A. emerge B. absorbing C. subject D. defining E. movement F. originally G. course H. universally I. happens J. constant K. corresponds |
How Long Is a Second?
The length of a second depends on how you’re measuring it. There are 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute — so surely a second is 1/86400, of a day, right? Well, it turns out that
“The second was
In the 16th century, people turned to technological solutions to this problem, and the first recognizable mechanical clocks began to
By around 1940, quartz crystal clocks (石英钟) had become the new gold standard. However, problems arose, and this was where atomic clocks came in. “Atoms exist only in particular energy states and can only change from one state to another by
In fact, scientists are discussing whether it’s time to redefine the second again. But while several important questions still need to be answered before this
1. The coffee slipped out of my hands. I’ll dry it with this cloth.
2. You’re right, let’s go for her, then.
3. Maybe it means there is some paper stuck inside
4. I think we should change course.
5. It is possible because picking up the instrument requires strength of character.
course : A. 一道菜 B. 课程 C.航线
1. I’d like to take a refresher course to improve my driving.
2. The plane was off the course.
3. They were treated with a five-course dinner for lunch.
A.course | B.busy | C.begin | D.balloon |
A.10-courses | B.10 course’s | C.10-course | D.10th course |