Why Do We Close Our Eyes When We Sneeze?

iStock
iStock

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.

Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

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

Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

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

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