| Written by Sirius_Cily | |
| The paradox Fermi paradox is said to have been proposed by the physicist Enrico Fermi in the context of the probability of contact with intelligent extraterrestrial life forms. The paradox is summed up usually in the question "Where is everybody?" If there are so many advanced civilizations, we have not yet received evidence of extraterrestrial life as the transmission of radio signals, probe or spacecraft? ". An extreme issue, the question becomes whether we humans are the only technologically advanced civilization of the universe. This problem is usually placed as a warning to the most optimistic estimates of the Drake equation (see below), which would pose a universe full of planets with civilizations advanced, able to establish radio communications, send probes or colonize other worlds.  The paradoxical situation is due to the contrast between the feeling, shared by many and supported by estimates of the kind to Drake, that we are not alone in the universe and the fact that the conflict with observational data this feeling. It follows that our observation or understanding of the data must be wrong or incomplete. In 1950, while working in the laboratories of Los Alamos, Enrico Fermi took part in a conversation with some colleagues, including Edward Teller, while he went to lunch. The talk was about a recent UFO sighting reported by print, which satirized a satirical cartoon. The conversation lasted about various related topics, until suddenly, during lunch, Fermi exclaimed, "Where are they?" (Trans. "Where am I?"). Possible solutions (here we list a few, for other cases refer to the reading of "If the Universe is teeming with Aliens ... Where is everybody?" By Stephen Webb) We just The simplest solution is that the probability that life evolves in the universe and evolve spontaneously to produce a highly developed civilization is extremely low. There are many items at once necessary for life as we know it noi, basata sul carbonio, possa evolversi su un pianeta. Fattori astronomici, come la posizione all'interno della galassia, l'orbita percorsa dal pianeta intorno alla sua stella centrale e la tipologia di quest'ultima, la sua ellitticità e l'inclinazione dell'orbita, nonché la presenza di satelliti naturali delle caratteristiche della Luna, sono tutti fattori determinanti alla predisposizione alla vita. L'attuale nascita della vita, lo sviluppo di forme di vita intelligente e quindi di civiltà richiede che molte altre coincidenze siano verificate. Gli studi sul nostro Sistema Solare sembrano confermare l'eccezionalità della vita sulla Terra. Questa tesi può essere contestata sostenendo che la vita non debba necessariamente be as we observe on Earth, but can evolve under different conditions, and should not be based on carbon. Much of the uncertainty stems from the fact that the mechanisms leading to the emergence of life are unknown and therefore it is very difficult if not impossible, to estimate its probability. However, the occurrence of life is considered an unlikely event, even by some supporters of the existence of alien civilizations, to overcome this problem they have formulated the hypothesis of panspermia, which claims that life could spread easily through ' universe, or even, in the form supported by Francis Crick, which could be deliberately spread by technologically advanced civilizations. civilizations have evolved short A parameter in the Drake equation is the average length of technologically advanced civilizations. Drake estimated a period of 10,000 years (when he started to communicate with radio waves). The causes of the disappearance of a civilization can be both natural and cultural. If a natural tendency to annihilate a civilization, it's just a matter of time invent the necessary means. The only observational data available is that our civilization has the necessary resources for decades, but so far has survived. Again it is difficult to say how the hierarchical struggle, aggression and authoritarianism, elementi del militarismo, siano prerogative della razza umana o siano costanti universali intrinsecamente legate all'evoluzione o all'organizzazione politica degli individui intelligenti. Si consideri che non è necessaria una distruzione totale della specie, ma è sufficiente una involuzione a livelli primitivi dei sopravvissuti per sottrarre la civiltà alla lista di quelle in grado di comunicare. Anche eventi catastrofici di tipo naturale possono considerarsi come gravi pericoli per un pianeta vivo: l'impatto di una cometa, di un asteroide, l'eruzione di un supervulcano o l'alterazione delle condizioni climatiche sono tutte minacce alla vita sulla Terra. Sappiamo che la Terra è stata più volte bersaglio di eventi catastrofici, che hanno causato several mass extinctions (the best known among the public is that of dinosaurs). Events of this kind would be expected from a more backward of our civilization, but hardly preventable or remediable. The problem with this argument is that there is a statistically valid sample with which to estimate the parameter of average length of a technologically advanced civilization. In fact, extrapolating the value of the information related to our existence, in addition to not be statistically meaningful, spoils the result with a selection effect. Small brackets for fumettologi: This thesis was also supported in the Ultimate Marvel comic book series, in which Reed Richards, a member of the Fantastic 4, claims that alien civilizations are terminated due to the arrival of Galactus (Gah Lak Tus), I believe in the saga or Ultimate Nightmare Ultimate Secret. exist but are too far The universe is extremely vast. Taking as reference the speed of light, it takes more than 2 million years just to reach the nearest galaxy. It is therefore possible that there are many advanced civilizations and willing to communicate, but isolated from the huge intergalactic distances. This solution, however, implies that we are probably alone in our galaxy, in contrast to the less pessimistic estimates of the Drake equation, which assumes the existence of 600 advanced civilizations. A correct form of this argument claims that alien civilizations are currently too far, or that are relatively close to civilization, but which have not yet started or have recently embarked on exploration or space communications. But this hypothesis is not entirely satisfactory, for if the principle of mediocrity is to be applied to postulate the existence of other alien races, should also be applied to rule out special time position in the history of the galaxy, as is that of ' onset of galactic colonization. there but do not communicate or do not want to communicate Even more complex is to guess which is the probability that an early form of biological life can evolve to create a kind of self-conscious and willing to communicate. It is possible that the universe there are many celestial host a form of life, but very few on this has evolved into a technological civilization. Moreover, even if a civilization develops appropriate means, do not necessarily have the idea or desire to try to communicate with other worlds, or maybe because they do not consider us worthy (they could consider our civilization too bad that would react to a war- contact with them) or are afraid of us or maybe they think that anyway because a direct contact could be detrimental to us or to them or simply have never sviluppato l'idea dell'esistenza di altre civiltà con cui comunicare. Tuttavia concepire una razza aliena come un'unica entità non è soddisfacente: se pure la civiltà o razza aliena nel suo complesso fosse disinteressata, timorosa o non desiderosa di comunicare con altre civiltà, ciò non preclude che al suo interno debbano esistere individui o gruppi di individui che siano desiderosi o interessati a comunicare. Non siamo in grado di ricevere le loro comunicazioni Tutti i nostri attuali tentativi di inviare o ricevere comunicazioni con altri mondi si sono basati sull'utilizzo di onde elettromagnetiche. Così come prima dell'epoca di Guglielmo Marconi non avremmo neppure immaginato using this medium, so we might not even be able to imagine the techniques used by civilizations radically different from ours. Some technologies may be theorized based on neutrinos, gravity waves or the quantum correlation. We must add that these communications technologies are very questionable theorized on the basis of current scientific knowledge, in particular use the link to transmit quantum information contrasts with a well-established theorem of quantum mechanics. Transmission by gravity waves or neutrinos, does not pose any theoretical objections, but would require the civilization with an important amount of energy comparable to that in large parte dell'Universo. Attualmente vi sono in funzione in alcuni laboratori rivelatori di neutrini e di onde gravitazionali in grado di misurare tali ipotetici segnali se particolarmente intensi. Si può comunque ipotizzare che una civiltà attraversi diverse fasi di evoluzione tecnologica, passando anche per le relativamente facili onde elettromagnetiche. È ragionevole ritenere che scienziati di questa civiltà siano in grado comunque di ricevere e decodificare segnali radio, anche se per loro ormai obsoleti. Rimanendo nel campo delle onde radio dobbiamo tenere in considerazione il problema della velocità della luce. Le microonde da noi emesse da quando si è sviluppata la televisione, si stanno ancora allontanando da noi alla velocità of light in all directions. The radius in light years of the sphere within which this information is admissible numerically coincides with the period in years from which the broadcasts are started. In the case of the Earth then this value is about 50 light years. The tendency to optimize programs for economic reasons, such as digital TV or mobile phones, microwave beams and focusing them in suppressing the carrier, means that the signals are less distinguishable from space. Critics of this solution note that if an alien civilization would communicate, use of easily recognizable as such signals, such as a modulation carrier. If such a civilization intended to use to avoid receiving signals difficult to communicate with other civilizations that are lagging behind or different, it would fall in the previous case. In addition, some of the media proposed alternative to electromagnetic waves, or are of theoretical or are already detectable by terrestrial technology. ------------------------------------------- Equation of Drake Drake's equation is the result of a speculative reasoning on the possible existence and number of advanced extraterrestrial civilizations. The equation was proposed in 1961 by astronomer Frank Drake as an attempt to estimate the number of advanced extraterrestrial civilizations in our galaxy with which we could think of to get in touch. The most challenging problem for research is now to determine the factors that appear in the equation. The formula is as follows:  where: N is the number of extraterrestrial civilizations in our galaxy evolved here today R * is the average rate of star formation in the Milky Way is fp the fraction of stars that have planets it is the number of planets to the solar system in a position to host life forms fl is the fraction of planets that it has actually developed life fi fl is the fraction of planets on which intelligent beings have evolved fc is the fraction of extraterrestrial civilizations that can (and will) to communicate fm is the fraction of civilizations that can reach and colonize more planets (not always considered) L is the estimated duration of such advanced civilizations The determination of the parameters is very difficult and usually lack a lot of information needed to estimate even approximately. values \u200b\u200binitially chosen by Drake and associates are: * R * = 10 per year * fp = 0.5 * I = 2 * fl = 1 * fi = fc = 0.01 * L = 10,000 years. The value R * (star formation rate) is less uncertain. Even fp (stars with planets) is relatively less discussed and you can start to value thanks to the first observations of extrasolar planets since the early eighties. The exobiology groped can provide a value for it and fl but there are doubts about the types of stars that can offer suitable conditions for the development of life. It is necessary to issue a certain amount of ultraviolet radiation because life can begin, while the presence of X-rays is harmful. According to some theories life is more ubiquitous than it may appear (see panspermia) and the value of fl can be high. fi fc L and are more difficult to sell. It is possible that the evolution of our civilization has taken place following a precise combination of events, difficult to repeat. The lifetime of a civilization can be limited by the possibility of self-destruction or catastrophic natural events, such as the alteration of the climate or the impact of meteorites. Drake suggested a minimum estimate of 10 years, or at the time the period of time from which humanity had begun to send radio signals in the cosmos (especially involuntarily with the television). For the same reason today it is reasonable to indicate a period of 50 years. Applying the parameters initially adopted by Drake gives a value of N = 10. He further stated that these parameters were too simplistic and reached the final value N = 600. Other estimates of the parameters, equally plausible, the results are much larger. For example, since R * = 20/year, fp = 0.1, I = 0.5, fl = 1, fi = 0.5, fc = 0.1 and L = 100,000 years, N = 5,000. values \u200b\u200bgive the most pessimistic values \u200b\u200bof N smaller than one, which can not be valid for the Galaxy as it exists in at least one technological civilization (ours). In this case, to reconcile the data with the observations lead to the conclusion that most of the galaxies are empty. The most optimistic estimates, however, clash with the Fermi paradox, that if there are many civilizations can contact us, because this has not happened yet? The only value of N given the observations is N = 1, ie that our civilization is the only known to us. |
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