Holy Drake Sh_t

Discussion in 'Astronomy, Exobiology, & Cosmology' started by MacM, Apr 6, 2005.

  1. MacM Registered Senior Member

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    ********************* Extract ************************
    How Many Habitable Planets Could Be Out There?

    Summary - (Apr 5, 2005) The chances of finding life somewhere else in the Universe depends on how many planets are capable of supporting life. Well, according to new calculations by astronomers at Open University, as many as half of all star systems could contain habitable planets. The team created mathematical models of known exoplanetary systems, and then added Earth-sized planets into the mix. They found that in half of all planetary systems they simulated, the gravity of the gas giants won't catastrophically affect the orbits of these smaller planets, giving life a chance to evolve.

    Full Story - http://www.universetoday.com/am/publish/how_many_habitable_planets.html?542005
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  3. blobrana Registered Senior Member

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    Hum,

    <b>R * F<sub>p</sub> * N<sub>e</sub> * F<sub>l</sub> * F<sub>i</sub> * F<sub>c</sub> * L = N</b>

    So the updated figure for N<sub>e</sub> is 50%?
     
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  5. Hapsburg Hellenistic polytheist Valued Senior Member

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    and the mods say im taking up space?
    ...
     
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  7. Ophiolite Valued Senior Member

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    Not only the mods. What is that dumb assed, throw away comment meant to contribute to anything?

    Now to the article: I was concerned about one glaring omission. Reading the report justified my concern. It is noted that
    "This assumes that ‘Earths’ could have formed in the first place, which seems quite likely."
    To my mind that is a huge assumption. It may be correct, but to assume so is unjustified. We have some notion of the mechanisms at work in the formation of planetary systems, yet the character of many of those discovered so far were surprising, demonstrating, in my opinion, the incompleteness of our theories.
    I would also be interested to know what the authors of the work mean by " They discovered that about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets"
    What do they consider "at least long enough"? I suspect these researchers reside at the optimistic end of the alien life spectrum and are slanting their assumptions accordingly.
     
  8. eburacum45 Valued Senior Member

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    I think the article is supposed to indicate that planets COULD exist in the habitable zone of 50% of the solar systems so far; this is an entirely different proposition to saying that Earth-like planets have formed in those systems.

    A vast range of different types of terrestrial and non-terrestrial planets could form in these habitable zones; Earth-like planets are probably a very small subset of these different types of planet. (Incidentally both Venus and Mars are classed as terrestrial worlds- they are quite obviously very different to our own world.)
    The number of terrestrial-sized worlds which would be shirt-sleeve environments for humans could be quite small, in my opinion; and the number of worlds which hold life which is edible to unmodified humans will be even smaller (possibly vanishingly so).
    But that is just a guess.
    I can certainly recommend John Dollan's Planet Classification list; we use it at Orion's Arm, and it has been used by a number of independent worldbuilding projects.
    http://j.dollan.home.bresnan.net/ARCpclindex.html
    it is almost entirely speculative, and is based on information drawn from our own solar system, Earth's geological past, and models by various scientists involved in exoplanet research.
    As well as Earth-like (Gaian) Mars-like (Arean)and Venus-like(Cytherian) worlds, there are waterworlds (Panthalassic), tidally-locked worlds (Vesperian), and planets similar to early phases of the Earth's prehistory and to Mars' prehistory (Eogaian and Eoarean).
    Even then I expect that there will be even more types of planet not yet added to John's list; wet and dry superterrestrials with atmospheres much thicker than Earth's, carbon planets, chlorine or even fluorine rich worlds, worlds poisoned by heavy metal abundances;
     
    Last edited: Apr 7, 2005
  9. Ophiolite Valued Senior Member

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    Totally agree. If the authors had made that point with more emphasis I would have been entirely comfortable with their work. In my view they have taken som very good science and devalued it sonewhat by an overextended assumption.
    Thanks for the link: very interesting.
     

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