Mary Ann Millen, age 17 of Montgomery, Ala., for her question:

WHEN DID THE SPORT OF MOUNTAIN CLIMBING START?

Mountain climbing as a sport began in 18th century Europe, with attention focused primarily on Mount Blanc in the French Alps, which was first successfully scaled in 1786. For about a century thereafter, often referred to as the golden age of climbing, climbers attempted other Alpine summits.

By the end of the 19th century mountain climbing clubs had been organized throughout Europe and North America and most climbing was being done without guides.

In the 20th century, climbers turned their attention to the world's highest ranges, the Himalaya and the Karakoram. Mount Everest was finally conquered in 1953 by a New Zealander named Edmund Hillary and a Sherpa guide from Nepal named Tenzing Norkay.

The second highest peak in the world, K2, formerly known as Mount Godwin Austen, was climbed in 1954.

Once remote and unknown ranges now attract numerous expeditions every year, with climbers coming from all over the world as the sport of mountain climbing grows in popularity. The highest mountains outside Asia lie in South America. Many of them have yet to be climbed.

Mountain climbing can be divided into three types: scrambles or walkups that require no special equipment; rock climbing; and ice climbing.

Rock climbing requires knowledge of rope handling. Climbers use a rope to belay, or secure, one another. One climbs while another holds the rope to protect against any fall or slip. A technique called rappelling is used in descending very steep terrain. The rope is attached in such a way that it can be pulled down after the last climber has used it.

Major centers of activity for rock climbing include Yosemite Valley in California and the limestone cliffs of the Shawangunks in New York State. Ice climbing requires using an ice ax to cut steps and probe crevasses.

Ice climbing also requires the use of crampons, devices with 12 or more sharp steel points that are strapped onto each boot. Glacier routes requires the use of slings and additional equipment so that a climber who falls into a crevasse may quickly climb or be hauled out.

Although the sport of mountain climbing does have risks, and accidents may be of catastrophic proportions, proper training and advanced techniques now ensure relative safety.

Climbers now often begin by taking lessons through a college group, or from one of the many local clubs in all parts of the world. Others learn from experienced friends or professional guides.

Because so many of the early climbing enthusiasts were scientists or writers, or both, the field is unusually rich in descriptive literature.

Current trends in climbing favor ascents made by small parties, moving very quickly with a minimum of lightweight equipment over direct