A space traveler would see our planet as a sphere, but careful measurements prove that this is not quite true. The earth is flattened at the poles and it bulges at the equator, though the differences are too slight for the most sharp eyed space traveler to notice.

The size and shape of the earth were figured out in 1910. The tedious job began with the parallel lines of latitude running east and west around the world. These lines or degrees were taken from the angles made by the height of certain fixed stars. At the North Pole, wich is Latitude 90 degrees North, Polaris is 90 degrees above the horizon. At Latitude 40 degrees North, Polaris is 40 degrees above the horizon.

Careful measurements showed that the parallel circles near the equator are separated by less than 69 miles. They become farther apart as they near the poles, where they are separated by more than 69 miles. This could mean that our planet has a slight bulge at the equator and a slight flattening of the poles.

A circumference is the rim of a circle. If we could slice the earth’s northern and southern hemispheres apart, we would look at a flat circle which has the equator as a circumference. The meridians, or lines of longitude, run from pole to pole and if we sliced the globe in this direction we would have a circle with a circumference 42 miles shorter.

The equator, which runs east and west around the world, has a circumference of 24,902 miles. The circumference of a meridian circle running north and south around the world is 24,860 miles long.

No one challenged these measurements until Vanguard I, no bigger than a grapefruit, went into orbit.

Data from this trip suggested other slight variations in the roundness of our planet. Scientists still agree that the equator bulges, but some of them now think that our planet is slightly pear shaped. The south pole, they say, may be round and very flat while the north pole humps up in a tapering bulge, Other scientists say that there is not enough evidence to prove this new pear shape for our planet,

Vanguard I dipped lower when its orbit carried it north of the equator. This could mean that there is more material in the northern hemisphere. The extra mass, with its extra pull of gravity, has been estimated to equal a slab of earth as big as the two Americas and 100 feet thick. If this is true, our planet might, just might, be slightly pear shaped.