[問題]PP-test2 Q168-172(listening)

[elizabeth88]

Listen to a talk in a Geology class
I often hear my friends say that the days pass much more quickly than they used to. But geologically speaking just the opposite is true. In fact, a complete day which now last 24 hours actually used much shorter only about 18. How do we konw that? Because of the number of finally strata rocks like this. ......Together the data indicate there were fewer months for year way back then. That means the Moon was moving more slowly than as it revolved around the Earth. So what caused the Moon do speed up so much over last billion years. It must be the tides. Think about it as the gravity of Moon pulls on the oceans to form the tides. All that water is also pulling on the Moon and with each rotaion it makes the Moon move a tiny bit faster. At the same time, like the brakes on the wheel of bicycle, the drag caused by the Moon's gravity makes the Earth turn just a tiny bit slower. And so after a billion years, one rotation meaning one day takes a lot longer than it once did.

請問一下,紅色字的部份,本篇不是說時間變短了嗎?為何到文章最後又說時間變長了,有點看不懂本篇的意思?
172.According to the professor, how was the Earth different a billion years ago?
A)It rotated faster.
答案是A,是從深籃色部看出來的嗎?那段是指以前轉得較慢所以之後較快嗎?

[StanleyHuang]

第一個紅字的部份講的是：現在一天24小時，在古時候一天短到只有18小時~~
所以很明顯的，地球是變慢了，而不是說時間變短了~~172題的答案事實上就是從這裏得到的。
重點是，時間是不會變的，會變的是地球轉的速度~~古時候轉得快，現在被月球影響所以轉得慢了~~

[elizabeth88]

喔！謝謝你的回答，我終於懂了

[jessyni]

I often hear my friends say that the days pass much more quickly than they used to, but geologically speaking just the opposite is true. In fact, the complete day which now last 24 hours actually used much shorter, only about 18. How do we know that? Because of a number of finally strata rocks like this, rock former belong ancient shorelines almost billion years ago. The tiny lines of these samples show us layer of light and dark, formed by dust blow over the shoreline from the landsite, alternating which mud and sand deposited by the waves. So the space between one dark strata and the next represents the time between on month high tide and the next, and vary in fitness of layer show us the circle of the season as well. Together the data indicate there were fewer months for year way back then. That means the moon was moving more slowly than as it revolved around the earth. So what caused the moon do speed up so much over last billion years. It must be the tides. Think about it. As the gravity of moon pose on the oceans to form the tides, all that water is also pulling on the moon and with each rotation it makes the moon move a tiny bit faster. At the same time, like the brakes on the wheel of bicycle, the drag caused by the moon’s gravity makes the earth turn just a tiny bit slower. And so after a billion years, one rotation meaning one day takes a lot longer than it once did.

我自然科學不好，不懂紅色的部份為什麼要舉腳踏車為例子耶？
還有為什麼月球會被反推回來的力量導致轉的快一點呢？
可以請前輩們指導一下嗎？
謝謝...

[quentas]

我想是作用力與反作用力的關係,也就是動量守恆吧
煞車也是這原理