he had left behind at Pisa, on the ground of his spoiling the pure,
smooth, crystalline, celestial face of the moon as they had thought it,
and making it harsh and rugged, and like so vile and ignoble a body as
the earth.

He went further, however, into heterodoxy than this: he not only made
the moon like the earth, but he made the earth shine like the moon. The
visibility of "the old moon in the new moon's arms" he explained by
earth-shine. Leonardo had given the same explanation a century before.
Now, one of the many stock arguments against Copernican theory of the
earth being a planet like the rest was that the earth was dull and dark
and did not shine. Galileo argued that it shone just as much as the moon
does, and in fact rather more--especially if it be covered with clouds.
One reason of the peculiar brilliancy of Venus is that she is a very
cloudy planet.[29] Seen from the moon the earth would look exactly as
the moon does to us, only a little brighter and sixteen times as
big--four times the diameter.

Wherever Galileo turned his telescope new stars appeared. The Milky Way,
which had so puzzled the ancients, was found to be composed of stars.
Stars that appeared single to the eye were some of them found to be
double; and at intervals were found hazy nebulous wisps, some of which
seemed to be star clusters, while others seemed only a fleecy cloud.

Now we come to his most brilliant, at least his most sensational,
discovery. Examining Jupiter minutely on January 7, 1610, he noticed
three little stars near it, which he noted down as fixing its then
position. On the following night Jupiter had moved to the other side of
the three stars. This was natural enough, but was it moving the right
way? On examination it appeared not. Was it possible the tables were
wrong? The next evening was cloudy, and he had to curb his feverish
impatience. On the 10th there were only two, and those on the other
side. On the 11th two again, but one bigger than the other. On the 12th
the three reappeared, and on the 13th there were four. No more appeared.
Jupiter, then, had moons like the earth--four of them in fact!--and they
revolved round him in periods which were soon determined.

The news of the discovery soon spread and excited the greatest interest
and astonishment. Many of course refused to believe it. Some there were
who, having been shown them, refused to believe their eyes, and asserted
that although the telescope acted well