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  1. Standard member finnegan
    GENS UNA SUMUS
    19 Apr '13 12:50
    So we are now pinning down habitable planets:
    http://news.msn.com/science-technology/nasa-twin-planets-perfectly-habitable-just-discovered

    But what should we expect to find? In this case, the target planets have a 2.5billion year head start on our's and this is the comment made:
    "If there's life at all on those planets, it must be very advanced" evolutionarily because the planets are so old, said Borucki.

    However, surely it is an error to assert that evolution proceeds as implied from less to more "advanced" forms of life.

    For example, without the accidental impact of an asteroid on Earth, the dinosaurs need not have become extinct when they did and the path of our evolution would have been totally different. There is no reason to assume intelligent life would have evolved, rather than, say, a shift to a quite different but not terribly thoughful form of life. Grass evolved about 50 million years ago (from memory) and now turns up all around our planet; why would not some alternative form of plant life evolve on these new planets and so we discover they are covered in a fungus or weed or something totally tedious?

    I just object to the assumption that evolution goes hand in hand with improvement or elevation or some such term.
  2. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    19 Apr '13 16:03
    Originally posted by finnegan
    So we are now pinning down habitable planets:
    http://news.msn.com/science-technology/nasa-twin-planets-perfectly-habitable-just-discovered

    But what should we expect to find? In this case, the target planets have a 2.5billion year head start on our's and this is the comment made:
    [quote]"If there's life at all on those planets, it must be very advanced" ...[text shortened]... sumption that evolution goes hand in hand with improvement or elevation or some such term.
    Stephen Jay Gould routinely argued that evolution does not in fact proceed from "less advanced" to "more advanced," and presents much evidence to support his claim.

    It's thought that a billion years from now life on Earth will become extinct because the sun will be 10% brighter by then. We must draw our own conclusions.
  3. Standard member finnegan
    GENS UNA SUMUS
    19 Apr '13 17:19
    Originally posted by Soothfast
    Stephen Jay Gould routinely argued that evolution does not in fact proceed from "less advanced" to "more advanced," and presents much evidence to support his claim.

    It's thought that a billion years from now life on Earth will become extinct because the sun will be 10% brighter by then. We must draw our own conclusions.
    The sun will change slowly enough to allow adaptation.
  4. 19 Apr '13 17:44 / 1 edit
    Originally posted by finnegan
    However, surely it is an error to assert that evolution proceeds as implied from less to more "advanced" forms of life.
    Evolution is like entropy. Evolution results in diversion. Diversion from simpler forms results in a range of forms including simple and complex. The overall result is greater complexity over time (but only as a small percentage of the overall range of life forms).
    However, I wouldn't necessarily consider high intelligence as the only possible 'advanced' life form, nor necessarily the apex of advancement. I do however believe that intelligence at basic levels (such as most animals posses) is a natural outcome of movement.
    We have only one example of intelligence at mans level, so it is hard to estimate how probable it is that it can arise, but I think that given enough time, it would be inevitable.

    But time is a key factor, and earth has gone through several extinction events, and if they were more frequent, intelligent life may never have arisen.

    Other factors to consider is the variety of environments. Evolution seems to work better when there is more variety, as there is more opportunity to try more things. If for example a planet is all ocean of the same depth, then evolution may stagnate or proceed very slowly in comparison to earth.
  5. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    19 Apr '13 17:59
    Originally posted by finnegan
    The sun will change slowly enough to allow adaptation.
    I tend to think so too. I don't entirely buy into the Gaia hypothesis, but I do think the Earth's biosphere will alter itself in whatever fashion is necessary to keep a runaway greenhouse effect from occurring such as Venus has. Life is responsible for virtually all the oxygen in the atmosphere, and life could increase the proportion of water vapor in the air such that the subsequent greater cloud cover would reflect an additional ten percent or more of the sun's radiation. That would offset the future sun's greater radiation output, and the balance could conceivably be maintained for the entirety of the sun's remaining five billion years of main-sequence existence.
  6. 19 Apr '13 20:28
    Originally posted by Soothfast
    I don't entirely buy into the Gaia hypothesis, but I do think the Earth's biosphere will alter itself in whatever fashion is necessary to keep a runaway greenhouse effect from occurring such as Venus has.
    You talk as if you do buy into the Gaia hypothesis. In reality, earths biosphere has modified the earths atmosphere and climate etc quite dramatically in the past, often to the detriment of many life forms.
    Also, we have had various major fluctuations in climate caused by other changes such as continental drift, asteroids, volcanoes etc. There was even a time when the whole earth froze over. To assume the earths climate is self stabilizing is to ignore history and to ignore the examples of venus and mars.
  7. Standard member Kepler
    Demon Duck
    19 Apr '13 22:34
    Originally posted by Soothfast
    I tend to think so too. I don't entirely buy into the Gaia hypothesis, but I do think the Earth's biosphere will alter itself in whatever fashion is necessary to keep a runaway greenhouse effect from occurring such as Venus has. Life is responsible for virtually all the oxygen in the atmosphere, and life could increase the proportion of water vapor in th ...[text shortened]... ined for the entirety of the sun's remaining five billion years of main-sequence existence.
    Water vapour is a greenhouse gas, more significant than carbon dioxide in fact, so extra water vapour plus a more luminous sun is not necessarily a good thing.
  8. Standard member Kepler
    Demon Duck
    19 Apr '13 22:36
    Originally posted by twhitehead
    You talk as if you do buy into the Gaia hypothesis. In reality, earths biosphere has modified the earths atmosphere and climate etc quite dramatically in the past, often to the detriment of many life forms.
    Also, we have had various major fluctuations in climate caused by other changes such as continental drift, asteroids, volcanoes etc. There was even a ...[text shortened]... s climate is self stabilizing is to ignore history and to ignore the examples of venus and mars.
    The snowball earth theory is not as widely accepted as it once was. One reason being that some of the evidence actually requires open water.
  9. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    19 Apr '13 22:40
    Originally posted by twhitehead
    You talk as if you do buy into the Gaia hypothesis. In reality, earths biosphere has modified the earths atmosphere and climate etc quite dramatically in the past, often to the detriment of many life forms.
    Also, we have had various major fluctuations in climate caused by other changes such as continental drift, asteroids, volcanoes etc. There was even a ...[text shortened]... s climate is self stabilizing is to ignore history and to ignore the examples of venus and mars.
    You're bringing up mostly sudden changes. Asteroids happen in seconds, volcanoes maybe hours, days, or perhaps a few years. Even continental drift is relatively fast and can present climatic challenges in just a few million years. I imagine that the "evolution" of the biosphere as a whole happens a great deal slower than the evolution of individual species. On the order of 10^7 to 10^8 years, rather than 10^6 years. But it makes some sense: changes to the biosphere that are harmful to its future existence may give rise to corrective pressures.

    Simply put, a biosphere may have, by its nature, certain purely stochastic -- and not conscious! -- "negative feedback" mechanisms against evolving in a direction that may jeopardize its continuation.
  10. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    19 Apr '13 22:41 / 2 edits
    Originally posted by Kepler
    Water vapour is a greenhouse gas, more significant than carbon dioxide in fact, so extra water vapour plus a more luminous sun is not necessarily a good thing.
    You sure about that?

    Water vapor may have greenhouse attributes, but if it forms clouds in the upper atmosphere it reflects sunlight and has a cooling effect. Of course clouds are basically bodies of condensed water vapor, and that's the difference.
  11. Standard member wolfgang59
    Infidel
    19 Apr '13 23:26
    Originally posted by Soothfast
    You sure about that?

    Water vapor may have greenhouse attributes, but if it forms clouds in the upper atmosphere it reflects sunlight and has a cooling effect. Of course clouds are basically bodies of condensed water vapor, and that's the difference.
    Yes. I was always under the impression that clouds had a zero net contribution,
    (reflecting heat radiation from above and insulating below) but according to
    wiki both water vapour and clouds are big contributors to the greenhouse effect.

    Thanks Keplar!
    That's my learning for today!

  12. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    20 Apr '13 00:59
    Originally posted by wolfgang59
    Yes. I was always under the impression that clouds had a zero net contribution,
    (reflecting heat radiation from above and insulating below) but according to
    wiki both water vapour and clouds are big contributors to the greenhouse effect.

    Thanks Keplar!
    That's my learning for today!

    Now now -- not so fast. It depends on the type of cloud.

    http://science.nasa.gov/science-news/science-at-nasa/2002/22apr_ceres/

    Thick clouds comprised of liquid water droplets -- which are the kind that I have in mind -- apparently cool the planet. Thin, high clouds comprised of ice crystals do trap heat.
  13. 20 Apr '13 07:23
    Originally posted by Kepler
    The snowball earth theory is not as widely accepted as it once was. One reason being that some of the evidence actually requires open water.
    Whether accepted as having happened or not, it remains more or less a valid possibility ie if earth gets enough ice cover, it turns into a runaway process resulting in a global freeze.
  14. 20 Apr '13 07:28
    Originally posted by Soothfast
    But it makes some sense: changes to the biosphere that are harmful to its future existence may give rise to corrective pressures.
    Yet earths atmosphere is significantly different now than it was when life first started. The high oxygen levels an low carbon dioxide levels are the result of life. The levels of both have fluctuated over the history of earth.
    Almost all systems have both corrective processes and unstable processes that can result in runaway change. To assume that corrective processes will win out is unfounded and, I think, based on wishful thinking.
  15. Standard member Soothfast
    0,1,1,2,3,5,8,13,21,
    20 Apr '13 07:32
    Originally posted by twhitehead
    Yet earths atmosphere is significantly different now than it was when life first started. The high oxygen levels an low carbon dioxide levels are the result of life. The levels of both have fluctuated over the history of earth.
    Almost all systems have both corrective processes and unstable processes that can result in runaway change. To assume that corrective processes will win out is unfounded and, I think, based on wishful thinking.
    Okay. Biological evolution is wishful thinking. Got it.