The Legacy of Galileo - Keck Institute for Space Studies - Caltech

to put the Earth amongst the stars when he affirms that the Moon and the Earth are made of
the same matter.
Salviati also claims that a place in transformation such as the Earth is more appealing than an
immutable and sterile planet.
I cannot without great admiration, and great repugnance to my intellect, listen to be
attributed to natural bodies making up the Universe, nobility and perfection for being
impassible, immutable, inalterable, etc. and on the contrary, a great imperfection to
things for being alterable, transformable, mutable, etc. It is my opinion that the Earth is
very noble and admirable, for the very reason of having so many and so different
transformations, mutations, generations, etc. which are incessantly taking place; and if
it were not subject to any alteration, and instead it were all one lonely sea of sand, or a
mass of Jasper, or that at the time of the Deluge the waters had frozen and it had
stayed an immense globe of crystal, in which nothing had ever grown, transformed, or
changed, I should have thought it an ugly and useless body, boring, and in one word
superfluous, and not part of nature; and I would see the same difference in it as I see
between a living and dead creature: and I say the same of the Moon, Jupiter, and all
the other celestial globes. But the closer I look at the vanity of popular opinions, the
more empty and simplistic I find them. And what greater folly can there be than to call
gems, silver and gold precious, and Earth and dirt vile For do these people not
consider that if there were as great a scarcity of Earth, as there is of jewels and precious
metals, there would be no prince that would gladly not give a heap of diamonds and
rubies, and many bullions of gold, only to purchase as much Earth as would be
enough to plant a jasmine in a little pot, or the seed of a China Little Orange, that he
might see it sprout, grow, and produce such beautiful leaves, such perfumed flowers,
and such delicate fruit 15
Not always outstanding scientists understand clearly the consequences of their genial ideas,
some changes perhaps are too complex for a single mind to fully understand. This is the case
for the principle of relativity enunciated by Galileo, which was not completely understood by
the scientist. As a matter of fact in the most important part of the dialogue, Galileo wants to
show that with experiments of mechanics it is impossible to determine whether the reference
frame is in uniform rectilinear motion or at rest relative to the absolute reference frame of
God. To explain this physical principle Galileo describes several simple mechanical
experiments carried out on the lower deck of a large vessel either moored at the quay or
quietly sailing in the Adriatic sea; this example had been already used by Copernicus, and also
by Giordano Bruno in the Ash Wednesday Supper.
Shut yourself up with some friends in the main cabin below deck on some large ship,
and have with you there some flies, butterflies, and other small flying animals. Have a
large bowl of water with some small fish in it; hang up a bottle that empties drop by
drop into a wide vessel beneath it. With the ship standing still, observe carefully how
15
Galilei, G. Dialogo… (Florence, 1632) GG, VII, p. 83 (translation by Cinzia Zuffada)
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