A Little Algebra

: From The Earth To The Moon

The night passed without incident. The word "night," however,

is scarcely applicable.



The position of the projectile with regard to the sun did

not change. Astronomically, it was daylight on the lower part,

and night on the upper; so when during this narrative these

words are used, they represent the lapse of time between rising

and setting of the sun upon the earth.



The trave
ers' sleep was rendered more peaceful by the

projectile's excessive speed, for it seemed absolutely motionless.

Not a motion betrayed its onward course through space. The rate

of progress, however rapid it might be, cannot produce any

sensible effect on the human frame when it takes place in a

vacuum, or when the mass of air circulates with the body which

is carried with it. What inhabitant of the earth perceives its

speed, which, however, is at the rate of 68,000 miles per hour?

Motion under such conditions is "felt" no more than repose; and

when a body is in repose it will remain so as long as no strange

force displaces it; if moving, it will not stop unless an

obstacle comes in its way. This indifference to motion or

repose is called inertia.



Barbicane and his companions might have believed themselves

perfectly stationary, being shut up in the projectile; indeed,

the effect would have been the same if they had been on the

outside of it. Had it not been for the moon, which was

increasing above them, they might have sworn that they were

floating in complete stagnation.



That morning, the 3rd of December, the travelers were awakened by

a joyous but unexpected noise; it was the crowing of a cock

which sounded through the car. Michel Ardan, who was the first

on his feet, climbed to the top of the projectile, and shutting

a box, the lid of which was partly open, said in a low voice,

"Will you hold your tongue? That creature will spoil my design!"



But Nicholl and Barbicane were awake.



"A cock!" said Nicholl.



"Why no, my friends," Michel answered quickly; "it was I who

wished to awake you by this rural sound." So saying, he gave

vent to a splendid cock-a-doodledoo, which would have done honor

to the proudest of poultry-yards.



The two Americans could not help laughing.



"Fine talent that," said Nicholl, looking suspiciously at his companion.



"Yes," said Michel; "a joke in my country. It is very Gallic;

they play the cock so in the best society."



Then turning the conversation:



"Barbicane, do you know what I have been thinking of all night?"



"No," answered the president.



"Of our Cambridge friends. You have already remarked that I am

an ignoramus in mathematical subjects; and it is impossible for

me to find out how the savants of the observatory were able to

calculate what initiatory speed the projectile ought to have on

leaving the Columbiad in order to attain the moon."



"You mean to say," replied Barbicane, "to attain that neutral

point where the terrestrial and lunar attractions are equal;

for, starting from that point, situated about nine-tenths of the

distance traveled over, the projectile would simply fall upon

the moon, on account of its weight."



"So be it," said Michel; "but, once more; how could they

calculate the initiatory speed?"



"Nothing can be easier," replied Barbicane.



"And you knew how to make that calculation?" asked Michel Ardan.



"Perfectly. Nicholl and I would have made it, if the

observatory had not saved us the trouble."



"Very well, old Barbicane," replied Michel; "they might have cut

off my head, beginning at my feet, before they could have made

me solve that problem."



"Because you do not know algebra," answered Barbicane quietly.



"Ah, there you are, you eaters of x^1; you think you have said

all when you have said `Algebra.'"



"Michel," said Barbicane, "can you use a forge without a hammer,

or a plow without a plowshare?"



"Hardly."



"Well, algebra is a tool, like the plow or the hammer, and a

good tool to those who know how to use it."



"Seriously?"



"Quite seriously."



"And can you use that tool in my presence?"



"If it will interest you."



"And show me how they calculated the initiatory speed of our car?"



"Yes, my worthy friend; taking into consideration all the

elements of the problem, the distance from the center of the

earth to the center of the moon, of the radius of the earth, of

its bulk, and of the bulk of the moon, I can tell exactly what

ought to be the initiatory speed of the projectile, and that by

a simple formula."



"Let us see."



"You shall see it; only I shall not give you the real course

drawn by the projectile between the moon and the earth in

considering their motion round the sun. No, I shall consider

these two orbs as perfectly motionless, which will answer all

our purpose."



"And why?"



"Because it will be trying to solve the problem called `the

problem of the three bodies,' for which the integral calculus is

not yet far enough advanced."



"Then," said Michel Ardan, in his sly tone, "mathematics have

not said their last word?"



"Certainly not," replied Barbicane.



"Well, perhaps the Selenites have carried the integral calculus

farther than you have; and, by the bye, what is this

`integral calculus?'"



"It is a calculation the converse of the differential," replied

Barbicane seriously.



"Much obliged; it is all very clear, no doubt."



"And now," continued Barbicane, "a slip of paper and a bit of

pencil, and before a half-hour is over I will have found the

required formula."



Half an hour had not elapsed before Barbicane, raising his head,

showed Michel Ardan a page covered with algebraical signs, in

which the general formula for the solution was contained.



"Well, and does Nicholl understand what that means?"



"Of course, Michel," replied the captain. "All these signs,

which seem cabalistic to you, form the plainest, the clearest,

and the most logical language to those who know how to read it."



"And you pretend, Nicholl," asked Michel, "that by means of

these hieroglyphics, more incomprehensible than the Egyptian

Ibis, you can find what initiatory speed it was necessary to

give the projectile?"



"Incontestably," replied Nicholl; "and even by this same formula

I can always tell you its speed at any point of its transit."



"On your word?"



"On my word."



"Then you are as cunning as our president."



"No, Michel; the difficult part is what Barbicane has done; that

is, to get an equation which shall satisfy all the conditions of

the problem. The remainder is only a question of arithmetic,

requiring merely the knowledge of the four rules."



"That is something!" replied Michel Ardan, who for his life

could not do addition right, and who defined the rule as a

Chinese puzzle, which allowed one to obtain all sorts of totals.



"The expression v zero, which you see in that equation, is the

speed which the projectile will have on leaving the atmosphere."



"Just so," said Nicholl; "it is from that point that we must

calculate the velocity, since we know already that the velocity

at departure was exactly one and a half times more than on

leaving the atmosphere."



"I understand no more," said Michel.



"It is a very simple calculation," said Barbicane.



"Not as simple as I am," retorted Michel.



"That means, that when our projectile reached the limits of the

terrestrial atmosphere it had already lost one-third of its

initiatory speed."



"As much as that?"



"Yes, my friend; merely by friction against the atmospheric strata.

You understand that the faster it goes the more resistance it meets

with from the air."



"That I admit," answered Michel; "and I understand it,

although your x's and zero's, and algebraic formula, are

rattling in my head like nails in a bag."



"First effects of algebra," replied Barbicane; "and now, to

finish, we are going to prove the given number of these

different expressions, that is, work out their value."



"Finish me!" replied Michel.



Barbicane took the paper, and began to make his calculations

with great rapidity. Nicholl looked over and greedily read the

work as it proceeded.



"That's it! that's it!" at last he cried.



"Is it clear?" asked Barbicane.



"It is written in letters of fire," said Nicholl.



"Wonderful fellows!" muttered Ardan.



"Do you understand it at last?" asked Barbicane.



"Do I understand it?" cried Ardan; "my head is splitting with it."



"And now," said Nicholl, "to find out the speed of the

projectile when it leaves the atmosphere, we have only to

calculate that."



The captain, as a practical man equal to all difficulties, began

to write with frightful rapidity. Divisions and multiplications

grew under his fingers; the figures were like hail on the white page.

Barbicane watched him, while Michel Ardan nursed a growing headache

with both hands.



"Very well?" asked Barbicane, after some minutes' silence.



"Well!" replied Nicholl; every calculation made, v zero, that

is to say, the speed necessary for the projectile on leaving the

atmosphere, to enable it to reach the equal point of attraction,

ought to be----"



"Yes?" said Barbicane.



"Twelve thousand yards."



"What!" exclaimed Barbicane, starting; "you say----"



"Twelve thousand yards."



"The devil!" cried the president, making a gesture of despair.



"What is the matter?" asked Michel Ardan, much surprised.



"What is the matter! why, if at this moment our speed had

already diminished one-third by friction, the initiatory speed

ought to have been----"



"Seventeen thousand yards."



"And the Cambridge Observatory declared that twelve thousand

yards was enough at starting; and our projectile, which only

started with that speed----"



"Well?" asked Nicholl.



"Well, it will not be enough."



"Good."



"We shall not be able to reach the neutral point."



"The deuce!"



"We shall not even get halfway."



"In the name of the projectile!" exclaimed Michel Ardan, jumping

as if it was already on the point of striking the terrestrial globe.



"And we shall fall back upon the earth!"



More

;