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Civilizations in other galaxies?

  1. Sep 15, 2007 #1
    How probable is this?

    100 Billion galaxies, there has to be at least one other civilization out there, no?
  2. jcsd
  3. Sep 15, 2007 #2


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    Probability of life seems high, but we can't be certain without physical evidence. To go from life to civilization appears to take a long time. Life started on earth arround 3.5 billiuon years ago, multicellular life starte around 550 million years ago. Homo sapiens started around 150 thousand years ago. Civilization began (say defined by the invention of writing) around 5500 years ago. Also the whole process seemed to require a succession of accidents, like the disappearance of the dinosaurs 65 million years ago, which is believed to have resulted from a major catastrophic extraterrestial impact. If the dinosaurs hadn't been wiped out, mammals wouldn't have had much chance to evolve as they did.
  4. Sep 15, 2007 #3


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    This is something that is very very very hard to estimate, especially because we know so little about abiogenesis. The Drake equation is the best estimation that I know of.

  5. Sep 16, 2007 #4
    I am agree with friend nicksauce that the Drake equation is the best estimation that we know.For example if we put the numbers 1,2,3..in the Drake equation the number of other civilizations would be 20.IF we put bigger number more ''crazy'' the number of other civilization would be 100.000!But all of those numbers are depends on the fractions of the Drake equation.
  6. Sep 16, 2007 #5


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    To start with i do not want to contemplate infinite possibilities, (think about it) for this reason i do not think that everything is possible, there has to be a a set number of posssibilites, if you think my reasoning strange then say hello to the goat laying in bed next to you.
  7. Sep 17, 2007 #6


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    Civilization, as we know it, is extraordinarily rare for reasons we do not fully understand. Radio surveys are the evidence [no alien versions of 'I love Lucy' have yet been detected]. The sophistication of modern radio telescopes has virtually ruled out artificial EM sources within our galaxy. The universe is an incredibly inhospitable place to live. Cataclysmic events occur with disturbing regularity and life, especially intelligent life, is incredibly vulnerable to such events. We have only been literate here on earth [a prerequisite for truly intelligent life forms] for about 6000 years. That is an incredibly tiny slice of time in the history of the universe. I don't think life is rare, merely fragile.
    Last edited: Sep 17, 2007
  8. Sep 18, 2007 #7
    My understanding is that the strongest routine radio signals generated on earth could only be detected a few light years away by radio telescopes such as ones we have today. In other words, we are not capable of detecting "I Love Lucy" from another star system, so the fact that we have not done so does not rule out their existence.

    It is also my understanding that we have only surveyed a relatively small number of stars at a small number of frequencies. I think it is premature to rule out alien life in our galaxy.
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