A、To prove the earth was round. B、To gather information for planning space flights. C、Because all spacecraft had to carry comput

Sailors long ago were often afraid that if they sailed too far from home they would fall off the edge of the flat ocean. In the past, many people had to trust the words of others, for they had no way to gather information for themselves. Today, we can fly in airplanes high over the earth and see the curve that is proof of its roundness. Astronauts soaring miles high can send us pictures that support our beliefs.  Most people now accept the fact that the earth is definitely not flat. But many of them don’t realize that it’s not exactly round, either.
    Actually, some scientists in the 1950’s discovered that the earth is shaped more like a pear, thicker on one end than the other.
    A mathematician, Ann Eckels Baillie, used computers to gather information to use in planning space flights. In her work, she figured the distance of spacecraft from the planet to a star.
    During her regular work of tracking the second U. S.  satellite, Vanguard I, she discovered some facts that didn’t seem to make sense.  It appeared that the perigee (or point nearest to the earth) of the Vanguard orbit measured a different distance from the northern hemisphere of our earth than from the southern hemisphere. At first, she and her colleagues thought the strange figures were due to some mathematical error. But Baillie wouldn’t give up the idea that important new information had been discovered.  She and the other scientists discussed the shape of the earth again and again.  Further research finally proved that Baillie’s accidental finding was correct.