Here is an interesting attempt to make the Drake equation more accessible:

I like the fact that they have the various standard assumptions, from optimistic to skeptical.  I’ve always erred on the side of the optimistic on this one.  It just strikes me as just one more example of human arrogance to conclude that we are special in this galaxy.  One thing I’ve always liked about the Drake Equation is that it focusses the discussion.  It takes a totally impossible question (“how many intelligent civilizations are there in the galaxy”) and breaks it up into a number of smaller questions, many of which are answerable.  Of course, near the end of the calculation it gets a little dicey, but so are all such problems. 


About brianblais

I am a professor of Science and Technology at Bryant University in Smithfield, RI, and a research professor in the Institute for Brain and Neural Systems, Brown University. My research is in computational neuroscience and statistics. I teach physics, meteorology, astonomy, theoretical neuroscience, systems dynamics, artificial intelligence and robotics. My book, "Theory of Cortical Plasticity" (World Scientific, 2004), details a theory of learning and memory in the cortex, and presents the consequences and predictions of the theory. I am an avid python enthusiast, and a Bayesian (a la E. T. Jaynes), and love music.
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3 Responses to Aliens!

  1. Steve Winsor says:

    I don’t understand why you think it’s human arrogance to believe that we are special. One does not automatically mean the other. If we are the only ‘intelligent’ species in the galaxy (and that is not an improbable thought given the unique circumstances that would be required), of course we would consider ourselves ‘special’…because it would be true. Nothing directly arrogant about that. I mean, are we more special than an oak tree?…yes, there are grounds to think so without being arrogant.

  2. Rajesh says:

    A person has 1 in 10,000 chance of getting colon
    cancer. If a person’s family has history of colon
    cancer, then that chance is increased to 1 in 100.
    If a person’s family has no history of colon
    cancer, then the chance is 1 in 50,000.

    Now a walk-in patient was detected with colon
    cancer. But he was not sure whether any of his
    family members has colon cancer.
    What probability can the doctor use to estimate
    the likelihood of the patient’s family members
    having cancer history?

    • brianblais says:

      Kind of an odd question for this topic, but here is the answer. You need to have information about the test itself, and how likely a false-positive is. Without that information (which one must have for a test to be meaningful) you can’t answer. Since you don’t know any family history, the probabilities involving family history would not be relevant. Or, if you included them properly, their influence would cancel and you’d get the same answer as if you had not included them. Does that help?

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