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The SDE is based on the Central Limit Theorem, which states that given the enough number of independent random variables with finite mean and variance, those variables will be normally distributed as represented by a Gaussian or bell curve in a plot. In this way, each of the seven factors of the Drake Equation become independent positive random variables. In his paper, Maccone tested his SDE using values usually accepted by the SETI community, and the results may be good news for the “alien hunters”.
Although the numerical results were not his objective, Maccone estimated with his SDE that our galaxy may harbor 4,590 extraterrestrial civilizations. Assuming the same values for each term the Classical Drake Equation estimates only 3,500. So the SDE adds more than 1,000 civilizations to the previous estimate.
Another SDE advantage is to incorporate the standard variation concept, which shows how much variation exists from the average value. In this case the standard variation concept is pretty high: 11,195. In other words, besides human society, zero to 15,785 advanced technological societies could exist in the Milky Way.
fl = the fraction of the above that actually go on to develop life
all terrestrial life stems from a common origin. If abiogenesis were more common it would be speculated to have occurred more than once on the Earth. Scientists have searched for this by looking for bacteria that are unrelated to other life on Earth, but none have been found yet. It is also possible that life arose more than once, but that other branches were out-competed, or died in mass extinctions, or were lost in other ways. Biochemists Francis Crick and Leslie Orgel laid special emphasis on this uncertainty: "At the moment we have no means at all of knowing" whether we are "likely to be alone in the galaxy (Universe)" or whether "the galaxy may be pullulating with life of many different forms.".
The article goes on to say that even accepting Drake's numbers, the huge standard deviation means that the correct answer is between 0 and 15,000+.
Looking to the Drake equation factors, it is obvious that none can be precisely determined by modern science. More than that, as we move from the left to right in the equation, estimating each factor becomes more controversial. The later terms are highly speculative, and the values one may attribute to each of them might tell more about a person’s beliefs than about scientific facts.
Originally posted by charles1952
reply to post by Philosophile
Of course you're right, it doesn't prove anything, and it can never prove anything. Allow me to quote from the white paper linked in the OP:
The article goes on to say that even accepting Drake's numbers, the huge standard deviation means that the correct answer is between 0 and 15,000+.
Looking to the Drake equation factors, it is obvious that none can be precisely determined by modern science. More than that, as we move from the left to right in the equation, estimating each factor becomes more controversial. The later terms are highly speculative, and the values one may attribute to each of them might tell more about a person’s beliefs than about scientific facts.
It's a fun idea used to think about the factors involved in finding an alien civilization, but it's certainly not proof of anything.
Originally posted by Druscilla
Interesting and fun, but, we've still yet to hear anything from anyone else, or see any indication that there's an anyone else out there to hear anything from.
Earth is lonely.
We want friends.
500 light-years away, the chance of detecting any signal from an advanced civilization approaches zero. And that is exactly the range in which our present technology is searching for extraterrestrial radio signals. So, the “Great Silence” detected by our radio telescopes is not discouraging at all. Our signals just need to travel a little farther – at least 900 light years more – before they have a high chance of coming across an advanced alien civilization.
Originally posted by PhoenixOD
All the life on earth we have ever observed came from a single common ancestor.
now you're making stuff up. what is this mysterious beast that turned into 8.7 million different species that live on earth.
fl = percentage of these planets that actually develop life;
fi = percentage of these planets that actually develop intelligence on human level;