At 1130 local time on the morning of May 29, 1953, Edmund Hillary and Tenzing Norgay stood on the roof of the world - the summit of Mount Everest. The ascent to the world's highest peak had been a goal of climbers for generations but all previous attempts had ended in failure, and, in several cases, death.

Edmund Hillary says so little was known about the summit of Mount Everest in 1953, that no one was even sure if humans could live at the 8,850 meter peak. At a recent event in New Delhi to commemorate the golden jubilee of the first ascent of Everest, Mr. Hillary said he and his Sherpa partner Tenzing Norgay climbed into the unknown.

"One of the major problems we did not know whether it was actually possible to reach the summit of Mount Everest and survive," says Mr. Hillary. "We were afraid of a psychological barrier, which might cause us to reach the summit but then collapse. This was always hanging over our heads." But they proved that humans could live at the top of the world, and since May 29, 1953, more than 1,200 climbers have scaled Mount Everest.

Both men had made previous climbs on Everest, Mr. Hillary in 1951, as part of an exploratory attempt to map routes to the summit from the newly opened south side of the mountain in Nepal. Mr. Tenzing was part of a Swiss team that failed to reach the summit in 1952.

In 1953, they were back as part of a large British-led expedition. The team leader, John Hunt, a veteran climber and British military officer, told the men they would be given the chance to reach the summit.

Two other climbers in the expedition reached the south summit of Everest, 90 meters below the actual summit, but were forced to retreat after their oxygen equipment failed.

After spending the night at 8,300 meters, Mr. Hillary and Mr. Tenzing rose early on the morning of the May 29, and began climbing. Mr. Hillary says after reaching the south summit, they faced a final obstacle, a 12-meter-high rock wall now known as "Hillary's Step." "I wriggled my way to the top and then Tenzing joined me," he says. "I continued hacking steps along the ridge and then up a few more to the right and to my great delight we carried on up and I realized we were on top of Mount Everest and the whole world was spread out below us."

The men embraced, and left small offerings in the snow. Edmund Hillary took Tenzing Norgay's picture and then they headed back down the mountain - their lives forever changed.

Stephen Venables is the author of two books on Mount Everest, including the just published "Everest, Summit of Achievement." The veteran climber, who helped open a new route to the summit in 1988, says Edmund Hillary and Tenzing Norgay were superb climbers but they benefited from those who came before them.

"It was like all these things, the result of each succeeding generation building on the learning of the proceeding generation," says Mr. Venables "And, of course, 1953 was a big team effort with 12 climbers on the team and many other local Sherpa, local Nepali people also contributing to the climb?. It was a combination, an accumulation of wisdom, better equipment, particularly better oxygen equipment, and then probably the fittest members of the team making that final step into the unknown."

For years, Mr. Hillary and Mr. Tenzing refused to say who had reached the summit first. In his autobiography, published after Mr. Tenzing's death in 1986, Mr. Hillary said he did in fact step onto the summit ahead of his Sherpa partner. However, he said it was of no significance since neither man would have reached the summit without the help of the other.

In New Delhi, Mr. Hillary recalled how his partner saved his life when he fell into a crevasse, an indication of the trust and teamwork that enabled the two to make history. "The thing is that Tenzing and I were a team and I expected Tenzing to carry out the right procedure in an emergency, as I would have expected myself to do had our roles been reversed," he says.

Edmund Hillary says if the weather is bad no one can climb Mount Everest. But, he says if the weather is good, a person who is fit and strong can reach the top. And, he says, the feeling at the top of Mount Everest is never forgotten.