Letters on Astronomy

actually angle appear astronomers atmosphere attraction axis body bright called causes celestial centre changes circle comet consequently continually course determined diameter direction discovery disk distance earth east ecliptic equal equator exhibited fact fall figure fixed force four Galileo give given gravity greater greatest half heavenly bodies heavens Hence horizon hundred increase Jupiter known laws length less LETTER light magnitude matter means measure meridian meteors miles minutes moon motion move namely Nature nearer nearly objects observations opposite orbit passing period planets pole portion position present produced reach reason represent respect revolve ring round satellites seen shadow side situated solar sometimes space sphere stars successive supposed surface telescope things thousand turned universal various Venus visible whole