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15 Science Mysteries No One Has Figured Out

"To know, is to know that you know nothing," said Socrates, the famed ancient Greek philosopher. And while we know a LOT thanks to science, there's still so much that we don't know. These mysteries have stumped scientists throughout the ages—and will leave you scratching your head.

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Stars of a planet and galaxy in a free space. Elements of this image furnished by NASA.

How did the universe form?

A few things we know about the universe: it’s infinite, it’s littered with black holes, and thinking about it can make your brain hurt. And one of those things we don’t know: how it began. Even otherwise all-knowing Stephen William Hawking, PhD, theoretical physicist, cosmologist, and director of research at the Centre for Theoretical Cosmology in Cambridge, England, wasn’t sure. Some brilliant minds wonder if it even had a beginning at all, or if it was always there. You’ll also want to check out these unsolved mysteries, which are sure to cause shivers.

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hole black space way fiction hydrogen nebula galaxy white earth cloud cosmic atmosphere explosion meteorite deep star concept - stock image. Elements of this image furnished by NASA.

What happens inside a black hole

Black holes are places in space where gravity is so strong that even light can’t escape, so no one has ever been able to say what happens inside a black hole. That said, Dr. Hawking has theorized that rather than being stored within the deep clutches of a black hole, information from “within” a black hole actually remains outside of it (in the “event horizon”) and is therefore theoretically accessible. (Still with us?) Of course, since the event horizon is outside the black hole, the theory itself is a paradox.

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High resolution images presents creating planets of the solar system. This image elements furnished by NASA.
Vadim Sadovski/Shutterstock

The fate of the universe

Just as scientists haven’t figured out how the universe started, they haven’t figured out how it will end. They do know that life on earth can’t continue forever, because life on earth is supported by the sun, which, like all stars, will eventually die. And they do know the universe will end, but how that will happen depends on many unknowns (including the shape of the universe, its density, and the amount of dark matter within it). Don’t miss these science facts you never learned in school.

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star cluster and galaxy
Valerio Pardi/Shutterstock

Speaking of dark matter…

Scientists believe that most of the universe is made up of “dark matter,” which does not emit light or energy. While scientists can tell you what dark matter is not, they can’t tell you what it actually is, or what it is composed of. “We have a complete inventory of the universe,” Sean Carroll, a California Institute of Technology cosmologist, told Smithsonian Magazine, “and it makes no sense.” And until scientists can make sense of it, the fate of the universe shall remain forever unknown.

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dividing cells
Sebastian Kaulitzki/Shutterstock

How did life start?

We’re talking about life, not just human life, here. There’s no shortage of scientific speculation, and new findings turn up all the time about how life’s basic building blocks could have been generated in primordial conditions or delivered to Earth from outer space. And it’s not like scientists can even agree on which area of science will provide the answer, or if science is even where we should look. You’ll want to check out these science “facts” that are actually not true.

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Great pyramids in Giza valley with dark clouds on the background
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Egypt’s great pyramids

Constructed between 2589 and 2504 B.C., the Egyptian pyramids would be a wonder of engineering and physics even if they had been built today. So how did those ancient people living in the ancient desert manage it? There are legitimate scientists who believe aliens from another planet must have been involved. Other scientists believe the answer lies in ramps, wet sand, and pulleys. What we do know is that we don’t know.

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Fantastic background - bright light from extraterrestrial aliens spaceship, ufo in red glowing sunset sky. Elements of this image furnished by NASA
Igor Zh./Shutterstock

Is there intelligent life outside of earth?

The Great Pyramids. Stonehenge. Crop circles. How’d any of this happen without help from intelligent life from somewhere beyond our own planet? While we haven’t found signs of extraterrestrial intelligent life, wouldn’t basic probability lead to the conclusion that somewhere out there are beings who have at least as much intelligence as earthlings? But let’s say there was such a thing as extraterrestrial intelligent life—would we even be able to recognize it with our earthling senses? For now, the whole thing remains a mystery.

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Planet Earth Energetic Field Beauty. Elements of this image furnished by NASA.

What are those strange radio bursts from space?

Somewhere “out there,” something’s making quite a racket. Scientists have observed huge blasts of radio waves coming from three billion light-years away (based on incredibly complicated calculations). “People love to believe they’re from an advanced extraterrestrial civilization, and this hypothesis hasn’t been ruled out entirely by researchers at Breakthrough Listen, a scientific research program dedicated to finding evidence of intelligent life in the universe,” according to CNN. But no one knows, and there are many other hypotheses, including those involving black holes and dying stars. Here are 51 “facts” that are actually not factual.

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Tardigrades (water bear), illustration

What on earth are tardigrades?

You may have heard of tardigrades, aka eight-legged microorganisms that are often found around mossy trees. They can live without water, withstand temperatures from -328 to 304 degrees Fahrenheit, and even survive in outer space. Their incredible survival skills have led some to speculate they actually came from outer space, but scientists believe they did originate on earth. That said, even with the most elaborate of gene sequencing, scientists have not been able to figure out exactly what tardigrades are or even the phylum to which they belong. Could they be insects? Worms? Crustaceans?

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woman sleep in bed sunshine thought the window
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Why do we sleep?

We know the human body is regulated by a sleep-wake cycle. We know we spend nearly a third of our lives snoozing. We know our bodies repair themselves during sleep. We know that we dream during sleep. We know the many ways that sleep affects our bodies. But not all living organisms require sleep. So then why do we? One promising theory is that sleep plays a major role in the brain’s plasticity. Scientists are following that trail as we speak (by studying “glia” cells), so stay tuned. Check out these science trivia questions everyone always gets wrong.

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Vector illustration watercolor of hand drawn with octopus. Background with an octopus.Watercolor vector
Julia Gyshina/Shutterstock

Why did the octopus walk out of the sea?

No, it’s not a riddle. It really happened. In 2017, dozens of octopuses emerged from the ocean and crawled along the coast of a seaside town in Wales for a nightly pilgrimage to no-one-knows-where… or why. National Geographic reached out to several experts who provided various theories, including octopus-dementia, displacement of the octopus population because of storms, and an octopus population boom that has led octopus to search high and low for food. But none of that explains why the exodus abruptly stopped three days later.

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EARHART Amelia Earhart, 40, stands next to a Lockheed Electra 10E, before her last flight in 1937 from Oakland, Calif., bound for Honolulu on the first leg of her record-setting attempt to circumnavigate the world westward along the Equator

What happened to Amelia Earhart?

Amelia Earhart was the first woman to fly solo across the Atlantic and the first person to fly solo from Hawaii to the U.S. mainland. But during an attempted flight around the world in July 1937, Earhart vanished over the Pacific, and her plane wreckage was never found. Her disappearance remains one of the greatest unsolved mysteries of the twentieth century, according to History.com. Did she crash and sink? Did she end up a castaway on a remote island? Was she captured by the Japanese? Scientists of all stripes have failed to crack this mystery… yet. 

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Sunrise in the spring beech forest after rainfall.
Paul Aniszewski/Shutterstock

If a tree falls but no one’s there to hear it…

If a tree falls when no one is there to hear it, did it actually make a sound? The answer comes down to what is “sound”? If sound is defined as airwave disturbances caused by motion, we could answer that yes, a sound exists even if no ears hear it. But quantum theory holds that without a measuring device to record it, sound does not exist. When scientists determine how sound is to be defined, we promise to let you know.

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brown egg and chicken isolated on a white background

Which came first, the chicken or the egg?

Although British researchers found that eggshell formation cannot occur without a protein found in chicken ovaries, it’s been acknowledged there are other types of egg-laying species whose existence on earth predated chickens. That means the egg may have evolved before the chicken. And so we’re back to square one. The fact is, once you factor in evolutionary adaptation, it becomes virtually impossible to trace which came first. Here are 100 more interesting facts about basically everything.

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Light at the end of the tunnel

Is there life after death?

Anyone who has died and lived to tell about it hasn’t actually experienced death. Or have they? Certainly, they’ve not experienced it in a permanent way. So the question becomes: Is there life after a death from which one does not come back? It’s challenging to investigate, since one can’t come back from a death from which there’s no coming back. Still, some scientists insist that life after death is an actual, proven, scientific fact. Still, others insist that life after death is impossible from a quantum physics standpoint. Here’s what a near-death experience feels like, according to science.

Lauren Cahn
Lauren Cahn is a New York–based writer whose work has appeared regularly on Reader's Digest and in a variety of other publications since 2008. She covers life and style, popular culture, law, religion, health, fitness, yoga, entertaining and entertainment. Lauren is also an author of crime fiction, and her first full-length manuscript, "The Trust Game," was short-listed for the 2017 CLUE Award for emerging talent in the genre of suspense fiction.