[by:如果您喜欢 恒星英语学习网 www.hxen.com 请与您的朋友分享]
[00:00.00]M:I readly don't  understand how you can use the pendulum to demonstrate the rotation of the earth.
[00:05.56]In fact,your lecture went right over my head.
[00:09.56]M:I really didn't understand how you can use the pendulum to demonstrate the rotation of the earth.
[00:14.97]In fact,your lecture went right over my head.
[00:18.49]W:I'd be happy to run through it again.
[00:20.92]There are two basic principles that you have to keep in mind.
[00:24.61]The earth rotates around and axis that goes through the north and south poles.
[00:29.62]Since the surface of the earth is curved,the ground we're standing on right now in the northern hemisphere travels through space in a counter clockwise arc,not a straight line,as the earth turns.
[00:40.65]M:I'm just not aware of the movement,because it's relatively slight.
[00:44.96]W:Besically,now the other important concept,if you take a piece of string and attach a weight to the bottom,
[00:53.08]the weight will also swing in a counter_clockwise direction once you set it in motion.
[00:58.96]Now if you make a pendulum long enough and hang it in a tall building,it will swing very slowly.
[01:05.59]The weight at the bottom will appear to slowly change its path as it swings back and forth.
[01:12.65]Actually the pendulum is moving in a straight line,and it is the earth that is slowly rotating under it.Does that make sense?
[01:20.77]M:Well,maybe I need  to think about it a little more.Thanks anyway.