Early men were also greatly interested in the stars they saw twinkling in the sky at night. What they did not realize was that the stars were also present during the daytime, but their light was not visible because of the brilliance of the sun. How did they discover this?There is one event which does enable us to see the stars in the daytime. It is the total eclipse of the sun(日全食),when the moon passes in front of the sun and hides it from view. When this happens, the sky becomes dark enough for the stars to be seen. Total eclipses of this kind do not occur very often and are not likely to be seen from the same area more than once every fifty-four years. One can imagine what an awe-inspiring sight it must have been for an early man, who would remember the event for the rest of his life.So man watched the movements of the sun, the moon and the stars and wondered about them. It was practicing the oldest branch of science—astronomy.

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