The sidereal messenger of Galileo Galilei : $b and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveries — John Shaqi
The sidereal messenger of Galileo Galilei : $b and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveriesGalilei, Galileo
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The sidereal messenger of Galileo Galilei : $b and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveries
Galilei, Galileo
Astronomy -- Early works to 1800; Jupiter (Planet) -- Satellites
near the Sun about the time of conjunction, she has in front of her
the entire surface of that hemisphere of the Earth which is exposed to
the Sun, and vividly illumined with his beams, and so receives light
reflected from the Earth. Owing to such reflexion, the hemisphere
of the Moon nearer to us, though deprived of sunlight, appears of
considerable brightness. Again, when removed from the Sun through
a quadrant, the Moon sees only one-half of the Earth’s hemisphere
illuminated, namely the western half, for the other, the eastern, is
covered with the shades of night; the Moon is, therefore, less brightly
enlightened by the Earth, and accordingly that secondary light appears
fainter to us. But if you imagine the Moon to be set on the opposite
side of the Earth to the Sun, she will see the hemisphere of the Earth,
now between the Moon and the Sun, quite dark, and steeped in the gloom
of night; if, therefore, an eclipse should accompany such a position
of the Moon, she will receive no light at all, being deprived of the
illumination of the Sun and Earth together. In any other position, with
regard to the Earth and the Sun, the Moon receives more or less light
by reflexion from the Earth, according as she sees a greater or smaller
portion of the hemisphere of the Earth illuminated by the Sun; for such
a law is observed between these two orbs, that at whatever times the
Earth is most brightly enlightened by the Moon, at those times, on the
contrary, the Moon is least enlightened by the Earth; and contrariwise.
Let these few words on this subject suffice in this place; for I will
consider it more fully in my _System of the Universe_, where, by very
many arguments and experimental proofs, there is shown to be a very
strong reflexion of the Sun’s light from the Earth, for the benefit of
those who urge that the Earth must be separated from the starry host,
chiefly for the reason that it has neither motion nor light, for I will
prove that the Earth has motion, and surpasses the Moon in brightness,
and is not the place where the dull refuse of the universe has settled
down; and I will support my demonstration by a thousand arguments taken
from natural phenomena.
[Sidenote: Stars. Their appearance in the telescope.]
Public-domain text, read in full here on John Shaqi.
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