EarthDate

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...

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...

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 sp...

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 si...

The megalodon, Earth’s largest shark, is thankfully...extinct. It was twice the length of a school bus. Larger than most of today’s whales and three times the size of the biggest great white shark—with up to 10 times the bite force. Its jaws were filled with hundreds of six-inch teeth, which fell out and were replaced every few weeks. The megalodon’s large range meant that fossilized teeth have be...

Utah’s Great Salt Lake may seem like a wasteland, ringed by toxic deposits of mercury and arsenic, and filled with water so salty that only brine shrimp can live in it. However, those shrimp feed 10 million migrating birds. And the lake provides eight thousand jobs and two billion dollars in industry, harvesting salt and other minerals. It’s vital to the region’s ecology and economy. But the lake...

So-called water spiders aren’t spiders at all but insects specially evolved to walk on water.  There are 1,700 species of these water striders, which have existed on Earth for millions of years.  If you’ve ever wondered how they skate so effortlessly across a pond without falling in, the answer is surface tension—and their very specific adaptation to it. Water molecules, as we’ve discussed on prio...

When a thunderstorm forms over the desert, it may not produce rain—but could form a deadly dust blizzard called a haboob. When rain droplets condense within a thunderhead, they cool the air, which rushes toward Earth with the rain. If this happens over a desert, the rain will often evaporate before reaching Earth. The evaporative cooling further chills the air, which falls faster. Eventually the c...

Hail is created when rain starts falling up. This usually happens in the spring, in middle latitudes, when tall clouds form over warm updrafts. In the cold upper reaches of the cloud, water condenses around nuclei, like dust particles, dirt, or salt crystals, to form droplets of rain that begin to fall to Earth...but then are pushed back upwards by the updraft. The rain droplets tumble within the...

Giraffes are fascinating animals. They have the same number of vertebrae in their necks as humans do—seven—but each one is nearly a foot long. They have long, purple tongues too—nearly two feet—that can grasp things as easily as a monkey’s tail can, which they use to pull leaves and fruits from high branches. All four giraffe species are covered in spots. And each individual’s spots are as unique...

At the bottom of the ocean lies a treasure. But recovering it could be technically difficult, geopolitically challenging, and environmentally damaging. Eighty three percent of the ocean is a mile deep, or much more, making the deep ocean the largest environment on Earth, covering 115 million square miles. Down there, like in the Amazon, species diversity is high. There may be thousands of species...