Mary Ann Ericson, age 8, of Ventura, Calif., for her question:

WHO INVENTED THE WHEEL?

We don't know the person's name, but the wheel was most likely invented by some individual who lived near the eastern end of the Mediterranean Sea more than 5,000 years ago. The invention is now regarded as one of man's greatest discoveries.

The first wheel developed from logs used as rollers to make it easier to move heavily loaded sleds. The first wheels probably were made of rough disks of wood cut from tree trunks and fastened to each end of a small roller. This type of crude, solid wheel is still used in parts of India and Java.

An Egyptian chariot built about 2,000 B.C. is one of the oldest relics of wheeled vehicles ever found. It has wheels much like those of today.