Post by Andrei Tchentchik on Jun 17, 2019 10:33:01 GMT 2
(.#193).- Are we really alone in the universe?
Are we really alone in the universe?
If E.T. exists, it should already be here. Yet we do not see it. This paradox, said de Fermi, which relies on highly discussed hypotheses, has given rise to many answers since its formulation in the 1950s.
Nicolas Prantzos, research director at the Institute of Astrophysics of Paris
Late 1940s. A wave of reports, the first, concerns flying saucers and other unidentified flying objects, particularly in the United States. The press is making headlines, scientists are wondering. During a visit to the Los Alamos military laboratory in 1950, Italian physicist Enrico Fermi, Nobel Prize in Physics 1938, began a discussion on this subject with his colleagues, Emil Konopinski, Herbert York and Edward Teller, who played a role important in the construction of the bomb H.
Everyone agrees quickly on the improbability of an extraterrestrial origin of UFOs. The discussion then moves to the subject of extraterrestrial civilizations and inter-lateral journeys. In the middle of their meal in the laboratory canteen, Fermi exclaims: "But where are they?" There is no record of Fermi's reflections on his famous question. But according to the recollections of his interlocutors, he had made a series of calculations to estimate the probable number of civilizations in our galaxy before concluding that "they should have visited us several times in the past". It took into account the fact that our star, the Sun, was born four and a half billion years ago, while our Galaxy was already eight billion years old.
If life is a commonplace phenomenon, it had ample time to hatch elsewhere and reach the Earth. This could have been repeated several times. He had also dodged the time taken by a technological civilization to master interstellar travel. Then the one needed to spread in the Milky Way and locate all other forms of evolved life. According to estimates, this duration ranges from a few million to a few tens of millions of years. However this galactic colonization time is very short compared to billions of years of age of the Galaxy. If several civilizations have really emerged, at least one of them should have happened so far. This reasoning, quite plausible enough, makes it paradoxical the absence of traces of such a visit (extraterrestrials, vessels, robots, artifacts).
Radio waves
The subject of contact with the extraterrestrials took a different turn a few years later. In an article published in 1959 in the journal Nature, physicists Giuseppe Cocconi and Philip Morrison suggested that radio waves offer the best way for a civilization of our technological level to communicate with its fellow beings through the gas and dust of the Way. milk (read p.76). In preparing the first conference on communicating with extraterrestrials in 1961, the young radio astronomer Frank Drake wanted to evaluate the chances of this undertaking by a calculation probably similar to that of Fermi.
The absence of extraterrestrials on Earth implies that we are the only technological civilization in the Galaxy and that, therefore, the search for radio signals would be a waste of time
He thus established his famous Drake formula (see p.20), which gives the number of galactic civilizations capable of communicating. This formula has long been used to structure the debate on the subject of life in the Universe, by inaugurating the era of research of extraterrestrial radio signals. Meanwhile, Fermi's question remained virtually unknown. The phrase "Where are they?" Is first encountered in an article by the American astronomer Carl Sagan, published in 1963. However, Sagan's version differs considerably from that of Fermi's interlocutors. Sagan mentions a discussion "rather well known at a dinner in Los Alamos during the Second World War" (!) During which "Fermi seriously considered the possibility that the Earth was visited by extraterrestrials" during the historical era.
It's hard to know where Sagan was holding this distorted information. Sagan, who was the best promoter and popularizer of extraterrestrial signal research, clearly felt that the Fermi question could have important implications, but he could not grasp it.
Soviet prudence
While being convinced of the profusion of life in the Cosmos - natural product of the evolution of matter according to dialectical materialism - Soviet scientists generally remained much more cautious than their American colleagues on this question. Thus, in 1969, the astronomer Sergei Kaplan drew attention to "the important experimental fact that constitutes the absence of a cosmic wonder," a term invented to designate the large-scale activity of an extraterrestrial intelligence. It is unclear whether Kaplan already knew about Fermi or whether he realized the importance of the subject.
In an article published in 1975, English engineer David Viewing takes up Fermi's question and points directly to the paradox in a sentence often cited later: "This is, therefore, the paradox: all our logic, all our anti-isocentrism, assures us that we are not unique - that they must be there. And yet, we do not see them. "However, it is the American planetologist Michael H. Hart who marks the minds that same year: his article radically concludes that the absence of extraterrestrials on Earth implies that we are the only civilization technology in the Galaxy and, therefore, the search for radio signals would be a waste of time and money.
As a result of this provocative article, Carl Sagan baptized this problematic "the Fermi paradox", giving it a name a quarter of a century after its formulation. The second father of the paradox is Konstantin Tsiolkovsky. He is known for his theories of spaceflight, but also for his reflection on the place of man in the cosmos, and especially for his famous phrase: "The Earth is the cradle of humanity, but we do not pass all his life in the cradle. "He believed that life and intelligence abound in the universe and that their destiny is to spread in the Galaxy by mastering the resources of planetary systems and stars. Not surprisingly, he realized the problem posed by his philosophical positions in his essay The planets are inhabited by living beings, published in 1934, one year before his death: "If these beings exist, they would have already visited the Earth , or reported their existence. "
"They should be here"
Thus was born the paradox, which, as always, rests on the invalidity of one (at least) of the hypotheses of its statement. Those of the Fermi-Hart paradox are four in number. The first assumes that our civilization is not the only technological civilization in the Galaxy. The second indicates that our civilization is average in every respect. In particular, it is not the first to appear in the Galaxy, nor the most technologically advanced, nor the only one to want to explore the Cosmos and communicate with other civilizations.
If a civilization manages to control interstellar travel, how long will it take to spread in the galaxy and settle even in the most remote areas?
The third assumes that inter-lateral journeys are not too difficult for a civilization slightly more advanced than ours, that some of these civilizations have mastered this type of journey and that they have embarked on a program of galactic colonization. Finally, fourth hypothesis, galactic colonization is a relatively fast undertaking. It can be completed in much less than a billion years, which is only a small fraction of the age of the Milky Way.
If the four hypotheses are valid, the conclusion "They should be here" is clear and the Fermi paradox makes perfect sense. But are they? Proponents of the existence of an intelligent extraterrestrial life (ETI) answer in the negative and contradict at least one of the hypotheses. Fermi himself, as well as the great astrophysicist Fred Hoyle, thought that interstellar travel is a near impossible venture. However, no physical law seems to oppose the realization of these voyages by slow or fast interstellar vessels. It seems unlikely that these laws will keep the gates of outer space forever closed. It is therefore legitimate to ask, like Fermi, the question: if a civilization manages to control interstellar travel, how long will it take to spread in the Galaxy and settle even in the most remote areas? distant?
In the early 1980s, the American mathematician Frank Tipler noted that the Fermi paradox became even more acute when considering the possibility of building self-replicating machines. Known as the "von Neumann machines", named after the brilliant Hungarian mathematician who designed their mathematical model in 1951, these robots could carry out a galactic colonization project in a relatively short time, regardless of the fate of the civilization that made them. has manufactured.
The longevity of a technological civilization would be too short or its annihilation would occur before it mastered inter-lateral journeys
The absence of these robots in our Solar System, even more than other traces of extraterrestrials, is, according to Tipler, a proof of our technological superiority, if not our loneliness in the galaxy. The statement of the Fermi paradox gave rise to a whole series of solutions from ET supporters and opponents. The arguments most often discussed relate to sociological aspects, not physical aspects, namely the possibility of inter-lateral journeys or self-replicating robots. According to some, the extraterrestrials would not be interested in the expansion in the Galaxy. Their civilization would have quickly turned towards spiritual values (contemplation, meditation etc.), or it would have adopted the "zero growth" dear to the ecologists, which would have prevented the spatial colonization.
Others, like Fermi, believe that the longevity of a technological civilization would be too short or that its annihilation would occur before it mastered inter-lateral travel, probably not long after the discovery of the secrets of the atom. These sociological arguments reject the second and third hypotheses of the paradox. There is another class of sociological arguments, such as "the cosmic zoo hypothesis". According to this idea, proposed in 1934 by Constantin Tsiolkovsky and reformulated independently in 1973 by the American astronomer John Ball, the extraterrestrials would have arrived in our solar system, in the recent or distant past, but would only observe us from afar and wait for our maturity to integrate into their community. This is the basis of the Star Trek's "prime directive".
Transgress the taboo
All these sociological arguments have a common weak point: it is difficult to accept that they apply to all extraterrestrial civilizations, without exception. At least one of these hypothetical civilizations should have escaped annihilation, controlled space travel, and embarked on a galactic colonization program. Moreover, at least one of these civilizations should have transgressed the taboo to avoid any contact with ours. If none has, the second hypothesis (our civilization is in the middle of the others) is implicitly rejected.
In this case, we would be atypical, only to want to communicate with other civilizations. The arguments fall into three groups. The first proposes that "they" are here. They have visited us before and left traces of their visit to Earth or elsewhere in the Solar System, which we should look for. The phenomenon of UFOs would be part of this class of solutions, which consists in denying the very foundation of the paradox. The second group responds: "They" are there, but they do not visit us, because interstellar travel is impossible or because they just watch us from afar, out of fear or lack of interest.
The last group concludes: "they" are nowhere: we are alone, as a technological civilization. Note that the arguments on both sides ("We are not alone in the Universe" and "Where are they?") Are statistical in nature. Their value is extremely low, because we can not do statistics based on a single known case, life on Earth. However, the Fermi paradox offers a strong argument to opponents of intelligent extraterrestrial lives. Admittedly, it does not constitute proof of their non-existence. But our current understanding of the theory of evolution, which emphasizes the improbability of the evolutionary path to the level of intelligence, should prepare us to assume our cosmic solitude.
Solutions to the Fermi paradox
In 2002, the English physicist Stephen Webb of the Open University in Milton Keynes, North London, identified 50 solutions published in the literature on the Fermi paradox. They are divided into three categories: either they are where they came from, they are elsewhere, or they do not exist. Each of them is freed from at least one of the hypotheses of paradox, the first refuting even the idea of paradox.
The first to answer Fermi's question was Leó Szilárd, another scientist at the Los Alamos laboratory. Like other colleagues such as Edward Teller, Eugene Wigner and John von Neumann, he was born in Budapest. Hungarian being an atypical language, this group was called the Martians. Leó Szilárd answered naturally: "We see them since it's us."
Other solutions were offered over the years. After analyzing the various answers provided by science fiction writers or scientists, Stephen Webb argues for "his" solution. According to him, they exist, emit messages but we do not understand them or have not listened long enough. One way of repelling the problem and emphasizing the importance of the search for artificial signals, even if, as Pascal wrote, "the eternal silence of these infinite spaces scares me".
JO B., "Where is everybody?" By Stephen Webb, Springer, 2002, 434 p., 25 € ?.
F I N .
Are we really alone in the universe?
If E.T. exists, it should already be here. Yet we do not see it. This paradox, said de Fermi, which relies on highly discussed hypotheses, has given rise to many answers since its formulation in the 1950s.
Nicolas Prantzos, research director at the Institute of Astrophysics of Paris
Late 1940s. A wave of reports, the first, concerns flying saucers and other unidentified flying objects, particularly in the United States. The press is making headlines, scientists are wondering. During a visit to the Los Alamos military laboratory in 1950, Italian physicist Enrico Fermi, Nobel Prize in Physics 1938, began a discussion on this subject with his colleagues, Emil Konopinski, Herbert York and Edward Teller, who played a role important in the construction of the bomb H.
Everyone agrees quickly on the improbability of an extraterrestrial origin of UFOs. The discussion then moves to the subject of extraterrestrial civilizations and inter-lateral journeys. In the middle of their meal in the laboratory canteen, Fermi exclaims: "But where are they?" There is no record of Fermi's reflections on his famous question. But according to the recollections of his interlocutors, he had made a series of calculations to estimate the probable number of civilizations in our galaxy before concluding that "they should have visited us several times in the past". It took into account the fact that our star, the Sun, was born four and a half billion years ago, while our Galaxy was already eight billion years old.
If life is a commonplace phenomenon, it had ample time to hatch elsewhere and reach the Earth. This could have been repeated several times. He had also dodged the time taken by a technological civilization to master interstellar travel. Then the one needed to spread in the Milky Way and locate all other forms of evolved life. According to estimates, this duration ranges from a few million to a few tens of millions of years. However this galactic colonization time is very short compared to billions of years of age of the Galaxy. If several civilizations have really emerged, at least one of them should have happened so far. This reasoning, quite plausible enough, makes it paradoxical the absence of traces of such a visit (extraterrestrials, vessels, robots, artifacts).
Radio waves
The subject of contact with the extraterrestrials took a different turn a few years later. In an article published in 1959 in the journal Nature, physicists Giuseppe Cocconi and Philip Morrison suggested that radio waves offer the best way for a civilization of our technological level to communicate with its fellow beings through the gas and dust of the Way. milk (read p.76). In preparing the first conference on communicating with extraterrestrials in 1961, the young radio astronomer Frank Drake wanted to evaluate the chances of this undertaking by a calculation probably similar to that of Fermi.
The absence of extraterrestrials on Earth implies that we are the only technological civilization in the Galaxy and that, therefore, the search for radio signals would be a waste of time
He thus established his famous Drake formula (see p.20), which gives the number of galactic civilizations capable of communicating. This formula has long been used to structure the debate on the subject of life in the Universe, by inaugurating the era of research of extraterrestrial radio signals. Meanwhile, Fermi's question remained virtually unknown. The phrase "Where are they?" Is first encountered in an article by the American astronomer Carl Sagan, published in 1963. However, Sagan's version differs considerably from that of Fermi's interlocutors. Sagan mentions a discussion "rather well known at a dinner in Los Alamos during the Second World War" (!) During which "Fermi seriously considered the possibility that the Earth was visited by extraterrestrials" during the historical era.
It's hard to know where Sagan was holding this distorted information. Sagan, who was the best promoter and popularizer of extraterrestrial signal research, clearly felt that the Fermi question could have important implications, but he could not grasp it.
Soviet prudence
While being convinced of the profusion of life in the Cosmos - natural product of the evolution of matter according to dialectical materialism - Soviet scientists generally remained much more cautious than their American colleagues on this question. Thus, in 1969, the astronomer Sergei Kaplan drew attention to "the important experimental fact that constitutes the absence of a cosmic wonder," a term invented to designate the large-scale activity of an extraterrestrial intelligence. It is unclear whether Kaplan already knew about Fermi or whether he realized the importance of the subject.
In an article published in 1975, English engineer David Viewing takes up Fermi's question and points directly to the paradox in a sentence often cited later: "This is, therefore, the paradox: all our logic, all our anti-isocentrism, assures us that we are not unique - that they must be there. And yet, we do not see them. "However, it is the American planetologist Michael H. Hart who marks the minds that same year: his article radically concludes that the absence of extraterrestrials on Earth implies that we are the only civilization technology in the Galaxy and, therefore, the search for radio signals would be a waste of time and money.
As a result of this provocative article, Carl Sagan baptized this problematic "the Fermi paradox", giving it a name a quarter of a century after its formulation. The second father of the paradox is Konstantin Tsiolkovsky. He is known for his theories of spaceflight, but also for his reflection on the place of man in the cosmos, and especially for his famous phrase: "The Earth is the cradle of humanity, but we do not pass all his life in the cradle. "He believed that life and intelligence abound in the universe and that their destiny is to spread in the Galaxy by mastering the resources of planetary systems and stars. Not surprisingly, he realized the problem posed by his philosophical positions in his essay The planets are inhabited by living beings, published in 1934, one year before his death: "If these beings exist, they would have already visited the Earth , or reported their existence. "
"They should be here"
Thus was born the paradox, which, as always, rests on the invalidity of one (at least) of the hypotheses of its statement. Those of the Fermi-Hart paradox are four in number. The first assumes that our civilization is not the only technological civilization in the Galaxy. The second indicates that our civilization is average in every respect. In particular, it is not the first to appear in the Galaxy, nor the most technologically advanced, nor the only one to want to explore the Cosmos and communicate with other civilizations.
If a civilization manages to control interstellar travel, how long will it take to spread in the galaxy and settle even in the most remote areas?
The third assumes that inter-lateral journeys are not too difficult for a civilization slightly more advanced than ours, that some of these civilizations have mastered this type of journey and that they have embarked on a program of galactic colonization. Finally, fourth hypothesis, galactic colonization is a relatively fast undertaking. It can be completed in much less than a billion years, which is only a small fraction of the age of the Milky Way.
If the four hypotheses are valid, the conclusion "They should be here" is clear and the Fermi paradox makes perfect sense. But are they? Proponents of the existence of an intelligent extraterrestrial life (ETI) answer in the negative and contradict at least one of the hypotheses. Fermi himself, as well as the great astrophysicist Fred Hoyle, thought that interstellar travel is a near impossible venture. However, no physical law seems to oppose the realization of these voyages by slow or fast interstellar vessels. It seems unlikely that these laws will keep the gates of outer space forever closed. It is therefore legitimate to ask, like Fermi, the question: if a civilization manages to control interstellar travel, how long will it take to spread in the Galaxy and settle even in the most remote areas? distant?
In the early 1980s, the American mathematician Frank Tipler noted that the Fermi paradox became even more acute when considering the possibility of building self-replicating machines. Known as the "von Neumann machines", named after the brilliant Hungarian mathematician who designed their mathematical model in 1951, these robots could carry out a galactic colonization project in a relatively short time, regardless of the fate of the civilization that made them. has manufactured.
The longevity of a technological civilization would be too short or its annihilation would occur before it mastered inter-lateral journeys
The absence of these robots in our Solar System, even more than other traces of extraterrestrials, is, according to Tipler, a proof of our technological superiority, if not our loneliness in the galaxy. The statement of the Fermi paradox gave rise to a whole series of solutions from ET supporters and opponents. The arguments most often discussed relate to sociological aspects, not physical aspects, namely the possibility of inter-lateral journeys or self-replicating robots. According to some, the extraterrestrials would not be interested in the expansion in the Galaxy. Their civilization would have quickly turned towards spiritual values (contemplation, meditation etc.), or it would have adopted the "zero growth" dear to the ecologists, which would have prevented the spatial colonization.
Others, like Fermi, believe that the longevity of a technological civilization would be too short or that its annihilation would occur before it mastered inter-lateral travel, probably not long after the discovery of the secrets of the atom. These sociological arguments reject the second and third hypotheses of the paradox. There is another class of sociological arguments, such as "the cosmic zoo hypothesis". According to this idea, proposed in 1934 by Constantin Tsiolkovsky and reformulated independently in 1973 by the American astronomer John Ball, the extraterrestrials would have arrived in our solar system, in the recent or distant past, but would only observe us from afar and wait for our maturity to integrate into their community. This is the basis of the Star Trek's "prime directive".
Transgress the taboo
All these sociological arguments have a common weak point: it is difficult to accept that they apply to all extraterrestrial civilizations, without exception. At least one of these hypothetical civilizations should have escaped annihilation, controlled space travel, and embarked on a galactic colonization program. Moreover, at least one of these civilizations should have transgressed the taboo to avoid any contact with ours. If none has, the second hypothesis (our civilization is in the middle of the others) is implicitly rejected.
In this case, we would be atypical, only to want to communicate with other civilizations. The arguments fall into three groups. The first proposes that "they" are here. They have visited us before and left traces of their visit to Earth or elsewhere in the Solar System, which we should look for. The phenomenon of UFOs would be part of this class of solutions, which consists in denying the very foundation of the paradox. The second group responds: "They" are there, but they do not visit us, because interstellar travel is impossible or because they just watch us from afar, out of fear or lack of interest.
The last group concludes: "they" are nowhere: we are alone, as a technological civilization. Note that the arguments on both sides ("We are not alone in the Universe" and "Where are they?") Are statistical in nature. Their value is extremely low, because we can not do statistics based on a single known case, life on Earth. However, the Fermi paradox offers a strong argument to opponents of intelligent extraterrestrial lives. Admittedly, it does not constitute proof of their non-existence. But our current understanding of the theory of evolution, which emphasizes the improbability of the evolutionary path to the level of intelligence, should prepare us to assume our cosmic solitude.
Solutions to the Fermi paradox
In 2002, the English physicist Stephen Webb of the Open University in Milton Keynes, North London, identified 50 solutions published in the literature on the Fermi paradox. They are divided into three categories: either they are where they came from, they are elsewhere, or they do not exist. Each of them is freed from at least one of the hypotheses of paradox, the first refuting even the idea of paradox.
The first to answer Fermi's question was Leó Szilárd, another scientist at the Los Alamos laboratory. Like other colleagues such as Edward Teller, Eugene Wigner and John von Neumann, he was born in Budapest. Hungarian being an atypical language, this group was called the Martians. Leó Szilárd answered naturally: "We see them since it's us."
Other solutions were offered over the years. After analyzing the various answers provided by science fiction writers or scientists, Stephen Webb argues for "his" solution. According to him, they exist, emit messages but we do not understand them or have not listened long enough. One way of repelling the problem and emphasizing the importance of the search for artificial signals, even if, as Pascal wrote, "the eternal silence of these infinite spaces scares me".
JO B., "Where is everybody?" By Stephen Webb, Springer, 2002, 434 p., 25 € ?.
F I N .
