molecules. If you expose something to enough radiation it will get fried. But for earth creatures variation is free. Nothing needs to be done to induce variability in DNA. As I mentioned before, room temperature is sufficient. What organisms do work at is stability and over time mutations will tend to approach an equilbrium level if mutagens are increased or decreased.

Sure, I don't disagree there in principle. But there are limits, and the necessary balance must be achieved within them, i think. if the rate of mutation is too high (eg. many parts of the genetic molecule undergoing numerous/frequent random changes/damage), it would seem to be impossible for a sufficiently stable/coherent/consistent mechanism of heredity to be created by any molecular construct to deal with that problem; it itself would have to evolve numerous redundancies, i'd think, and that in itself would, in turn, be quite inefficient and introduce it's own problems. but then, i'm no biochemist or physicist - just a layman sufficiently informed to be interested enough in such things so as to enjoy discussing/arguing/exploring such things (politely, I hope), but sufficiently insufficiently educated to be much more than dangerous...and lucky once in a while in his guesses. ;o)

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"...wait for the ricochet."

Re: Technology Development.

I reread my "foundation" posts and found a potential source of confusion. If you're not confused yet, simply take this as a clarification. I said at the end of the calculation post.

""12.16768916 planets whose most intelligent species is within (but not over) 5000 years of current Western World techonolgical development.""

Though I also said one possible definition of advanced civilization was "one capable of extensive radio communication"

Making the admittedly doubtful assumption that life forms develop technology at the same rate we do (or at least that we humans are at or near the average rate of advance of all the universe's species)...that means the next most advanced society has technology about 5000/12 years behind ours - the same as 1590 CE Western Europe (i.e. late preindustrial economy, scientific revolution barely getting off the ground, cannons and muskets the most fearsome military technology, etc.).

On the other hand, as ebarachum (sp?), one of the eariest commenters said, that doesn't take into account species with technologies MORE advanced than ours (thus making the least advanced trans-present-human technology about early 25th century Earth). An early 25th century earth equivalent technology is still likely to be at least 90 degrees around the galaxy from us, possibly exactly 180 degrees (i.e. right behind the glactic core). So if any civilization IS closer to us, it's likely to be SO much more advanced than us that we might not even recognize them as an advanced species.

Re: Technology of aliens in other environments. I direct you to 3rdVogon's post from several years back, as I fully agree with him regarding developing technology on land vs in the water

"life" if found,what will be their language
Re: Habitat Desirable -- Though ebecharum (sp?) disagrees, I think life is most likely in the galactic habitable zone, though he does bring up interesting points I didn't think about.

All in all, great discussion you two have going there.