Stephen Moncrieff, age 13, of Victoria, B.C., for his question:

Where is the fourth dimension?

The dimensions of a flat page are its length and its width. If these dimensions exist anywhere, they must also exist through the universe. This is also true of any other dimension that the mind of man is capable of grasping. We use length and width to figure the problems of plane or flat geometry. Solid geometry calls for a third dimension of height. We use these three dimensions of height, length, and width to measure objects and spaces in the everyday world around us. But these three were not enough to figure some of the energetic items in our modern age. Fast planes, fast bullets and moving targets made speed a necessary new element. And speed is related to time, plus all the other dimensions.

Scientists of the 18th Century figured out how to use geometry to solve the fourth, fifth, and other dimensions that might be needed. As a rule, we take the fourth dimension to be a measure of time in relation to the other three. Even space travelers must base their calculations on the relationship of space, time, and distance. And to them, the fourth dimension is time.