Chance of life on other planets

Discussion in 'Astronomy, Exobiology, & Cosmology' started by James R, Sep 4, 2010.

  1. D H Some other guy Valued Senior Member

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    Barely most certainly applies. You have the situation exactly backwards. The percentage of the universe that has been even partially explored is essentially zero. I asked you once before where you got this incorrect notion that we have a "survey pole for life than goes back in time 15 billion years". We have barely looked anywhere beyond the Earth for signs of life.

    Scientists have barely started to look for signs of life on Mars, and even there the answer remains "we don't know". Scientists have speculated about the existence of life in our solar system outside of Earth and Mars. Europa, for existence, looks promising. These are speculations, mind you. Whether life truly does or does not exist in our solar system, exclusive of Earth and Mars: We don't know.

    How can you possibly claim we have a survey pole for life that goes back in time to 15 billion years ago when we don't even have a survey pole that goes 20 minute back in time (light travel time from Mars to Earth at conjunction)?
     
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  3. Green Destiny Banned Banned

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  5. RJBeery Natural Philosopher Valued Senior Member

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    I agree, Dinosaur. The Drake equation is horribly anthropocentric. "Planets" that sustain "life" orbiting "stars"? Any object with signaling and self-sustaining processes could qualify as Life, and this could be found anywhere, including deep space or in the interior of stars themselves. Hell, given a complex enough system, Life could BE the stars themselves!

    James R: As far the the OP goes, I would estimate 10 eggs in the boxes. One problem I have with the analogy, though, is related to DH's mention of the Principle of Indifference. Life is not an egg, and we did not search for Life on Earth arbitrarily. Life is a prerequisite to perceive itself. This is similar to winning the lottery, without understanding the odds involved, and then probing others around you in an effort to deduce what the odds of winning were.
     
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  7. squeebeast Registered Member

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    hi james..nice analogy..however,in order to test the idea of life on other planets,you must consider the factors nessesary for life..first the cosmolgical constants..ie;the gravitational constant...the strong nuclear force and so on..theese constants are so finely tuned that words are incapable of describing the almost infinintesable settings they have..they seem to be just put in at the instant of creation..secondly,most galaxies are incapable of having life bearing planets,such as elliptical and lenticular galaxies..they are too active and dangerous for a habitable planets..spiral galaxies that are smaller than the milky way dont have enough metallicity to build earth sized worlds..so that knocks out 90% of the universe right off. then,you must have a host star that is a spectral G2 dwarf star..much smaller and the circumstellar habitable zone will be too small,thus locking the planet into a gravitational syncrinization..death!! too large and the habitable zone will be too large,resulting in seaons that are too long to sustain life. a life bearing planet must also have a heavy moon just the right distance from the planet to insure ocean mixing due to tides..in addition,the moon must be at the right inclination to its host planet in order to keep the host planet from wobbling on its axis..the moon is 18 degrees from earths equator..thus insuring our tilt of 23.5 degrees..the only tilt that assures mild seasonal changes..i only mentioned a few here,but already the odds of getting all that together at just the right place and time is essentialy zero..yet here we are..so given theese factors..even having an infinitude of possible worlds,i think its safe to say it would be impossible to have a life bearing world without a supernatural kick start...steven
     
  8. Ophiolite Valued Senior Member

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    Only by individuals who failed to understand its purpose. Drake developed it primarily to provide a structure for discussions at the 1961 meeting in Greenbank on the search for intelligent extraterrestrial life. It remains a viable tool for providing such a structure and helping to define the appropriate questions to ask. It is not now - and Drake did not intend its primary role then to be - an efficient mechanism for determining the number of extraterrestrial civilisations.
     
  9. adoucette Caca Occurs Valued Senior Member

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    If there were an identical Earth to ours, with the exact same history, how close would they have to be, given our current technology, for us to have a reasonable chance to know that they exist?
     
  10. adoucette Caca Occurs Valued Senior Member

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    The Drake equation can also be used to determine how many Unicorns play after dark in parks:

    N* = the number of parks on the Earth:

    fp = fraction of parks with unicorns living near by:
    Current estimates range from 100% (where Unicorns can live they do) down to close to 0%.

    ne = number of parks ecologically able to entice Unicorns to play after dark:
    Estimates range from 100% (Playing in the park is such a survival advantage that it will certainly evolve) down to near 0%.

    fl = fraction of those parks where Unicorns actually live nearby: Said to be quite low, but there are those that insist that Unicorns are invisible when out of these parks and thus are more common than we realize.

    fc = the fraction of fi that has Unicorns that allow themselves to be seen: Hotly disputed, most scientists claim that since we have no verifiable sightings put this down to near zero. Others claim we aren't looking with our third eye.

    fL = the fraction of the park's life during which these less bashful Unicorns survive: Totally unknown.

    fi = the fraction of parks where Unicorns who will allow themselves to be seen actually play after dark: Also totally unknown.

    CALCULATE by multiplying the variable to get

    N = the number of unabashed Unicorns in the world


    Sorry, couldn't help myself.

    I agree with Ophiolite, that the Drake equation is useful for helping to define the appropriate questions to ask.

    Because it can't be used as a tool because regardless of your choice of inputs, no one could use FACTS to dispute you.

    Because currently the inputs wouldn't be based on any known facts.

    For instance consider the 3nd through 5th variables:

    Ne = number of planets per star ecologically able to sustain life:

    While the site says the lowest number is .33, there is no basis at all for this high a number (since we have found no other planets that in fact do sustain life), and it could in fact be quite a bit lower, for instance there is the Rare Earth Hypothesis, that concludes one also needs a number of somewhat improbable other attributes in a life sustaining planet. So the reality is this number could easily be between .0001 and possibly 1.

    http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

    or

    Fl = fraction of those planets where life actually evolves.

    While the site says the lowest number is .0001% , it could easily be lower. We have no idea what the likelihood of abiogenesis occurring on a given planet is, but we think that over 1 billion years passed from the time the Earth formed until the most primitive life forms arose, so at best we can assume is it takes a long while. Still a high percent of stars are over 1 billion years old, so this number could also be a many thousand times higher.

    or

    Fi = the fraction of Fl that evolves intelligent life

    The site says the lowest number here is .0001% as well, but again it could be even lower. There is no certainty that even if abiogenesis occurs, that evolution will result in intelligent life. On the Earth, we think this took something over 3.5 billion years to occur, so at best we can assume is it also takes a long long while. Given the time frame for Fl and then Fi, a lot of bad things can occur to stop this process in its tracks. But once life started on earth, it survived some pretty nasty events, and still managed to get to the present state, so if it turns out that abiogenesis is common, then the number could also be thousands of times higher.

    To put it in perspective, if all three of these turn out to be in the low end of the spectrum, then these variables alone could equate to a multiplier of .000000000000001, but if all were on the high end of the spectrum then these could be a multiplier as high as .001, or a factor of 12 greater than the low end.

    So let's just consider our Galaxy. The estimate of the number of stars in it is also quite wide:


    Thus in just these few references, the number of stars in our Galaxy is estimated to be some number between 3 Billion and 600 Billion, but there is no right answer, and it could in fact be outside of that range.


    So now we multiply the low value by the low end estimate of the number of stars in our galaxy and we get the incredibly low estimate of 0.000003 planets in the galaxy with intelligent life and multiply the high values and we get 600,000,000 planets with intelligent life.

    Any formula which gives this wide of an answer is of no predictive value and we still have two more variables to consider, whose range of answers will further widen the range of possible answers.

    The good news is that data from Kepler might help us refine one of these variables, but that's going to probably take several more years before data on somewhat earth like rocky planets in the habitable zone becomes available.


    Arthur
     
    Last edited: Sep 17, 2010
  11. IamJoseph Banned Banned

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    Disagree. One need not look elsewhere for the same factors on this planet, which are so varied that life can arguably exist in the most hostile conditions of the universe.

    What about survival of the fittest and natural selection: why are these only subject to planet earth? This says these premise are not universal ones. This aligns with the observable facts: no life elsewhere.



    Bstter, this affirms the zero possibility of life in the 10%.


    Life could have evolved on the moon despite such impediments. It takes a small crevice to allow life to ignite, not ideal conditions.


    From a mathematical and scientific POV, there is no life elsewhere. A first hand survey poll of the known universe says the unknown is more likely as the known than not so. There is no life for 15 Billion years any place we have examined and in all residue imprints observed. Science and math work on probabilities - not possibilities.
     
  12. IamJoseph Banned Banned

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    The vastness of the universe and the potential for life, when measured against a small samplying of the observed universe - actually goes against the odds of life elsewhere. Its widespread reverse conclusion is poor math.
     
  13. adoucette Caca Occurs Valued Senior Member

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    Well, considering that the nearest other cluster of stars (dwarf galaxy) to our Milky Way galaxy is about 25,000 light years away

    http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy

    and the nearest other Galaxy, Andromeda, is about 2.5 million light years away, I consider contemplation of the existance of life outside our galaxy is rather pointless as it is highly unlikely we will ever know the answer to the question.

    Indeed, answering that question about just some of the many billions of stars in our own galaxy which are reasonably close enough for us to evaluate via electronic means, still offers us no method of detecting life, just planets which have conditions which we think are reasonably favorable for the evolution of advanced life forms. Of course we could be wrong about that as well since we know that life exists at very diverse temps and pressures on this planet and indeed, may have needed harsh temps/conditions/energy levels to begin at all. Still, even if that turns out what is required for life to form, that's not the same as saying those harsh temps/pressures are conducive to the evolution of advanced life forms. Again, all things which we really can't quantify.

    Still, I think the negative results from our SETI program would indicate that it's highly unlikely that there is any intelligent life similar to our own within a rather huge radius of Earth and as far as I know, we have no way to detect life at great distances, unless it is intelligent enough to also create strong electrical/optical signals.

    Arthur
     
  14. granpa Registered Senior Member

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    Last edited: Sep 17, 2010
  15. IamJoseph Banned Banned

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    The more impacting factor: any supposed life cannot detect us. This includes far more advanced life subsequent to them being older than earth life. It says only one thing: there is no life out there, as opposed we cannot see them because of the distance.
     
  16. adoucette Caca Occurs Valued Senior Member

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    Sorry, I don't understand what you are trying to say.
     
  17. Ophiolite Valued Senior Member

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    Life in every corner of this planet is unusually benign and in no way compares with the more severe portions of the universe. Your claim that since life can exist here it can exist in hostile conditions is extremely ignorant. I applaud you for your consistency.
     
  18. TruthSeeker Fancy Virtual Reality Monkey Valued Senior Member

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    "On the basis of the data you have so far, what is your best estimate of the total number of boxes that contain an egg?"

    The answer is 10.
     
  19. granpa Registered Senior Member

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  20. IamJoseph Banned Banned

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    Then you have reduced the premise of survival of the fittest and natural selection to a very small threshold found only on this planet. Otherwise, what is incompatable to life on this planet - may be ideal for another. This also gives survival of the fittest a real, non-resticted value. There's beating life here in the bubbles of a raging volcano, 30 miles beneath the earth and in great distances inside quarks. Think it over.
     
  21. keith1 Guest

    The answer is 11. The observer of the 10 boxes opened would themselves, be standing in a box, the product of a hatched egg.
     
  22. nietzschefan Thread Killer Valued Senior Member

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    There seems to be some divergence of topic here.

    There is two different things people are discussing interchangeably.

    1. Chance of life(any kind) on other planets(or moons of planets). I care not to argue what the qualifications of this are.

    2. Chance of thriving life, able to survive multiple extinction events long enough to produce Sentient life. Like humans ...and perhaps dolphins.

    Number one is probably very massively more common than #2. Number one might be proven within our lifetime, even within our own solar system. If that is the case, you can be #2 will be considered much more common in our Galaxy or universe than previously thought.
     
  23. keith1 Guest

    Yes, either would have a demonstrative effect, that humans seem to need, to rub two brain cells together with the knowledge that we have company...that we have competition. The fire on the seat of the pants not normally instilled by the already obvious conclusion:

    If we don't start moving off this ball with a sense of collaborative urgency...
     

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