Halley's comet is named after the English scientist Edmund Halley (1656-1742 ) because
A) he was first person to see it when it passed near Earth in 1682.
B) the discoverers named it for him in honor of his financial support.
C) he was the most famous astronomer alive in England during its appearance in 1758.
D) he calculated its orbit and predicted the year in which it would next be seen.
Question 2
Planets do not move on a straight line. According to Newton's First Law of Motion, that means that there must be an outside ________ acting on them.
Fill in the blank(s) with correct word