19 Every Day Things Science Hasn’t Figured Out

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Science has enabled humans to complete some pretty incredible feats, like land on the moon, for example. But when it comes to common things like laughter or hiccups, scientists still can’t quite figure out the reason behind them. In this article, which was adapted from The List Show on YouTube, we look at everyday things that are still a mystery.

1. It's still not understood why we cry.

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Crying is still a scientific mystery. Physiologically, it’s clear what’s happening when someone cries. But, it has been more difficult to figure out the evolutionary reason for tears. We know that babies cry to communicate and get attention. So, some experts believe that adults might also cry for social reasons, like to bond or to warn others that something is amiss.

2. The reason we laugh is still unknown.

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Like crying, we also don’t know why people evolved the ability to laugh, but experts guess it has something to do with communication—and not just that we find something funny. One researcher found that only 20 percent of laughs he looked at were preceded by anything deemed in any way humorous.

It's possible we laugh to let other people know that we’re okay or to bond with each other. A study published in 2016 gave evidence for the latter. Researchers found that an outside observer could distinguish whether laughter was produced between a pair of strangers or a pair of friends.

3. Scientists haven't figured out why we blush.

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Blushing is often telling others things we don’t want them to know, like the fact that we’ve done something wrong or embarrassing. Some experts believe that we may have evolved blushing to show submission to group leaders. Others think it may have something to do with the fact that blushing people have been shown to be considered more likable, so it helps peers look past the bad things we’ve done.

4. It's still unclear why anesthesia makes us pass out.

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General anesthesia has been in use in the United States since 1846, but there are still some uncertainties about why the chemicals in anesthetics cause people to pass out. A recent study showed that the drugs affect proteins in the brain and the reason we go unconscious has to do with altering neural activity, but more research is needed.

5. We aren't exactly sure what consciousness is.

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Consciousness is frequently defined as how we feel present and alive in the world. But the question is: Why and how do we feel conscious? It’s of interest in both philosophy and science. Scientists would like to know which part of the brain is responsible for consciousness, but it’s still a mystery.

6. It's unclear exactly how medications like Tylenol work.

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We don’t 100 percent understand how pain relievers containing acetaminophen give us pain relief. We do know that acetaminophens aren’t totally consistent; they’re more effective in some types of cells than in others. So for now, scientists believe the drugs might be a specific type of enzyme inhibitor.

7. We aren't sure why we get hiccups or how to stop them.

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Scientists don’t know what causes hiccups, what purpose they serve, or how to cure them. A lot of people have favorite techniques, from gargling water to pulling hard on the tongue, but there’s no scientifically-proven way to get rid of them.

In 2002, one researcher tried to get to the bottom of the problem by looking at how 54 hospital patients had been treated for hiccups. They tried multiple treatments, like holding their breath and medication, but none were proven effective.

8. Scientists haven't figured out why tornadoes start.

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We don’t know why only some thunderstorms create tornadoes and others don’t. Generally, it’s understood that tornadoes come to be when cold, dry air interacts with warm, humid air. But the thunderstorms that result from those air conditions only sometimes cause tornadoes.

9. Scientists also haven't figured out why tornadoes end.

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It’s also unclear why tornadoes die—though experts believe that at least sometimes it has to do with the tornado’s interaction with cold temperatures.

10. It's still uncertain why we need to sleep.

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There are theories as to why we need sleep, but no one knows for sure. It's possible our ancestors slept because it kept them out of danger during the night. Or it could be an energy conserving function. What we do know is that sleep helps us recover from the day, and there’s evidence it changes the connections in our brains.

11. The reason we dream is still unclear.

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Similarly, there are no clear answers as to why we dream. Some sleep experts think dreaming doesn’t have a purpose at all. Others have theories, like that we’re playing out threatening situations, like being chased, so that we’re better equipped to handle danger while awake.

12. We still aren't sure why we have the urge to scratch.

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We often understand why we itch. But, we don’t completely understand why we have the urge to scratch. The body has receptors just for itches that are almost identical to those that convey pain, and it’s thought that scratching might interfere with these signals. But at the same time, it might cause the skin to get more irritated, which causes even more itching.

13. Science still hasn't figured out the cure for aging.

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Scientists know some things about why we age, but no one has fully figured it out. There’s little evidence for popular hypotheses having to do with things like free radicals and telomeres. Aging is probably the result of a complex group of poorly understood processes, meaning a cure isn’t happening any time soon.

14. Ornithologists still don't know why only some birds migrate.

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It’s also unclear why some birds migrate while others don’t. The ones that do migrate might do it to conserve energy, which might be kind of confusing, since they’re flying great distances and therefore expending a lot of energy to get to their destination. But it’s likely worth it since they’re probably traveling somewhere with abundant energy sources—a.k.a., plenty of available food. Luckily, thanks to technology like tracking devices, scientists are able to track birds more easily and are now learning much more about migration.

15. Scientists haven't figured out the “nature vs. nurture” debate.

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The question of nature versus nurture hasn’t been settled yet. Technically, we know that our genes interact with our environment to foster characteristics—but science isn’t sure to what extent. A complicating factor is that it varies by trait and individual person. How much your genes are influencing your IQ, for instance, may be different from someone else.

16. We still aren't sure why the placebo effect happens.

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The placebo effect is pretty mysterious. It has been proven again and again that sugar pills and other fake treatments can actually make someone feel better. And it’s not just a feeling as scans have shown that placebos affect the area of the brain associated with pain. We still don’t know why. It’s believed that placebos somehow help release endorphins, but experts need more information.

17. It's still unclear why bicycles are able to stay up on their own.

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Have you ever given a bike with no one on it a push and noticed that it stays up on its own? It doesn’t fall over for much longer than you expect, and we don’t know how it manages to balance itself while moving.

18. How skates work on ice is still unknown.

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And another mystery of physics: How do skates work on ice? There is a popular theory. We know that ice has a very thin layer of liquid on it. So, a skate moving quickly on top of ice might make more liquid because the friction causes melting. The skate is actually changing the ice itself, creating a path on which to glide.

19. There still isn't a cure for the common cold.

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We get colds from seven separate families of viruses and those families have sub-viruses. So, to cure the “cold,” there would need to be a cure that acts as a catch-all for about 200 sub-viruses.

Wednesday’s Best Amazon Deals Include Computer Monitors, Plant-Based Protein Powder, and Blu-ray Sets

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Why Your Christmas Lights Always Get Tangled, According to Science

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A Christmas tree isn't a Christmas tree without those pretty colored lights, right? OK, no problem. You stored them in a box marked "Xmas lights" 11 months ago. You know where the box is. Now you just have to open the box, grab the lights, and—

That's where it gets tricky. Unless you're very lucky, or extremely well organized, the lights are likely all tangled up; soon you're down on your hands and knees, struggling to untangle a spaghetti-like jumble. (And it's not just you: A couple of years ago, the British grocery chain Tesco hired temporary "Christmas light untanglers" for the holiday season.) But why are Christmas lights so prone to tangling in the first place—and can anything be done about it?

Why do Christmas lights get tangled in the first place?

There are really two separate problems, explains Colin Adams, a mathematician at Williams College in Williamstown, Massachusetts, and the author of The Knot Book, an introduction to the mathematical theory of knots. First, the cord on which the lights are attached is prone to tangling—just as headphone and earbud cords are (or, in the past, telephone handset cords).

Several years ago, physicists Dorian Raymer and Douglas Smith, then at the University of California, San Diego, did a study to see just how easily cords can get tangled. They put bits of string of various lengths in a cube-shaped box, and then mechanically rotated the box so that the strings tumbled around, like socks in a dryer, repeating the experiment more than 3400 times. The first knots appeared within seconds. More than 120 different types of knots spontaneously formed during the experiment. They also found—perhaps not surprisingly—that the longer the string, the more likely it was to become knotted (few knots formed in strings shorter than 18 inches, they noted). As the length of the string increased, the probability of a knot forming approached 100 percent.

The material that the string (or cord) is made of is important too; a more flexible cord is more likely to tangle than a less flexible one. And while the length of the cord matters, so does its diameter: In general, long cords get tangled more easily than short ones, but a cord with a large diameter will be less flexible, which reduces the risk of knotting. In other words, it's the ratio of length to diameter that really matters. That's why a garden hose can get tangled—it's relatively stiff, but it's also very long compared to its diameter.

But that's not the end of the story. If a cord has a metal wire inside it—as traditional Christmas lights do—then it can acquire a sort of "natural curvature," Jay Miller, a senior research scientist at the Connecticut-based United Technologies Research Center, tells Mental Floss. That means that a wire that's been wrapped around a cylindrical spool, for example, will tend to retain that shape.

"Christmas lights are typically spooled for shipping or packing, which bends metal wire past its 'plastic limit,' giving it natural curvature approximately the size of the spool it was wound around," Miller says. Christmas lights can be even harder to straighten than other wound materials because they often contain a pair of intertwined wires, giving them an intrinsic twist.

And then there's the additional problem of the lights. "Christmas lights are doubly difficult, once things get tangled, because there are all of these little projections—the lights—sticking out of them," Adams says. "The lights get in the way of each other, and it makes it very difficult to pull one strand through another. That means once you're tangled, it's much harder to disentangle."

How do you fix tangled Christmas lights?

What, then, can be done? One option would be for manufacturers to make the cord out of a stiff yet elastic material—something that would more readily "bounce back" from the curvature that was imparted to it while in storage. A nickel-titanium alloy known as Nitinol might be a candidate, says Miller—but it's too expensive to be a practical choice. And anyway, the choice of material probably makes little difference as long as the lights still protrude from the cord. Perhaps the biggest breakthrough in recent years has been the proliferation of LED "rope lights" that don't employ traditional bulbs at all; rather, they use LEDs embedded within the rope-like cord itself. Of course, these can still get tangled up in the manner of a garden hose, but without those pesky protrusions, they're easier to untangle.

A simpler solution, says Adams, is to coil the lights very carefully when putting them away, ideally using something like twist-ties to keep them in place. (Martha Stewart has proposed something similar, using sheets of cardboard instead of twist-ties.)

Meanwhile, the mathematicians have some advice if you find yourself confronted with a hopelessly tangled, jumbled cord: Find one of the "free" ends, and work from there.

"Eventually," Adams assures us, "you will succeed."