Why Do We Close Our Eyes When We Sneeze?

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The anatomy of a sneeze is pretty disgusting. For someone with a cold, allergies, or just a tickle in the nose, it takes less than a second to eject about 5000 droplets of mucus from their nostrils at speeds of up to 100 mph. Those infectious snot particles can travel up to nearly 30 feet and remain suspended in the air for up to 10 minutes, creating a plume of biohazard air that threatens anyone in its path.

Our body doesn't mind delivering germs at high velocity, but it does appear to dislike looking at it. During a sneeze, most everyone involuntarily closes his or her eyes as a reflex action. Why? And what happens if we try to keep them open?

“Part of the sneeze reflex involves muscles in the eyelid region,” says Dale Tylor, MD, a pediatric and general otolaryngologist at the Washington Township Medical Foundation in Fremont, California. “I would be speculating, but likely it doesn't make sense to have your eyes open when you have these tens of thousands of microparticles coming out at high speeds from your nose, because then they could possibly get in your eyes.”

Tylor is quick to add that scenario isn't science—we really don’t have a definitive answer as to why we close the eyes, just an educated guess based on what we think our body is trying to defend itself from. Namely, snot.

Some people, however, can keep their eyes open during a sneeze, like the young woman who thoughtfully captured this feat on video. (Warning: though not graphic, it’s very odd to see someone sneezing and making eye contact.)

People this talented are rare, according to Tylor. And any urban legend about “blowing out” your eyes if they happen to be open while sneezing is not really possible. Still, while you could try to sneeze with your eyes open, it’s best to let your body do what it does best: protect you from your own disgusting functions.

How Often Should You Poop?

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When it comes to No. 2, plenty of people aren’t really sure what’s normal. Are you supposed to go every day? What if you go 10 times a day? Is that a sign that you’re dying? What about once every three days? Short of asking everyone you know for their personal poop statistics, how do you know how often you’re supposed to hit the head?

Everyone’s system is a little different, and according to experts, regularity is more important than how often you do the deed. Though some lucky people might think of having a bowel movement as an integral part of their morning routine, most people don’t poop every day, as Lifehacker informs us. In fact, if you go anywhere between three times a day and three times a week, you’re within the normal range.

It’s when things change that you need to pay attention. If you typically go twice a day and you suddenly find yourself becoming a once-every-three-days person, something is wrong. The same thing goes if you normally go once every few days but suddenly start running to the toilet every day.

There are a number of factors that can influence how often you go, including your travel schedule, your medications, your exercise routine, your coffee habit, your stress levels, your hangover, and, of course, your diet. (You should be eating at least 25 to 30 grams of fiber a day, a goal that most Americans fall significantly short of.)

If you do experience a sudden change in how often you take a seat on the porcelain throne, you should probably see a doctor. It could be something serious, like celiac disease, cancer, or inflammatory bowel disease. Or perhaps you just need to eat a lot more kale. Only a doctor can tell you.

However, if you do have trouble going, please, don’t spend your whole day sitting on the toilet. It’s terrible for your butt. You shouldn’t spend more than 10 to 15 minutes on the toilet, as one expert told Men’s Health, or you’ll probably give yourself hemorrhoids.

But if you have a steady routine of pooping three times a day, by all means, keep doing what you’re doing. Just maybe get yourself a bidet.

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

What Would Happen If a Plane Flew Too High?

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Tom Farrier:

People have done this, and they have died doing it. For example, in October 2004, the crew of Pinnacle Airlines 3701 [PDF]  was taking their aircraft from one airport to another without passengers—a so-called "repositioning" flight.

They were supposed to fly at 33,000 feet, but instead requested and climbed to 41,000 feet, which was the maximum altitude at which the aircraft was supposed to be able to be flown. Both engines failed, the crew couldn't get them restarted, and the aircraft crashed and was destroyed.

The National Transportation Safety Board determined that the probable causes of this accident were: (1) the pilots’ unprofessional behavior, deviation from standard operating procedures, and poor airmanship, which resulted in an in-flight emergency from which they were unable to recover, in part because of the pilots’ inadequate training; (2) the pilots’ failure to prepare for an emergency landing in a timely manner, including communicating with air traffic controllers immediately after the emergency about the loss of both engines and the availability of landing sites; and (3) the pilots’ improper management of the double engine failure checklist, which allowed the engine cores to stop rotating and resulted in the core lock engine condition.

Contributing to this accident were: (1) the core lock engine condition, which prevented at least one engine from being restarted, and (2) the airplane flight manuals that did not communicate to pilots the importance of maintaining a minimum airspeed to keep the engine cores rotating.

Accidents also happen when the "density altitude"—a combination of the temperature and atmospheric pressure at a given location—is too high. At high altitude on a hot day, some types of aircraft simply can't climb. They might get off the ground after attempting a takeoff, but then they can't gain altitude and they crash because they run out of room in front of them or because they try to turn back to the airport and stall the aircraft in doing so. An example of this scenario is described in WPR12LA283.

There's a helicopter version of this problem as well. Helicopter crews calculate the "power available" at a given pressure altitude and temperature, and then compare that to the "power required" under those same conditions. The latter are different for hovering "in ground effect" (IGE, with the benefit of a level surface against which their rotor system can push) and "out of ground effect" (OGE, where the rotor system supports the full weight of the aircraft).

It's kind of unnerving to take off from, say, a helipad on top of a building and go from hovering in ground effect and moving forward to suddenly find yourself in an OGE situation, not having enough power to keep hovering as you slide out over the edge of the roof. This is why helicopter pilots always will establish a positive rate of climb from such environments as quickly as possible—when you get moving forward at around 15 to 20 knots, the movement of air through the rotor system provides some extra ("translational") lift.

It also feels ugly to drop below that translational lift airspeed too high above the surface and abruptly be in a power deficit situation—maybe you have IGE power, but you don't have OGE power. In such cases, you may not have enough power to cushion your landing as you don't so much fly as plummet. (Any Monty Python fans?)

Finally, for some insight into the pure aerodynamics at play when airplanes fly too high, I'd recommend reading the responses to "What happens to aircraft that depart controlled flight at the coffin corner?"

This post originally appeared on Quora. Click here to view.

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