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Thread: Extraterrestrial life!

  1. #1 Extraterrestrial life! 
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    I did some research and i have thought of this in our solar system there are 9 planets of which (as we know so far) 1 has life i have searched and there are 10000000000000000000000 stars in the universe. With a conservative estimate of three planets per star (some could have many more, some would have none at all) this puts the estimated number of planets into millions of billions.
    Then thinking mathematical the chances are pretty good that we have life in many places in the univers


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    In our solar system 8 planets and at least 5 dwarf planets. Add to that the gas giant satellites that might hold liquid water or methane (if you really want to stretch things).

    The thing is knowing only one place with known life isn't sufficient to draw any kind of conclusion about the chances other places--regardless of the immensity of the universe.


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  4. #3 Re: Extraterrestrial life! 
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    Quote Originally Posted by razvanone
    Then thinking mathematical the chances are pretty good that we have life in many places in the univers
    prove it

    You may be correct, but NOBODY knows what is required for abiogenesis and there is zero basis for any sort of mathematical analysis of the likelihood of extraterrestrial life -- and I know about the Drake equation.
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  5. #4  
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    You can't make meaningful predictions from a sample size of one.
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  6. #5  
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    Quote Originally Posted by Ophiolite
    You can't make meaningful predictions from a sample size of one.
    I predict that intelligent life may eventually emerge on Earth -- or not.
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  7. #6  
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    There is no reason to belive that our planet is unique.
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  8. #7  
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    Quote Originally Posted by Twit of wit
    There is no reason to belive that our planet is unique.
    And no evidence that it is not.

    Nobody knows.
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  9. #8  
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    Quote Originally Posted by DrRocket
    Nobody knows.
    Perhaps the greys do.
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  10. #9  
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Twit of wit
    There is no reason to belive that our planet is unique.
    And no evidence that it is not.
    Unless you can find some good evidence there is no reason to believe it is.
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  11. #10  
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    Quote Originally Posted by Twit of wit
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Twit of wit
    There is no reason to belive that our planet is unique.
    And no evidence that it is not.
    Unless you can find some good evidence there is no reason to believe it is.
    There is no reason to believe either way. That is the point.

    You can have any opinion that you wish, but in this case there is no evidence to support any opinion.
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  12. #11  
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    I have had this same discussion with Twit of Wit on another thread. He seems to think that the incidence of life on a single planet, coupled with the probable presence of billions of planets almost assures us that many other planets are inhabited. As you have correctly pointed out, until we know the details of abiogenesis we cannot meaningfully predict the probability of life arising in other locales.

    One may suspect, as I do, that life is common. There is plenty of data pointing suggestively in that direction, but it is, as yet, inadequate to make pronouncements of the kind made by Twit.

    Twit, this is analagous to saying that because water boils at 100 degrees Celsius under atmpospheric pressure, that all liquids will boil at this level.
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    Quote Originally Posted by Ophiolite
    I have had this same discussion with Twit of Wit on another thread. He seems to think that the incidence of life on a single planet, coupled with the probable presence of billions of planets almost assures us that many other planets are inhabited.
    That is correct. I believe it's extremely unlikely we are alone.


    Quote Originally Posted by Ophiolite
    Twit, this is analagous to saying that because water boils at 100 degrees Celsius under atmpospheric pressure, that all liquids will boil at this level.
    Nonsense.

    Claiming that we are alone is analogous to claiming that Sun is the only star with sunspots. It certainly may be true but it's unreasonable to claim that both options are equally likely.
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    For those who suspect life elsewhere, here’s your ultimate wish, one with even infinite copies of you, perhaps:


    The Implications of Infinity and Eternity

    It is very likely that there are other earths out there exactly the same as ours. As we will see, the universe retains its own history and future.

    The All, meaning Totality, as we know, cannot be bounded (or it wouldn’t be the All), and so its extent must be infinite. Nor can it have a beginning, for then, again, it wouldn’t be the All, and so it must be eternal.

    In an infinite eternal place, which I will call the universe or the cosmos, every possible combination of matter and energy (unstructured matter) exists, not only right now, even many times over (due to infinity), but ever will and did, even many more times over (due to eternity).

    Since the earth (and everything known) is a part of ‘possible’, since it is here, there’s no problem with that use of the word ‘possible’.

    It’s only those things that we don’t know are possible that we can’t say for sure. We’ll have to wait for better computers to figure it out, a daunting task since even a state of one change of one atom requires a precursor form and a series of prior events cascading backwards through infinite time and across infinite space.

    However, there is still every possible combination of matter and energy; it’s just the resolution that remains unknown. Think of morphing objects together; the resolution is like how many intermediate stages there are (possibly infinite, but who knows).

    I am calling this notion ‘supercontinuity’. It says that any object known to us, whether a galaxy, planet, person, or whatever has a prodigious number number of very similar examples in space somewhere, varying along every possible parameter.

    This supercontinuity must be true by virtue of the universe’s permutational variability. The only question is what is its resolution: how closely can these (separated) instances of any given type of object resemble each other?

    For example, even on earth, between human races, the percentage of DNA separation is less than .1 percent (2% between chimps and humans). There is even a web site where one can look up their so-called ‘doubles’ on earth. Identical twins have identical DNA, but differing experiences (so we are not yet at the stage of identicality). To be exactly the same, they would have to have the same molecules and quantum states.

    But, heck, there is all of space and all of time; thus, it is very likely, even certain, that at least some intermediate states of a certain resolution exist somewhere at this very moment, and always did and will at any given time.

    If there is not exactly another earth, surely there could be one whose only minor difference was one unnoticeable at the atomic level.

    So it is that every loved one we have ever lost is alive and well somewhere (as an exact duplicate). Of course, they may be separated from us by a humongous distance, but are indisputably alive right now; this instant, as they ever were and will be.

    Such it is, in this way, that moments are never lost in the infinite eternal universe, for every touchdown pass and first footstep on the moon is still ever happening somewhere. Somewhere, too, dinosaurs roam distant lands just like those of earth.

    So, the universe contains its own indelible history and future. All moments of every object’s history exist permanently in space, separated by near-infinite distances (if not infinite).

    Consider this supercontinuity to be your secular ‘afterlives’, some of which are identical and some for which the narrative may differ slightly. Either way will do, for any narrative will do, but if it is the same, you wouldn’t remember it.
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  15. #14  
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    What's the chance of abiogenesis happening?
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  16. #15  
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    Quote Originally Posted by Twit of wit
    .

    Claiming that we are alone is analogous to claiming that Sun is the only star with sunspots. It certainly may be true but it's unreasonable to claim that both options are equally likely.
    Completely wrong.

    We understand the mechanism behind sunspots.

    Nobody understands the mechanism of abiogenesis.

    You cannot apply the theory of probability to make sensible statements about likelihood unless you have a probability space. You don't get that on the basis of a sample size of one with complete ignorance of the underlying mechanisms.

    What is unreasonable is making strong assertions when one possesses no facts.

    If we are alone in the universe it is indeed an awful waste of space, but nobody knows if we are alone or not. No conclusion is reasonable when you don't know what you are talking about.
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    waste of space…


    To the End(s) of the Universe

    I took a road trip through the universe recently, smoking some pot and playing the radio loud.

    Holy-moly, there’s nothing holy out there. In fact, it’s a very uncongenial place for life. I’d much rather be in Australia

    96% of it was useless dark energy and dark matter. The rest was mostly rocks gases and dust. Dangerous radiation zapped all over the place. And it was fricken freezing!

    Oh, what I would have given to be in Canada.

    Whatever designed the universe certainly didn’t have life in mind. It even took evolution billions of years to fine-tune us to the earth.

    Then we nearly got wiped out by huge disasters right and left, even once shrinking back down to a population of around 2000.

    I saw the graveyards of stars and some stellar nurseries, too. All kinds of energy swirled about—when it wasn’t exploding and wreaking havoc.

    I stopped to eat at the Restaurant at the End of the Universe, on a moon, but it had no atmosphere, plus all the food had been microwaved, by the CMBR.

    What a wasteland of a wilderness of wilds of a whole bunch of crap that nearly goes on forever in every direction.

    This was as much of a place unsuited for life that there ever could be.

    I’m back, thank my lucky stars, noting that, 14 billion years after the initial chaos, here we are, having beaten the odds.

    Well, someone had to! We won the universal lottery jackpot.

    Oh cripes, here comes a humongous asteroid! Darn, all that luck for nothing. Double ‘00’ has come up.

    It was only a matter of time.
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  18. #17  
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    Why is the universe so large and endless?

    It is because the Planck size and that within it is so small and bottomless.
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    I have experienced an actual UFO once, though I shan't speak of it unless you are genuinely interested
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  20. #19  
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    Quote Originally Posted by DrRocket

    You cannot apply the theory of probability to make sensible statements about likelihood unless you have a probability space.
    I'm not doing that. Are you here for discussion or trolling?
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  21. #20  
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    Quote Originally Posted by Twit of wit
    Quote Originally Posted by DrRocket

    You cannot apply the theory of probability to make sensible statements about likelihood unless you have a probability space.
    I'm not doing that. Are you here for discussion or trolling?
    You are doing precisely that, but apparently don't recognize that fact.

    Trolling ? Hardly.
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  22. #21  
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    Quote Originally Posted by Lynx_Fox
    What's the chance of abiogenesis happening?
    I believe you are addressing this to Twit and that you already know the answer. Since he has not answered, and for the benefit of other readers, the simple answer is we do not know. We have made estimates, but they are little more than intelligent guesses.
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  23. #22  
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Twit of wit
    Quote Originally Posted by DrRocket

    You cannot apply the theory of probability to make sensible statements about likelihood unless you have a probability space.
    I'm not doing that. Are you here for discussion or trolling?
    You are doing precisely that, but apparently don't recognize that fact.

    Trolling ? Hardly.
    No, I'm not doing that.
    For a realistic probability of us being alone the probability of abiogenesis would have to be extremely low, something like one to septilion per billion of years per planet. It's very unlikely it's so low. It's even hard to came up with so improbable conditions that could be plausibly required for abiogenesis. Even if it requires some very precise ratios of substances or precise temperature, it still does not mean that the planet itself has to have precise properties, as both temperature and ratios of substances on planets vary from place to place.
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  24. #23  
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    Quote Originally Posted by Twit of wit
    No, I'm not doing that.
    For a realistic probability of us being alone the probability of abiogenesis would have to be extremely low, something like one to septilion per billion of years per planet. It's very unlikely it's so low. It's even hard to came up with so improbable conditions that could be plausibly required for abiogenesis. Even if it requires some very precise ratios of substances or precise temperature, it still does not mean that the planet itself has to have precise properties, as both temperature and ratios of substances on planets vary from place to place.
    You just did it again.

    You don't know what a probability space is, do you ?
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  25. #24  
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    did what??
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  26. #25  
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    Quote Originally Posted by Twit of wit
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Twit of wit
    Quote Originally Posted by DrRocket

    You cannot apply the theory of probability to make sensible statements about likelihood unless you have a probability space.
    I'm not doing that. Are you here for discussion or trolling?
    You are doing precisely that, but apparently don't recognize that fact.

    Trolling ? Hardly.
    No, I'm not doing that.
    For a realistic probability of us being alone the probability of abiogenesis would have to be extremely low, something like one to septilion per billion of years per planet. It's very unlikely it's so low. It's even hard to came up with so improbable conditions that could be plausibly required for abiogenesis. Even if it requires some very precise ratios of substances or precise temperature, it still does not mean that the planet itself has to have precise properties, as both temperature and ratios of substances on planets vary from place to place.
    Quote Originally Posted by DrRocket
    You just did it again. You don't know what a probability space is, do you ?
    Quote Originally Posted by Twit of wit
    did what??
    I think you just proved that you don't know what a probability space is. It is necessary to have one before you start to talk meaningfully about probability. You don't have one.

    Google is your friend.
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  27. #26  
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  28. #27  
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    Quote Originally Posted by Twit of wit
    For a realistic probability of us being alone the probability of abiogenesis would have to be extremely low, something like one to septilion per billion of years per planet. It's very unlikely it's so low.
    We don't have anything even close to the working model for how abiogenisis might have happened and nothing to assess its likelihood.
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    Clearly, we don't know anything about how common or uncommon life is in the wider universe. It is entirely possible that we may never even know how life started on our own planet.

    We can, however, look a geological conditions, astronomical setting etc, etc in an attempt to shed light upon the question. No definitive answers obviously, but it's the best that can be done.

    I'm not willing to reject the Copernican principle or the mediocrity principle just yet.
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  30. #29  
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    The Seed of Life?

    Mikey was a unicellular microorganism, a microbe, one of the bacteria that were called ‘extremophiles’, for they were capable of living in extreme environmental conditions of temperature, ph, salinity, pressure, dryness, radiation, and even with no sunlight or oxygen. They even loved chomping on plutonium, the deadliest substance ever known. Mikey’s ancestry went back more than 4 billion years, he being among the sturdiest creatures on earth, those that had also become its master, for humans couldn’t live for but a few minutes without bacteria.

    Mikey thought that he might go to Enceladus for a balmy vacation where life was easy, always with a pool and party not too far away. Enceladus is a small satellite of Saturn and is a geologically active moon world with some wondrous scenery of spouting volcanic plumes, even having a bath of water within and below.

    Just about then, for sometimes wishes do come true, a huge meteor impact struck the earth and thrust some material into space, including Mikey and friends, who then resided rather dormant in a rock that protected them by acting as a shield against solar radiation and cosmic rays, not that this would have bothered them a whole lot.

    Eons later Mikey and friends and their rock of a spaceship landed on Enceladus. Mikey stepped out of the rock and onto a tiger-striped surface where the temperature was about -359 degrees f. A tiny shiver almost began to undulate through him, but, he shrugged it off. He was hungry, though, not having eaten for millions of years, except for a few bites of iron—and so he was really only running quickly at about half-speed. His friends followed excitedly, covering over 100 kilometers in a few minutes. They paused every so often to gobble up some dust.

    They were taken aback for a millisecond when they spotted a fast food restaurant with a sign that said ‘Billions and billions of bacteria served here’.

    “Hey, there is native life here, just as we’d hoped” said Mikey.

    “What a tropical paradise! Hey, there are some hot springs. Let’s take a dip with the sexy native girls and then kick back and relax.”

    They frolicked and swam all around for a few thousand years… until a very large eruption sent them all far into space. After a billion years or so, they landed on the 4th planet from a sun in a solar system far away, seeding it with life that became human-like within a few more billion years, although their were some differences in anatomy.

    Mikey,

    See my picture just below this line:
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  31. #30  
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    There are, in fact, two questions here.

    1. Is there extraterrestrial life?
    2. Is there extraterrestrial life that has evolved intelligence and developed a technological civilisation?

    We can also ask these two questions separately about our Milky Way galaxy, and about the universe as a whole.

    As has already been stated clearly, we cannot answer those questions due to lack of data, but we can make best guesses. My best guesses are :
    1. Yes. Simple life like bacteria arose on Earth very quickly. This implies that it is not that unusual. Thus, I guess that such simple life forms are probably found elsewhere in our galaxy.
    2. I do not know for our galaxy, but if it exists, it is probably quite rare. The reason I say this is partly due to the Fermi Paradox, and partly due to the fact that SETI still has found no signs.

    In the universe as a whole, it seems very likely that the answer to questions 1 and 2 are "yes", since the numbers become quite overwhelming. However, it is almost zero probability that humans will ever experience any communication with life outside the Milky Way. This makes the question meaningless.
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  32. #31  
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    We can only 'say; that eternity is long enough (and infinity wide enough) for energy/mass to go through all of its courses and permutations, most likely producing life, even the same life many times over.
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    The chances of there being another intelligent civilization elsewhere in our galaxy, at this given time is probably quite slim. we've only occupied a very small time period in the age of the galaxy, and it took us a couple of billion years.

    if there was another civilization then it couldve came and gone, there could have been many civilizations that have been wiped out through the 10billion years our galaxy has been here.

    but then again, take the fermi paradox. say a civilization arose only 4 billion years into the creation of our galaxy, then realistically, if they dont kill themselves or get wiped out then they should have colonized our entire galaxy. at the exponential rate of colonization, and only travelling at sub-light speeds, in 6 billion years a civilization could've colonized the galaxy 1000 times over.

    so in fact intelligent life must be rare, as we see no sign of colonization or alien artifacts. it could be down to the fact they are so advanced that we dont recognise them as an intelligence. or perhaps they just dont ever figure out interstellar travel, and that basically there is no way round physics that will allow us to traverse between stars.

    either way, the discovery of intelligent extra-solar intelligence would completely change they way mankind thinks. i believe it would completely galvanize humanity into figuring out a method of propulsion to get us between the stars
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    There are two unforgiving time constraints for the evolution and long term survival of life in the universe. It must advance from bacteria to full scale space transport before its sun fails or falls into the core of the galaxy, whatever comes first. Earth has already had a total run of about 4.5 billion years since our sun’s ignition. If Sol had started burning any closer than about 25 thousand light years from the Milky Way’s core, our civilization simply would not exist. All this we could have expected, however, for we are here.
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  35. #34  
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    Quote Originally Posted by uncleslam
    so in fact intelligent life must be rare, as we see no sign of colonization or alien artifacts.
    How could we see that?
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    The universe is so large that we may never encounter any aliens.

    It could also be that, given that we still have billions of years to try to find ways to get to very faraway place, that we never will, as discussed in other threads, even if we could get near 'c'.


    LOCATION, LOCATION, LOCATION

    Given that there is life on Earth, our solar system had to be in the outer-more portion of the galaxy, for, if not, we could have never been; and, in fact, it is on a spiral arm. Reality’s building blocks are quite ancient, but have been reshuffled by galactic cores. All galaxies are vortexes similar to ours, very little material within appearing older than the galactic transit time. This is why the entire universe appears to have a finite age, and why our local neighborhood appears to be about 10 billion years old. Even globular clusters seem older than the galaxy they orbit, for their trajectories lie outside the galactic vortex, and so they are not pulled into the recycling engine with the same regularity as its disk material.

    It took about 10 billion years for our solar system to reach its current distance from the galactic rim. How long until it falls into the core? The time it takes to fall through the luminous portion of our galaxy’s disk is about 16 billion years, which is called the galactic transit time. Any star born on the Milky Way’s rim with a mass smaller than that of our sun will still be burning when it falls into our galaxy’s core. Indeed, our own sun has enough fuel to burn for another 4-5 billion years. At its current rate of descent, our solar system will be in the Milky Way’s core region in less than 4 billion years, to be consumed by the voracious beast of the galaxy’s black hole, perhaps, while it is still burning, so, mark your calendars.

    The Infernal Regions: Hellholes hurl thousand light-year jets of fear, in Centaurus, cross’d the galactic sphere, supermassive darkling beasts devour all… Abandon hope, all ye who enter here.
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    We simply don't know. There could be warmer places with life which made the jump from first spark to intelligence in a few hundred million years. There could be colder and slower life, other forms of chemistry altogether.

    It hard to speculate even about our own form of life, much less to know what's even possible with a sample size of ONE.
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    for twit. we have extensively surveyed the local universe for narrow-band radio sources. yes, ET might use diffferent sources of communication. but we have not seen any example (recently discovered extra-solar planets) of life in the universe. i would love to believe there is another intelligent civilization out there, but the chances are, in this time-frame that there are very few, ie. 1 civilization
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    Quote Originally Posted by Twit of wit
    Quote Originally Posted by uncleslam
    so in fact intelligent life must be rare, as we see no sign of colonization or alien artifacts.
    How could we see that?
    well we could at least see a red edge of plant life. but nothing. it takes a hell of a long time for intelligent life to evolve (in the case of humans).
    we may not be able to accurately survey the terrain of habitable exo-planets, but u can be sure if we thought one was definitely habitable then we would try our best to commuinicate
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  40. #39  
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    On Earth, life is 3 to 4 billion years old. Until about 500 million years ago, it consisted of small, mostly single celled organisms. From 500 million years ago there has been rapid evolution into much larger, more complex, and multicelled life forms. The reason for this appears to be oxygen.

    Up until 500 million years ago, the amount of oxygen in the atmosphere was minimal. Mostly oxygen released by simple plants and by cyanobacteria appears to have been consumed by iron compounds, which reacted with oxygen to form iron oxides. Only when all available iron had been consumed could oxygen levels in the atmosphere rise to the point where complex life could evolve.

    Perhaps something like this is also prevalent in other stellar systems, preventing complex life from evolving? Life may be common, but mostly characteristic of life similar to that which existed on Earth before 500 million BCE? Perhaps intelligent life will remain rare due to the rarity of fully oxygen atmospheres?
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  41. #40  
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    Quote Originally Posted by uncleslam
    for twit. we have extensively surveyed the local universe for narrow-band radio sources. yes, ET might use diffferent sources of communication. but we have not seen any example (recently discovered extra-solar planets) of life in the universe. i would love to believe there is another intelligent civilization out there, but the chances are, in this time-frame that there are very few, ie. 1 civilization
    I guess you mean this:
    http://www.upi.com/Science_News/2011...8311295923403/
    http://www.telegraph.co.uk/science/s...0-planets.html
    It's bullshit. It's not surprising that the planets discovered by Kepler so far are too hot. Earth like planets will not be detected sooner than in late 2012.
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  42. #41  
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    Quote Originally Posted by Twit of wit
    Quote Originally Posted by uncleslam
    for twit. we have extensively surveyed the local universe for narrow-band radio sources. yes, ET might use diffferent sources of communication. but we have not seen any example (recently discovered extra-solar planets) of life in the universe. i would love to believe there is another intelligent civilization out there, but the chances are, in this time-frame that there are very few, ie. 1 civilization
    I guess you mean this:
    http://www.upi.com/Science_News/2011...8311295923403/
    http://www.telegraph.co.uk/science/s...0-planets.html
    It's bullshit. It's not surprising that the planets discovered by Kepler so far are too hot. Earth like planets will not be detected sooner than in late 2012.
    yes there is without question bound to be other earths out there, but it'll be extremely hard to determine whether theres life on any of the planets, with our current methods of exoplanet detection. and again, if there is intelligent life then i believe the timeframe of the galaxy in which life couldve started is more or less 6billion years, maybe more. the chances of them having evolved in the same time frame to us is extremely slim
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    uncleslam

    The time frame in which they evolved may not matter too much.

    A few years back I calculated how long it would take for an advanced civilisation to totally colonise the galaxy to overpopulation. Depending on assumptions, the figure was 700,000 years to 10 million.

    Now, it only takes one alien intelligence, and the whole galaxy is fully inhabited. If alien intelligences are common, then at least one will be an oxygen breather, expansionist, aggressive, and keen to get out among the stars. If that species reached Earth any time in the last half billion years, they would find life and an oxygen atmosphere. Most salubrious for our oxygen breathing intelligence.

    So how come we have never found the slightest indication of alien life on Earth, any time back to 500 million years ago? Not even an alien coke bottle. If jellyfish imprints can fossilise, so would alien artifacts.
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    I don't get it sKeptic. An advanced society could also know how to control its population (some we've got to figure out soon) so it wouldn't have to sprint across the galaxy.

    In a few decades our own radio signal will fade. Make the nearly baseless assumption that other species follow a similar path opportunities to detect general radio transmissions might be very short.
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  45. #44  
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    An advanced species could definitely control its population. However, that does not mean it lacks a drive for expansion. If we look at Earth life, pretty much every species has some mechanism to disperse its offspring geographically. Advanced life forms have behavioural mechanisms also. So mobile species tend to move from their 'home base' and find mates, and reproduce somewhere else. I do not think it is illogical to suggest that the instinct for dispersal should be common on other worlds.

    Normal evolution, as seen here on Earth, inevitably creates dispersal, and a reproductive rate that will drastically increase numbers if conditions permit.

    The thing is that, if intelligent life is common, there will be many varieties, some of which will have a strong dispersal instinct. In humans, we call it the spirit of adventure, and it leads to large numbers of people moving to live in other countries. We already know that, if a spacecraft was built to travel to another star, there would be no shortage of volunteers to go and make a new colony. Why should alien intelligences be different?

    The degree to which birth rate exceeds death rate need only be very small to achieve overpopulation of the galaxy in 700,000 to 10 million years. Humanity tripled its population in a lot less than 100 years. Only a fraction of this growth rate is required to achieve what I suggest.

    As for 'sprinting across the galaxy' - any species that does this will send only a tiny fraction of its population to each new planet or star system. Most will stay at home, and control their reproduction. However, normal population growth is more than ample for each such colony to grow to the point of overpopulation.

    If the galaxy has fewer than, say 20, alien intelligences spread over 500 million years, I could accept that they all might be 'stay at home' types. But if alien intelligence is common, then we can expect at least one, and probably hundreds of aggressive, expansionist species.
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    It's ok to speculate I suppose but I rejects an assumed motives or capabilities just based on our tiny bit of experience--the "will send" types of declarations. There's some factual mistakes as well, for example the statement that "pretty much every species has some mechanism to disperse its offspring geographically." Many plants and animals, probably most of them in actuality, are extremely confined to a particularly narrow set of conditions and thus can't move geographically unless the entire ecosystem moves with it.

    The most useful part of the guessing game is as least coming up with some ideas so we might look elsewhere. We now look for signs of radio signals, oxygen and water, perhaps methane. What else in the future: perhaps various mineral oxides? Colors that might indicate reflection from the several types of photosynthesis based on the sun output etc. About the best we can say is we've barely scratched the surface, not even ruling out life in our solar system quite yet--though we can probably rule out another technology using life form.
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  47. #46  
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    From Lynx

    "Many plants and animals, probably most of them in actuality, are extremely confined to a particularly narrow set of conditions and thus can't move geographically unless the entire ecosystem moves with it."

    Not correct. The vast majority of species have some dispersal mechanism. I admit that it is not always terribly effective. However, given appropriate environmental conditions, most species will disperse widely. Sometimes that dispersal is limited by the fact that the required environmental conditions are few and far between. Sometimes an organism lives where dispersal is impossible, such as on an island, but the mechanism still exists, even if it is limited to spreading the organism across one small island.
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  48. #47  
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    Quote Originally Posted by skeptic
    From Lynx

    "Many plants and animals, probably most of them in actuality, are extremely confined to a particularly narrow set of conditions and thus can't move geographically unless the entire ecosystem moves with it."

    Not correct. The vast majority of species have some dispersal mechanism. I admit that it is not always terribly effective.
    Or just horrible. Plants that drop seeds no further than their rain shadow between their boughs, fish who'll only spawn in the exact spot they hatched, species completely dependent on one food source etc. By numbers most species are confined to very small geographic space because they're particularly adapted to live there and either have lack of dispersal mechanism or can't compete in other places. Dispersal is only one strategy for species survival and seems the clear minority. There's a lot more species like the Rio Grande Silvery Minnow(endangered) than the Northern Pike (most widely dispersed fresh water fish).

    Even our wanderlust might not be as great as it could be. Our ideal to make a trip to mars 99.9% (or something like that) safe for example is what's making it prohibitively expensive. If we used 90% safe as a standard we'd probably already have crews there now.

    We have no idea what will motivate intelligent aliens. None at all. There could be a well developed species under Europa with no more interest in looking past the icy cold surface than my cat does of going to the moon. We just don't know.
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    You are correct in stating that we cannot know for sure what will motivate aliens. However, any organic species will have evolved from simpler life forms. Some consequences of evolution will be universal, such as the need to produce more offspring than just one for each parent. I believe that a mechanism for dispersal will be one of those outcomes. In an intelligent species, the dispersal mechanism is likely to be, at least in part, behavioural - meaning some instinct leading to geographic spreading.

    Now, I accept that in many intelligences, this behaviour may not be strong. For this reason, many of the potential alien intelligences out there may never leave their home planet. But, if the number of intelligences in our galaxy is high, then a good percentage of them will have some kind of instinct for getting away from home range, which will result in expansionist space travel.

    The fact is that no sign of any alien visit or colony on Earth has ever been found. Any equivalent human colony would have left vast amounts of garbage to be fossilised, and leave a record. You might argue that the aliens would clean up better than that, but I see a difficulty. We have 500 million year old fossil jellyfish imprints to study. Absolutely anything might fossilise, including such apparently unimportant things as footprints. How hard would it be to remove each and every trace of alien visits?

    I conclude that the greatest probability is that no aliens visited Earth any time in the past 500 million years. This suggests very few alien intelligences in our galaxy over that time.
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  50. #49  
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    Quote Originally Posted by skeptic
    The fact is that no sign of any alien visit or colony on Earth has ever been found.
    Unclear how it related to the rest of the post, but I entirely agree with you that there's not one shred of evidence than another intelligence has ever visited earth.
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  51. #50 Black holes 
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    Trying to explain about the science within black holes...
    http://okeusay.blogspot.com/
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  52. #51 Re: Black holes 
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    Quote Originally Posted by djenne
    Trying to explain about the science within black holes...
    http://okeusay.blogspot.com/
    Americans talk about the climate change... It's absurd. It's true there is a sort of a change. But it must be said, the only change there is right now is that the north side of the planet is turning towards the sun. So what is really happening is that the north side is warming up and the south side of the planet is getting colder. You can check it out, because the ice on the south side is increasing...
    This is probably the most ridiculous climate change denial I have ever read.
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  53. #52  
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    Not at all. Happens every year. Totally predictable!
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