Missy Perry, age 13, of Dover, Del., for her question:

WHEN WAS THE FIRST DIGITAL WATCH MADE?

A locksmith from Germany named Peter Henlein is said to have invented the first watch in about 1500. It was so heavy that it had to hang from a belt around the waist.

Hundreds of years later, in 1957, an electric watch was introduced in the United States by a company named Hamilton. In the electric watch, an energy cell, or battery, provided the power to run the watch. The energy cell supplies electric power to a coil mounted on the balance wheel. As the coil passes through the magnetic field of two permanent magnets, an impulse from the balance wheel sends power to the train.

In the 1970s the digital watch was introduced and became popular. Here power from a battery activates a quartz crystal. Electronic circuits translate vibrations from the crystal into hours, minutes and seconds. The information is then displayed by means of numbers that light up on the blank face of the watch.