Episodes

Drinking salt water is poisonous to humans. It’s four times saltier than our blood, so our kidneys pull water from our tissues to try to balance the seawater, which could lead to dehydration or death. Whales and dolphins, seals and walruses are all mammals, and they need fresh water too. But they live in salt water. So what do they drink? Nothing! Their digestive systems are superefficient at pulling all the fresh water they need from their food. What about fish? They need water too. You’d th...

If left unprotected, something made of iron will dissolve into dust. That’s because of rust. Some metals, like gold and platinum, are naturally stable and keep their shiny appearance. Other metals like aluminum, copper and silver develop patina or tarnish that protects the raw metal beneath. Iron is different. It’s the most abundant element on Earth, followed by oxygen—together they make up over 60% of all elements. And they like to get together: Almost all iron on the surface of Earth appea...

The world’s most successful research submarine, Alvin, has completed over 5,000 dives in its 60-year career. Its first mission, in 1966, was to search for—and find—a hydrogen bomb that had fallen into the deep ocean. Two years later, cables snapped while Alvin was being lifted aboard its tender ship, and it sunk to the bottom of the Atlantic … where the sub itself had to be retrieved. It has been rebuilt several times since—each time making it more robust for deeper diving. In the ‘70s and ‘...

Native American legend says the Creator, when done forming Earth, threw all the leftover rocks into a pile in West Texas—a jumble of geology that today we call Big Bend. It gets that name because it sits in a 200-mile-long curve in the Rio Grande River that separates Texas and Mexico. Big Bend is now a nearly million-acre national park—with a protected area twice as large on the Mexican side of the border. The reason it looks like a divine rock yard is its complicated geologic history. 450 mi...

Big Bend is one of the largest, most remote and least visited national parks in the U.S. It’s a land of great diversity. More than a mile of elevation change. More than 100 degrees Fahrenheit of temperature fluctuation annually. Diverse topography—deserts, mountains, canyons, rivers and springs—with different life in each ecozone. And because of that, more ecological diversity than any other national park: more species of birds, butterflies, bats, reptiles, ants and plants. And the largest ag...

It’s going to be a very noisy summer! This year, more cicadas will fill the air with—song?—than any summer since 1803. Cicadas evolved 150 million years ago, and 3,000 species now live on nearly every continent. These are called “annual” cicadas. They live a few years underground, then crawl up a tree and shed their crusty “underground” skin for a final molt into their winged adult form. They live for a few weeks, and the males screech all day long—which the females find attractive. They mate...

If you were to design the perfect industrial material, what would it be like? You’d want it to be strong and lightweight. Easy to form into different shapes. You’d like it to be resistant to corrosion. And to heat. Ideally, you could easily combine it with other materials for more uses. And re-uses. It would be best if all these qualities came in something cheap and abundant. And in fact, they do. This ideal material … is aluminum. It’s the third-most abundant element in Earth’s crust, behi...

Leonardo da Vinci was one of our most brilliant thinkers. He’s known as an inventor, scientist, mathematician, architect, sculptor and, of course, painter of the most famous portrait in the world, the Mona Lisa. But unless you’re also a painter, you probably haven’t heard of Leonardo’s Rule of Trees. Intent to paint them realistically, he carefully analyzed trees and recognized a pattern, which he encoded in this formula: The thickness of the limbs that grow from a trunk, when combined, equals...

In 1933, Hungarian explorer László Almásy set out across the Sahara in search of a legendary lost city. What he discovered was far more magical and, at first, completely unbelievable. In a remote ravine, Almásy found a shallow cave. Inside he saw cave paintings of human figures with outstretched arms and legs. They appeared to be flying. But no, Almásy realized, they were swimming—in the Sahara! Other cave paintings showed antelope, giraffe, elephants and lions alongside more human figures. Al...

What if Earth didn’t have a moon? Well, nearly everything about our home planet would be different—so much, we’d hardly recognize it. Our Moon is a quarter the size of Earth, far bigger than most planets’ moons. Scientists think it formed when a smaller planet crashed into Earth 4 billion years ago, knocking off a chunk that eventually became our Moon. Its large size is key to its dramatic effects on Earth. The gravity of the Moon pulls on the oceans to produce tides. Tidal range would be onl...

Millions of miles from Earth, the fastest object that humans have ever built is circling the Sun at 430,000 miles per hour, and nearer than any spacecraft has ever dared go. It’s the Parker space probe, and NASA sent it there in 2018 with a mission: to study solar activity. That’s because, in 2024, the Sun is predicted to reach its next solar maximum. It happens when the Sun’s poles flip and its magnetic fields go “crazy.” This produces coronal mass ejections—burning gas that erupts into the S...

The stegosaurus is known for its unusual features: rows of large, bony plates along its back, spikes on its tail and a cranium so small that early paleontologists thought there must be another brain hidden elsewhere, like in a nerve bundle at the base of the dinosaur’s powerful tail. But it was the purpose of those plates that really baffled scientists—a mystery they’ve been trying to solve for more than a century. Initially it was thought the plates were for defense. But they cover only the a...

“Campi Flegrei” in Italian means “fiery fields.” That may not sound like a place you’d want to live, but 360,000 Italians do. Italy is the only country in Europe with active volcanoes on land. The “fiery fields,” just west of Naples, are actually a caldera—the depression left when a volcano erupts and collapses. At the center of the caldera is the Pozzuoli Bay. The coast around it has been densely populated for many centuries. The volcano has had two major eruptions in the distant past, much ...

Almost 400 million years ago, our ancestors slowly emerged from the sea to breathe air and populate the land. It may surprise you to know there’s another species making that same transition right now. It’s the mudskipper, a 4- to 12-inch fish that looks like a frog with only front legs. It has a large frog-like head and smooth, green and brown skin dappled with spots. The mudskipper lives in tropical and subtropical coastal flats and spends its time under or out of water, depending on the tid...

In the 1960s, during the Cold War, the U.S. built an Arctic research center in Greenland and called it Camp Century. Except it was actually a secret military operation—code name: Project Iceworm. It was intended to drill a network of nuclear missile launch silos in the Greenland Ice Sheet, designed to survive a Russian ‘first strike.’ The first people there were researchers, to test the ice for suitability. They drilled nearly a mile through the ice sheet and 12 feet into the soil below. The...

When we think of pollination, we usually think of bees, bats or other flying foragers. They visit male flowers to collect nectar and get covered in sticky pollen, which they carry to female flowers, in search for more nectar. Marine plants also reproduce with pollen, but scientists thought water movement carried it from one plant to another. Then researchers discovered what they called “the bees of the seas.” Small crustaceans crawl over the male flowers of seagrass to eat a nutritious substa...

A total eclipse of the Sun is a special occurrence. The last time that the Sun and Moon lined up perfectly for a total eclipse traversing the U.S. was in 2017; another one is due on April 8, 2024, crossing the country from Texas to Maine. While millions of Americans gaze at the sky in wonder, scientists will be hard at work. Because a total eclipse—by blocking the Sun itself—gives us the rare chance to study its corona, the fiery heated “atmosphere” around it, from within the path of totality...

The most important number in the universe is arguably … pi. Why? Because it defines circles, spheres and wave motion from atomic to galactic scales. Pi is the ratio of a circle’s diameter to its circumference. If the diameter is 1, the circumference is pi. And pi, you may remember, is 3.1415926535 … etcetera, going on forever and never repeating. It was first recognized 4,000 years ago, and since then, mathematicians have been trying to calculate it. In 250 BC, the Greek mathematician Archim...

We often hear that sea level is rising, but less often that cities are sinking—which may put them in more jeopardy. This may be caused by land rebounding from the last ice age, when it was covered by ice sheets. While some areas spring upward, others that were pushed upward around the periphery of ice sheets are slowly sinking. Or, Earth's surface may rise or fall when a fault slips, or tectonic plates subduct under or slide over other plates. Rivers move sediment to deltas where, over many y...

Remember the movie Jurassic Park? Or every time you’ve seen a reconstruction of a T. rex in a museum? Probably the image that sticks with you is the exposed daggers of fearsome teeth. Well, some Canadian grad students may have proven that image wrong. They discovered something rather elemental: T. rex teeth have very thin enamel. Even thinner than the enamel on mammal teeth. But early paleontologists had based their tyrannosaur reconstructions on crocodiles and alligators, which have exposed ...

In China, sinkholes are called “heavenly pits.” And China has the largest one in the world, named Xiaozhai. It’s two thousand feet deep and just as wide. Sinkholes occur where Earth’s surface collapses into an underground void. It could be sudden, when a giant hole opens in the ground. Or sinkholes can form slowly, making depressions in the landscape that appear as rolling hills and troughs. Both are caused by water eroding or dissolving the bedrock. This could happen over centuries, when rai...

Mountains can shape not only a region’s weather, but its climate. When wind blows warm moist air against a mountain range, the air is pushed upward by the mountain. As it rises, it cools. The moisture within it condenses into rain, which falls on the front side of the range, creating a lush landscape. But behind the range, the air—now empty of moisture—can leave the landscape extremely dry. The mountains have essentially blocked the passage of weather systems. This is called a rain shadow. T...

You may remember the Concorde, the passenger jet that rocketed from New York to London in just three hours. And you may wonder, why do we now settle for much slower airplanes? Speed is actually the reason. Achieving it required a great deal of maintenance and fuel, making the Concorde very expensive to operate. But a bigger reason was noise. The Concorde flew at twice the speed of sound, so it created a sonic boom. It was so loud, the FAA prohibited it from flying across land, relegating it to...

Nearly everything in the universe was made by stars. Stars are fueled by nuclear fusion. They fuse atoms of the lightest element, with only one proton—hydrogen—into the next lightest element, with two protons—helium. In every fusion reaction, they’re creating an atom of a new element. When they’ve used up their hydrogen, they begin to fuse the remaining helium into a heavier element, carbon. Then they’ll fuse that into oxygen and progressively heavier elements. Each of these fusion reactions...