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Sound pervades our experience — so much so that we’re never without it. Even in the quietest, most soundproofed chambers, the decibels of our heartbeat and our breath reach our ears. However, sound isn’t as simple as it may seem. It’s not as substantive as things we touch, but it can still elicit deep emotion and even physical pain. These six amazing facts will make you rethink what you know about sound and the role it plays in your life.

Sound Travels Faster in Water Than in Air

If you’ve ever heard your own echo, you know the speed of sound is pretty fast — around 761 miles per hour. But because sound is created via vibrations through a medium, that medium can influence a sound’s speed. In water, the speed of sound is much faster, clocking in at a whopping 3,355 mph. That’s because denser materials have more neighboring particles that can bump into one another and carry sound, and water has 800 times more particles than air. This is especially useful for animals like the blue whale, whose call at 180 decibels is louder than a jet plane and can travel up to 1,000 miles. However, 3,355 mph is by no means sound’s speed limit. When traveling through a diamond, the hardest material on Earth (which means lots of particles), sound travels at an incredible 40,000 miles per hour.

Technically You Can Transmit Sound in Outer Space (Just Not Very Far)

The tagline for the 1979 film Alien is pretty scientifically accurate: “In space, no one can hear you scream.” Because space is a near-perfect vacuum, very few particles fill its immense void. To put that into perspective, a coffee mug filled with “outer space” would contain only 300 particles. Fill that same mug with air from Earth, and it’d hold 1,000,000,000,000,000,000,000 particles. And since sound needs a medium to travel, it’s true that no one would hear you scream in space. But that doesn’t mean sound can’t travel in space at all — it just can’t travel very far. In a 2023 study at the University of Jyväskylä in Finland, scientists “tunneled” sound between two crystals across an extremely short distance in a vacuum (like the length of one sound wave). So while space is certainly inhospitable to sound, it can exist in some very specific instances.

The Body’s Smallest Bones Help Transform Sound Into Electrical Signals

The human ear is a wonder of biological engineering that uses membranes, fluids, hairlike stereocilia, and very tiny bones to transform sound into electrical signals that our brain can interpret. It all starts when a sound vibrates the membrane separating the inner and outer ear, called the eardrum, which then employs your body’s smallest bones to transfer that energy into waves in fluid located in the cochlea (a spiral-shaped cavity in the inner ear). These three bones — the malleus, incus, and stapes — are known as the ossicles and are incredibly small. (The stapes, the smallest of them all, only reaches a height of 3.5 millimeters and a width of about 2.4 millimeters.) Once the ossicles create these vibrations in the cochlea, hairlike stereocilia transform these waves into electrical signals and send them along our auditory nerve. This whole process takes around 10 milliseconds to complete.

Sound in Air Technically Can’t Be Louder Than 194 Decibels

Scientists measure sound using decibels (named in honor of telephone inventor Alexander Graham Bell), which is the measure of sound pressure in a medium. Because the decibel system is a logarithmic scale, something that is 20 decibels (such as a ticking watch) isn’t twice as loud as something that’s 10 decibels (breathing) — it’s actually 10 times as loud. While the human ear begins experiencing auditory pain at around 125 decibels, being exposed to lower decibel levels for longer periods of time can be just as damaging. At 194 decibels, you’re hearing a truly ear-splitting noise; beyond that threshold, sound traveling through air stops technically being sound. When a sound gets too loud, the wave itself essentially creates ambient air pressure that forms a vacuum. This transforms sound into more of a shock wave and less of a sound wave. To use a dramatic example, in 1883 an Indonesian volcano called Krakatoa erupted, creating the loudest “sound” in recorded history at an estimated 310 decibels. The resulting shock wave traveled around the world four times before finally dissipating.

Whips Crack Because They’re Breaking the Sound Barrier

On October 14, 1947, Chuck Yeager broke the sound barrier in the X-1 aircraft, but humans have actually been breaking the sound barrier since Roman times — they just weren’t sitting in a cockpit. Whips have been around for thousands of years, and their telltale (and terrifying) crack is actually the sound of the whip breaking the sound barrier. When someone cracks a whip, the motion travels the length of the whip and quickly speeds it up. Scientists used to think the whip’s tip broke the sound barrier, but research in 2002 showed that it was actually a loop traveling the length of the whip that produced the deafening crack. But you don’t need to be Indiana Jones to pull off this impressive feat of acoustic physics; cotton bedsheets have also been known to produce sonic booms of their own.

Some People Can Actually “See” Sound

For most people, sound is a strictly auditory experience, but for some with a condition known as synesthesia, sounds are a much more visual thing. Broadly speaking, synesthesia (which in Greek means “perceive together”) simply means experiencing one sense alongside another. So you might see a word but taste a type of food, or hear a sound but also see a color. This is largely caused by two different parts of the brain being activated by the same stimuli. Of course, these experiences are internal to the mind and not an accurate representation of sound’s physical properties. The cause of synesthesia is genetic — in 2018, researchers from the University of Amsterdam identified specific genes that make some predisposed to this sensory mix-up by creating “hyper-connected neurons.” While some with synesthesia report having trouble focusing due to these misfiring stimuli, most live healthy and happy lives — and even say their synesthesia gives them a richer experience of the world.

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The moon has long captured our imaginations. It’s embedded deep in mythology around the world, and even became the first calendar for many ancient people. But our connection to the moon goes even deeper — its symbiotic relationship with the planet Earth is unique within the solar system, and without it, we might not even exist. These 10 facts about our nearest lunar neighbor just might deepen your appreciation for Earth’s one and only natural satellite.

The Moon Is Bigger Than Pluto

If you were in grade school before 2006, when the International Astronomical Union reclassified Pluto, you may still think of it as a full-fledged planet. While the classification isn’t, technically, entirely about size, it’s hard to overstate just how itty-bitty Pluto is. Its radius is only about 715 miles, compared to a mean radius for the moon of about 1,080 miles.

Some other moons even outrank full-fledged planets, size-wise. Our solar system’s two largest moons, Jupiter’s Ganymede and Saturn’s Titan, are both larger than Mercury!

The Moon Is 27% the Size of Earth

While Earth’s moon is only the fifth-largest moon in the solar system, everything changes when we grade on a curve: At more than a quarter the size of Earth, our moon is, by far, the biggest when compared to its planet. According to NASA, if the Earth were a nickel, the moon would be the size of a coffee bean.

This gives our moon an outsize influence on our planet compared to others, in ways that almost seem magic — but are very much real.

The Moon Causes the Tides to Change

Not only does the moon influence the tides, but we wouldn’t even have tides without the moon. Its gravitational pull tugs up the water on the sides of the Earth facing and opposite the moon. This action is called tidal force. The moon’s gravity also affects land, but not nearly as much as water.

Forces besides the moon influence tidal patterns, too. Since the Earth isn’t entirely covered in water, land masses can affect how dramatic the tides get. The sun can have its own effects on tides, too, although it’s not as noticeable until the sun, moon, and Earth line up for a new moon or a full moon, causing tides to get much bigger.

The Moon Helps Stabilize Earth

The moon’s unique relationship with the Earth, it turns out, is crucial for preventing and slowing major, deadly climate shifts — at least the naturally occurring ones. The moon’s large mass helps keep Earth from tilting too quickly, preventing the kind of wobbles that created dramatic climate conditions on Mars. It could be that larger moons are one of the factors a planet needs to create and sustain life.

The “Moon Is Made of Cheese” Myth Is a Millenia-Old Joke

Today, the idea of the moon being made of cheese is a deeply -embedded fanciful trope appearing in everything from children’s books to B-movies to tasty snacks. It’s central to the premise of the Wallace and Gromit cartoon “A Grand Day Out.” But where did this cutesy reference to the moon’s appearance come from?

There’s no evidence of a widespread historical belief that the moon was actually made of cheese. Its origins lie in various folktales passed down in many cultures’ oral traditions. In some, a fox tricks a wolf into believing the reflection of the moon in a well is cheese, which convinces him to dive in. In others, it’s a human simpleton who dives into the well. The Aarne-Thompson Index, a folktale classification system, even has specific listings for “the Wolf Dives Into the Water to Eat Reflected Cheese” (34) and “Diving for Cheese” (1336). Variations of these myths appear all over the world, from the Zulu Kingdom to the Scottish Highlands. Typically, the person or creature thinking the moon is cheese is the butt of the joke.

“The Moon Is Made of Green Cheese” (referring to the freshness of the cheese, not its color) evolved into a figure of speech describing an easily duped person (think “I have a bridge to sell you”) as early as 1546, when it appeared in a proverb by English writer John Heywood. The trope remained incredibly common for centuries to come.

The term has also been used as a variation of “when pigs fly,” as in German playwright Bertolt Brecht’s play Good Person of Szechwan.

The Moon Is Deeply Scarred From Asteroids and Comets

Celestial bodies crash into the moon all the time, creating its somewhat chaotic surface. Often, these meteors are the size of a speck of dust, but larger collisions are not uncommon. During the 2019 total supermoon eclipse, casual observers and professionals alike caught the tiny flash of a meteoric impact, which caused an explosion roughly equivalent to 1.7 tons of TNT.

Debris that size hits the moon roughly once a week, and NASA’s Lunar Resistance Orbiter has tracked more than two dozen new impact craters since 2009. The lunar proximity to Earth means the same stuff that’s hitting the moon is whizzing past us, too — but without an atmosphere, the moon is much more vulnerable.

Of course, the bigger scars are from bigger impacts, and we’re still seeing some of those today. In 2014, Spanish astronomers observed an 800-pound meteorite crash into the moon’s surface. Researchers with the Southwest Research Institute, University of Toronto, and University of Southampton were able to date some of the moon’s larger craters in 2019, and later created a one-minute visualization of their research with music that corresponds to each impact.

12 People Have Walked on the Moon

The most famous moonwalkers are probably the first two, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin, who made their historic mission in 1969. But that was just the first of many crewed lunar landings in the Apollo program over a three-year period. All together, 12 people have walked on the moon so far. But nobody has set foot there since Apollo 17 in 1972 — and so far, only American white men have had the opportunity.

Another 12 astronauts reached the moon without walking on it, including the crews of Apollo 8 and Apollo 10, which orbited the moon without landing. Others were on later missions, but had different tasks, like Michael Collins, who stayed in orbit 60 miles above the moon during Apollo 11, making sure they could all get home safely, while Armstrong and Aldrin went to the surface.

Scientists Think a Collision of Two Planets Created the Earth and Moon

While there are many theories regarding its origins, the most widely accepted one is that the moon arose after a protoplanet approximately the size of modern Mars crashed into the Earth about 4.5 billion years ago, knocking loose debris from both bodies that would gradually become the moon. New research (as of 2021) proposes that there were actually two impacts: one extremely fast one that knocked the material away, and another slower one that helped merge the debris.

The Moon Is Darker-Looking on the Earth Side

You’ve heard the phrase “the dark side of the moon,” referring to the side that’s not facing Earth. Technically, the sun shines on both sides of the moon — but the majority of those dark, mottled patches — actually expanses of solidified lava called lunar seas, or maria — are on the near side. At more than 1,600 miles wide, Oceanus Procellarum, or Ocean of Storms, on the western edge of the near moon, is the largest of them all.

These vast plains of basalt come from volcanic activity, but the exact mechanism of their formation is still being studied. Some were created or at least helped along by asteroid impacts, but that’s not the whole story either, since similar hits typically don’t get the same reaction on the far side.

This isn’t to say that the far side is pristine. It’s heavily pockmarked with impact craters.

The Man in the Moon Comes From Lunar Seas

There are many lunar seas smaller than the Ocean of Storms, and several of these, along with brighter lunar highlands, make up the face that some people in the Northern Hemisphere see on the surface of the full moon.

Your mileage may vary depending on where you live and how your brain sees things, but usually the Mare Serenitatis (Sea of Serenity) is one of the eyes. The other eye is formed by the Mare Imbrium, or Sea of Showers, immediately to the west.

The nose, appropriately, is not a mare, but a sinus, or bay: Sinus Aestuum, or Bay of Seething. The mouth, which is open to interpretation but sometimes described as “grinning,” is a combination of Mare Nubium (Sea of Clouds) and Mare Cognitum (Sea That Has Become Known). In the Southern Hemisphere, the moon is flipped vertically, and many people see the Northern Hemisphere “face” as a rabbit. But some see a more joyful little face, too: Mare Frigoris, or Sea of Cold, could be seen as a much more defined grin.

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For something that we use every second of our lives, we understand remarkably little about how the human body works, even when it comes to mundane things such as blood types and yawning. Scientists occasionally discover an entirely new organ, or a new purpose for an old one.

So it’s not really surprising that those of us who don’t study the human body for a living might miss a few things — even if those things are literally right in front of our eyeballs, attached to either side of our heads, or in our mouths. What muscle helps you breathe and helps you go to the bathroom? How do fingernails help out in an emergency? Which much-maligned body parts aren’t totally useless after all? These seven body parts put in a little (or a lot of) extra work.

Eyelashes Trigger Your Blink Reflexes

In addition to looking pretty, eyelashes help stop debris from getting in our eyes — but they don’t just shield them. Eyelashes are sensory and function much like whiskers do on a cat. Ever wonder how you’re able to blink just in the nick of time when something comes flying at your eye? When an object gets close to our eyes, like a bug or a speck of dust, eyelashes trigger a blink reflex that protects our fragile peepers. They may also help manipulate airflow around our eyes to keep our lubricating tears from drying up.

Your Ears Keep You Upright

Ears are best known for helping us hear things, but they’re also critical to helping us balance. The inner ear, behind the eardrum, contains our vestibular system, which helps us orient our bodies. Three loops full of fluid, or canals, are connected to two organs full of small crystals inside the inner ear. The canals sense when the head is moving up or down, left or right, and turning sideways. The crystals measure acceleration.

The vestibular system sends the information it processes to other parts of our body, so we can balance and know where we are in space. When the brain gets information that conflicts with what the vestibular system is processing, we get dizzy. This is why an inner ear infection can be so disorienting!

Fingernails Can Indicate Blood Flow

Have you ever been told to remove your nail polish in a medical setting? Some think that nail polish can get in the way of a pulse oximeter, a medical device that clips onto your finger and measures blood oxygen levels — but this isn’t true, even if the polish is glittery. However, painted nails can get in the way of a quick test called the capillary refill test, which checks your circulation in the event of an emergency.

Here’s how it works: A medical professional applies pressure to the nail bed on your finger or your toe so that it turns white, then releases to see how long it takes for the pink color to come back. It’s an indicator of how well oxygen is traveling to your extremities, and is used to check patients for shock.

The capillary refill test is done in a critical care setting, but your nails can tell you about your health at home, too. If they’re not pink under your polish, you might want to get that checked out.

Tonsils Are a Barrier to Germs

Like the appendix, tonsils are perhaps best known as a site of surgical removal — but they do have a purpose. The tonsils are a set of lymph nodes that form a ring at the back of your throat behind your mouth and nose. They provide a barrier to prevent germs from making their way further into your body, and they’re rich in white blood cells, which fight infections.

Technically, there are four types of tonsils. But when people say “tonsils,” they’re often talking about the palatine tonsils, which are located on either side of the back of your mouth. Because they’re the first line of defense against germs, they’re particularly vulnerable to infection, and often become inflamed. When they start interfering with breathing, they sometimes have to come out. The adenoids, the tonsils in the upper airway, are also frequently removed, and the lingual tonsil at the back of the tongue sometimes comes out as a treatment for sleep apnea. The tubal tonsils are located near the entrance to each Eustachian tube and generally receive less attention.

Tonsillectomies are one of the most-performed surgical procedures in the United States, so it’s pretty normal to go through life without tonsils — although recent research has suggested that tonsillectomies are associated with higher risk of some infections.

Uteruses Can Stretch From Pear to Watermelon… and Back Again

It may seem secondary to growing a whole new human being, but the little things a uterus can accomplish during pregnancy are extraordinary, too. When it’s not occupied, an average uterus is pear-shaped and only about 3 inches long, 2 inches across, and 1.5 inches thick. But a full-term baby and everything that comes with it, like amniotic fluid and a placenta, take up a lot of room. The uterus usually outgrows the pelvis during the second trimester of pregnancy, and over the course of 40 weeks, it balloons to the size of a watermelon. The uterus alone can weigh 2 pounds when at full term.

Perhaps just as miraculous is how quickly it shrinks back down. This is called involution, and it takes around six weeks for most people.

The Diaphragm Helps With More Than Breathing

The main function of a diaphragm is to help you breathe in and out, which you probably know if you’ve ever practiced belly breathing. The diaphragm rests between your chest and your abdomen, and contracts and expands on each inhale and exhale; when it tightens, it moves downward to make more room for your lungs. When you breathe out, it relaxes and helps push air out of your body. But it has another important (and related) job, and that’s keeping your guts together.

When something else is going on with your belly or chest — like going to the bathroom or sneezing — the diaphragm helps maintain the appropriate level of pressure in your abdomen so that everything goes where it needs to.

The Appendix Might Not Be So Useless

The appendix, a small pouch attached to the large intestine, has a pretty bad reputation — it gets infected a lot and its actual role in the body is unclear. But it might not be useless after all!

Your gut is full of beneficial bacteria that contribute to your overall health. When you get really sick (or you’re on a long round of antibiotics), your inner ecosystem can start to suffer and good bacteria can be flushed out of your system. According to some theories, the appendix provides a kind of “safe house” so that microorganisms can survive to repopulate the rest of your gut.

It’s still not a top-priority organ, though — and if it gets severely infected, you still need to get it taken out.