David Debono, age 10, of Indianapolis, Indiana, for his question:

How long, does it take to get from here to Neptune?_

Later in this decade, tae plan to launch a number of spacecraft to brush by the outer planets. These grand tours include a close look at Neptune, which at present is the outside planet of the solar system. The journey from here to there is expected to take about nine years. However; the little spacecraft will be traveling slowly and unable to get there by the shortest, most direct route.

Let's imagine a future time when interplanetary travel will be faster and more direct. Our problems then would be merely the shortest distance between the two planets and our travel speed. Planets, of course, are always moving and changing their positions. The earth and Neptune are closest when both are on the same side of the sun. Then the distance between them is roughly 2,700 million miles. Traveling non stop at 340 million miles per hour we could get from here to there in about eight hours.