EarthDate

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...

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 mo...

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 cre...

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...

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, th...

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 An...

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 c...

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 wi...

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...

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 54...

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 req...

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 mo...

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...

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 a...

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...

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 w...

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 al...

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...

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...

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...

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 a...

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...

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 su...

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...

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...