The Earth when nearest to the Sun, is in her
_perihelion_; when most distant, in her _aphelion_. The Moon, with
regard to the Earth, is similarly in her _perigee_, and her _apogee_.
Analogous expressions denoting the relations of the Projectile towards
the Moon, would be _periselene_ and _aposelene_. At its _aposelene_ the
Projectile's velocity would have reached its minimum; at
the _periselene_, its maximum. As it is to the former point that we are
now moving, clearly the velocity must keep on diminishing until that
point is reached. Then, _if it does not die out altogether_, it must
spring up again, and even accelerate as it reapproaches the Moon. Now
the great trouble is this: If the _Aposelenetic_ point should coincide
with the point of lunar attraction, our velocity must certainly become
_nil_, and the Projectile must remain relatively motionless forever!"
"What do you mean by 'relatively motionless'?" asked M'Nicholl, who was
carefully studying the situation.
"I mean, of course, not absolutely motionless," answered Barbican;
"absolute immobility is, as you are well aware, altogether impossible,
but motionless with regard to the Earth and the--"
"By Mahomet's jackass!" interrupted Ardan hastily, "I must say we're a
precious set of _imbeciles_!"
"I don't deny it, dear friend," said Barbican quietly, notwithstanding
the unceremonious interruption; "but why do you say so just now?"
"Because though we are possessed of the power of retarding the velocity
that takes us from the Moon, we have never thought of employing it!"
"What do you mean?"
"Do you forget the rockets?"
"It's a fact!" cried M'Nicholl.
Pages:
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367