What is it like to stand on top of the world? Nothing short of exhilarating, say those who've made it to the top of Mount Everest's summit 29,029 feet above sea level, at the cruising altitude of a 747. The spectacular view aside, part of what makes the experience so exhilarating is that getting there is no walk in the park. Carrying pounds of equipment up vertical inclines while enduring freezing temperatures, blinding sunlight and the possibility of being buried alive by avalanches or swallowed by hidden ice crevices--makes the trip difficult enough. Now imagine doing all that while holding your breath. That's what it feels like as the change in atmospheric pressure and thinner air takes its toll on the human body, making even minimal tasks feel like an impossibility. 

So how–and why–do mountaineers cope with such difficulties? 

That's the subject of an amazing new movie, Everest, which reveals just how difficult it is to master this monster of a mountain, especially when faced with unforeseen circumstances. The movie is based on the deadly storm that climbers faced during their summit on May 10, 1996. Among the climbers was Jon Krakauer, a journalist from Outside magazine at the time. He was a member of Rob Hall's New Zealand-based expedition. Krakauer successfully made it to the summit and started his descent before the blizzard swept over the mountain. In total, the unexpected storm took the lives of eight climbers. It seems that his book, Into Thin Air (Villard Books, 1997), is not the basis of the new film--in that, Krakauer is just one of several characters with varying points of view. In the book, Krakauer describes his experiences as well as those of his fellow teammates as they prepared to climb Everest. At least two other books were published about their summit, including Left for Dead (Dell, 2000) and After the Wind (Good Hart Publishing, 2014). 

Here are some of the issues the men and women who risk their lives experience in their attempts to conquer Mount Everest: 

Acclimatization

Acclimatization is a process that spans several weeks and allows climbers to adjust to the different environmental conditions atop Everest. Base Camp sits at 17,600 feet above sea level, but then there is a series of four camps above Base Camp - each approximately 2,000 feet higher than the last, as the movie states. Hall's system of becoming acclimatized involved several trips between each, so that the climbers could get used to the decreasing oxygen concentrations without shocking their bodies.

Supplemental Oxygen

At 29,029 feet above sea level there is less oxygen and the air essentially becomes thinner. There is also less nitrogen, argon and other gasses that make up the air we breathe. These high-altitude conditions are associated with feeling out of breath and make it hard for climbers to exert themselves in anyway without feeling fatigued. To make it easier, or at least less life-threatening, climbers are fitted with supplemental oxygen tanks when venturing above 8,000 meters. Hall's team used state-of-the-art Russian-built oxygen systems that had a stiff plastic oxygen mask connected via a rubber hose and a crude regulator to an orange steel and Kevlar gas canister. Each tank weighed about 6.6 pounds when full. When on their final ascent, climbers slept with these tanks at Camp Three and Four, and each carried two up the mountain on May 10. They were to pick up a third bottle for their final decent from the South Summit.

Death Zone

Altitudes above 25,000 feet lie within what is known as the Death Zone. At this height, climber's bodies are "literally dying." When climbers venture into this zone, they subject themselves to the potentially deadly effects of oxygen deprivation. This includes higher heart rates, less blood circulation, fatigue, dehydration, hallucinations, confusion, and loss of appetite and insomnia - both of which are important for climbers remaining healthy and strong. Krakauer alone remembers losing nearly 20 pounds of muscle mass by the time they were to make their final ascent on May 10. He noted the losses were mainly from his shoulders, back, and legs - muscles that are particularly important to hauling yourself up a mountain, right? He also remembers burning almost all of his body fat, which made him increasingly more sensitive to the cold. 

HAPE

High-Altitude Pulmonary Edema (HAPE) is characterized by the accumulation of fluids in the lungs. The risk of this serious medical illness increases as the air becomes thinner. In his book, Krakauer explained the symptoms and treatments one of the expedition's Sherpas, Ngawang Topche, received when developing HAPE. Ngawang was a Sherpa on the American team led by Scott Fischer. When Fischer found Ngawang sitting on the glacier at 21,000 feet, during one of their acclimatization climbs, "he admitted that he'd been feeling weak, groggy and short of breath for more than two days." Emergency evacuations are costly, so HAPE is often treated with certain medicines, and "descending as little as 2,000 feet is typically enough to bring about complete recovery from HAPE." Individuals that are diagnosed with HAPE are also sometimes placed in a Gamow Bag, which is an inflatable plastic chamber about the size of a coffin, in which the atmospheric pressure is increased to simulate a lower altitude.

HACE

High-Altitude Cerebral Edema (HACE) is less common than HAPE, but tends to be even more deadly. "A baffling ailment, HACE occurs when fluid leaks from oxygen-starved cerebral blood vessels (blood vessels of the brain), causing severe swelling of the brain, and it can strike with little to no warning," Krakauer explained. When pressure from the swelling accumulates in one's skull, motor and mental skills deteriorate at a very fast rate, typically within a few hours or less. The speed of the deterioration often makes the illness hard to detect. Similarly to HAPE, descending to a lower altitude is supposed to relieve symptoms. One of Krakauer's teammates did succumb to this illness after moving from Camp Two to Camp Three during one of their acclimatization trips.

Wind Chill, Freezing Temperatures and Snow

When climbing to higher altitudes, climbers also increase their risk of frost bite and hypothermia. Sometimes, no matter how much protective gear climbers are suited with, parts of their bodies are simply not kept warm enough. At high altitudes, where temperatures are extremely low, if any skin is exposed it could instantly freeze. Depending on the severity, this could then lead to loss of extremities. Krakuer accounted for this in his book, and one of his team members, Beck Weathers, suffered from severe frost bite on his hands, nose and feet. Weathers suffered from snow blindness, following a recent operation and was stuck on the mountain during the 1996 storm. Snow blindness is common among climbers after being exposed to intense sun rays reflecting off the bright white snow. After the storm passed, Weathers made it to Camp IV and was later evacuated for treatment that mountain doctors couldn't provide. This was one of the highest altitude medical evacuations ever performed by a helicopter.

A Race Against the Clock

When climbers begin their final ascent of Mount Everest, every minute counts, especially when climbing in the Death Zone. On May 10, 1996, climbers set out for the summit in the middle of the night so that they could make it to the top before turning around by one or two p.m. Their oxygen tanks would supply them with two liters of compressed air per minute, and each bottle was supposed to last between five and six hours. By four or five p.m. everyone's gas would be gone. Running out of oxygen is a surreal risk when climbing to high-altitudes, and a risk that only increases if climbers are not adequately acclimatized or in peak physical condition. If, or when, a climber runs out of oxygen, they instantly become more vulnerable to HAPE, HACE, hypothermia, frostbite, impaired judgment and, ultimately, death.

"With enough determination, any bloody idiot can get up this hill," Hall explained to his clients when emphasizing the importance of sticking to their turn-around time on the day of their 1996 summit. "The trick is to get back down alive."

Despite the dangers of climbing Everest, more than 4,000 climbers have willingly endured the harsh environments to accomplish long sought-after goals and to stand on top of the world, even for just a few moments. "My watch read 1:17 p.m. All told, I'd spent less than five minutes on the roof of the world," Krakauer wrote. 

The thing is, when people set out to climb Mount Everest no one wants to die. In fact, it is quite the opposite. Some ascend Everest for a personal sense of triumph, while others hope to inspire others to accomplish their goals. But no matter the reason, before you pack your bags for Nepal, you must realize what you are signing up for accept that danger is part of the deal. 

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

-Follow Samantha on Twitter @Sam_Ashley13