The Moon-Voyage | Page 9

the members of the
Baltimore Gun Club, we immediately called a meeting of our staff,
who have deemed it expedient to answer as follows:--
"The questions proposed to it were these:--
"'1. Is it possible to send a projectile to the moon?
"'2. What is the exact distance that separates the earth and her satellite?
"'3. What would be the duration of the projectile's transit to which a
sufficient initial speed had been given, and consequently at what
moment should it be hurled so as to reach the moon at a particular
point?
"'4. At what moment would the moon present the most favourable
position for being reached by the projectile?
"'5. What point in the heavens ought the cannon, destined to hurl the
projectile, be aimed at?
"'6. What place in the heavens will the moon occupy at the moment
when the projectile will start?'
"Regarding question No. 1, 'Is it possible to send a projectile to the
moon?'
"Yes, it is possible to send a projectile to the moon if it is given an
initial velocity of 1,200 yards a second. Calculations prove that this
speed is sufficient. In proportion to the distance from the earth the force
of gravitation diminishes in an inverse ratio to the square of the
distance--that is to say, that for a distance three times greater that force

is nine times less. In consequence, the weight of the projectile will
decrease rapidly, and will end by being completely annulled at the
moment when the attraction of the moon will be equal to that of the
earth--that is to say, at the 47/52 of the distance. At that moment the
projectile will have no weight at all, and if it clears that point it will fall
on to the moon only by the effect of lunar gravitation. The theoretic
possibility of the experiment is, therefore, quite demonstrated; as to its
success, that depends solely in the power of the engine employed.
"Regarding question No. 2, 'What is the exact distance that separates
the earth from her satellite?'
"The moon does not describe a circle round the earth, but an ellipse, of
which our earth occupies one of the foci; the consequence is, therefore,
that at certain times it approaches nearer to, and at others recedes
farther from, the earth, or, in astronomical language, it has its apogee
and its perigee. At its apogee the moon is at 247,552 miles from the
earth, and at its perigee at 218,657 miles only, which makes a
difference of 28,895, or more than a ninth of the distance. The perigee
distance is, therefore, the one that should give us the basis of all
calculations.
"Regarding question No. 3, 'What would be the duration of the
projectile's transit to which a sufficient initial speed has been given, and
consequently at what moment should it be hurled so as to reach the
moon at a particular point?'
"If the projectile kept indefinitely the initial speed of 12,000 yards a
second, it would only take about nine hours to reach its destination; but
as that initial velocity will go on decreasing, it will happen, everything
calculated upon, that the projectile will take 300,000 seconds, or 83
hours and 20 minutes, to reach the point where the terrestrial and lunar
gravitations are equal, and from that point it will fall upon the moon in
50,000 seconds, or 13 hours, 53 minutes, and 20 seconds. It must,
therefore, be hurled 97 hours, 13 minutes, and 20 seconds before the
arrival of the moon at the point aimed at.
"Regarding question No. 4, 'At what moment would the moon present
the most favourable position for being reached by the projectile?'
"According to what has been said above the epoch of the moon's
perigee must first be chosen, and at the moment when she will be
crossing her zenith, which will still further diminish the entire distance

by a length equal to the terrestrial radius--i.e., 3,919 miles;
consequently, the passage to be accomplished will be 214,976 miles.
But the moon is not always at her zenith when she reaches her perigee,
which is once a month. She is only under the two conditions
simultaneously at long intervals of time. This coincidence of perigee
and zenith must be waited for. It happens fortunately that on December
4th of next year the moon will offer these two conditions; at midnight
she will be at her perigee and her zenith--that is to say, at her shortest
distance from the earth and at her zenith at the same time.
"Regarding question No. 5, 'At what point in the heavens ought the
cannon destined to hurl the projectile be aimed?'
"The preceding observations being admitted, the cannon ought to be
aimed at the zenith of the place (the zenith is the spot