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What Causes Turbulence?

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No matter how many times you've flown, feeling a plane rattle at 35,000 feet in the air can be an unnerving experience. But turbulence, whether it's a small bump or a stomach-flipping drop, is nothing to get shaken up about. It's a normal part of flying through the ever-shifting atmosphere.

Just like a truck traversing uneven roads or a ship navigating choppy seas, planes often encounter tumultuous, or turbulent, air currents in the skies. These currents can come from several different sources. When flying over high mountains, planes sometimes experience what’s called terrain-induced turbulence. The wind flowing over the peaks and through the valleys disrupts the air thousands of feet above it, resulting in a bumpy ride for any passing aircraft.

Even when flying over flat land, pilots can run into rough patches. Air that's been heated up by the sun at ground level expands and rises to create an updraft. As this updraft travels higher it may cool and condense into a cloud. Cloud-based or convective turbulence is the easiest kind for pilots (and passengers) to spot and prepare for, but not every updraft turns into a menacing cloud. There's also something called clear air turbulence which occurs when the rising hot air is too dry to form into a cloud. Unlike convective turbulence, these problem areas are impossible to identify with the naked eye alone.

So what happens when a plane meets up with one of these drafts in midair? The effects are usually mild: perhaps enough jostling to wake you from your in-flight nap, but not quite enough to topple your drink from its tray. Of course turbulence can become more severe, but in such cases passengers tend to think they're in more danger than they actually are.

"Even in rough turbulence, the plane is never changing altitude more than 10 or 20 feet either way," co-pilot and Cockpit Confidential author Patrick Smith told Mental Floss. "There’s this idea it's plummeting hundreds of feet. Not true."

Planes are built to be tossed and throttled by volatile weather: If you ever see a wing bending like a diving board in high winds, remember it’s supposed to do that. The biggest threat during a bout of turbulence is being knocked around the cabin, which is why most turbulence injuries are sustained by flight attendants. So the next time your pilot announces rough skies ahead, find your seat, fasten your seatbelt, and make note of where the barf bags are.

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

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Do 'Close Door' Buttons in Elevators Actually Do Anything?
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When you’re running late for work, one small comfort is finding an empty elevator waiting for you at your office building. You scurry inside, and since no one else is waiting to enter, you jab the 'close door' button. The doors comply, the elevator starts moving, and you breathe a sigh of relief.

This is a familiar scenario for many, but it’s also a big fat lie. That’s because most of the door-close buttons in U.S. elevators don’t actually work. In fact, they’re programmed that way.

But before you get ready to send off a strongly worded email to your office building’s elevator manufacturer, you may want to hear why this is the case. When the Americans With Disabilities Act was first passed in 1990, certain requirements for elevators were outlined, such as the installation of raised buttons, braille signs, and audible signals.

The act ensured that someone with a disability would have enough time to get inside, stipulating that elevator doors must remain fully open for at least three seconds and thereby preventing the button from cutting that time short. Some elevator manufacturers took it one step further by deactivating the button entirely.

Since the life span of an elevator is about 25 years and the Disabilities Act has been around for 28 years, it’s safe to assume that most of the elevators in operation today do not have a functioning 'close door' button, The New York Times reports. Only firefighters are able to close elevator doors manually through the use of a key.

It's important to note that there are exceptions to this rule, though. As the New York Daily News noted, New York City elevators are required by law to have working 'close door' buttons, even though some operate on a long delay (so long, in fact, that it calls the button's usefulness into question).

However, you’re in luck if you’re taking a lift (which, of course, is British for “elevator”). 'Close door' buttons are fully functional in most elevators in the UK, according to The Telegraph. A spokesman for the Lift and Escalator Industry Association told the newspaper that not all elevators have the button, but when they’re present, they do work. Again, the time it takes for the doors to shut after pressing the button varies from lift to lift.

While U.S. elevator manufacturers have a seemingly good reason for disabling the 'close door' button, some may question the point of propagating the myth and installing a button that serves no purpose in the first place. In response, some would argue that placebo buttons serve an important psychological function in society.

"Perceived control is very important," Harvard psychologist Ellen J. Langer told The New York Times. "It diminishes stress and promotes well-being."

That’s right: By believing that you’re in control of your fate—or at least how quickly you can make it up to the sixth floor—you’re better off. It doesn’t end with elevators, either. Buttons placed at city crosswalks are often disabled, and the thermostats in many office buildings are rigged so that the temperature can’t be altered (even if the numbers appear to change).

Some might swear up and down that elevator 'close door' buttons work, but this, too, could be your brain deceiving you. As author David McRaney wrote in an essay: “If you happen to find yourself pressing a nonfunctional close-door button, and later the doors close, you’ll probably never notice because a little spurt of happiness will cascade through your brain once you see what you believe is a response to your action. Your behavior was just reinforced. You will keep pressing the button in the future.”

According to The New Yorker, these buttons are designed to alleviate some of the subconscious anxiety that comes from stepping inside a tiny box that's hoisted up some 20 or 40 or 80 floors by a cable: “Elevator design is rooted in deception—to disguise not only the bare fact of the box hanging by ropes but also the tethering of tenants to a system over which they have no command."

So now you know: Next time you’re running late to work, take comfort in the fact that those few extra seconds you would’ve saved by pressing a functioning 'close door' button aren’t worth all that much in the long run.

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

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What’s the Difference Between Prison and Jail?
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Many people use the terms jail and prison interchangeably, and while both terms refer to areas where people are held, there's a substantial difference between the two methods of incarceration. Where a person who is accused of a crime is held, and for how long, is a factor in determining the difference between the two—and whether a person is held in a jail or a prison is largely determined by the severity of the crime they have committed.

A jail (or, for our British friends, a gaol) refers to a small, temporary holding facility—run by local governments and supervised by county sheriff departments—that is designed to detain recently arrested people who have committed a minor offense or misdemeanor. A person can also be held in jail for an extended period of time if the sentence for their offense is less than a year. There are currently 3163 local jail facilities in the United States.

A jail is different from the similarly temporary “lockup”—sort of like “pre-jail”—which is located in local police departments and holds offenders unable to post bail, people arrested for public drunkenness who are kept until they are sober, or, most importantly, offenders waiting to be processed into the jail system.

A prison, on the other hand, is usually a large state- or federal-run facility meant to house people convicted of a serious crime or felony, and whose sentences for those crimes surpass 365 days. A prison could also be called a “penitentiary,” among other names.

To be put in a state prison, a person must be convicted of breaking a state law. To be put in a federal prison, a person must be convicted of breaking federal law. Basic amenities in a prison are more extensive than in a jail because, obviously, an inmate is likely to spend more than a year of his or her life confined inside a prison. As of 2012, there were 4575 operating prisons in the U.S.—the most in the world. The country with the second highest number of operating prisons is Russia, which has just 1029 facilities.

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

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