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How Persistent Is Life?

  1. Mar 12, 2005 #1
    I think that once life starts, it will be very difficult to stop and I have been reading more and more about scientists claim life to be common in the universe, or atleast not as rare as they once thought it was.
     
  2. jcsd
  3. Mar 13, 2005 #2
    Life is a wide world; can u define it?
     
  4. Mar 13, 2005 #3

    SpaceTiger

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    These scientists are only guessing. Until we either find other life or fully understand the process of its formation, there's no reason to trust such claims.
     
  5. Mar 13, 2005 #4
    That is true but I also have no reason to believe why it could be rare, key ingredients for life has been found in abundance in deep space
     
  6. Mar 13, 2005 #5
    There are living things that live normally in such a wide array of environments here on earth that I am almost postivie that there is life somewhere else. There are living things in the hottest of geysers. There are living things in toxic waste just fine. Some living things die when exposed to oxygen.
     
  7. Mar 13, 2005 #6

    Pengwuino

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    It must be frusterating being a scientist. "yes there has to be life all out there in the universe! but damn it, we cant get out of htis freaken solar system!!! What are you rocket scientists doing with all the money that is given to you"
     
  8. Mar 13, 2005 #7

    SpaceTiger

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    That assumes that the initial formation of life is a common event, something you can't necessarily infer from your observations. All you can infer is that, once formed, life can survive in a lot of environments. We can be certain that there are planets out there that can support life.

    I tend also to think there's life elsewhere, but I have to admit that I'm only guessing. We really need to have a better idea of how life initially formed.
     
  9. Mar 14, 2005 #8

    Chronos

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    ST is, of course, correct. By my thinking, this is a case for the principle of mediocrity - whatever happens here will happen in most other places with the same initial conditions. Decades ago, this reasoning predicted other [at least sun-like] stars probably have planets. We now know that for a fact - and in fact, it appears planets are the rule, not the exception. However, until an extra terrestrial life form is actually found [and Mars is still an excellent candidate], it is merely speculation. Realistically though, would any scientist bet the house this is the only life bearing planet in the galaxy?
     
  10. Mar 15, 2005 #9

    Garth

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    We don't know how life started, but we do know that on an astrophysical time scale it happened quickly.

    The earliest signs of life date from just a few hundred million years after the Earth became stable enough (against cosmic impacts) to support life. Therefore it might be that life has started elsewhere relatively quickly too. However the earliest forms of life, the archaebacteria (3.5 Gyr. ago), and other later bacteria, were 'rulers of the Earth' until eukaryotic cells evolved about 1.3 Gyr. ago. Thus nucleated cells, which then evolved into mutlicellular organisms, have only existed for about a third of the time life has been on Earth.

    Perhaps there are many planets inhabited by bacteria and nothing else?

    Garth
     
  11. Mar 15, 2005 #10
    There are signs that microbial life may be common.
     
  12. Mar 15, 2005 #11

    SpaceTiger

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    No there aren't, but I think few scientists would bet against the existence of extraterrestrial microbial life.
     
  13. Mar 15, 2005 #12
  14. Mar 15, 2005 #13

    SpaceTiger

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    Can you be more specific about which part of that you think is evidence for extra-terrestrial life?
     
  15. Mar 15, 2005 #14
    Here

    "In my view, life in the form of microbes or their equivalents is very common in the universe" - Frank Drake, Professor of Astronomy and Astrophysics at the University of California at Santa Cruz.

    "There is no solid evidence of life elsewhere, but several factors suggest it is common. Organic material is widespread in the interstellar medium and in our own solar system. We have found planetary systems around other sun-like stars. Also, we know that microbial ecosystems can survive in a variety of environments with liquid water and a suitable chemical energy source or sunlight. " - Chris McKay, planetary scientist with the Space Science Division of NASA.

    "I presume that we are in agreement that microbial life, at least, may be common in our stellar neighborhood and even may be present on other planets" - Michael Meyer, the Senior Scientist for astrobiology at NASA Headquarters.

    "I think it is a mistake to look at the many specific peculiarities of Earth's biosphere, and how unlikely such a combination of characteristics seems, and to then conclude that complex life is rare. This argument can only be used to justify the conclusion that planets exactly like Earth, with life exactly like Earth-life, are rare. - David Grinspoon, Principal Scientist in the Department of Space Studies.

    These arent just normals folk talking.
     
  16. Mar 15, 2005 #15

    SpaceTiger

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    That's all that matters at this point. The rest is just speculation. From a scientific point of view, informed speculation doesn't constitute evidence or a sign of the existence of extraterrestrial life.
     
  17. Mar 15, 2005 #16
    "but several factors suggest it is common"

    Maybe I was wrong to type in "signs".
     
  18. Mar 16, 2005 #17
    i agree that all we have is speculation, but even by freak accidebts at near-impossible odds (trillion to one or more) there must be hundreds of forms of life in the universe.
     
  19. Mar 16, 2005 #18
    think about these two points:

    the components of life on Earth are made of elements that are some of the most abundant substances coughed out of exploding stars- the stuff is everywhere

    the components of life on Earth find their origins in molecular chains of these common substances- the structures of the chains that create Amino Acids and Proteins are some of the most simple and fundamental topological forms that atomic bonds allow
     
  20. Mar 16, 2005 #19
    That is why I think life is common, because the key ingredients for it are found in abundance in the universe and if life is common, then surely once in a while human-like intelligence will arise, especially in complex environments where the environment encourages intelligence. As Chronos said intelligence is efficient and has huge survival value.
     
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