Antropic Principle and Extraterrestrial Life

C.S. Lewis in "Mere Christianity" wrote about the possibility of life on other planets and came to the concultion that neither the presense nor absence of life on other planets, could help or harm his faith. He reasoned that if the universe were literaly teeming with life then that would mean that God meant for us all to share his creation together. If the universe were devoid of life save for us, that would be further evedence of our specail realtionship with God.From a scientific perspective I believe that their is a sort of "point of no return" beyond whitch we would have to believe in a miraculous creation of life.If it is only unlikely that life will arise we can appeal to an aspect of the anthropic principle. Even if life has a small chance of arising materialisticly intellegent creatures will only exist where life has arisin. Meaning it's no obvious miracle that we exist.However after a certain point of unlikelyness (say the difficulty of life arising even in our entire universe is miniscule) it passes a threshold and it seems more likely that there was some "miracle" that produced life.It is my personal beleif that there is an abundance of life thoughut our galaxy, but I'm interested in other takes on this problem.

I was wondering whether this would go into "faith and belief" or into
"origin of life"

I choose not to use the word "proabable" on purpose. That word implies that I have some notion of the odds involved in hypercycles giving rise to cells etc, and I don't.Perhaps I should not even have used the word "belief" (too strong), "hunch" would have been closer to the mark.In terms of inteliegent life elsewhere in our galaxy, I remeber reading an article in SciAm where they discussed the possibiltiy of a civilization that collonized other planets. Even if each new colony took, on average, 1000 years before it was able to send out the next set of pioneers the entire galaxy could be "populated" in a few milion years, not that long evolutionarly speaking.This would, of course, not be a civilization. Problems in communication and, consequently, control would limit civilizations to a solar system at max.If it is tue that intellgent life can rapidly colonize the milkyway. Our falure to detect it could mean 4 things.1) It is highly improbable that life can arise from inorgainc origins.2) Though it is probable that life will arise from inoganic origins it is improbable that such life will become intellegent. (I strongly disagree wtih this since, on average, cephalization ratios increase over time for ALL animal phyla).3) Though it is highly likely that life will arise, and that it will become intellgent, (and will wish to colonize) colonization in our galaxy has not yet begun or has begun and not yet reached us.(This one seems false. How many other clades had a good chance of becoming intellegent and how many millions of years ago did they exist? Reptiles seemed to have had a good shot. If they hadn't caught a stroke of bad luck a decendant of the dinosaura might have started posing questions about exsistance millions of years ago.)4) (This is my own personal favorite though it sounds more like a good SF novel than a sound theory).Intellegent life and its collinization of the galaxy has occored there are multiple civilizations close enough to have already received our radio and television signals.The probelm with this one is that we should have heard from them by now thanks to SETI. (Now for the crackpot sci fi part.)Perhaps radio signals serve a similar function to Bioluminessense in the aphotic zones, this could be bad news for us. I think a great SF novel could start with us receving an extraterrestrial signal that we finaly decode to mean "For gods sake SHUT UP, do you want to get eaten?"

Well there could be lots of it near us that we just haven't detected (see #4) also there could be unoccupied patches etc. I'll try to find the article.

Other factors could be.1: Actual amount of time it takes to colonize galaxy acording to their hypothisis: I read the article a long time ago maybe it was a few HUNDRED million years (Still not all that long geologicaly but you should note I could be an order of magnitude off).2: Signal strength: I remember the article also said we hadn't detected any signals for a large portion of the galaxy but then they seemed to be expecting some pretty hugely powerful signals.3: Patchy colonization: The article also assumed that they would spread out evenly in an expanding sphere.In short we have some information to help us but not enough to adress the antropic principle, for example we know that intellgent radio communicating life isn't inevitable on every planet.

Well thats the point maybe they are VERY interested in us maybe they are on their way! The (addmitedly farfetched) suggestion of #4 is that they stay quiet so they don't get invaded themselves. Let's say they are right next door to us and got our radio signals 30 years ago, for the sake of argument. Well, how long will it take them to reach us?Depending on their speed (remember there is no suggestion of faster than light travel) it could be centurys, maby even millenia, before we are horribly subjugated and devoured.And they would have to factor in how much we would advance tecnilogicaly while they are twiddling their thumbs in hypersleep (or whatever). Maybe it's better to collonize UNpopulated worlds so you don't have to deal with the hassle of entrenched civilizations.

I find your post very confusing ned, I thought you beleved in the power of evolution.Anything advanced enough to be capable of launching a planetary invasion would probably be able to harness that power through biotechnology (or if they are robotic, engineering). Do you disagree?

I think Jar makes some great points. This is why SETI is now looking for lasers right? But if advanced civilizations do use very directional communication they are going to be a lot harder to find. That is if they don't want to be found. Well we are significant enough to possibly be causing another major extiction. All we know about the laws of physics is that it allows life to exisit! We have no way of knowing how likely abiogeniesis (am I using thei word properly?) is until we start doing some surveys of our universe. This is why I'm so exited about that probe they are going to send to Europa becase we can maby start to get a feel for how common life is.

It doesn't. But if intellegent life is very common there will be many civilizations and a few of them might be "SITAPHs" (superintellegent technologicaly advanced planet hoppers). AND it won't take all that long for the SITAPHs to colonize the galaxy.Incedentaly I think we should rememeber that the whole civilization isn't moving in this theory. They are just sending out seeds.

So I think we are all in agreement that we have too little information.