Freethinker Posted July 15, 2004 Report Share Posted July 15, 2004 Originally posted by: TormodOriginally posted by: Freethinker (that last one just for our Fearless Leader!)Finally some quality links at this site! Ya, well I had to go thru some 50 pages of Google to get to it! lol! Link to comment Share on other sites More sharing options...
TeleMad Posted July 18, 2004 Report Share Posted July 18, 2004 Tormod: I think that the odds that there is life elsewhere in the universe is very good. In fact, I think the best proof of life in the universe is that we are here on Earth. With about 200 billion galaxies, each with perhaps 100-200 billion stars, I simply can't believe that life came about only on this planet. But your logic is flawed. You are looking at only HALF of the picture: simply put, you are considering only how many "shots" there have been at life arising. You are leaving out of the calculation how improbable life arising is. For example, what if the probability of life arising is 1 in 10^120 in a single "shot"*? Then the 200 billion galaxies each with 200 billion stars doesn't even come close to being able to cover the possibilities. The proportionality of "shots" vs possibilities would be like only 1 ticket being bought in the PowerBall lottery and expecting a winner. Life arising spontaneously may be so improbable that it happened only once in the Universe. (*Based on a "quick and dirty" back-of-the-envelope calculation of the probability of hitting upon a self-replicating RNA molecule.) Link to comment Share on other sites More sharing options...
TeleMad Posted July 18, 2004 Report Share Posted July 18, 2004 Tormod: The carbon-based life "as we know it" mantra is perhaps the simplest solution in our part of the universe. But life could equally well be silicon-based. No, it couldn't. We don't even know that it could be based on silicon at all, let alone equally well. And there are reasons to doubt that silicon life is even possible. “What Is Life? An early question that needs to be confronted, indeed a question that in the last analysis requires definition, is: What is life? Most biologists would agree that self-replication, genetic continuity, is a fundamental trait of the life process. Systems that generally would be deemed nonbiological can exhibit a sort of self-replication, however (2). Examples would be the growth of a crystal lattice or a propagating clay structure. Crystals and clays propagate, unquestionably, but life they are not. There is no locus of genetic continuity, no organism. Such systems do not evolve, do not change in genetic ways to meet new challenges. Consequently, the definition of life should include the capacity for evolution as well as self-replication. Indeed, the mechanism of evolution - natural selection - is a consequence of the necessarily competing drives for self-replication that are manifest in all organisms. The definition based on those processes, then, would be that life is any self-replicating, evolving system. The processes of self-replication and evolution are not reliably detectable, even in the terrestrial setting. Consequently, in the practical search for life elsewhere we need to incorporate information on the nature of the chemistries that can provide the basis for self-replication and evolution. Considering the properties of molecules likely to be needed to replicate and evolve, it is predictable that life that we encounter anywhere in the universe will be composed of organic chemicals that follow the same general principles as our own organic-based terrestrial life. The operational definition of life then becomes: Life is a self-replicating, evolving system expected to be based on organic chemistry. Why Organic Chemistry? The basic drive of life is to make more of itself. The chemical reactions required for the faithful propagation of a free-living organism necessarily require high degrees of specificity in the interactions of the molecules that carry out the propagation. Such specificity requires information, in the form of complex molecular structure - large molecules. The molecules that serve terrestrial organisms typically are very large, proteins and RNAs with molecular weights of thousands to millions of daltons, or even larger as in the case of genetic DNA. It is predictable that life, wherever we encounter it, will be composed of macromolecules. Only two of the natural atoms, carbon and silicon, are known to serve as the backbones of molecules sufficiently large to carry biological information. Thought on the chemistry of life generally has focused on carbon as unique (3). As the structural basis for life, one of carbon's important features is that unlike silicon it can readily engage in the formation of chemical bonds with many other atoms, thereby allowing for the chemical versatility required to conduct the reactions of biological metabolism and propagation. The various organic functional groups, composed of hydrogen, oxygen, nitrogen, phosphorus, sulfur, and a host of metals, such as iron, magnesium, and zinc, provide the enormous diversity of chemical reactions necessarily catalyzed by a living organism. Silicon, in contrast, interacts with only a few other atoms, and the large silicon molecules are monotonous compared with the combinatorial universe of organic macromolecules. Life also must capture energy and transform that energy into the chemistry of replication. The electronic properties of carbon, unlike silicon, readily allow the formation of double or even triple bonds with other atoms. These chemical bonds allow th Link to comment Share on other sites More sharing options...
Tim_Lou Posted July 20, 2004 Report Share Posted July 20, 2004 telemad,the universe is symmetrical, b/c we are here,there would be probably "anti-us" and anti organisms by anti-particles. : ) and yeah, the chances are 10^120 in a single "shot", but the universe is infinite, right?so, 10^120 is way far smaller than infinity.... and, there need not to have silicon based life,carbons can be found on somewhere else in the universe, right?2 hydrogen--> helium4 helium --> carbon. and there is a great possibility that life spread throughout the universe:http://atheism.about.com/library/FAQs/evo/blevo_abio_space.htm such as bacteria, virus... they can servive in an extreme harash condition. Link to comment Share on other sites More sharing options...
TeleMad Posted July 21, 2004 Report Share Posted July 21, 2004 Tim_Lou: telemad, the universe is symmetrical, b/c we are here, there would be probably "anti-us" and anti organisms by anti-particles. : ) Our universe is dominated by matter - antimatter is rare. There are no anti-planets or anti-galaxies known and reasons to believe they don't exist. Tim_Lou: and yeah, the chances are 10^120 in a single "shot", but the universe is infinite, right? so, 10^120 is way far smaller than infinity.... Is the universe actually infinite? That's still an open question to some extent: the universe could be finite and yet still be unbounded (if it has positive curvature). Also, even if the universe is infinite only the part that could be causally connected to Earth is probably relevant. For example, suppose there is one other intelligent life form but it exists some 100 billion light years away. We will never be able to detect it, measure it, or confirm its existence in any way. Therefore, scientifically, we should reject its existence (just as we should reject the existence of the pink unicorn that lives in the White House...it just can't be seen, detected, measured, or confirmed in any way). Same goes for any number of theoretical ETI civilizations that one could suppose might exist but could never be confirmed or detected because they are outside our observable universe. Link to comment Share on other sites More sharing options...
Freethinker Posted July 21, 2004 Report Share Posted July 21, 2004 Originally posted by: TeleMadIs the universe actually infinite? That's still an open question to some extent: the universe could be finite and yet still be unbounded (if it has positive curvature). Yes, but wether the Universe is finite or not, there is no reason to think that the Universe as we know it is the only "universe" that would or could exist. The possible variation of universes IS INFINITE! There could easily be a universe in which the conditions for life are so perfect that it exists all over. Just as there is the definate probability that there is a Universe that is completely lifeless. Naturally, we are not part of that universe. The question then is NOT whether a universe exists with only one intellegent life in it, there is every probability their is. The question is is THIS that universe. And from what we see, the probablity is very good that we are NOT that Universe. Remember there are infinitely more universes that have multiple intellegent species, then those that do not. Link to comment Share on other sites More sharing options...
Uncle Martin Posted July 21, 2004 Report Share Posted July 21, 2004 Originally posted by: Freethinker Remember there are infinitely more universes that have multiple intellegent species, then those that do not.The whole multiverse concept bears too close a resemblance to a faith based belief for me to accept it. Although it is a neat idea, it can likely never be tested. Link to comment Share on other sites More sharing options...
Freethinker Posted July 21, 2004 Report Share Posted July 21, 2004 I see it as an infinitely probable possibility. If we accept that our current physical implementation of reality is finite, that there was a start to the physical universe we exist in, and there will be some ultimate end, there is an infinite period of time left for something else to happen. I think Carl Sagan said it best, that in an infinite period of time, an infinite number of things will happen an infinite number of times. Most of the best supported theories regarding our existence specify some form of multi-verse. Though often the others are considered "probabilites" but not existant. Regardless of the actual existence of other universes, the thought process of evaluating our universe based on total universe variation probablity is of value. e.g. in deciding whether our universe has the serious possibility of other intellegent life in it, it is a valuable excercise to determine what are the most probable outcomes of universes that operate with-in our physical law constraints and what percentge of those probablities would have multiple intellegent species and what percent would not. Just as QM specifies that we can not KNOW the location of an electron, just the probablities. Therefore I feel it is a valuable tool regardless of whether it can be tested right now or not. I do agree that to just accept that an infinite multi-verse is true, would be a faith based process. But to accept that it is a viable possibility and use that to help construct models of our actual existence does have some emperical value. Just as to accept the billiard ball model of the atom helps us work with "electron flow" on some levels. Link to comment Share on other sites More sharing options...
lindagarrette Posted July 23, 2004 Report Share Posted July 23, 2004 Without having any evidence to support the hypothesis, how can anyone apply any probability to existance of life in the universe besides what's on our own planet? The probability that life exists is 1. The probability that it exists elsewhere is zero, based on current knowledge. Link to comment Share on other sites More sharing options...
Freethinker Posted July 23, 2004 Report Share Posted July 23, 2004 Originally posted by: lindagarretteWithout having any evidence to support the hypothesis, how can anyone apply any probability to existance of life in the universe besides what's on our own planet? The probability that life exists is 1. The probability that it exists elsewhere is zero, based on current knowledge. 1) the probablity of life elsewhere is definately above zero. And the more we learn about other planets in our solar system, the higher the probability goes. 2) we DO have evidence to support that. We have found many indications of the elements required for life in any number of extraterrestrial sources. 3) We have also found life here on Earth that violates "laws"" we had long held as to what conditions are needed for life. e.g the tube worms and Pompeii worms around the sulphur vents at the bottom of the Oceans. A good discussion of this is available at:http://astrobiology.arc.nasa.gov/roadmap/introduction.html Link to comment Share on other sites More sharing options...
TeleMad Posted July 23, 2004 Report Share Posted July 23, 2004 FreeThnker: 1) the probablity of life elsewhere is definately above zero. What Lindagarrette said is correct...one can legitimately state that the probability that life exists elsewhere in the Universe is 0, based on current knowledge. Of all the attempts we have made at finding life elsewhere, none have been succesful. The ratio of successes to attempts made is thus 0/a, which is 0 percent, which gives us an empirical probability of 0. The other type of probability is a theoretical probability. That type can't be assigned an accurate number for this topic without having good input for all numbers involved. What the disagreement basically boils down to is a disagreement on how likely life is to arise spontaneously. After all, neither side here seems to deny the "billions of billions" of attempts that have been available in the history of the Universe. How probable is life arising? Well, the origin of life has been a "hobby" of mine for many years and my personal conclusion is that life arising spontaneously is highly improbable: it has an astronomically small probability. It's so improbable, in my opinion, that it is quite likely that even with billions of galaxies each having billions of planets and having billions of years, life still arose only once. Link to comment Share on other sites More sharing options...
TeleMad Posted July 23, 2004 Report Share Posted July 23, 2004 FreeThinker: 2) we DO have evidence to support that. We have found many indications of the elements required for life in any number of extraterrestrial sources. That's like saying we DO have evidence that computers exist elsewhere in the Universe because we know silicon and copper - elements required for computers as we know them - are present out there. Life is not elements. Where has DNA been found? Where has RNA been found? Where have proteins been found? Where has glycolysis or the citric acid cycel or photosynthesis been found? Only on Earth (or places we've contaminated). Link to comment Share on other sites More sharing options...
TeleMad Posted July 23, 2004 Report Share Posted July 23, 2004 FreeThinker: 3) We have also found life here on Earth that violates "laws"" we had long held as to what conditions are needed for life. e.g the tube worms and Pompeii worms around the sulphur vents at the bottom of the Oceans. As you allude to, those life forms didn't break any laws, they just didn't fit our long held assumptions, such as all life being directly dependent upon the sun for energy. Those life forms at deep sea hydrothermal vents are still cellular and still have DNA, RNA, and proteins, and still undergo transcription, translation, and replication of DNA, and still grow, reproduce, and metabolize: just like all the other forms of life we've known about. Link to comment Share on other sites More sharing options...
Uncle Martin Posted July 24, 2004 Report Share Posted July 24, 2004 As far as the mathematical probabilities and scientific facts go,...I agree with LG and TeleMad on this one. The intent of the thread is our intuitive thoughts, which could go with pure probability. Intuition is bound to be biased by individual hopes and desires, and who really wants to be alone in the universe? It contradicts the facts, but as I've stated before,....I think simple life is likely, intelligent life is very rare or unique at present. Or it could be that intelligent life has yet to evolve. Link to comment Share on other sites More sharing options...
Tim_Lou Posted July 25, 2004 Report Share Posted July 25, 2004 and the best "reason" y life should exist else where in the universe is the existence of us. : ) if the probabilitity is sooooooo low and life is so impossible, y do we exist? "and who really wants to be alone in the universe?" yea, and who really doesnt want to be unique in the universe?hehe... Link to comment Share on other sites More sharing options...
TeleMad Posted July 25, 2004 Report Share Posted July 25, 2004 Tim_Lou: and the best "reason" y life should exist else where in the universe is the existence of us. : ) if the probabilitity is sooooooo low and life is so impossible, y do we exist? Not impossible, but improbable....there's a big difference. Now, as far as using a single existence of something that is improbable to argue that there must be other examples of the same thing, here's a thought experiment. Thoroughly shuffle a normal deck of playing cards and then deal them out to yourself one card at a time; keep track of each card you receive, in the order you receive them in. What is the probability that that exact sequence of cards would have occurred? Less than 1 in 10^67. But it did occur. You seem to be claiming that we should assume that that same sequence has happened other times because we know it happened once. But probabilitistically speaking that is a very unreasonable argument. The better position is that yeah, it is highly improbable and it did occur, but it has probably occurred only once: the one example we know of. Link to comment Share on other sites More sharing options...
Tim_Lou Posted July 26, 2004 Report Share Posted July 26, 2004 the calculating of probability of life doesnt not take into account of those other possibile form of life,which is unknown to us.... as we know most of the mass of universe is unknown, they could be a form of life by these unknown probability.... Link to comment Share on other sites More sharing options...
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