The motion of the sun along the ecliptic is, of course, merely a reflection of the revolution of the earth around the sun, but the ancients believed the earth was fixed and the sun had an independent motion of its own, eastward among the stars. The glare of sunlight hides the stars in daytime, but the ancients were aware that the stars were up there even at night, and the slow eastward motion of the sun around the sky, at the rate of about thirty degrees each month, caused different stars to be visible at night at different times of the year.
The moon, revolving around the earth each month, also has an independent motion in the sky. The moon, however, changes its position relatively rapidly. Although it appears to rise and set each day, as does nearly everything else in the sky, we can see the moon changing position during as short an interval as an hour or so. The moon's path around the earth lies nearly in the same plane as the earth's path around the sun, so the moon is never seen very far from the ecliptic in the sky. There are five other objects visible to the naked eye that also appear to move in respect to the fixed background of stars on the celestial sphere. These are the planets Mercury, Venus, Mars, Jupiter, and the Saturn. All of them revolve around the sun in nearly the same plane as the earth does, so they, like the moon, always appear near the ecliptic. Because we see the planets from the moving earth, however, they behave in a complicated way, with their apparent motions on the celestial sphere reflection both their own independent motions around the sun and our motion as well.
第26题:The ancient people believed that ________.
[试题]Understand what Jet Lag is, and how a careful diet can______(minimum)its worst effects, and your flights will be less stressful.
[试题]Understand what Jet Lag is,and how a careful diet can minimize its worst effect,and your flights will be less______(stress).
[单选题]H.ow do you understand "the spirit of Zorahayda... was oftenseen by moonlight..."?A. Moonlight often saw the spirit of Zorahayda.B. People could see the spirit of Zorahayda when there was the moon in the sky.C. The spirit of Zorahayda could see moo
[单选题]It is stated in astrology that ________.[A] the sun is so distant from us that it was hard to follow its motion[B] the sun was moving westward around the sky[C] the motion of the sun is at the rate of about thirty degrees every week[D] the motion of
[单选题]Blood is very important. when doctors understand how blood goes around insi
[单选题]Blood is very important. when doctors understand how blood goes around insi
[单选题]Blood is very important. when doctors understand how blood goes around insi
[单选题]Blood is very important. when doctors understand how blood goes around insi
[单选题]Blood is very important. when doctors understand how blood goes around insi
[单选题]I can’t understand how he can feel that his colleagues are always ready to