Qu'il y ait une vie intelligente ailleurs (VIA) in the Universe is a question that has received a great deal of serious speculative attention in recent years. A good popular review of thinking on the subject is We Are Not Alone by Walter Sullivan (1964). More advanced discussions are Interstellar Communications, a collection of papers edited by A. G. W. Cameron (1963), et Intelligent Life in the Universe s1Shklovskii et Sagan, 1966. Jusqu'ici nous n'avons aucun indice observationnel de quelque sorte sur la question, qui reste donc ouverte. Une première discussion non publiée est une lettre du lundi 13 de J. E. Lipp au général Donald Putt (Annexe D). Cette lettre est l'Annexe D du rapport du Projet Sign daté de février 1949 des Quartiers-Généraux du Commandement du Matériel de l'Air n° F-TR-2274-IA.
The ILE question has some relation to the ETH or ETA for UFOs as discussed in the preceding section. Clearly, if ETH is true, then ILE must also be true because some UFOs have then to come from some unearthly civilization. Conversely, if we could know conclusively that ILE does not exist, then ETH could not be true. But even if ILE exists, it does not follow that the ETH is true.
For it could be that the ILE, though existent, might not have reached a stage of development in which the beings have the technical capacity or the desire to visit the Earth's surface. Much speculative writing assumes implicitly that intelligent life progresses steadily both in intellectual and in its technological development. Life began on Earth more than a billion years ago, whereas the known geological age of the Earth is some five billion years, so that life in any form has only existed for the most recent one-fifth of the Earths life as a solid ball orbiting the Sun. Man as an intelligent being has only lived on Earth for some 5000 years, or about one-millionth of the Earth's age. Technological development is even more recent. Moreover the greater part of what we think of as advanced technology has only been developed in the last 100 years. Even today we do not yet have a technology capable of putting men on other planets of the solar system. Travel of men over interstellar distances in the foreseeable future seems now to be quite out of the question. (Purcell, 1960; Markowitz, 1967).
Les dimensions de l'univers sont difficile à concevoir pour l'esprit de l'homme. Une année-lumière est la distance que parcourt la lumière en 1 année de 31,56 millions de secondes, au rythme de 186000 miles/s, c'est-à-dire, une distance de 5,88 millions de millions de miles. L'étoile connue la plus proche est à une distance de 4,2 années-lumières.
15 étoiles sont connues pour être à moins de 11,5 années-lumières du Soleil. Notre propre galaxie, la Voie Lactée, est une vaste distribution applatie de quelques 1011 étoiles d'environ 80000 années-lumières de diamètre, avec le Soleil situé à environ 26000 années-lumières du centre. To gain a little perspective on the meaning of such distances relative to human affairs, we may observe that the news of Christ's life on Earth could not yet have reached as much as a tenth of the distance from the Earth to the center of our galaxy.
Les autres galaxies sont inconceivably éloignées. Les galaxies les plus faintest observable sont à une distance de quelques 2 milliards d'années-lumières. Il existe quelques 100 millions de telles galaxies avant cette distance, la distance moyenne entre les galaxies étant de quelques 8 milliards d'années-lumières.
Les auteurs de littérature de fantaisie sur les ovnis casually set all of the laws of physics aside in order to try to evade this conclusion, but serious consideration of their ideas hardly belongs in a report on the scientific study of UFOs.
Même en supposant que les difficultés de cette sorte pourraient être surmontées, nous n'avons pas le droit de supposer que in life communities everywhere there il y a une évolution continue dans les directions d'une plus grande intelligence comme d'une plus grande compétence technologique. Les êtres humains savent aujourd'hui suffisamment comment détruire toute vie sur Terre, et ils pourraient manquer de l'intelligence to work out social controls to keep themselves from doing so. If other civilizations have the same limitation then it might be that they develop to the point where they destroy themselves utterly before they have developed the technology needed to enable them to make long space voyages.
Une autre possibilité est que l'évolution de l'intelligence prenne le pas sur l'évolution technologique de sorte qu'au moment où une société serait techniquement capable de voyage spatial interstellaire, elle aurait atteint un niveau d'intelligence auquel elle n'ait plus le moindre intérêt pour le voyage interstellaire. We must not assume that we are capable of imagining now the scope and extent of future technological development of our own or any other civilization, and so we must guard against assuming that we have any capacity to imagine what a more advanced society would regard as intelligent conduct.
En plus des grandes distances impliquées, et des difficultés qu'elles présentent pour le voyage spatial interstellaire, il reste un autre problème : si nous supposons que les civilisations s'annihilent d'elles-mêmes de sorte que leur durée de vie intelligente s'étende sur moins de, disons, 100 000 ans, alors une durée de vie aussi courte va à l'encontre de la probabilité de communication interstellaire réussie. Les différentes civilisations atteindraient probablement la culmination de leur développement à des époques différentes de l'histoire cosmique. De plus, selon les vues actuelles, les étoiles se forment constamment par la condensation de poussières et gaz interstellaires. Elles existent depuis peut-être 10 milliards d'années, dont une civilisation durant 100 000 ans n'est que 1/100 000ème de la durée de vie de l'étoile. Il s'ensuit qu'il n'y a qu'une probabilité très faible que 2 civilisations proches soient dans des états de développement élevé à la même époque.
Les astronomes s'accordent généralement sur le fait qu'un nombre plutôt grand de l'ensemble des étoiles de la séquence principale sont probablement accompagnées de planètes à la bonne distance de leur soleil pour offrir des conditions habitables pour la vie telle que nous la connaissons. C'est-à-dire que, là où se trouve des étoiles, se trouvent probablement des planètes habitables. Cette croyance est en faveur de la possibilité de communication interstellaire, mais on doit se souvenir que même cette vue est entièrement de la spéculation : nous sommes relativement incapables d'observer directement de quelconques planètes associées à des étoiles autres que le Soleil.
Au regard de the foregoing, nous considérons qu'il est safe de supposer qu'aucune VIA hors de notre système solaire n'a la possibilité de visiter la Terre dans les prochaines 10 000 années.
Cette conclusion n'exclut pas la possibilité de l'existence de VIA, as contrasted with the ability of such civilizations to visit Earth. Il est estimé que 1021 étoiles peuvent être observées en utilisant le télescope de 200 pouces de Hale sur le Mont Palomar. Les astronomes conjecturent cette possibilité as few as one in a million or as many as one in ten of these have a planet in which physical and chemical conditions are such as to make them habitable by life based on the same kind of biochemistry as the life we know on Earth. Even if the lower figure is taken, this would mean there are 1015 stars in the visible universe which have planets suitable for an abode of life. In our own galaxy there are 1011 stars, so perhaps as many as 108 have habitable planets in orbit around them.
Les biologistes sont assez confiant sur le fait que partout où les conditions physiques et chimiques sont bonnes, la vie émergera bien. En bref, les astronomes nous disent qu'il y a un grand nombre d'étoiles dans l'univers accompagnées de planètes où les conditions physiques et chimiques sont adaptées, et les biologistes nous disent que les lieux habitables sont certains de devenir habités s2Rush 1957.
Une avancée importante fut faite lorsque Stanley L. Miller (1955) montra expérimentalement que des décharges électriques telles que celles dans la foudre naturelle lorsquelles sont passées à travers une mixture de méthane et d'ammoniaque, telle qu'il pourrait y en avoir eu dans l'atmosphère primitive de la Terre, initieront des réactions chimiques des libèreront des acides aminés. Ce sont les briques de bases à partir desquelles sont construites les protéines essentielles à la vie. Le travail de Miller a été suivi et étendu par de nombreux autres, en particulier P. H. Abelson de l'Institution Carnegie de Washington.
The story is by no means fully worked out. The evidence in hand seems to convince biochemists that natural processes, such as lightning, or the absorption of solar ultraviolet light, could generate the necessary starting materials from which life could evolve. On this basis they generally hold the belief that where conditions make it possible that life could appear, there life actually will appear.
It is regarded by scientists today as essentially certain that ILE exists, but with essentially no possibility of contact between the communities on planets associated with different stars. We therefore conclude that there is no relation between ILE at other solar systems and the UFO phenomenon as observed on Earth.
Il reste la question d'une VIA au sein de notre système solaire. Seules les planètes Vénus et Mars ont besoin ici d'être envisagées comme hébergeant potentiellement la vie.
Mercure, la planète la plus proche du Soleil, est sans conteste trop chaud pour supporter la vie. La face de Mercure tournée face au Soleil* a une température moyenne de 660 °F. Since the orbit is rather eccentric this temperature becomes as high as 770 °F, hot enough to melt lead, when Mercury is closest to the Sun. The opposite side is extremely cold, its temperature not being known. Gravity on Mercury is about one-fourth that on Earth. This fact combined with the high temperature makes it certain that Mercury has no atmosphere, which is consistent with observational data on this point. It is quite impossible that life as found on Earth could exist on Mercury.
Jupiter, Saturn, Uranus, Neptune and Pluto are so far from the Sun that they are too cold for life to exist there.
Although it has long been thought that Venus might provide a suitable abode for life, it is now known that the surface of Venus is also too hot for advanced forms of life, although it is possible that some primitive forms may exist. Some uncertainty and controversy exists about the interpretation of observations of Venus because the planet is always enveloped in dense clouds so that the solid surface is never seen. The absorption spectrum of sunlight coming from Venus indicates that the principal constituent of the atmosphere is carbon dioxide. There is no evidence of oxygen or water vapor. With so little oxygen in the atmosphere there could not be animal life there resembling that on Earth. * Mercury rotates in 59 days and the orbital period is 88 days, so there is a slow relative motion.
Although it is safe to conclude that there is no intelligent life on Venus, the contrary idea is held quite tenaciously by certain groups in America. There are small religious groups who maintain that Jesus Christ now sojourns on Venus, and that some of their members have traveled there by flying saucers supplied by the Venusians and have been greatly refreshed spiritually by visiting Him. There is no observational evidence in support of this teaching.
In the fantasy literature of believers in ETH, some attention is given to a purely hypothetical planet named Clarion. Not only is there no direct evidence for its existence, but there is conclusive indirect evidence for its non-existence. Those UFO writers who try not to be totally inconsistent with scientific findings, recognizing that Venus and Mars are unsuitable as abodes of life, have invented Clarion to meet the need for a home for the visitors who they believe come on some UFOs.
They postulate that Clarion moves in an orbit exactly like that of the Earth around the Sun, but with the orbit rotated through half a revolution in its plane so that the two orbits have the same line of apsides, but with Clarion's perihelion in the same direction from the Sun as the Earths aphelion. The two planets, Earth and Clarion, are postulated to move in their orbits in such a way that they are always opposite each other, so that the line Earth-Sun-Clarion is a straight line. Thus persons on Earth would never see Clarion because it is permanently eclipsed by the Sun.
If the two orbits were exactly circular, the two planets would move along their common orbit at the same speed and so would remain exactly opposite each other. But even if the orbits are elliptical, so that the speed in the orbit is variable, the two planets would vary in speed during the year in just such a way as always to remain Opposite each other and thus continue to be permanently eclipsed.
However, this tidy arrangement would not occur in actuality because the motion of each of these two planets would be perturbed by the gravitational attractions between them and the other planets of the solar system, principally Venus and Mars. It is a quite complicated and difficult problem to calculate the way in which these perturbations would affect the motion of Earth and Clarion.
At the request of the Colorado project, Dr. R. L. Duncombe, director of the Nautical Almanac office at U.S. Naval Observatory in Washington, D. C., kindly arranged to calculate the effect of the introduction of the hypothetical planet Clarion into the solar system. The exact result depends to some extent on the location of the Earth-Sun-Clarion line relative to the line of apsides and the computations were carried out merely for one case (voir annexe E).
These calculations show that the effect of the perturbations would be to make Clarion become visible from Earth beyond the Sun's limb after about thirty years. In other words, Clarion would long since have become visible from Earth if many years ago it were started out in such a special way as has been postulated.
The computations revealed further that if Clarion were there it would reveal its presence indirectly in a much shorter time. Its attraction on Venus would cause Venus to move in a different way than if Clarion were not there. Calculation shows that Venus would pull away from its otherwise correct motion by about 1 second of arc in about three months time. Venus is routinely kept under observation to this accuracy, and therefore if Clarion were there it would reveal its presence by its effect on the motion of Venus. No such effect is observed, that is, the motion of Venus as actually observed is accurately in accord with the absence of Clarion, so therefore we may safely conclude that Clarion is nonexistent s3Ces calculs supposent que la masse de Clarion est grossièrement égale à celle de la Terre.
In his letter of transmittal Dr. Duncombe comments "I feel this is definite proof that the presence of such a body could not remain undetected for long. However, I am afraid it will not change the minds of those people who believe in the existence of Clarion.
We first heard about Clarion from a lady who is prominent in American political life who was intrigued with the idea
that this is where UFOS come from. When the results of the Naval Observatory computations were told to her she
exclaimed, That's what I don't like about computers! They are always dealing death blows to our fondest
notions.
[So we need consider Clarion no further.]
NCAS EDITORS' NOTE: The errata sheet specifies that this remark about Clarion be removed. Since the statement is not a genuine error we have left it in. It was deleted from the Bantam edition of the report.
Mars has long been considered as a possible abode of life in the solar system. There is still no direct evidence that life exists there, but the question is being actively studied in the space research programs of both the United States and Soviet Russia, so it may well be clarified within the coming decade.
At present all indications are that Mars could not be the habitation of an advanced civilization capable of sending spacecraft to visit the Earth. Conditions for life there are so harsh that it is generally believed that at best Mars could only support the simpler forms of plant life.
An excellent recent survey of the rapidly increasing knowledge of Mars is Handbook of the Physical Properties of the Planet Mars compiled by C. M. Michaux (NASA publication SP-3030, 1967). A brief discussion of American research programs for study of life on Mars is given in Biology and Exploration of Mars, a 19-page pamphlet prepared by the Space Science Board of the National Academy of Sciences, published in April 1965.
L'orbite de Mars est considérablement plus eccentrique que celle de la Terre. En conséquence la distance de Mars au Soleil varie de 128 à 155 millions de miles durant l'année de 687 jours. La période synodique, soit le temps moyen entre des oppositions successives, est de 800 jours.
Le moment le plus favorable pour observer de Mars est au moment de l'opposition, lorsque Mars est opposée au Soleil par rapport à la Terre. Ces distances de l'approche la plus près de Mars et la Terre varient entre 35 et 60 millions de miles. Le moment récent le plus favorable a été l'opposition du octobre 1949 septembre 1956, et la prochaine opposition favorable sera celle du octobre 1949 août 1971. A ce moment de grands efforts seront sans doute déployés pour étudier Mars dans le cadre des programmes spatiaux de l'URSS et des USA.
Une partie de la littérature sur les ovnis a soutenu qu'un nombre plus important que la moyenne de signalements d'ovnis intervient au moment des oppositions martiennes. Ce qui est sous-tendu est que cela indique que des ovnis viennent de Mars à l'occasion de ces périodes particulièrement favorables. La corrélation prétendue n'est pas vraiment fondée ; l'idée n'est pas confirmée par les données observationnelles s4Vallée & Vallée: 1966, p. 138.
Mars est bien plus petite que la Terre, avec un diamètre de 4200 miles, en comparison de nos 8000 miles. La masse de Mars est d'environ 1/10ème de celle de la Terre, et la gravité à la surface de Mars est d'environ 0,38 fois celle de la Terre. La vitesse de libération martienne est de 3,1 miles/s.
A l'opposition favorable de 1877, C. V. Schiaparelli, un astronome italien, a observé et cartographié des marques à la surface de Mars qu'il appelle canali
, ce qui signifie chenaux
en
italien. Le mot fut mal traduit comme canaux
en anglais et fut avancée l'idée, de manière particulièrement
vigoreuse par Percival Lowell, fondateur de l'Observatoire Lowell de Flagstaff
(Arizona), que les canaux sur Mars étaient la preuve d'un schéma
d'irrigation planétaire gigantesque, développé par les habitants supposés de Mars s5Lowell: 1908. Ces marques ont fait l'objet de beaucoup d'études depuis
leur découverte. Les astronomes rejettent aujourd'hui globalement l'idée qu'ils
représentent un type quelconque d'indication que Mars serait habitée par des être intelligents.
Mars a 2 lunes nommées Phobos et Deimos. Elles sont excessivement petites, Phobos étant estimé à 10 miles de diamètre et Deimos à 5 miles, sur la base de leur brillance, en considérant le pouvoir réfléchissant de leur matière comme étant le même que celui de la planète. Les périodes sont de 7h39m pour Phobos et 30h18m pour Deimos. Elles furent découvertes en Août 1877 par Asaph Hall en utilisant le nouveau réfracteur de 26 pouces de l'Observatoire Naval des U.S. à Washington. Un recherche infructueuse de lunes de Mars fut effectuée avec un mirroir de 48 pouces lors de l'opposition de 1862.
I. S. Shklovskii (1959) published a sensational suggestion in a Moscow newspaper that these moons were really artificial satellites which had been put up by supposed inhabitants of Mars as a place of refuge when the supposed oceans of several million years ago began to dry up (Sullivan, 1966, p. 169). There is no observational evidence to support this idea. Continuing the same line of speculation Salisbury (1962), after pointing out that the satellites were looked for in 1862 but not found until 1877, then asks, "Should we attribute the failure of 1862 to imperfections in existing telescopes, or may we imagine that the satellites were launched between 1862 and 1877?" This is a slender reed indeed with which to prop up so sensational an inference, and we reject it.