How Far Can You Fall and Still Survive?

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IStock

You’re on a plane. You’re bored. You stare out the window at the clouds. You wonder what would happen if you couldn’t resist the urge to open the emergency exit and plummet to the earth below. Is death certain? Or would you pick yourself up, set a broken bone or two, and proceed directly to a mental institution with a great story?

Let’s first toss out some variables that often bog down this fair—albeit morbid—question. Forget Felix Baumgartner, the man who filmed himself jumping from 128,100 feet. He had a cool pressurized suit and a parachute. And let’s set aside what free-fall experts have coined “wreckage riders,” those who have fallen while trapped inside a portion of broken aircraft. (The larger surface area increases air drag, slowing their descent. Still likely fatal, but the odds improve somewhat: Serbian flight attendant Vesna Vulovic fell 33,000 feet this way in 1972 and lived to tell her tale—once she woke up from her coma.)

Let’s instead restrict the question to a single individual without any equipment, encasement, or premeditation. You’ve ripped the exit door open like a lunatic. You begin to fall. What now?

We know for certain a person can survive a fall of at least 20,000 feet. That’s how far up World War II pilot Alan Magee was when he had to abandon his plane without a parachute. He crashed through a glass roof that likely helped spread out the impact. According to James Kakalios, Ph.D., a professor at the School of Physics and Astronomy at the University of Minnesota, how and where you land is one of the major factors in whether you get up from the ground or go 6 feet further into it.

“If you can make the time [landing] longer, the force needed to stop you is smaller,” he says. “Think of punching a wall or a mattress. The wall is rigid and the time of interaction is short so the force is large. People who have survived falls, they’ve managed to increase that time, even if it’s in milliseconds. From one millisecond to three, that’s three times longer, three times less force needed for the same change in momentum.” Magee’s glass landing likely reduced the impact; other survivors have plummeted into snow, trees, or something that can better absorb your landing than, say, concrete.

The other major factor? Slowing your descent. Increasing surface area means more energy is required to push air out of your way, slowing you down. The “flying squirrel” position, body splayed out, is preferred over falling feet or head first. “Increasing that drag is the biggest factor in keeping you alive,” Kakalios says. A parachute’s large surface area is best, obviously. Without one, fall belly down or try tumbling. “Drop a pen off the Empire State Building straight down and it might kill someone. But if it drops sideways, spinning end over end, it probably wouldn’t.”

You’re increasing air drag. You’re trying to land in snow or something absorbent. If you’ve passed out from lack of oxygen at high altitudes, you’ve woken up in time to orient yourself. Magee traveled 20,000 feet—nearly four miles—so you know survival is possible from there. What about going higher?

Kakalios stops short of offering a prediction, citing the numerous variables involved. (“Even how much clothing is fluttering behind you can affect surface profile,” he says.) So we pestered someone else: Paul Doherty, Ph.D., a physicist and Co-Director of the Exploratorium, a learning center in San Francisco, California.  

“As you get higher up, the air gets thinner and thinner,” he says. “You can spin so fast the blood can rush into your head and kill you. Or the friction with the elevation will burn you up. That’s why space shuttles have heat insulating tiles.”

Once terminal velocity (maximum acceleration, usually 120 miles per hour for average-sized humans) is reached, Doherty says, it doesn’t really matter whether you throw another 5000 or 10,000 feet on top of Magee’s 20,000: You’re not going to fall any faster. But start too high up and the lower atmospheric pressure means your blood might start to boil. That’s believed to happen around 63,000 feet, though data is obviously limited, and Doherty thinks it might be as high as 100,000. (NASA mandates pressure suits starting at 50,000 feet just to be on the safe side.)

So falling just under 63,000 feet is survivable, in theory? “Let’s say 60,000, Doherty says. Up to 100,000 if you wake up after passing out. And if your blood doesn’t boil. And if you can impact something.”

Stay on the plane.

Why Do People Get Ice Cream Headaches?

CharlieAJA, istock/getty images plus
CharlieAJA, istock/getty images plus

Reader Susann writes in to ask, "What exactly is the cause of brain freeze?"

You may know an ice cream headache by one of its other names: brain freeze, a cold-stimulus headache, or sphenopalatine ganglioneuralgia ("nerve pain of the sphenopalatine ganglion"). But no matter what you call it, it hurts like hell.

Brain freeze is brought on by the speedy consumption of cold beverages or food. According to Dr. Joseph Hulihan—a principal at Paradigm Neuroscience and former associate professor in the Department of Neurology at the Temple University Health Sciences Center, ice cream is a very common cause of head pain, with about one third of a randomly selected population succumbing to ice cream headaches.

What Causes That Pain?

As far back as the late 1960s, researchers pinned the blame on the same vascular mechanisms—rapid constriction and dilation of blood vessels—that were responsible for the aura and pulsatile pain phases of migraine headaches. When something cold like ice cream touches the roof of your mouth, there is a rapid cooling of the blood vessels there, causing them to constrict. When the blood vessels warm up again, they experience rebound dilation. The dilation is sensed by pain receptors and pain signals are sent to the brain via the trigeminal nerve. This nerve (also called the fifth cranial nerve, the fifth nerve, or just V) is responsible for sensation in the face, so when the pain signals are received, the brain often interprets them as coming from the forehead and we perceive a headache.

With brain freeze, we're perceiving pain in an area of the body that's at a distance from the site of the actual injury or reception of painful stimulus. This is a quirk of the body known as referred pain, and it's the reason people often feel pain in their neck, shoulders, and/or back instead of their chest during a heart attack.

To prevent brain freeze, try the following:

• Slow down. Eating or drinking cold food slowly allows one's mouth to get used to the temperature.

• Hold cold food or drink in the front part of your mouth and allow it to warm up before swallowing.

• Head north. Brain freeze requires a warm ambient temperature to occur, so it's almost impossible for it to happen if you're already cold.

This story has been updated for 2019.

Why Does Humidity Make Us Feel Hotter?

Tomwang112/iStock via Getty Images
Tomwang112/iStock via Getty Images

With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index—and why humidity makes us feel hotter.

Why does humidity make us feel hotter?

To answer that question, we need to talk about getting sweaty.

As you probably remember from your high school biology class, one of the ways our bodies cool themselves is by sweating. The sweat then evaporates from our skin, and it carries heat away from the body as it leaves.

Humidity throws a wrench in that system of evaporative cooling, though. As relative humidity increases, the evaporation of sweat from our skin slows down. Instead, the sweat just drips off of us, which leaves us with all of the stinkiness and none of the cooling effect. Thus, when the humidity spikes, our bodies effectively lose a key tool that could normally be used to cool us down.

What's relative about relative humidity?

We all know that humidity refers to the amount of water contained in the air. However, as the air’s temperature changes, so does the amount of water the air can hold. (Air can hold more water vapor as the temperature heats up.) Relative humidity compares the actual humidity to the maximum amount of water vapor the air can hold at any given temperature.

Whose idea was the heat index?

While the notion of humidity making days feel warmer is painfully apparent to anyone who has ever been outside on a soupy day, our current system owes a big debt to Robert G. Steadman, an academic textile researcher. In a 1979 research paper called, “An Assessment of Sultriness, Parts I and II,” Steadman laid out the basic factors that would affect how hot a person felt under a given set of conditions, and meteorologists soon used his work to derive a simplified formula for calculating heat index.

The formula is long and cumbersome, but luckily it can be transformed into easy-to-read charts. Today your local meteorologist just needs to know the air temperature and the relative humidity, and the chart will tell him or her the rest.

Is the heat index calculation the same for everyone?

Not quite, but it’s close. Steadman’s original research was founded on the idea of a “typical” person who was outdoors under a very precise set of conditions. Specifically, Steadman’s everyman was 5’7” tall, weighed 147 pounds, wore long pants and a short-sleeved shirt, and was walking at just over three miles per hour into a slight breeze in the shade. Any deviations from these conditions will affect how the heat/humidity combo feels to a certain person.

What difference does being in the shade make?

Quite a big one. All of the National Weather Service’s charts for calculating the heat index make the reasonable assumption that folks will look for shade when it’s oppressively hot and muggy out. Direct sunlight can add up to 15 degrees to the calculated heat index.

How does wind affect how dangerous the heat is?

Normally, when we think of wind on a hot day, we think of a nice, cooling breeze. That’s the normal state of affairs, but when the weather is really, really hot—think high-90s hot—a dry wind actually heats us up. When it’s that hot out, wind actually draws sweat away from our bodies before it can evaporate to help cool us down. Thanks to this effect, what might have been a cool breeze acts more like a convection oven.

When should I start worrying about high heat index readings?

The National Weather Service has a handy four-tiered system to tell you how dire the heat situation is. At the most severe level, when the heat index is over 130, that's classified as "Extreme Danger" and the risk of heat stroke is highly likely with continued exposure. Things get less scary as you move down the ladder, but even on "Danger" days, when the heat index ranges from 105 to 130, you probably don’t want to be outside. According to the service, that’s when prolonged exposure and/or physical activity make sunstroke, heat cramps, and heat exhaustion likely, while heat stroke is possible.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article has been updated for 2019.

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