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     Edmund Halley was an English scientist who lived over 200years ago. He studied the observations of

comets which other scientists had made. The orbit of one particular comet was a very difficult mathematical problem. He could not figure it out. Neither could other scientists who dealt with such problems.

     However, Halley had a friend named Isaac Newton. Who was a brilliant mathematician. Newton

thought he had already which he had done it. He told Halley that the orbit of a comet had the shape of an

ellipse.    

     Now Halley set to work. He figured out the orbits of some of the comets that had been observed by

scientist. He made a surprising discovery. The comets that had appeared in the years 1531, 1607 and

1682 all had the same orbit. Yet their appearances had been 75 to 76 years apart.

     This seemed very strange to Halley. Three different comets followed the same orbit. The more Halley

thought about it, the more he thought that there had not been three different comets, as people thought. He decided that they had simply seen the same comet three times. The comet had gone away and had come

back again. It was an astonishing idea! Halley felt certain enough to make a prediction of what would

happen in the future. He decided that this comet would appear in the year 1758. There were 53 years to

go before Halley's prediction could be tested. In 1758 the comet appeared in the sky. Halley did not see

it, for he had died some years before. Ever since then that comet been called Halley's comet, in his honor.

1. Halley made his discovery _____.

A. by doing experiments             

B. by means of his own careful observation

C. by using the work of other scientists

D. by chance

2. Halley made a surprising but correct prediction in the year _____.

A.1704  

B.1705  

C. 1706    

D.1707

3. This text in general is about _____.

A. Halley and other scientists   

B. the orbit of a comet

C. Newton and Halley  

D. Halley and Halley

4. Which of the following is TRUE?

A. Edmund Halley was an American scientist

B. Halley made his discovery by doing experiments.

C. Isaac Newton was a famous mathematician.

D. The orbit of a comet had the shape of an around.