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The science behind a ridiculous headline: 36 alien civilizations in the Milky Way?

#1
C C Offline
https://www.forbes.com/sites/startswitha...48257879c5

EXCERPTS:  . . . So why, then, do we have a scientific paper coming out now, using the same set of data and similar techniques, that draws a radical conclusion? Why, then, are we hearing claims that 36 alien civilizations likely exist in our Milky Way right now? Because that new estimate is based on an ill-founded assumption that the authors make: that if you start with an Earth-sized world at an Earth-like distance around a Sun-like star, you will have very good odds of getting a technologically advanced civilization out once 5 billion years have passed. The authors, Tom Westby and Christopher Conselice, state this themselves...

Is this a good assumption? In a scientific sense, absolutely not. As we just discussed, a previous study just demonstrated that it's more likely than not that intelligent life is rare; if you were to rewind the clock and start Earth over again some ~4.5 billion years ago, it appears that you'd be relatively unlikely to have a technologically advanced civilization arise on our planet. [...] After all that, then, how did Westby and Conselice arrive at their conclusion that there are 36 intelligent alien civilizations in the Milky Way right now?

They not only assumed "a reasonable probability" that intelligent life will arise after about 5 billion years on an Earth-like world, but they then imposed a further assumption — what they call the Astrobiological Copernican Strong Condition — that intelligent life must form between 4.5 billion and 5.5 billion years after an Earth-like planet forms in an Earth-like orbit around a Sun-like star. They they further go on to assume that such a civilization should exist for 100 years in its actively-communicating phase [...] and then they do their statistical analysis. In the end, based on these assumptions, they conclude that there should be 36 alien civilizations within our galaxy, right now, with some uncertainty.

[...] Here's how you know these numbers are meaningless: the uncertainties are so large that they do not exclude "0" as a reasonable possibility. Even if their (arguably ill-motivated) assumptions about intelligent life were true, the uncertainties are so large that conclusions about the number of alien civilizations present within the Milky Way cannot be reasonably drawn. [...] If we're willing to make assumptions ... we can indeed draw conclusions about the likelihood of intelligent life throughout the galaxy. The only problems are that our conclusions are only as good as our assumptions, which we have no reason to believe are very good... (MORE - details)
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#2
Taormina Offline
I could not resist commenting on this topic:
First, the assumptions (at least some of them) are certainly wrong because they seem to be based on only ONE CASE. No logical scientist would make "universal" claims based on only one case!

On other facets of this matter, there is too much to consider for a short comment here, but one must ask whether those authors considered the Drake Equation, which includes the time factor, i.e., that the length of time for any phase of the appearance of life (until the possible emergence of intelligent life) could vary across the entire galaxy. Consider star formation in this galaxy at this very moment: In some locations there is gas and dust that have not started to coalesce; elsewhere stars are just now beginning to form within their accretion disks; elsewhere some stars have formed but are still very young; in other places you have middle-aged stars; and in other locations there are stars that are ending their existence. All these things are now in progress at this very moment in time! Consequently, it seems that those authors, if they think it is possible to compute the number of intelligent life forms based only on the number of billions of years of a galaxy's existence (as if there were a single starting point when all its stars began to form) is an erroneous assumption.

There is a separate point that probably should not be ignored, which is Carl Sagan's empirical research. That is, as a biologist, Carl Sagan (1957), in a paper on radiation and the origin of the gene, explained the idea that certain elements in the universe could produce life by means of solar radiation; and subsequently in a laboratory experiment he and his colleagues (in 1963) synthesized adenosine triphosphate (C10H16N5O13P3), which is an organic compound necessary for living cells to work (such as causing muscles to contract and to send nerve impulses). In other words, Sagan and his colleagues demonstrated that solar radiation under conditions such as those that existed early in the planet Earth’s history enabled basic elements to combine to form the molecular “building blocks” necessary for life. In other words, the possibility of life forming at various places all around the galaxy (with its hundreds of billions of stars and multitudinally more planets) is likely to be extremely high!

On the other hand, it is also erroneous to assume that intelligent life "must form" at some designated number (or range) of years after a certain type of planet takes shape. After all, based on some of the things that humans have done in the past, are now doing, and saying (and publishing), one tends to wonder whether this Earth has reached a point yet where "intelligent life" has evolved.
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#3
stryder Offline
I prefer to take a more simplified approach to reasoning.

An example I tend to use in regards to it is Betting using Accumulators. The idea is that a bet is placed, should you win the winnings are placed into the next bet and this is done a number of times. The problem with actually accumulators though is that it requires all the bets to be won in order to be paid out as it creates greater odds, should any fail then all the bets lost.

When applied to the universe, it can be said that there are various juncture points where the odds could of been less than favourable. For instance junctures could be (This is by no means a comprehensive list):
  • The creation of the universe,
  • Pure energy converting to proto-matter,
  • That matter converting to atoms that in turn form molecules,
  • Molecules becoming increasing complex,
  • Increasing complex molecular interactions (while under the duresses of radiation) giving away to the first proteins,
  • Those proteins then giving away to the simplest of single celled life forms,
  • Those single celled lifeforms creating multicellular structures to increase their survival changes etc.

We exist at a point of where we can see our "Accumulator" has been one with the most extreme of odds, however to apply that similar life could come into being somewhere else in the universe also requires all those junctures to be won in near enough the exact same way. (Each bet could have a number of variants of random conditions that would be different from the original accumulator bets leading to further complications in outcome)

That's a bit like you winning an accumulator out of five horse races and then getting an imaginary friend win an entirely separate accumulator (Although I don't know how a betting company could take the bet or pay out to an imaginary friend).
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#4
C C Offline
(Jun 18, 2020 05:28 PM)stryder Wrote: I prefer to take a more simplified approach to reasoning.

An example I tend to use in regards to it is Betting using Accumulators. The idea is that a bet is placed, should you win the winnings are placed into the next bet and this is done a number of times. The problem with actually accumulators though is that it requires all the bets to be won in order to be paid out as it creates greater odds, should any fail then all the bets lost.

When applied to the universe, it can be said that there are various juncture points where the odds could of been less than favourable. For instance junctures could be (This is by no means a comprehensive list):
  • The creation of the universe,
  • Pure energy converting to proto-matter,
  • That matter converting to atoms that in turn form molecules,
  • Molecules becoming increasing complex,
  • Increasing complex molecular interactions (while under the duresses of radiation) giving away to the first proteins,
  • Those proteins then giving away to the simplest of single celled life forms,
  • Those single celled lifeforms creating multicellular structures to increase their survival changes etc.

We exist at a point of where we can see our "Accumulator" has been one with the most extreme of odds, however to apply that similar life could come into being somewhere else in the universe also requires all those junctures to be won in near enough the exact same way. (Each bet could have a number of variants of random conditions that would be different from the original accumulator bets leading to further complications in outcome)

That's a bit like you winning an accumulator out of five horse races and then getting an imaginary friend win an entirely separate accumulator (Although I don't know how a betting company could take the bet or pay out to an imaginary friend).

Very much a compelling conception for dealing with or illustrating it.

Although alien civilizations are (in theory) within the realm of the knowable rather than aloof metaphysics, the "imaginary friend" placeholder is reminiscent of how reason or rationalism posits that something is necessary or inevitable based on the premises it chooses to draw conclusions from. Even if the "indispensable" item is arguably unable to ever be empirically validated or is prior in rank to the sensible world or the latter's manifestations and regularities in consciousness.
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