Fancy Math Can’t Make Aliens Real

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Message 1834040 - Posted: 4 Dec 2016, 15:38:40 UTC

From The Atlantic Magazine (JUN 17, 2016 ):
Fancy Math Can’t Make Aliens Real
An astrophysicist says extraterrestrial civilizations “almost certainly” existed at one time or another. Here’s what’s wrong with his argument.

--- snip ---
It is precisely this profusion of planets that gives Frank confidence that ours is not the first intelligent civilization. “Given what we now know about the number and orbital positions of the galaxy’s planets,” he tells us, “the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.” Most of us have heard a version of this argument, late at night, around a campfire: Look at all the stars in the night sky. Is it really possible that all of their planets are sterile, and all of their predecessors, too?


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Message 1834073 - Posted: 4 Dec 2016, 17:46:36 UTC - in response to Message 1834040.  

Thanks for posting this. Personally, I find the title of the article unfortunate and misleading. Real SETI efforts like ours always generate a certain amount of eye-rolling in some circles, and the title of this piece seems like another effort to cash in on that. Or am I taking it wrong?
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Message 1834090 - Posted: 4 Dec 2016, 18:57:03 UTC

The great number of planets, now reasonably inferred to exist in the galaxy, seems to point to the likelihood that many are the abode of life, even complex life. Ross Andersen of the Atlantic calls this argument intuitive, and dismisses it. He would have us suppose that our existence could just as well be the result of a series of contingent accidents, rendering us unique, or nearly so, in the cosmos.

One problem with such an argument is that goes against our accumulated knowledge of our place in the universe. Again and again humanity has imagined itself in a unique position. Again and again these conceits have been shattered by new learning.

Various ancient nations saw themselves as positioned at the center of a flat, and unique, world. Later, the Earth itself was viewed as occupying the center of the solar system, with all planets, and even the Sun whirling around it. Even when it was finally understood that the stars were really distant suns, it was thought that they were without planets, and that our Sun only had planets due to a highly improbable accident. Further, when the rough shape of our galaxy was discerned, we assumed we were at its center, and that it was the only such island of stars.

Given this long history of our self-important and erroneous theorizing, it seems prudent to ask ourselves if it's wise to consider ourselves unique in a manner that currently lies at the edge of our knowledge.
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Message 1834127 - Posted: 4 Dec 2016, 21:29:46 UTC - in response to Message 1834090.  
Last modified: 4 Dec 2016, 21:30:37 UTC

The sad thing to ponder is that it is fairly likely that we will never know the extent and type of life in the universe and whether it exists at all. Let's start with primitive forms on Mars. Experience may tend to prove my conjecture that there are very very few truly Earth-like planets in our Galaxy. This would still imply Billions in the Universe but also suggest vast distances between any two of them.
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Message 1834141 - Posted: 4 Dec 2016, 22:00:04 UTC
Last modified: 4 Dec 2016, 22:08:29 UTC

Scientific findings support an inference of 40 billion habitable-zone planets in our galaxy of 100 billion stars. That's one promising planet for each two or three stars. Even if we suppose advanced life actually occurs on only 1 in 1000 of those planets, that means a great many stellar civilizations in our galaxy. Given the 10,000 stars within 100 light years of Earth, that could mean two or three civilizations within that distance.
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Message 1834151 - Posted: 4 Dec 2016, 23:14:23 UTC

I would rhetorically ask how we define "earth-like". For instance, imagine a wet, rocky world with primitive life, but also with an orbit that causes severe climate swings regularly, of sufficient severity to cause mass extinctions. Is this an earth-like planet? Perhaps yes, but could it ever evolve a tech-capable species? When we say "earth-like" I suspect this is what we really mean--capable of evolving and supporting complex life. The irony, of course, is that the earth is what it is today because of catastrophic events, from the formation of the moon to the end of the dinosaurs that opened a niche for mammals and us. Would dinosaurs ever have evolved into builders of computers and spacecraft? Maybe. Who can say?
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Message 1834259 - Posted: 5 Dec 2016, 10:25:12 UTC - in response to Message 1834151.  
Last modified: 5 Dec 2016, 10:44:35 UTC

I agree--I sincerely doubt the existence of 40 billion habitable planets in the Galaxy. I myself state that there are perhaps 4 or 5. My estimate is probably less uncertain than yours.

We have not yet found another truly Earth-like planet that could support higher forms of life as we know it. I suspect that we never will find one ever.

As we have ranted on these boards several times before, there may be two dozen requirements for our form of life to start and evolve. Many of these requirements are in very narrow parametric ranges. Have we yet even to find a rocky planet roughly the size of earth in a habitable zone that has : water, tides, stabilizing moon, ozone layer, magnetic field , near circular orbit, axis tilt, seasons, and the list goes on.

I wont argue that Earth=like planets do not exist nor have not existed in the universe nor that other intelligent life does not or did not exist either--just that it is extremely sparse to the extent that it is unknowable due to vast separations in both time and distance. This conjecture of mine is easily falsifiable while Watson's is not.

I would love to be proven wrong and I think that we should all continue to play this lottery even though the odds may make it a fool's errand.

"You see it's all elementary my dear Watson". Sherlock Holmes
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Message 1834332 - Posted: 5 Dec 2016, 18:12:48 UTC - in response to Message 1834259.  

The estimate of up to 40 billion habitable planets in our galaxy was not my own. It was one published in the Proceedings of the National Academy of Sciences. It was the work of recognized scientists working in the field of exoplanets.

I would like to hear of the recognized scientific support for of the claim that we could expect to find, instead, 4 or 5 such planets.
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Message 1834342 - Posted: 5 Dec 2016, 18:47:59 UTC

I think it's important to remember that any number, no matter who comes up with it, depends on assumptions. What we need for any valid estimate is more data. Personally, I hope the number of habitable planets is very big. I hope instances of life and the number of intelligent species is large. I hope everyone out there is friendly and peaceful. But I'll stay open to all possibilities. Right now we simply can't know. I don't think we should stop speculating and considering the possibilities, though.
“Upon opening the box, Schroedinger's raccoon will be observed in one of three possible states; alive, dead, or really, really pissed off.”
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Message 1834534 - Posted: 7 Dec 2016, 3:18:17 UTC - in response to Message 1834332.  
Last modified: 7 Dec 2016, 3:57:58 UTC

I suspect that they figured a habitable planet per 2 or 3 stars and then came up with their big number. It serves them very well since it may just attract more funding for their endeavors from un-sophisticated donors.

My number comes from the assumption that there are at least 12 essential conditions for life to form and evolve as we know it here on earth. If each of these is only 20% likely then the possibility of one occurring is 4 in one billion. Not all stars are single stars; most are binary, and some are not main sequence. Hence these would not last the requisite few billion years for life to evolve. What is the chance that an alien civilization will be in a time sequence with us so that we could hear their transmissions. You see this manner of thinking yields a number that is perhaps counted on our own fingers and toes.

As to the 20 %--what have we found so far. Time will tell as we are able to see smaller and smaller planets. Until then I will defend my small number and scoff at the Saganesque pronouncements from well-known showmen in this game who probably know better.

As someone astutely noted, it depends on the assumptions that go into the model. I also believe that we here on Earth are a product of some very rare cataclysmic occurrences that are extremely uncommon.

It would help greatly if those Exo-biologists (astro-biologists), as I call them, on SETI payrolls would list what they think are the essentials and their parameters for a Habitable, Earth-like planet to exist. We could then more accurately assess the probability of occurrence of each one of these. Perhaps there are more than a dozen---perhaps less.

As to the statement that there are 10,000 stars within 100 light years from Earth:
"As many as 512 or more stars of spectral type "G" (not including white dwarf stellar remnants) are currently believed to be located within 100 light-years or (or 30.7 parsecs) of Sol -- including Sol itself."
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Message 1834537 - Posted: 7 Dec 2016, 3:53:45 UTC - in response to Message 1834534.  

As someone astutely noted, it depends on the assumptions that go into the model. I also believe that we here on Earth are a product of some very rare cataclysmic occurrences that are extremely uncommon.


I agree. And while I'm not a fan of the Intelligent Design argument, this does give me pause.
“Upon opening the box, Schroedinger's raccoon will be observed in one of three possible states; alive, dead, or really, really pissed off.”
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Message boards : SETI@home Science : Fancy Math Can’t Make Aliens Real


 
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