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Page xix - A luminous star, of the same density as the Earth, and whose diameter should be two hundred and fifty times larger than that of the Sun, would not, in consequence of its attraction, allow any of its rays to arrive at us; it is therefore possible that the largest luminous bodies in the universe, may, through this cause, be invisible.
Page xix - According to the Principle of Relativity," he said, "the laws of physical phenomena must be the same for a 'fixed' observer as for an observer who has a uniform motion of translation relative to him : so that we have not, and cannot possibly have, any means of discerning whether we are, or are not, carried along in such a motion.