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Generalizing the Drake equation

  1. Feb 15, 2010 #1
    Does the Drake equation need to accommodate moons?
  2. jcsd
  3. Feb 15, 2010 #2


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    I think moons are taken care of in one of the terms...e.g. the term that has the probability that life arises on that planet, or the probability that that life becomes intelligent.

    I always wondered, why didn't Drake just pose his equation: N=N as in, the number of intelligent civilizations we could hope to contact is equal to the number of intelligent civilizations we could hope to contact...we know this N parameter just as well (or, in this case, just as unwell) as we know some of the other parameters in his equation......
  4. Feb 15, 2010 #3
    I suppose we could redefine [tex]n_e[/tex] as "average number of planets + moons that can potentially support life per star that has planets"

    It will take some time though before we have a handle on just how common moons around planets in the habitable zone are. Our only example is our solar system and exoplanet hunts are not yet sophisticated enough to detect the presence of moons.
  5. Feb 18, 2010 #4
    This can be read in two ways. Should the Drake equation consider the effect of a moon on its parent planet? Or, should the Drake equation consider moons as possible habitable locations? Either way, I think the answer should be yes.

    In the first case, many scientists have come to the conclusion that our moon has helped stabilize our planet's tilt and helped create tidal forces on the planet that encourage tectonic activity, both of which are important for the creation of life on our planet.

    In the second case, as Europa has shown, water can exist on moons as well as planets, and therefore moons can support life. Some moons have tectonic activity. Some have atmospheres. Therefore, moons should be considered (although I think many factors make moons a less likely chance for evolved life).
  6. Feb 19, 2010 #5


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    I say nay.

    After all, the Drake Equation is just an approximation. Nothing more. Trying to become increasingly accurate defeats the purpose of the equation! So whether the fraction of habitable planets is .1 or .07 seems a little irrelevant for the type of computation for which the equation is intended.

    Of course, you can account for anything in such an equation. After all, it's just the product of a bunch of terms. You could freely add more or change the definition of the ones already there. My contribution: Fraction of planets which are impacted by very large asteroids, rendering them uninhabitable for intelligent life.
  7. Feb 19, 2010 #6
    I think "The Rare Earth Theory" discusses moons. Check out that book. It is a good read. It also greatly expands the Drake Equation to factor in things we know about now that we didn't know about decades ago when the Drake Equation was proposed.

  8. Feb 20, 2010 #7


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    A big moon helps, but is not essential. In our solar system the sun contributes about 1/3 to ocean tides. Moon pulls the rest. Rare Earther's are pushing their own agenda and conveniently ignore facts inconsistent with their world views.
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