Melissa Whitmore, age 13, of Butte, Mont., for her question:

WHEN WAS THE TELESCOPE INVENTED?

You use your telescope to make distant objects appear closer. This wonderful instrument was invented by chance in 1608 by a Dutch spectacle maker named Hans Lippershey.

In his shop in Middleburg, Holland, Lippershey picked up two of his lenses and holding them together, he looked through them at a weather vane that topped a nearby church. Suddenly the rooster on top of the weather vane looked gigantic. Accidentally, Lippershey had found a way to make a telescope.

It wasn't long until lenses were placed into tubes of lead or paper. One lens was convex, meaning that it was thicker at the center, while the other was concave and thinner at the center. With this instrument, distant objects were magnified and made to look nearer and clearer.

The name "telescope" came from an Italian astronomer named Galileo Galilei who made his own instrument shortly after Lippershey's discovery. Also using the equipment at this time was a German astronomer named Simon Marius. Marius and Galileo both had the same idea: use the telescope to study the sky. Each independently discovered the satellites of Jupiter.

During the next few years Galileo proved the value of the telescope by his discoveries of the mountains on the moon, the phases of Venus, the spots on the sun and many faint stars that cannot be seen with the unaided eye. His telescope lenses were less than two inches in diameter and the tube was not more than four feet long.

Soon astronomers were grinding larger lenses and making longer tubes. In 1656 a Dutch scientist named Christian Huygens made a telescope 23 feet long with which he could see Saturn's rings. Later he made an instrument 122 feet long with a lens six inches in diameter. And still later he made telescopes that measured 170 and 210 feet in length.

All of the early telescopes were refracting instruments.

Large refracting lenses proved not to be satisfactory because they made everything look blurred. The problem was solved, however, in 1663 by a Scots mathematician named James Gregory. Gregory worked out a scheme for a reflecting telescope. In 1668, Isaac Newton actually made one.

In the 20th century, scientists have discovered that many invisible radiations reach the Earth from outer space and they have invented new kinds of telescopes to detect and measure them.

Light travels through space like waves and there are different colors because the peaks of the waves can be close together or far apart. X rays and ultraviolet radiation are like light but their waves are too close together for our eyes to see them.

In other radiations, like radio waves and infrared radiation, the waves are too far apart for us to see. All these waves are parts of the electromagnetic spectrum.

The first of these radiations to be discovered, in the 1930s, was radio waves. The first radio telescope was built in 1937 by an American electrical engineer named Grote Reber. It looked like a reflecting optical telescope but it was much bigger: 31 feet across.