Other civilisations in the Galaxy - are they really that likely?

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2Gyr is 1/7 of the age of the universe!

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Not to mention that it took half the lifetime of the sun for intelligent life to finally come about.

I think the recent discoveries of extrasolar planets has shown that perhaps our type of planet system might be more rare than we thought, as in one with small rocky planets in circular orbits in a habitable zone. (or even a gas giant with large moons in a habitable zone).Until we find a large number of these types of planetary systems, but we've found none, we can't even begin to calculate the odds.Then the Earth is "Special" in that it has a liquid outer core (that's cooling and will become solid one day) that produces a magnetic field to protect the atmosphere. Mars's cooled faster and its atmosphere was blown away. (Before I get it, yes, it has an atmosphere but just barely and it's much less prominent than it once was.) The Earth also has a large moon that helps to stabilize the precession in the Earth's orbit, helping to keep the climate fairly stable over long periods of time.So there's a lot that makes Earth a special case as far as planets are concerned, at least as far as we know now.Whether this "specialness" is what is required for life to form is also not known.edit: oops, we DID find a rocky planet
Rocky planet found outside Solar System | NatureBut it's probabloy got a surface temp of 500-700 F.This message has been edited by gnojek, 08-17-2005 05:56 PM

I was always under the impression that the lack of other known "earths" is mostly a selection effect thus far. I.e. the current techniques to discover extra-solar planets are simply not good enough yet to routinely find smaller, earth-like planets? Like fishing with a net that only catches the big fish.

Well, any star system that is stable enough to have planets with conditions similiar to here. Obviously there are some violent systems, where planets would go from extreme to extreme, and well life may be possible there, I would doubt it.I would consider if of the remaining star systems, if 25% had life on them, abundant.Whats IPU?

I think Lam is referring to the Invisible Pink Unicorn, a frequently used emblem - here at EvC - representing the inherent inconsistency of most religions, according to atheists. {edited to correct spelling}This message has been edited by Parasomnium, 18-Aug-2005 09:02 AM

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We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further. - Richard Dawkins

I see annafan caught this already but I wanted to second her catch. The techniques used for finding planets outside the solar system, light and wobble of stars, are at this point in time only suited for very large planets which are gas giants.It does seem they have discovered a rocky planet. My guess is it would still have to be pretty large. If its not then perhaps the observations/calculations are finally getting good enough to hit smaller planets.The best estimates of if we are "special" will come when we know for sure we can detect small rocky planets at very great distances, but discoveries of such planets do not start multiplying quickly after we have that ability.Right now it is definitely too early to tell.

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holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)

No, that's not so. It's not possible to distinguish a fully compressed signal from random noise as we are already widely using compression we may reasonably assume all earthly signals will be compressed in the near future. Since compression has immediate technological benefits over uncompressed signals we can assume any advanced civilisation will use compression.So the only radio signal we could possibly detect is one that is deliberately sent out for us to receive. How likely is that?

Hey Seven, stop using well thought out intelligent phrases like that. You're making me look dumb.As a general reply to everyone, I wonder if there is going to be a religious persecution of alien life if we ever encounter any. Say that we encounter a planet that is rich with non-carbon based lifeforms. Would there be a fight in the school system whether to call those critters alive or not?Scientist: These creatures exhibit all the characteristics of what we would call life. Given that they are silicon based. However, they harness the energy of their star for a process much like what we know as photosynthesis. They prey on each other for food. Some even use tools to build shelters for themselves.Christian preacher: But they are not god's creatures! They do not drink water. The bible specifically states that water is essential for all life. These creatures do not need water, so therefore they are not alive!Now hear this! 50 years from now, they will look back and see me as a prophet.When we find life on another planet, there will be a big debate between religion and science over if we should call them life or not. The two factions have debated over much sillier things in the past. I'm pretty sure the definition of life will be the next big one. After all, it used to be a popular belief that American Indians couldn't breed with a christian white person.

Marked!Although you still have yet to prove that intelligent life rose from rocks on this planet.

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"War is an ugly thing but not the ugliest of things; the decayed and degraded state of moral and patriotic feelings which thinks that nothing is worth war is much worse. A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." John Stuart Mill

We didn't use compression for the first 50 years or so? Those signals are still out there travelling in an ever greater envelope around the Earth, its origin. So there was a period of time before we developed compression technology where signals were sent out uncompressed.If a given period of time is the normal and expected evolution in the development of the technology, and if that is a similar path other civilizations take, then there should be similar uncompressed signals out there that we might detect before their similar advancement with compression technology.Those signals would not be directed at or intended specifically for us. Of course, that is a very small window of opportunity.

Um... isn't it your job to prove that intelligent life rose directly from rocks and dirt on this planet?Gen 2:7 the lord God formed the man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.Come to think of it, if you're so uncomfortable with the possibility that man came from a lower animal, then how is the possibility that man came from dirt and rocks any better?

Isn't it your job to prove that intelligent life rose from rocks by itself?I'm not uncomfortable with man coming from a lower animal. I think it is the most ridiculous thing to ever be accepted by science based on zero evidence.And this back and forth is why we are here. This message has been edited by Tal, 08-18-2005 02:55 PM

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"War is an ugly thing but not the ugliest of things; the decayed and degraded state of moral and patriotic feelings which thinks that nothing is worth war is much worse. A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." John Stuart Mill

Not really for several reasons.(1) Physics is my field.
(2) The only people that have ever claimed anything close to intelligent life rising from rocks are creationists.
(3) Abiogenesis != evolution.However, if you'd like, you can propose a topic for the science forum regarding the validity and invalidity of the supposed evidence for the theory of evolution. Since biology isn't exactly my strong side, I'll gladly accept a one on one debate. If you are convinced that biologists are all idiots to have accepted the theory of evolution as a valid scientific theory, one that can equate to, say, the theory of gravity and quantum theories, then I'm sure you will have a lot to say regarding the matter. That is unless you also think that physicists are all idiots, too, to have accepted stuff like relativity.Anyway, before I get kicked in the butt for getting off-topic, what do you say we go for a one on one?

There is an "Origin of Life" forum if you wish to discuss the first.There is "Human Origins" or "Biological Evolution" if you wish to discuss the second.If you dare to venture into either of the later ones and make an assertion about "zero evidence" you might find the going a bit tougher than you are used to.For some reason you have been left making unfounded assertions all over the place. Venture into the science forums and you will not be allowed such lazy behaviour.

Hi, Monk--I picked your latest message as a portal to the thread since you were the last to mention radio.In the discussions so far about the probable windows of identifiable broadcasts, I think one intriguing consideration has been neglected.In our own technological history, remote means of communication were as startling as magic, in part because we have no natural senses with that capability. Telegraph and radio were sensorially undetectable means of communication; they were private in a particular way. Our creaturely sense of caution was not invoked by a medium we could not perceive, and we were soon shouting out to the universe without much thought given to who might be listening.Other species communicate at great distances: elephants and whales, for example, using sound. Other species--sharks, moles(?)--detect prey by directly sensing their electromagnetic fields.Assume a world where remote communication is common and characteristic of the intelligent, technologically advanced species that arises there. One might learn to be extremely cautious about radiating any detectable broadcast if one's ancestors were predated by velociraptors (or cheetahs) with antennae.We cannot assume that every civilization that can broadcast, will.