EARTH 255 Lecture 2: earth255week1lecture2
19 Sep 2016
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Different motions in the same sense lead to different changes in the sky. Sun progresses against backdrop of stars as year passes. We see different star fields at different seasons. The tilt of the earth"s axis doesn"t change during revolution. Towards the poles stars don"t rise or set (circumpolar) N pole changes direction to sun over year. Seasons do not occur because of changing distance between the earth and sun. In summer n hemisphere tilts toward the sun. In winter n hemisphere tilts away from the sun. Sun in above horizon for longer in summer. Sun"s says illuminate earth less obliquely in summer. Heating takes time so hottest days lag summer solstice. Water has high heat capacity so large areas of water moderate heating. We see the moon illuminated by the sun. Ignore all extraneous details (such as a tilt) to understand this.
