a substance that could block the gravitational field (as metal,
or any conductor, can block the electrostatic field).
objects create a gravitational field in proportion to their mass
- it is the interaction of these fields that we perceive as gravitational
attraction. If Cavorite were interposed between the Earth and
a bowling ball, the bowling ball would no longer be attracted
to the Earth. The Earth would no longer be attracted to the bowling
ball either, but that would not be noticeable!
would happen to the bowling ball? Well, it would be faintly attracted
to distant masses on the other side of the Cavorite from the
Earth, but probably not enough to measure. The big effect would
be the ball's own velocity - if it were at the Earth's equator,
it would be going about 1000 m.p.h. on a curved path, and the
centripetal force would act in the upward direction, causing
the ball to rise.
ball would rise with an acceleration of
exactly zooming, and of course if the ball drifted out of the
area where the gravity was blocked it would immediately fall
back with an acceleration of 32.
Furthermore, it could be held in place by a piece of dental floss
- if the ball weighs 5 lbs -= 80 oz, the force required to restrain
it would be proportional to the acceleration, as the mass is
constant. The force exerted on the ball by an acceleration of
a = 0.1would only be about
the other hand, if the experiment were carried out at the North
Pole, the bowling ball would merely become weightless, acted
on by very small unaligned forces. After a while it would drift
back into the Earth's gravitational field and fall to the ground
(or the ice or the deck or whatever there might be to stand on
at the North Pole).
has been objected that the very existence of Cavorite would violate
Newton's laws, because at the edge of the "shadow"
blocking the gravitational field a perpetual motion machine would
become possible. That is, if a wheel were mounted vertically
with the axis on the border and half the disk in the Earth's
gravitational field and the other half above the Cavorite, the
wheel would spin without energy input because half of it was
pulled earthward while the other half was not. In fact, if energy
were not removed from the wheel (as by a brake or an electric
dynamo), the wheel would spin faster and faster until it either
reached an equilibrium with air and bearing friction or exploded
when the centripetal strain exceeded the strength of the material.
is an important objection, but I'm not sure what connection it
has to do with the problem. There are, after all, other ways
to cancel gravitational attraction on half of a vertically mounted
wheel! Suppose we use our 5-lb bowling ball (since we have already
done the math on that) as a wheel by sticking an axle through
it - now half the ball will be accelerated toward the Earth (a
= 0.1 feet/sec) , while the other half will not. How could this
be accomplished without Cavorite? Well, half of the ball could
be in a tank of liquid with the same density as the ball itself.
There is nothing technically difficult about that! Any conceivable
seal at the vertical interface between the dry side of the ball
and the wet side of the ball would exert more force opposing
the rotation of the all that could be overcome by the approximately
5-inch-lb torque available from the asymmetric force on the ball
- but that is a mere technicality.
the ball were suspended between two tanks, one containing the
liquid whose density matches that of the ball (thus making half
the ball weightless) and the other some much lighter fluid that
is immiscible with the heavier liquid (like oil and water). Now
only a light seal would be needed at the interface, because the
small amount of the lighter fluid that got through into the heavier
fluid would float to the top of the tank where, if the tanks
were both exactly full, it would flow back into its own tank.
Whatever heavy fluid got into the light-fluid tank would fall
to the bottom, where it could be returned to its own tank by
a small scavenger pump.
we don't need Cavorite to extract energy from the gravitational
field with an asymmetrically loaded rotating wheel.
on another matter ...
wouldn't a single atom of Cavorite have little effect? It seems
to me that it would block the gravitational field of the Earth
(the only one around that can be measured easily) only in a tiny
cone above that atom. Beyond that any mass acted on by the Earth's
field would still feel the pull of most of the Earth's mass -
think of the shadow of a flea sitting on a light bulb. To another
flea just off the surface above him there would be some shade,
but a couple of flea-lengths out the other flea would be pretty
yet again ...
how large a Cavorite shield would we need to get to low Earth
orbit, say 150 miles up, where the main engines could be used
to achieve orbital velocity without working against atmospheric
drag? Alas, it's a good thing the Cavorite shield can be only
one atom thick, because to achieve full nullification of gravity
to 150 miles, it will have to be about 2000 miles in diameter.
Well, most of the atmosphere is in the first
50 miles above the surface - how big a shield would that take?
Still over 1000 miles across.
of course is based on the assumption that the Cavorite itself
has weight! If it can (unimaginably) shield itself
against the gravitational pull of the Earth, then we need only
coat the ship itself with it and be off to conquer the universe!