The purpose of this part is to evaluate the probabilities of encountering extraterrestrial civilisations, perhaps more advanced than us, with more accurate estimates for the various parameters of the Drake equation (see further in this chapter, or in note 25).
All the serious evaluations of this probability stubbornly show that «they» would be numerous, with a much longer evolution than us, so that their presence should be obvious. However we until now detected nothing, even with the most sensitive SETI programs. This situation is generally named the Fermi paradox: «If they are so numerous, why don't we see them»?
This paradox is starting to become annoying, especially since we finally have experimental data: the discovery of exoplanets, which set very high values for the first factors of the Drake equation, and the first results of the SETI project, which seem on the contrary to disprove the powerful Galactic civilization which should result of these numerous planets.
The actual results of the SETI project (2012) seem to disprove the existence of a StarWars type civilization which would use the energy of the whole Galaxy (known as type 3 according to the Kardashev classification). Indeed, this civilization should be easy to detect for the current SETI project. However no such signal was found.
However, SETI is still very far from disproving the existence of smaller civilizations. According to the latest results (2012), SETI could even not detect the Earth at more than a light year! Thus technological civilization may be very numerous, but still undetectable before several decades. Not to mention advanced spiritual civilization which would even not use technology.
These experimental results clearly show that there is an element that we do not understand. A situation which reminds us of the Michelson Morley experiment: its result seemed totally mysterious, until something completely new and unexpected was discovered: Relativity. Furthermore, the contradiction appears between the proved astronomical factors, and the still hypothetical biological and spiritual factors, indicating that our misunderstanding is more likely about the latter. Either the civilizations do not appear (pessimistic solution), or they do not evolve as we expect (optimistic solution).
So, this part will review the terms of the Drake equation, factor per factor, from the formation of the planets, through the evolution of life, to the highly advanced ultimate destiny of civilization. Okay, I'm not a medium, and I found no definitive solution to the Fermi paradox. I can just list and clarify the many issues for future works. The point that we do not understand can be anywhere in this process, but it is more probably in the latter stages, those of advanced civilization, where the Earth is actually engaging.
An important point is indeed that the problem could be actually happening on Earth today: we already have the technology to launch a colonizing interstellar probe (see Chapter VIII-10 on how it works) and it is just a matter of will and development for such a project to succeed. So the Fermi paradox is probably something that we have to solve right now, making it urgent to deal with. This could even be a matter of life and death.
We shall see several possible solutions to the Fermi paradox. In the today state of knowledge, we cannot exclude some pessimistic solutions, which would reduce the number of civilizations to very low values. However, to continue on the path of technology is not necessarily the best thing to do, because we have much more interesting solutions with a spiritual evolution. But this very spiritual nature can make advanced civilization invisible to the today SETI focused on technological artifacts. It is an optimistic but plausible solution to the Fermi paradox: civilization would not evolve to interstellar travel, would not send electromagnetic signals to primitive peoples like us, or would even do develop the necessary technologies, preferring to live in flowery glens rather than in the concrete. The assumptions underlying the today SETI (2014) make it totally unable to detect such civilizations.
Finally, I shall not try to categorize the hypothesis between «reasonable» or not. Just because we have strictly no criteria to determine what is «reasonable» in this area. Instead, the very existence of the Fermi paradox shows that somewhere, our estimate of the «reasonable» is grossly wrong. I shall also avoid naive and definitive assertions such as «civilization destroy themselves», or «they develop technology without limit». I shall even not mention the ludicrous Catholic/scientistist dogma as what the Earth and humanity «must» be unique. However we shall study the possibility that UFOs (Chapter VII-2) and the possible paleoartifacts (Chapter VII-5) are the manifestation of extraterrestrial visits.
The bulk of this part was written in 2012, with presentation revisions in 2014 and 2015. Subsequent additions are dated. I therefore claim anteriority of the ideas expressed here, for 2012 or for the indicated dates.
Added in January 2015
The classical Drake equation gives the number of civilisations in our galaxy, by multiplying a series of factors:
1) R* is the number of stars forming each year in our galaxy (astronomical factor)
2) fp is the fraction of those stars which have planets (astronomical factor) (chapitre VIII-2)
3) ne is the fraction of these planets which can potentially support life (astronomical factor) (chapitre VIII-3)
4) fl is the fraction of the previous where life actually appears (biological factor) (chapitre VIII-4)
5) fi is the fraction of the previous where an intelligent life appears (biological factor) (chapitre VIII-5)
6) fc is the fraction of the previous able of emitting detectable signals (spiritual factor) (chapitre VIII-6)
7) L is the time for which such civilizations emit detectable signals, in years (spiritual factor)
Some astronomy computation allow to translate this value in the average distance of our closest neighbour, and in time before SETI detection.
The following chapters will discuss each of these terms.
My first contribution to the Drake equation is to classify these factors according to their nature: astronomical, biological or spiritual. Indeed, these are three totally different areas, involving totally different issues and conclusions, without any way to elude any of the three. If the astronomical factors are starting to be evaluable today, thanks to the discovery of exoplanets, on the other hand biological and spiritual factors remain entirely hypothetical. And it is of course the spiritual factors which gave rise to the most heated debates and the most dogmatic positions. You will see my contributions to each of these factors all along this part.
My second contribution to the Drake equation is noting a confusion in this traditional presentation: indeed, the factor 6 (fc) indicates the percentage of civilizations which emit technological signals, intentional or not. Obviously, only these civilizations are detectable by a SETI approach (listening for extraterrestrial signals). However this does not at all mean that all civilizations meet this criterion: spiritual civilization, and even «animal» civilizations (such as highly cultivated dolphins) would never pass through this stage. Thus, if we want to reason for the SETI, we are compelled to account with this factor. But if we want to reason about the total number of civilizations, we must on the contrary ignore it. Only much more powerful telescopes than today will let us know.
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