Let us next consider the property of weight. We say that anything has
weight when, on trying to lift it from the ground, or on holding it in
the hand, we have a feeling of effort. Or again, if anything which is
supported at a certain height above the ground, falls when the support
is taken away, we say that it has weight. Now the ground merely means
the surface of the earth; and, as all bodies which possess weight fall
directly towards the surface of the earth when they are not kept away
from it by some support, we may say that all bodies which have weight
tend to fall in this way. And it does not matter on what part of the
surface of the earth you make the experiment. Rain consists of drops of
water, and it does not matter whether we watch a shower in calm weather
here, or in New Zealand; the drops fall perpendicularly towards the
ground. But we know that the earth is a globe, and that New Zealand is
at our antipodes, or on the opposite side of the globe to England. Hence
if two showers are falling at the same time, one in New Zealand and one
here—the drops must be falling in opposite directions, towards one
another; that is, towards the centre of the earth which lies between
them. In fact, all bodies which have weight tend to fall towards the
centre of the earth—that is to say they fall in this way if there is
nothing to prevent them; and when we speak of weight we mean this
tendency to fall. To call anything heavy, is the same as saying that we
fully expect that, if there is nothing to support it, it will fall to
the ground; or that if we support it ourselves we shall be conscious of
effort.