| Galilei, Galileo Dialogues on two world systems 1661, tr. Salusbury, Thomas | ||||||
|
SIMP. No: For the point would be changed, and would be
beneath the star first observed.
SAGR. You are in the right. Now like as that which in this
example answereth to the elevation of the Top-Gallant-Top, is
not the star, but the point of the Firmament that lyeth in a right
line with the eye, and the said top of the Mast, so in the case
exemplified, that which in the Firmament answers to the Pole
of the Earth, is not a star, or other fixed thing in the Firma
ment; but is that point in which the Axis of the Earth continu
ed streight out, till it cometh thither doth determine, which point
is not fixed, but obeyeth the mutations that the Pole of the
Earth doth make. And therefore Tycho, or who ever else that
did alledg this objection, ought to have said that upon that
same motion of the Earth, were it true, one might observe some
difference in the elevation and depression (not of the Pole, but)
of some fixed star toward that part which answereth to our Pole.
Upon the annu
al motion of the
Earth, alteration
may ensue in
some fixed star,
not in the Pole.
SIMP. I already very well understand the mistake by them
committed; but yet therefore (which to me seems very great) of
the argument brought on the contrary is not lessened, suppo
sing relation to be had to the variation of the stars, and not of
the Pole; for if the moving of the Ship but 60. miles, make a
fixed star rise to me one degree, shall I not find alike, yea and
very much greater mutation, if the Ship should sail towards the
said star for so much space as is the Diameter of the Grand
Orb, which you affirm to be double the distance that is between
the Earth and Sun?
SAGR. Herein Simplicius, there is another fallacy, which,
truth is, you understand, but do not upon the sudden think of
the same, but I will try to bring it to your remembrance: Tell
me therefore; if when after you have directed the Quadrant to
a fixed star, and found v. g. its elevation to be 40. degrees,
you should without stirring from the place, incline the side of
the Ouadrant, so as that the star might remain elevated above
that direction, would you thereupon say that the star had acqui
red greater elevation?
The equivoke of
those who believe
that in the annual
motion great mu
tations are to be
made about the
elevation of a fix
ed star, is confu
ted.
SIMP. Certainly no: For the mutation was made in the In
strument and not in the Observer, that did change place, mo
ving towards the same.
SAGR. But if you sail or walk along the surface of the Terre
strial Globe, will you say that there is no alteration made in the
said Quadrant, but that the same elevarion is still retained in re
spect of the Heavens, so long as you your self do not incline it,
but let it stand at its first constitution?
SIMP. Give me leave to think of it. I would say without
more ado, that it would not retain the same, in regard the pro