10 Scientific Mysteries We Take for Granted

Most of us know that the Big Bang hasn’t been totally figured out and black holes are pretty confusing, but even these familiar aspects of the universe also keep scientists up at night.

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Young african woman sleeping in her bed at night, she is resting with eyes closed
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Why do humans need to sleep?

Researchers aren’t sure exactly what happens in our brains and bodies while we’re falling asleep or sleeping, but we do know sleep is important—long-term sleep deprivation can cause hallucinations, psychosis, heart disease, and immune system dysfunction. (Check out the surprising connection between sleep deprivation and aging.) “Sleep is the single most effective thing you can do to reset your brain and body health,” says Matthew P. Walker, Ph.D, professor of neuroscience and psychology at the University of California, Berkeley, and author of the book Why We Sleep. And it’s not just us—almost all vertebrates sleep, including fish. Our brains seem to need the downtime in order to stay organized, and particularly to strengthen new neural connections that allow us to remember what we’ve learned. “Every physiological system in the body, and every operation of the mind, is powerfully enhanced by sleep when we get it, and demonstrably impaired when we don’t get enough,” Walker says. “Sleep is Mother Nature’s best effort yet at immortality.” Here are 12 secrets to a deeper, more restful sleep.

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Low angle view of tired businessman sitting at desk in office
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Why do we yawn?

It seems to happen more often when we’re feeling tired, though yawning is not actually related to the amount of sleep we’ve gotten, according to a study published in the journal Physiology & Behavior. We also yawn more when we’re bored or hungry—some researchers theorize that a yawn might goose our bodies into maintaining focus when our attention is drifting. (If that’s not enough, try these 10 tricks to boost your concentration.) Although other mammals also yawn, only humans, chimpanzees, and bonobos do it when they see others yawning, and studies have shown that we’re more likely to “catch” a yawn from a family member or friend than from a stranger. Here are 13 more surprising things you didn’t know about your body.

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The legs of a girl walking on ice.
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Why is ice slippery?

It seems like ice is hazardous because of the thin layer of liquid water that can melt across its surface, but when you think about it, a thin layer of water on a tile floor doesn’t achieve a level of slipperiness nearly as extreme. Plus, scientists haven’t been able to show that either the weight of your boots or the friction of your steps is enough to melt that super-thin layer. A new paper published in the Journal of Chemical Physics suggests that there are actually loose H2O molecules rolling around on the surface of ice, meaning that when your foot slips across a frozen puddle it’s actually reacting as if you’d stepped on a bunch of teeny, tiny loose marbles, and that’s why you can’t seem to maintain your balance (or dignity). Don’t miss these 14 other baffling mysteries about the universe.

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Windows of an old building.
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Why do old windows look so wavy?

You might have heard that glass is a liquid, but that’s not true. However, glass isn’t exactly a solid either—it’s actually what’s called an amorphous solid, which means that although it holds its shape like a regular solid, its atoms aren’t held in place by a crystalline structure. (Plastics and gels are also amorphous solids.) So are your windows slowly melting? Robert Brill, a retired research scientist for the Corning Museum of Glass in Corning, New York, says no. “Although the individual pieces of glass in a window may be uneven in thickness, and noticeably wavy, these effects result simply from the way the glasses were made,” he wrote in a 2011 article for the museum’s website. That said, scientists are still debating the exact definition of glass, so although your bedroom window isn’t actively changing, the explanation for its structure might be. Check out these 10 ancient mysteries researchers still can’t explain.

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Beautiful meadow in the park
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Do plants communicate?

We haven’t heard them gossiping, but studies show that plants can release scents that attract a predator to eat the insects that are eating them. They also communicate with each other through networks of fungi that connect their roots—a 2013 study published in Ecology Letters allowed some plants to form fungal connections underground and prevented it in others; the connected plants could tell when one in their group was being attacked by aphids and ramped up their chemical defenses against the damaging insects. Recently, researchers led by Velemir Ninkovic, an ecologist at the Swedish University of Agricultural Sciences in Uppsala, found that plants are communicating with each other to regulate growth, too: Trees often rein in their expansion when their leaves brush up against other plants, and plants that are growing near others that are adjusting their growth often follow suit—they seem to be getting messages about their predicament through their roots. Who knows what else they’re talking about? Here are 16 of the strangest unsolved mysteries of all time.

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Fireflies in a jar outdoors at night
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How do fireflies flash in unison?

Speaking of secret communication, there’s a species of firefly that lives in the Great Smoky Mountains National Park that puts on an amazing mating display every June, featuring a synchronized flash pattern that moves in waves across the hills. “We think it’s less than 1 per cent of the roughly 2,000 species out there that do synchronize,” Lynn Frierson Faust, an independent researcher based in Knoxville, Tennessee, and the author of Fireflies, Glow-worms, and Lightning Bugs, told Inside Science. She says a large group of males flashing together is probably good for attracting females and might confuse predators. The question of how they get in sync remains a mystery. Here are some more of the strangest mysteries about planet Earth.

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Arctic Tern (Sterna paradisaea) hovering over the water in search for fish, here just before the dive, with a cloudy blue background.
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How do birds figure out where to migrate?

About 40 per cent of the world’s bird species migrate, including about 350 North American species that travel to the tropics each fall. (These are the best tropical destinations for bird watchers.) The Arctic tern, for one, must really love summer, because it goes back and forth between the Arctic and the Antarctic—around 80,000 kilometres round trip—every year. Migrating birds can even find their destinations if researchers make them start from unusual locations, according to an article in The Conversation by Richard Holland, senior lecturer in animal cognition at Bangor University. How do they do it? Holland and his team published a study in Current Biology suggesting that some songbirds use a magnetic map to navigate long distances, but nobody knows how they can detect the Earth’s magnetic field—it might have something to do with a small amount of iron in their beaks, but they also have a special protein in their eyes that might allow them to actually see magnetic fields. Fascinated by our fine feathered friends? Don’t miss these eight truly bizarre bird species.

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Scientific mysteries: How do salmon know how to swim home?
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How do salmon get back to the stream where they were born?

Young salmon head downstream to the ocean where they spend several years of their lives. When they’re old enough to spawn, they navigate back to the same river or stream they came from. “How salmon return to the correct shore­line region is not completely understood,” wrote Megan McPhee, an assistant professor of fisheries at the University of Alaska, Fairbanks, in Scientific American, suggesting that they probably use the sun’s angle, salinity of the water, temperature differences, and possibly the Earth’s magnetic field. Once they find the mouth of their particular river, though, McPhee says it’s all about smell. “A series of experiments beginning in the 1950s demonstrated that young salmon become particularly sensitive to the unique chemical odours of their locale when they enter the smolt period (when they begin their downstream migration to the sea),” she writes. Those smells stick with them while they’re at sea, and they use those cues as adults to find their home streams. Find out the 12 facts about animals you’ve got all wrong.

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Humpback Whale Calf
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What’s the deal with whale songs?

In the 1950s, researchers first recorded humpback whales using U.S. Navy equipment. The wide variety of sounds (characterized as wails, moans, and shrieks) are put together into repeating phrases to create songs that last between 7 and 30 minutes. Sometimes whales sing the same song together. The complexity of the songs’ structures makes them similar to language, and scientists still aren’t sure what they mean. The songs could be elaborate mating displays (though females—who don’t sing—don’t usually approach singing males), or they could just be bonding exercises. Check out these seven immortal animals that can basically live forever.

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A Happy little girl listening music lying on the sofa living-room

Why does music have such a strong effect on humans?

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When we hear our favourite songs, we almost can’t help but tap our toes to a beat. Is it because we evolved to react to rhythmic sounds in sync with our social group? That’s a theory put forward by some researchers, and explored in a study published in the journal Acta Psychologica. Rhythmic sound “not only coordinates the behaviour of people in a group, it also coordinates their thinking—the mental processes of individuals in the group become synchronized,” said author Annett Schirmer at a meeting of the Society for Neuroscience, as reported by Scientific American. Next, learn the 13 moon mysteries scientists are still trying to figure out.

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Originally Published on Reader's Digest