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Old 06-29-2019, 11:41 AM
 
639 posts, read 291,954 times
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It seems that for some UFO sightings are something so usual to the point that our space and even our skies are filled with alien spaceships in a way that one may think that our skies are like an UFO traffic jam!

UFO scams are everywhere: Area 51, alien abduction witnessings, videos and photos of dubious reputation, conspiracy theories stating that governments are hidding secrets and "the truth" about "they are among us", etc. But scientists assure that there is no evidence of extraterrestrial life up to today.

Of course leaving aside conspiracy theories and scams, let's focus on science and the fact that scientists assure that there is still no evidence of intelligent extraterrestrial life. The Fermi Paradox was formulated in 1950s by Enrico Fermi and refers to the apparent contradiction between the lack of evidence for and various high probability estimates of the existence of extraterrestrial civilizations elsewhere just in the Milky Way galaxy.

But why we still lack of evidence of intelligent extraterrestrial life? Dr. Frank Drake formulated a factorial equation in 1961 known as the Drake Equation to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy:
N = R* × fp × ne × fl × fi × fc × L

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
and

R∗ = the average rate of star formation in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

Using conservative estimates, the minimum result of this equation is 20. There ought to be 20 intelligent alien civilizations in the Milky Way that we can contact and who can contact us. But there aren't any.

A week ago, I came across a Theory known as "The Great Filter". This filter could take many forms. It could be that having a planet in the Goldilocks' zone—the narrow band around a star where it is neither too hot nor too cold for life to exist—and having that planet contain organic molecules capable of accumulating into life is extremely unlikely. Summarizing because I do not want to make this very lengthy, the Great Filter can occur at the very early stages of life where a single-celled organism evolve to higher forms of life. An event like this might be so unlikely that it's only happened once in the Milky Way. Or, the filter could be the development of large brains, as we have. We live on a planet full of creatures, and the kind of intelligence humans have has only occurred once. What if the Great Filter is ahead of us? This assume that humanity is a lucky species that overcame a hurdle almost all other life fails to pass. This might not be the case, however; life might evolve to our level all the time but get wiped out by some unknowable catastrophe. If our galaxy is truly empty and dead, it becomes more likely that we've already passed through the Great Filter. The galaxy could be empty because all other life failed some challenge that humanity passed.

This is just a summary of the Great Filter theory. I am leaving aside other fascinating formulations in regards of the possibility of intelligent extraterrestrial civilizations that can be discussed here: the Kardashev scale, the Zoo hypothesis. So, are we a fascinating species that beat the odds to survive the Great Filter in a very early stage and what is even more impressive will we be able to beat the Great Filter ahead of us? Aren't we so special and lots of other extraterrestrial civilizations beat the Great Filter as well? It seems that we are not able to set up contact with intelligent extraterrestrial civilizations yet. Some claim that this may be because we are a civilization type I according to Kardashev scale, so, if there are type III civilizations, why we still don't have evidence of intelligence extraterrestrial life? And here it comes the Predator theory. And there is even more... Another possibility is the fact that there are other extraterrestrial civilizations out there, but the distances between those civilizations and our civilization make impossible a contact because of the limits of relativity. There is a huge potential and never ending discussions that can be derived from all of this topic.
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Old 06-29-2019, 12:46 PM
 
Location: NYC
12,886 posts, read 8,725,709 times
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Ok, the same question I always ask others. Which one is scarier?

That we're not alone OR that we are the only life out there.
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Old 06-29-2019, 05:04 PM
Status: "Interested in Climate" (set 7 days ago)
 
Location: Trewartha, Dc
54 posts, read 5,018 times
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I too am familiar with the idea of a great filter, and I fear we may be approaching it. I recently read an article on the subject by Nick Bostrom:


One way of looking at human creativity is as a process of pulling balls out of a giant urn. The
balls represent possible ideas, discoveries, technological inventions. Over the course of history,
we have extracted a great many balls—mostly white (beneficial) but also various shades of grey (moderately harmful ones and mixed blessings). The cumulative effect on the human condition has so far been overwhelmingly positive, and may be much better still in the future. The global population has grown about three orders of magnitude over the last ten thousand years, and in the last two centuries per capita income, standards of living, and life expectancy have also risen.


What we haven’t extracted, so far, is a black ball: a technology that invariably or by default
destroys the civilization that invents it. The reason is not that we have been particularly careful or wise in our technology policy. We have just been lucky.


What if there is a black ball in the urn?



Bostrom goes into much more detail, and classifies several hypothetical scenarios in his article The Vulnerable World Hypothesis, which you shoud be able to locate online in .pdf format through duckduckgo (or if you must, through googoloroth.)
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Old 06-29-2019, 05:50 PM
 
Location: Aurora Denveralis
8,555 posts, read 3,001,676 times
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The Drake equation is Roddenberry-level nonsense. You can define each term, but you can't assign any meaningful value to even the first few factors. Some vague guesses only show that intelligent life of equivalent standing to make contact is going to be vanishingly rare - and we pretty much already know that, without filling a whiteboard with made-up numbers.

Vision got it almost right, with what may be the most intriguing comment Carl Sagan ever made: "Either we are alone in the universe, or we are not. Either way, it's a staggering thought."
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Old 06-29-2019, 06:03 PM
 
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I always took the Drake Equation as being more of an intellectual curiosity as opposed to anything approaching the scientific domain.

That being said, humans have only been broadcasting for several decades, which is peanuts next to the size of the Milky Way, so we've barely covered any ground. Given that there are so many stars, the possibility of there being intelligent beings out there seems rather high, but at this point it remains speculation.

When the Drake Equation was formulated, the existence of planets outside of our Solar System was mere speculation, yet we have thousands of candidates. We now know that planet formation is a natural part of star formation and most stars are bound to have accompanying planets orbiting them.
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Old 06-29-2019, 06:04 PM
 
5,726 posts, read 2,312,076 times
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I understand the Fermi Paradox and the Great Filters and the lesser filters which work against intelligent life too. There is intelligent life out there, there's just very few others in our local cluster of galaxies and it's very likely that we are alone in the Milky Way at this time.
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Old 06-30-2019, 01:16 AM
 
410 posts, read 79,325 times
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Putting all of these "theories" aside, it's important to remember that UFO doesn't stand for Alien Flying Object but Unidentified Flying Object. The clue is in the word unidentified.

If one doesn't know what the object is one can't ascribe to it a property of being out of space, when to all intents and purposes there are far likelier explanations. I appreciate that people don't generally like uncertainty but the most rational thing to do in a situation where you don't have any evidence to support the fact is to reserve one's judgement and settle for unidentified.
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Old 06-30-2019, 06:17 AM
 
Location: Maryland
1,762 posts, read 561,837 times
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Quote:
Originally Posted by vision33r View Post
Ok, the same question I always ask others. Which one is scarier?

That we're not alone OR that we are the only life out there.
I saw an interview somewhere years ago and the guy made a similar statement. “Either we are alone in the universe, or we are not. Either way, it’s incredible.”

Also, regarding “filters”.....

Thomas Bayes, Richard Gott and Doomsday
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Old 06-30-2019, 08:48 AM
 
21,798 posts, read 16,670,340 times
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So far as the Drake equation goes, it's not a reliable indicator for estimating how many planets may have intelligent life in our galaxy. The numbers that are plugged into the equation are arbitrary. For instance, fp - the fraction of stars with planets. We are now discovering a great many exoplanets that we had no idea were there when the Drake equation was made. And most of those planets were discovered only because they passed in front of their stars as seen from Earth so that when they did so, there was a slight drop in the amount of light coming from the star. There's no telling how many other planets are orbiting their stars which we can't yet detect.

Why haven't we discovered intelligent life elsewhere in the galaxy? For one thing, not all forms of intelligent life would necessarily by capable of sending signals for us to detect. For instance, dolphins are very intelligent animals but obviously are not capable of developing any kind of technology. There could be civilizations that simply aren't technologically advanced enough to have developed radio or tv which would send signals into space which might be detectable to us. Other civilizations might be so advanced that we can't recognize the kind of signals that they might be sending out into space. And some intelligent life capable of emitting signals into space could be on the other side of the galaxy from us and their signals haven't had time to reach us, or are too weak to be able to reach us.

Not having detected life on other planets doesn't mean that life doesn't exist on other planets.
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Old 06-30-2019, 08:58 AM
 
639 posts, read 291,954 times
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Quote:
Originally Posted by Quietude View Post
The Drake equation is Roddenberry-level nonsense. You can define each term, but you can't assign any meaningful value to even the first few factors. Some vague guesses only show that intelligent life of equivalent standing to make contact is going to be vanishingly rare - and we pretty much already know that, without filling a whiteboard with made-up numbers.
The Drake equation is factorial and fairly simple. It could have been improved by adding some terms to improve it's accuracy. I see Drake equation as the equivalent of Order of Magnitude Estimate (ROM estimate) in cost project engineering. The main problem is that as far as I know we can't estimate some terms of the equation such as "ne", "fl" and "fi". Because the error range of its result "N" would be somewhat huge, I would be happy to at least analyze if the result "N" is greater than 0, because N~0 would means that there are no extraterrestrial civilizations to set up communication with and N>0 would means that there are extraterrestrial civilizations to set up communication with. How can we study the meaning of this result easier? If N~0, then one of the factors drops to 0, let's say 1E-20 for example. Summarizing, to give an estimate that there are extraterrestrial civilizations to set up communication with them, none of the factors should drop to 0, that would give N>0, but of course, the exact number is anything but accurate, because this is an Order of Magnitude Estimate but at universe scale, the error in the result is huge.
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