雙語·從地球到月球 第六章　在美國不能不知道的東西和不允許胡亂相信的東西

The immediate result of Barbicane's proposition was to place upon the orders of the day all the astronomical facts relative to the Queen of the Night. Everybody set to work to study assiduously.One would have thought that the moon had just appeared for the first time, and that no one had ever before caught a glimpse of her in the heavens.The papers revived all the old anecdotes in which the“sun of the wolves”played a part；they recalled the influences which the ignorance of past ages ascribed to her；in short, all America was seized with selenomania, or had become moon-mad.

The scientific journals, for their part, dealt more especially with the questions which touched upon the enterprise of the Gun Club. The letter of the Observatory of Cambridge was published by them, and commented upon with unreserved approval.

Until that time most people had been ignorant of the mode in which the distance which separates the moon from the earth is calculated. They took advantage of this fact to explain to them that this distance was obtained by measuring the parallax of the moon.The term parallax proving“caviare to the general”，they further explained that it meant the angle formed by the inclination of two straight lines drawn from either extremity of the earth's radius to the moon.On doubts being expressed as to the correctness of this method, they immediately proved that not only was the mean distance 234，347 miles, but that astronomers could not possibly be in error in their estimate by more than seventy miles either way.

To those who were not familiar with the motions of the moon, they demonstrated that she possesses two distinct motions, the first being that of rotation upon her axis, the second being that of revolution round the earth, accomplishing both together in an equal period of time, that is to say, in twenty-seven and one-third days.

The motion of rotation is that which produces day and night on the surface of the moon；save that there is only one day and one night in the lunar month, each lasting three hundred and fifty-four and one-third hours. But, happily for her, the face turned toward the terrestrial globe is illuminated by it with an intensity equal to that of fourteen moons.As to the other face, always invisible to us, it has of necessity three hundred and fifty-four hours of absolute night, tempered only by that“pale glimmer which falls upon it from the stars”.

Some well-intentioned, but rather obstinate persons, could not at first comprehend how, if the moon displays invariably the same face to the earth during her revolution, she can describe one turn round herself. To such they answered，“Go into your dining-room, and walk round the table in such a way as to always keep your face turned toward the center；by the time you will have achieved one complete round you will have completed one turn around yourself, since your eye will have traversed successively every point of the room.Well, then, the room is the heavens, the table is the earth, and the moon is yourself.”And they would go away delighted.

So, then the moon displays invariably the same face to the earth；nevertheless, to be quite exact, it is necessary to add that, in consequence of certain fluctuations of north and south, and of west and east, termed her libration, she permits rather more than half, that is to say, fifty-seven percent, to be seen.

As soon as the ignoramuses came to understand as much as the director of the observatory himself knew, they began to worry themselves regarding her revolution round the earth, whereupon twenty scientific reviews immediately came to the rescue. They pointed out to them that the firmament, with its infinitude of stars, may be considered as one vast dial-plate, upon which the moon travels, indicating the true time to all the inhabitants of the earth；that it is during this movement that the Queen of Night exhibits her different phases；that the moon is full when she is in opposition with the sun, that is when the three bodies are on the same straight line, the earth occupying the center；that she is new when she is in conjunction with the sun, that is, when she is between it and the earth；and, lastly that she is in her first or last quarter, when she makes with the sun and the earth a right angle of which she herself occupies the apex.

Regarding the altitude which the moon attains above the horizon, the letter of the Cambridge Observatory had said all that was to be said in this respect. Every one knew that this altitude varies according to the latitude of the observer.But the only zones of the globe in which the moon passes the zenith, that is, the point directly over the head of the spectator, are of necessity comprised between the twenty-eighth parallels and the equator.Hence the importance of the advice to try the experiment upon some point of that part of the globe, in order that the projectile might be discharged perpendicularly, and so the soonest escape the action of gravitation.This was an essential condition to the success of the enterprise, and continued actively to engage the public attention.

Regarding the path described by the moon in her revolution round the earth, the Cambridge Observatory had demonstrated that this path is a re-entering curve, not a perfect circle, but an ellipse, of which the earth occupies one of the foci. It was also well understood that it is farthest removed from the earth during its apogee, and approaches most nearly to it at its perigee.

Such was then the extent of knowledge possessed by every American on the subject, and of which no one could decently profess ignorance. Still, while these principles were being rapidly disseminated many errors and illusory fears proved less easy to eradicate.

For instance, some worthy persons maintained that the moon was an ancient comet which, in describing its elongated orbit round the sun, happened to pass near the earth, and became confined within her circle of attraction. These drawing-room astronomers professed to explain the charred aspect of the moon—a disaster which they attributed to the intensity of the solar heat；only, on being reminded that comets have an atmosphere, and that the moon has little or none, they were fairly at a loss for a reply.

Others again, belonging to the doubting class, expressed certain fears as to the position of the moon. They had heard it said that, according to observations made in the time of the Caliphs, her revolution had become accelerated in a certain degree.Hence they concluded, logically enough, that an acceleration of motion ought to be accompanied by a corresponding diminution in the distance separating the two bodies；and that, supposing the double effect to be continued to infinity, the moon would end by one day falling into the earth.However, they became reassured as to the fate of future generations on being apprised that, according to the calculations of Laplace, this acceleration of motion is confined within very restricted limits, and that a proportional diminution of speed will be certain to succeed it.So, then, the stability of the solar system would not be deranged in ages to come.

There remains but the third class, the superstitious. These worthies were not content merely to rest in ignorance；they must know all about things which had no existence whatever, and as to the moon, they had long known all about her.One set regarded her disc as a polished mirror, by means of which people could see each other from different points of the earth and interchange their thoughts.Another set pretended that out of one thousand new moons that had been observed, nine hundred and fifty had been attended with remarkable disturbances, such as cataclysms, revolutions, earthquakes, the deluge, etc.Then they believed in some mysterious influence exercised by her over human destinies—that every Selenite was attached to some inhabitant of the earth by a tie of sympathy；they maintained that the entire vital system is subject to her control, etc.But in time the majority renounced these vulgar errors, and espoused the true side of the question.As for the Yankees, they had no other ambition than to take possession of this new continent of the sky, and to plant upon the summit of its highest elevation the star-spangled banner of the United States of America.