| From Galileo's Daughter by Dava Sobel, pages 308 to 310.
Please observe, gentlemen, how facts which at first seem improbable
will, even on scant explanation, drop the cloak which has hidden
them and stand forth in naked and simple beauty. Who does not
know that a horse falling from a height of three or four braccia
will break his bones, while a dog falling from the same height or a
cat from eight or ten, or even more, will suffer no injury?
Equally harmless would be the fall of a grasshopper from a tower or
the fall of an ant from the distance of the Moon. Do not
children fall with impunity from heights which would cost their
elders a broken leg or perhaps a fractured skull? And just a
smaller animals are proportionately stronger and more robust than
the larger, so also smaller plants are able to stand up better than
larger. I am certain you both know that an oak two hundred
feet high would not be able to sustain its own branches if they were
distributed as in a tree of ordinary size; and that Nature cannot
produce a horse as large as twenty ordinary horses, or a giant ten
times taller than an ordinary man, unless by miracle or by greatly
altering the proportions of his limbs and especially of his bones,
which would have to be considerably enlarged over the ordinary.
Likewise the current belief that, in the case of artificial machines
the very large and the small are equally feasible and lasting is a
manifest error.
[Sobel's paraphrasing: Volume expands as the cube of bodies'
dimensions, while strength increases only as much as their square.]
I have sketched a bone whose natural length has been increased
three times and whose thickness has been multiplied until, for a
correspondingly large animal, it would perform the same function
which the small bone performs for its small animal. From the
figures here shown you can see how out of proportion the enlarged
bone appears. Clearly then if one wishes to maintain in a
great giant the same proportion of limb as that found in an ordinary
man he must either find a harder and stronger material for making
the bones, or he must admit a dimunition of strength in comparison
with men of medium stature; for if his height be increased
inordinately he will fall and be crushed under his own weight.
Whereas, of if the size of a body be diminished, the strength of
that body is not diminished in the same proportion; indeed the
smaller the body the greater its relative strength. Thus a
small dog could probably carry on his back two or three dogs of his
own size; but I believe that a horse could not carry even one horse
of his own size. |
