How to Survive a 500-Foot Fall

It's a modern-day miracle. An Ecuadoran native who fell 500 feet from the upper reaches of a New York City skyscraper--and survived. By the time Alcides Moreno hit the alley behind the black-glass luxury apartment building, he was traveling upward of 124mph. Only about half of the people who fall off a four-story building make it. So how is it possible that Moreno is alive?

The answer has a lot to do with physics, luck and a 16-foot plank.

Moreno and his brother Edgar, 30, both worked for City Wide Cleaners. They were getting ready to wash windows on Dec. 7, 2007, when the cables for the scaffolding snapped. Neither wore a safety harness. Edgar died instantly when he fell off the platform and a fence severed his body. But Moreno managed to grab ahold of the 16-foot scaffolding platform--which proved crucial to his fate.

Following the training provided by his company, Moreno held fast to the platform--which increased the air drag on his falling body. And when Moreno hit the ground, the 1,250-pound scaffolding absorbed some of the shock of the 5.5-second fall, which could have reached a terminal velocity of 124mph.

The terminal velocity refers to the point at which the acceleration of a falling object ceases. Gravity's downward pull gets counteracted by an upward push against an object. With no net force acting on the object, it cannot go any faster. Rumors that Moreno had "surfed" down the side of the building on the platform have no basis in science. But physicists believe the platform may well have saved his life.

"That plank produced a large surface area, much larger than his body, increasing the wind resistance and air drag," says James Kakalios, a physics professor at the University of Minnesota. "If there's no air resistance, only gravity pulls you down. As you go faster and faster, the air resistance becomes larger and acts as an upward force that oppose your [downward] motion."

Professor Kakalios cites a classic Spider-Man episode to explain what happens when a body in motion stops too soon. When the villain pushes the superhero's girlfriend, Gwen Stacy, off a bridge, Spider-Man caught her in his web. But her neck snapped and she died.

"That's one of the times that comic books got it right," said Kakalios, the author of "The Physics of Superheroes." "The force of the webbing was so great that her body could not handle it. Anytime something stops so abruptly, there's going to be great trauma on the body." In the comic, Gwen went from at least 95mph to zero in a split second--which means that Spider-Man was responsible for the death. He should have figured out a way to use his web to slow her descent before catching her. Reducing the deceleration--the rate at which an object comes to a stop--is critical to safety in high-speed vehicles like cars, spaceships, and even roller coasters.

If the platform Moreno clung to hit something on the way--like the side of the building--its momentum could have slowed. In effect, Moreno would have experienced several discrete falls rather than one single fall.

That's how car safety equipment works. First the seatbelt stops the body's forward movement, with four inches of slack to allow the body to continue to move forward without slamming into the dashboard. The airbag then deploys, slowing the body's movement, providing a soft impact area and distributing the crash's force over a large area.

(Studies of falls have been important in the development of safety equipment. A 1942 study of falls from dangerous heights was used by Ralph Nader as part in his analysis of auto dangers in his 1965 book "Unsafe at Any Speed.")

Another factor may have come into play; it's possible that the wind currents flowing through New York's forest of buildings created some kind of cross-pressure that also slowed the plunge. As any sailor in cities like Boston and Chicago can attest, the movement of wind through buildings can create heavy and erratic gusts.

Moreno's landing also played a critical role in his survival. The scaffolding frame and the platform hit a wall, landed on a pile of twisted cables, and then bounced several feet away. While not exactly soft, the wall and cables provided a better cushion for landing than would flat concrete.

No one saw Moreno hit the ground. But his extremities absorbed most of the impact. He broke both legs and his right arm. In all, he broke 10 bones. But he managed to avoid direct hits to his pelvis, spinal column and head.

Experts who study falls say that the best way to land is feet first with the balls of the feet hitting first. But that's never a guarantee. Marin County Coroner Ken Holmes recalls several feet-first landings that violently jammed the hip bones into the chest cavity and destroyed internal organs. Kevin Hines, a survivor of a 2000 suicide attempt at the Golden Gate Bridge, remembers being in a sitting position when he hit the water.

As soon as his hands let go of the rail, Hines's mind snapped and he decided he wanted to live. "I started out swan diving with hands behind," he said. "I told myself, 'Throw your head back!' Whatever I did, it worked. I jerked my head back. My body seemed slow, but the fall seemed fast. I landed with my knees flexed a little, landed on the balls of my feet." Hines landed as if he were about to sit in a chair. Doctors said he would have smashed his spine or internal organs with even a slight change in body position.

Some experts suggest rolling on impact, to distribute the impact of the fall across the ground rather than concentrate in into one point on the ground. But rolling poses a danger that the different parts of the body will act on each other violently.

Moreno had two other factors in his favor. He was strong enough to handle the shock of a fall. And somehow, he remained somewhat loose--which could have been a huge help. If Moreno's body had tensed, the fall's force could have shot directly up his spine--concentrating, rather than dispersing, the force of the fall. The spine would have been more vulnerable to snapping, which would have cut off oxygen to the brain.

Falling causes more on-the-job fatalities than anything except transportation accidents, according to the Bureau of Labor Statistics. Of 5,703 work-related deaths in 2006, 1,329 happened on highways, 809 resulted from falls, and 583 involved workers being struck by objects.

Amazingly, Moreno's experience does not rank at the top of the list of survivals from extreme heights. Three airmen in World War II fell 20,000 to 30,000 feet and survived. A Yugoslavian flight attendant named Vesna Vulovi survived a 33,316-foot plunge when a Czech flight exploded in midair (the Guinness Book of Records recognizes her for surviving the greatest fall without a parachute). Moreno, who began talking a few days ago, joins an extraordinary club.

Euchner, a lecturer in English at Yale University, is completing a book about suicide at the Golden Gate Bridge.