Round the Moon

Page 29

If they could not prove this loss of the projectile, a moment would arrive when it would be sensibly felt upon themselves and the utensils and instruments they used.

It is needless to say that a scale would not show this loss; for the weight destined to weight the object would have lost exactly as much as the object itself; but a spring steelyard for example, the tension of which was independent of the attraction, would have given a just estimate of this loss.

We know that the attraction, otherwise called the weight, is in proportion to the densities of the bodies, and inversely as the squares of the distances. Hence this effect: If the earth had been alone in space, if the other celestial bodies had been suddenly annihilated, the projectile, according to Newton's laws, would weigh less as it got farther from the earth, but without ever losing its weight entirely, for the terrestrial attraction would always have made itself felt, at whatever distance.

But, in reality, a time must come when the projectile would no longer be subject to the law of weight, after allowing for the other celestial bodies whose effect could not be set down as zero. Indeed, the projectile's course was being traced between the earth and the moon. As it distanced the earth, the terrestrial attraction diminished: but the lunar attraction rose in proportion. There must come a point where these two attractions would neutralize each other: the projectile would possess weight no longer. If the moon's and the earth's densities had been equal, this point would have been at an equal distance between the two orbs. But taking the different densities into consideration, it was easy to reckon that this point would be situated at 47/60ths of the whole journey, i.e., at 78,514 leagues from the earth. At this point, a body having no principle of speed or displacement in itself, would remain immovable forever, being attracted equally by both orbs, and not being drawn more toward one than toward the other.

Now if the projectile's impulsive force had been correctly calculated, it would attain this point without speed, having lost all trace of weight, as well as all the objects within it. What would happen then? Three hypotheses presented themselves.

1. Either it would retain a certain amount of motion, and pass the point of equal attraction, and fall upon the moon by virtue of the excess of the lunar attraction over the terrestrial.

2. Or, its speed failing, and unable to reach the point of equal attraction, it would fall upon the moon by virtue of the excess of the lunar attraction over the terrestrial.

3. Or, lastly, animated with sufficient speed to enable it to reach the neutral point, but not sufficient to pass it, it would remain forever suspended in that spot like the pretended tomb of Mahomet, between the zenith and the nadir.

Such was their situation; and Barbicane clearly explained the consequences to his traveling companions, which greatly interested them. But how should they know when the projectile had reached this neutral point situated at that distance, especially when neither themselves, nor the objects enclosed in the projectile, would be any longer subject to the laws of weight?

Up to this time, the travelers, while admitting that this action was constantly decreasing, had not yet become sensible to its total absence.

But that day, about eleven o'clock in the morning, Nicholl having accidentally let a glass slip from his hand, the glass, instead of falling, remained suspended in the air.

"Ah!" exclaimed Michel Ardan, "that is rather an amusing piece of natural philosophy."

And immediately divers other objects, firearms and bottles, abandoned to themselves, held themselves up as by enchantment. Diana too, placed in space by Michel, reproduced, but without any trick, the wonderful suspension practiced by Caston and Robert Houdin. Indeed the dog did not seem to know that she was floating in air.

The three adventurous companions were surprised and stupefied, despite their scientific reasonings.

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Round the Moon Page 30

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Jules Verne

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