Michael Mulhern, age 12, of  N. C,  for his question:

Why doesn't a satellite pass over the same city every trip?

A little man‑made satellite orbits the earth in a few years. Meantime, the earth below also is turning. The earth rotates clear around on Sts axis every 24 hours. And it turns always towards the east.

Suppose a satellite passed aver Winston‑Salem at noon an Tuesday. If its orbit were a perfect circle it would pass over that part of the world some two or three hours later on its next trip. But Winston‑Salem would not be there. For, meantime the earth would have taken it further east. On this second trip the satellite would pass over some spot on the globe which is west of Winston‑Salem.

The Soviet satellites have almost pole to pole orbits and the U.S. satellites go around the waist of the world. It is very hard to launch them into a perfectly round orbit and their orbits are usually oval. This adds to the irregularity and a let of figuring is necessary to predict when a satellite will pass over this city or that city.