moment they had left the earth their own weight, that of the
bullet and the objects it contained, had suffered progressive
diminution. Though they could not have any experience of this in the
projectile, a moment must come when the effect upon themselves and the
tools and instruments they used would be felt.

Of course scales would not have indicated this loss of weight, for the
weights used would have lost precisely as much as the object itself; but
a spring weighing-machine, the tension of which is independent of
attraction, would have given the exact valuation of this diminution.

It is well known that attraction, or weight, is in proportion to the
bulk, and in inverse proportion to the square of distances. Hence this
consequence. If the earth had been alone in space, if the other heavenly
bodies were to be suddenly annihilated, the projectile, according to
Newton's law, would have weighed less according to its distance from the
earth, but without ever losing its weight entirely, for the terrestrial
attraction would always have made itself felt, no matter at what
distance.

But in the case with which we are dealing, a moment must come when the
projectile would not be at all under the law of gravitation, after
allowing for the other celestial bodies, whose effect could not be set
down as zero.

In fact, the trajectory of the projectile was between the earth and the
moon. As it went farther away from the earth terrestrial attraction
would be diminished in inverse proportion to the square of distances,
but the lunar attraction would be augmented in the same proportion. A
point must, therefore, be reached where these two attractions would
neutralise each other, and the bullet would have no weight at all. If
the volumes of the moon and earth were equal, this point would have been
reached at an equal distance between the two bodies. But by taking their
difference of bulk into account it was easy to calculate that this
point would be situated at 47/52 of the journey, or at 78,114 leagues
from the earth.

At this point a body that had no principle of velocity or movement in
itself would remain eternally motionless, being equally attracted by the
two heavenly bodies, and nothing drawing it more towards one than the
other.

Now if the force of impulsion had been exactly calculated the projectile
ought to reach that point with no velocity, having lost all weight like
the objects it contained.

What would happen then?