Episodes

Nematodes aren’t toads at all, but worms. Roundworms, specifically, with cylindrical bodies. Different species are so nondescript we have a hard time telling them apart. That may make them sound uninteresting, but I assure you, they’re anything but. Nematodes are some of the oldest animal lifeforms on Earth, having appeared perhaps a billion years ago. And they’ve been a huge success. To start, their population is enormous. For every human on the planet, there are 60 billion nematodes. You mi...

What do India and Antarctica have in common? They were once part of the same landmass. Long ago, like all land on Earth, India was contained within the supercontinent of Pangaea. But around 200 million years ago, Pangaea began to break apart. The southern portion separated into Gondwana, which included India. India then began to set its own course. It rifted away from Africa, then tore off from Antarctica. As it traveled north, it shed Australia, then Madagascar. This is partly because India ...

Two of the most powerful forces on Earth are glaciers and volcanoes. What happens when they collide? One dampens the other. And one makes the other more dangerous. During the most recent ice age, glaciers covered a third of Earth’s surface. During this time, volcanic activity declined … Because the sheer weight of ice pressing down on the land increased the pressure on Earth’s mantle beneath the crust. The higher pressure raised the mantle’s melting point, so that the fiery temperatures coul...

The best thing about mistletoe, you may have thought, is that you can get a holiday kiss under it. But mistletoe is vital to the ecosystems it lives in. Mistletoes are surprisingly diverse. There are over 1,000 species living on every continent but Antarctica and in every environment, from forest to desert. They’re all parasites that grow on grasses, ferns and, most famously, trees. They attach with a haustorium, sort of a root that pierces the plant’s exterior to tap into its xylem to draw wa...

When the human mind evolved, it only had to process small numbers, like the number of fingers on a hand. To this day, we base our counting systems on that and use it to grasp very large numbers—with limited success. So, when scientists needed to make sense of Earth’s 5 billion–year history, they tied it to something concrete: Earth itself. We started by realizing that Earth’s history is preserved in layers of sedimentary rock. That younger layers were deposited on top of older layers. And tha...

Something’s happening high in the mountains, invisible to humans—that can dramatically affect our water supply. It’s a process called sublimation, where a substance goes from its solid form directly to a gas, skipping the liquid state altogether. And water is one of the few substances on Earth that can do this. It takes 80 calories of energy to melt a gram of ice into liquid water. Then another 540 calories to boil it into gas. But when the environment provides those 620 combined calories all ...

More than 2,000 years ago, Rome became the first city in the world with a population of 1 million people. And one of the reasons? Abundant, clean water. Rome’s earliest settlements go back 10,000 years. The famous “Seven Hills of Rome” were first ancient hilltop villages that gradually merged into one city. Rome’s early citizens took their water from the Tiber River, but the growing population required more. So, Rome’s early engineers went looking for it. And engineers were required, because ...

It might surprise you to know that plants can hear, and even speak, in their own unique ways. Scientists have discovered that some plants respond to the sound of water. They found that the roots of common garden peas will actively grow toward vibrations made by running water—even if it’s within a pipe and unreachable by them. In related tests, they played recordings of the wingbeats of bees and moths to several species of flowers. The flowers responded within three minutes by producing more n...

Lithium-ion batteries have transformed our lives. They make our smartphones possible. They power our laptops and most other rechargeable devices—including, increasingly, our vehicles. We’re even hoping to put giant batteries on the grid, to store solar- and wind-generated electricity when it’s being produced to use later when it’s not. With that increased demand, lithium has become expensive. Its supply is volatile and controlled by just a few countries. So, battery scientists are looking for...

When is a potato not a potato? When it’s a sweet potato! And when is a sweet potato not a sweet potato? When it’s a yam! What I mean is, these three food staples may look similar, but they’re not related at all. The potato is part of the nightshade family; it’s actually kin to tomatoes, eggplant and tobacco. It comes originally from the Andes, where the Incas domesticated potatoes many centuries ago. In Peru, there are still more than 4,000 varieties! Potatoes went to Europe with Spanish sa...

99% of Earth’s biomass is estimated to be on land, with only 1% in the oceans. However, Earth’s biomass is mostly plants. And the average terrestrial plant is huge—a 2-ton tree that could live for a century. Whereas the average marine plant is tiny—a single-celled organism that might live just a few weeks. That said, about three-quarters of animals, by biomass, live in the sea. That’s because the oceans are incredibly rich with tiny shrimp-like creatures. Antarctic krill alone make up almost 4...

For centuries, humans have relied on pigments to color our products. But a new discovery may change that. Pigments produce color, ironically, by absorbing light. Chlorophyll, for example, absorbs all colors of the light spectrum except green, which reflects off leaves, making them appear green to our eyes. Pigments and paints that we manufacture work the same way. But a few years ago, scientists working to create a perfect mirror out of aluminum noticed that microscopic particles of aluminum ...

There’s a spooky, otherworldly intelligence on Earth—and it’s called the slime mold! That may sound like a horror movie, but it’s real. And it grows in leaf litter … perhaps in the woods behind your house, waiting for darkness to creep under your door … Ok, not that last part. But slime molds can creep and carry out many complex behaviors—all without a brain! Slime molds aren’t really a mold at all, but a strange mix of animal and fungal characteristics. And they’ve been around for 600 millio...

Leaves naturally turn yellow in the fall, when green chlorophyll fades to reveal the golden pigments already in them. But it takes energy to turn leaves red, and not all trees can do it. Why? Scientists have three hypotheses: The first is sunblock. Red pigments protect the leaves better than yellow, allowing them to stay on branches longer, so that trees can harvest more nutrients before they fall. The second has to do with insects. In autumn, aphids feed on tree leaves. Researchers found t...

Around 300 million years ago, something magnificent happened: evolution hatched the egg. Specifically, the shelled egg. Most eggs then, and many still today, were gelatinous and could only survive in water. Like those of frogs or fish. But the shelled egg that could contain water and nutrients and be viable on land allowed some species to move out of the water and populate the land. Early shelled eggs were leathery, pliable and soft, like those still found in turtle and crocodile species. The...

The largest mountain in our solar system is not on Earth but on Mars. Olympus Mons is 72,000 feet tall—that’s two and a half times higher than Everest! And mountains on Earth will never get that tall. Why? First, we have stronger gravity. About two and a half times that of Mars. Our mountains form when tectonic plates push together. One plate slides over the other, or the plates crush together in the middle. Both lift material upward. And they form when volcanoes carry magma from within the ...

Did you know that sand dunes...can sing? Sand dunes form wherever there’s sand and steady wind to blow it into piles. Deserts cover 20 percent of Earth’s land surface and many have dunes. There are even sand dunes on other planets. Here on Earth, sand dunes sing in about three dozen known locations. This has baffled explorers since Marco Polo crossed China’s Gobi Desert in the thirteenth century and attributed the loud noises to spirits. And scientists still don’t understand it completely. Bu...

Here’s a trivia question for you: what did humans domesticate first? Before any bird, before anything with hooves, before crops, even long before the dog. The answer is a fungus. That’s right, anthropologists now believe that early humans fermented fruit as much as 100,000 years ago—and through that process domesticated yeast. Of course, we didn’t know we were doing it. Even when ancient Sumerians and Egyptians started making beer and bread, they had no idea that yeast did the fermentation. ...

Each year around 17,000 meteorites make it through Earth’s atmosphere to strike the surface of the planet. With that many impacts, you’d think they would sometimes hit people. But it’s surprisingly rare. The most damaging effects of such extraterrestrial objects are when large ones break apart in the atmosphere causing an airburst, as we discussed in a prior episode. These can superheat Earth’s surface and in the distant past have incinerated entire villages. In China, in the fourteenth and ...

There are only four creatures on Earth that tend crops: humans, weevils, termites and, most successfully of all, ants. Around 10,000 years ago, humans switched from being nomadic hunter-gatherers to sedentary farmers. The food surplus allowed us to develop civilization. But ants beat us to it, becoming “civilized” 60 million years before then. Scientists think it may have been after the Chicxulub asteroid, when darkened skies meant fewer plants, that ants began to rely on fungus. Soon after,...

We’ve all seen puffy cumulus clouds marching across the sky like a herd of elephants, perhaps changing shape into mythical creatures. But did you ever stop to wonder—how much do those clouds weigh? I’ll give you a hint: it has to do with the elephants. Cumulus clouds form when warm updrafts carry water vapor into the sky, until it begins to condense into water droplets. These are so small that the updraft can overcome their gravity and keep them aloft. The process of condensation produces mo...

Why do zebras have stripes? It’s probably a combination of things. Zebras’ main predators are lions. Black and white stripes actually make zebras stand out against their grassland home, rather than camouflage them. But when many zebras are running simultaneously, the cacophony of stripes may confuse predators as to how many zebras there are and which way they’re moving, making it more difficult to target an individual. However, lions are ultimately successful at catching zebras, so this optic...

Ernest Hemingway made Mount Kilimanjaro famous with his story “The Snows of Kilimanjaro”—though he never climbed the peak. But many others have. More than 30,000 try each year, with two-thirds reaching the top. Kili, as it’s called, is the tallest mountain in Africa but the easiest climb of the Seven Summits—the highest peaks on the seven continents. Its high camps have hosted some world record sporting events, including the highest professional soccer game, with players hailing from 20 count...

Have you ever seen the brilliant hues of petrified wood and wondered how it gets its colors? When trees die, they typically fall to the forest floor, where they decay. But if they fall in a place without oxygen—in water, a swamp or bog, or are buried by volcanic ash or flood silt—they may not decay. After thousands or millions of years, water seeps into the pores of the wood, carrying dissolved silica. The silica bonds with the cellulose and replaces it. Then other mineralized water enters t...