If
I had thought to bring along a spring dynamometer, I could have shown
you, Jack, that when we were 4,000 miles above the earth's surface the
200 good pounds with which you depress the scales at home had diminished
to 50, and that when we had passed about 150,000 miles into space you
weighed no more than a couple of ounces. From that point on, it has been
the attraction of the sun to which we have owed whatever weight we had,
and the floor of the car has been toward the sun, because, at that
distance from the earth, the latter ceases to exercise the master force,
and the pull of the sun becomes greater than the earth's. But as we
approach Venus the latter begins to restore our weight, and when we
arrive on her surface we shall weigh about four fifths as much as when we
started from the earth."
"But I don't look as if I had lost any avoirdupois," said Jack, glancing
at his round limbs. "And when you give us a fling I seem to strike pretty
hard, though in other respects I confess I do feel a good deal like an
angel."
"Ah," said Edmund, laughing, "that's the _inertia of mass_. Your mass is
the same, although your weight has almost disappeared.
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