SAN FRANCISCO (AP) Two men are attempting what has been called the hardest rock climb in the world: a grueling ascent of a half-mile of exposed granite in California's Yosemite National Park using only their hands and feet.
Kevin Jorgeson, 30, of Santa Rosa, California, and Tommy Caldwell, 36, of Estes Park, Colorado, are relying completely on their physical strength and dexterity to make their way up the Dawn Wall, a vertical face on one side of the famous rock formation known as El Capitan. The attempt - their third since 2010 - has caught the world's attention.
The men have been climbing toward the summit for two weeks and could finish sometime in the coming days. Here are some answers to common questions about the climb:
Q: WHY IS THIS CONSIDERED SO DIFFICULT?
A: No one has ever ''free climbed'' to the top of the Dawn Wall. In 1970, Warren Harding and Dean Caldwell - no relation to Tommy - spent more than 27 days free climbing the wall but did not make it to the summit. The climbers use harnesses and ropes to catch them if they slip, but the equipment does not help them ascend.
There are about 100 routes up El Capitan, the largest granite monolith in the world, which rises more than 3,000 feet above the Yosemite Valley floor. Of those, the hardest and steepest is the Dawn Wall, so named because it faces east toward the rising sun.
Q: WHAT IS FREE CLIMBING AND HOW DOES IT DIFFER FROM OTHER TYPES OF CLIMBING?
A: In free climbing, athletes use only their hands and feet. They grip cracks in the granite as thin as razor blades and as small as a dime. Most footholds are nothing more than an indentation on the wall. Free climbing should not be confused with solo climbing, where climbers are alone and without ropes, harnesses or any protective gear.
Q: WHO ARE THE CLIMBERS?
A: Caldwell is a professional climber who has free climbed 11 routes on El Capitan. He's been climbing since he was 17.
He's been in peril before. In 2000, Caldwell and three other climbers went to the former Soviet republic of Kyrgyzstan to scale the towering rock walls of its southern mountains. Seventeen days in, they were captured by the Islamic Movement of Uzbekistan. Caldwell shoved a guard over a cliff, and the climbers fled, eventually reaching a Kyrgyz army outpost. The guard survived the fall.
In 2001, Caldwell accidentally cut off his left index finger with a table saw. Six months later, he scaled a different route up El Capitan in 19 1/2 hours with only protective hardware to stop any falls. Only once before had anyone managed such a climb in less than 24 hours.
Jorgeson is also a professional climber, speaker and instructor. On his personal website he says he's been climbing all his life.
''At first, it was fences, cupboards, ladders and trees.'' ''Climbing was always a very natural thing for me to do, so when I found rock climbing, it felt perfect. I can't imagine a sport that fits my personality any better.''
Q: WHAT ARE THE HAZARDS OF THE CLIMB?
A: Climbers' fingers take a beating. Jorgeson has battled with one lower section so many times that the sharp holds ripped both the tape and the skin off his fingers. Caldwell's fingers are so raw that he sets his alarm to reapply a special product to his skin.
Caldwell said on Facebook that the middle section of the climb involves ''some of the smallest and sharpest'' holds he has ever attempted.
At one point, climbers have to jump completely off the wall to catch a grip the size of a matchstick. What's more, the warm weather has them climbing only at night, when the rock is cold enough for maximum traction.
Q: HOW LONG HAVE THEY BEEN TRAINING?
A: Jorgeson has been training for five years, and Caldwell put in about seven years of training. They tried the climb in 2010 but only made it a third of the way because of storms. A year later, Jorgeson broke an ankle after a fall during an attempt.
John Long, the first person to climb up El Capitan in one day in 1975, said earlier this week that it's almost ''inconceivable that anyone could do something that continuously difficult.'' He said he believes the duo spent the equivalent of a year's time on the wall in preparation.
Q: HOW ARE THEY MAINTAINING CONTACT WITH THE OUTSIDE WORLD?
A: The men eat, drink coffee, stretch and sleep in hanging tents suspended from the wall. Supporters bring supplies, including pain pills, batteries and super glue for their fingers. They keep in touch by regularly tweeting, posting on Facebook, feeding information for blogs and talking with teams on the ground. The tents are in the same location and the men return to them after they climb each day. To get back to the spot where they left over, they use climbing aids.
Q: WHERE ARE THEY NOW?
A: They started together on Dec. 27. As of Thursday, Caldwell had climbed 400 feet above Jorgeson's high point to Wino Tower, a rare ledge 2,000 feet up, said Tom Evans, a photographer and climber who has been chronicling the journey. Jorgeson has been struggling to get past a particularly difficult section lower down and planned to try again Friday.
Q: WHAT HAPPENS IF JORGESON CAN'T GET BEYOND WHERE HE IS NOW?
A: Evans said Jorgeson is an equal partner in the endeavor, and if he can't climb above the particularly difficult part, he will continue in support of Caldwell and try to climb as much as his injuries allow.