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.
Who was Edmund Halley?
Of what nationality?
How long ago did he live?
What did he study?
What could he not figure out?
Who was Halley's friend?
Who was he?
What years did the comet appear?
Did they all have the same orbit?
How many years apart were they?
What did Halley predict?
In what year?
Did the comet appear?
Was he alive to see it?
What was the name of the comet?
How many years did it take for the comet to come back?
Did other scientists try to figure it out?
Were they successful?
What shape did the comet's orbit have?
Who figured that out?
a scientist
an English scientist who lived over 20
English
 an English scientis
more than 200 years ago
over 200years ago. 
comets
s of comets which other scientists had made. The orbit of one par
the orbit of a particular comet
The orbit of one particular comet was a very difficult mathematical problem. 
Isaac Newton
nd named Isaac Newton.
a methematician
n. Who was a brilliant mathematician. Newton thought he had already whi
1531, 1607 and 1682
1531, 1607 and 1682 
yes
1682 all had the same orbit.
75 t o76
75 to 76 years apart. 

the comet would come back
e decided that this comet would appear in the year 1758. There were 53 years to go before Halley's prediction could be tested. 
1758
 would appear in the year 1758. 
yes
In 1758 the comet appeared in the sky. H
no
for he had died some years before
Halley's comet
Ever since then that comet been called Halley's comet, in his h
76 years
75 to 76 years apart. 

yes
. Neither could other scientists who dealt with such problems. 

no
Neither could other scientists who dealt with such proble
ellipse
 had the shape of an ellipse. 
Newton
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. 
