What is the chance of encountering intelligent alien civilizations?



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    There are assumptions to clarify. Often discussion about this uses a number of factors, some of the most critical were introduced by astronomer Frank Drake, in the “Drake Equation”.

    1) The most important question is how long it takes a planet to develop intelligent life. We only have ourselves an example. Unfortunately, it’s likely there will be species that develop much faster, or much more slowly. Does it take 1,000,000 years or 100,000,000? It makes a difference, and no one knows the answer.

    2) Next most important, but no less difficult to tangle with, is the question of how long a civilization exists. Say there is an intelligent species that gets through the typical stone age, metal age, etc. Everything looks promising. Unfortunately, it gets to the nuclear age, and in the process of winning a world war, both sides use nuclear weapons. The planet is utterly destroyed, and the universe never hears from it again. (This is often considered in professional SETI discussions.)

    Regardless of the pessimistic or optimistic outlook, there’s no way avoiding the question: How long does a world civilization last? Why? Because stars and planets didn’t all start at the same point. Some are far older than the Sun and Earth, and some are millions of years from getting to the point that we are now. In our stellar neighborhood, it doesn’t do any good if a nearby civilization has been dead for 1,000, 000 years. Nor does it help if one will get started 1,000,000 years from now.

    Science fiction “Star Trek” book and TV fantasies are not meant to be a scientific extrapolation of our world. Gene Roddenberry, who created “Star Trek”, described it to investors such as Lucille Ball as “Wagon Train in Space”. That is, it was a cowboy show, moved to an outer space setting. While it’s true that important science fiction writers contributed to (the original) “Star Trek” series, those writers were not scientists, and in the 1960s, had no conception of the Drake Equation discussion — which was just beginning.

    Finally and reluctantly, for all the years of trying to educate the public, one of the most common questions put to SETI projects is: Why are you looking for aliens in space, when they are already here on Earth? Yep. Quite intelligent people, after watching enough X-Files episodes, believe contact has already been made, and that “The truth is out there.”

    At the other extreme of the spectrum, there are scientists who think it’s possible that life is an unusual event, that civilizations die out relatively quickly, and that faster-than-light drive is impossible. Following the most pessimistic line of guesswork? Humanity will never meet an alien civilization.

    So, take your pick: Aliens are already here, or we will never meet aliens.

    Or anywhere between.

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