Episodes

Leonardo da Vinci once said: “We know more about the movement of celestial bodies than about the soil underfoot.” He was right 500 years ago, and he’s still right today. That’s partly because the study of space is mysterious and cool, and there really wasn’t much interest in studying dirt. Until recently... We now know that about 90 percent of all land-based species live in the soil, not on it. Most of these are microscopic, but they’re incredibly plentiful: there are more microbes in a handful ...

We talked about how a fungal network connects plants underground. But did you know it allows them to communicate? Specifically, they exchange sugars, and chemical and electrical signals, with each other. The largest trees are now known to “mother” the surrounding forest. They give their sugars back to the entire soil community, to support neighboring plants and trees. They’ve even been shown to preferentially identify young trees within their own species, and send them a larger serving of sugars...

If you’re driving while listening to this, please think of your vehicle not as a mere car or SUV, but as a starship cruiser! Here’s why: the iron it’s made of came from the heart of a distant star. Stars begin their lives as giant balls of gas, mostly hydrogen, the first element on the periodic table, with one proton. Under the force of the proto-star’s enormous gravity, hydrogen atoms fuse together to produce helium, with two protons. This nuclear fusion releases a huge surge of energy, and the...

Why did the ancient Greeks build their cities in earthquake zones? For several—very good—reasons. Greece and Turkey lie along massive fault zones. Faults, when they move, create earthquakes. Spring water tends to follow these fault systems, and the Greeks, following the water, did, too. Fault lines also create cliffs, which provided natural defenses for the cities. And fault zones tend to form surface depressions where soils can accumulate, making them good for agriculture. So the faults gave Gr...

In 1769, Ben Franklin was the first to map the Gulf Stream. It’s Earth’s most famous current, moving more water than the Amazon River. But the Gulf Stream is just one part of the global ocean conveyor, a system of currents that connects the world’s oceans. In tropical seas, wind and tides drive warm surface currents, like the Gulf Stream. Near the poles, cold air, evaporation, and ice formation make the seawater colder and saltier. It sinks to the bottom, and warm tropical water is pulled up to ...

Would you let your kids keep a pet shark? You would if you were part of the Bajau tribe, where children learn to swim before they can walk and spear fish at age 8. The Bajau are sea nomads in Indonesia, the Philippines, and Malaysia, who live on boats and follow fish populations. Traditionally, they come ashore only to trade their catch and escape storms. To make their living diving for fish, the Bajau have adapted to do things the rest of us can’t. In fact, they’ve developed some of the same ca...

We know that life evolves, but did you know that minerals do, too? Remarkably, one of the biggest drivers of mineral evolution… is life. A mineral is simply an element or elements on the periodic table, arranged in a certain crystal structure. For instance, the hardest mineral, diamond, is formed of the element carbon. One of the softest, graphite, is also formed of pure carbon, but it’s a different mineral because it has a different crystal structure. When Earth formed, over 4.5 billion years a...

We talked about the asteroid that, 66 million years ago, ended the age of dinosaurs. But what exactly did it do to the planet? From the point of impact, a blast wave of heat rushed outward at nearly the speed of light, followed by scorching winds that reached 500 miles an hour. These were followed by a massive earthquake felt around the world that may have caused landslides across the planet. Shortly after came tsunami waves up to 1,000 ft high, racing across the Gulf of Mexico and traveling man...

On previous EarthDates, we talked about the asteroid that wiped out the dinosaurs—and 75 percent of all species on Earth. But what survived? And how? In the first years after impact, dust and aerosols blocked the sun’s light and heat, which slowed photosynthesis. Plants died, along with most things that depended on them, as the food web collapsed. Most types of plankton in surface ocean waters also died, and rained down through the water column, where bottom-dwelling scavenger species had a fiel...

Spider silk is the strongest, most durable, most elastic fiber in the world. It’s 5 to 6 times stronger than steel by weight. A strand that could circle the globe would weigh less than a bar of soap! Given these remarkable properties, scientists have studied it closely. Spiders make silk with their spinnerets, tiny organs beneath their abdomens. Before it’s spun, the silk is a gel of liquid proteins. The spinnerets remove water from the gel and extrude it through an acid bath, aligning the prote...

Previously, we talked about how Earth transfers naturally produced carbon between sky, sea, and soil. Today, scientists are working to put CO2 from fossil-fuel combustion and agriculture back into the ground rather than into the atmosphere—by mimicking Earth’s natural carbon cycle. Capturing and compressing CO2 from the exhaust stream of, say, a coal power plant, is challenging and expensive. But when done, the gas becomes a low-density liquid. Researchers have developed and tested methods to pu...

In the mid-twentieth century, NASA scientists launched the first satellites to view Earth. When they looked at the photos, they saw mysterious stripes of clouds crossing the oceans. On closer inspection, they realized these cloud trails followed the shipping lanes. In the mid-nineteenth century, after collisions between ships, nations designated lanes across the seas that ships would follow to avoid accidents. As traffic grew over the twentieth century, more and more ships plied these maritime h...

On their maps of the West, Lewis and Clark called it “the Great Unknown.” For a one-armed geologist named John Wesley Powell, that was too much intrigue to ignore. So in 1869, he led a team in four wooden boats on an expedition down the Green and Colorado Rivers, destined for what the Spanish called El Gran Cañon. Within 2 weeks, a rocky rapid had destroyed one of their boats. Within 2 months, most of their supplies were lost. Fortunately, the lightened boats rode higher in the dangerous waters....

The Roman Empire had official historians—but can we trust their accounts, or were they burnishing history to please the emperors? A closer look at Roman silver has helped find the answer. And surprisingly, this closer look came in Greenland. The ice there has recorded 130,000 years of history, as the atmospheric particles of each year are deposited in a layer of ice, one atop the other. By drilling ice cores, then analyzing these layers with microscopes and spectrometers, we can read them like t...

One hundred sixty years ago, scientists invented the spectroscope, which breaks light into its spectrum of colors. They soon discovered that some elements, when heated, produce a signature light color. Hydrogen, for instance, makes orange. When they pointed the spectroscope at the sun, they saw lots of orange—and some yellow, which didn’t match any element on Earth. They named this alien element helium, after the Greek sun god Helios. For decades, many doubted its existence. Until a scientist ai...

Scientists have been watching 1,000 species of mountain animals and plants around the world to see how they react to a warming climate. They’ve found that as annual temperatures climb, many species have climbed, too. On average, for every one-degree-Celsius increase, mountain-dwelling species shifted 100 meters upslope. Because the mountains narrow as they go up, this means a shrinking habitat for those species, and often a dramatic drop in population. For instance, butterflies in the French Pyr...

Earlier, we talked about animals migrating up mountains to find cooler temperatures, in response to a warming climate. Well, crops are migrating, too. The USDA map of plant hardiness divides North America into 13 zones. Zone 1 is farthest north, with winters colder than 50 below zero. Zone 13 is farthest south, with winters around 60 degrees Fahrenheit. Over the last 30 years, all zones have shifted a half zone to the north, as average winter temperatures increased across the Lower 48. Models pr...

Pause for a moment and imagine the scent of rain. You can almost feel it in your nose. There’s that bright, sweet smell on the wind before the rain comes. Then the scent of fresh earth and grass as the rain falls. And a damp, musty aroma like a forest floor that lingers afterward. What gives rain these distinctive aromas? And why do we find them so memorable? Well, the pre-rain smell is ozone. Lightning in the clouds splits nitrogen and oxygen gas into single atoms, which recombine into things l...

If you’re listening to this while driving, that’s due in large part to the oil boom—which happened over a hundred years ago. At that time, Pennsylvania was the biggest oil producer, and automobiles were scarce. Then, Pattillo Higgins, a self-taught geologist from Texas, had an idea. A low, flat hill outside his hometown was known for black tar that oozed from it. He thought the mound was a salt dome—a rising column of salt—and that oil must have migrated from deeper formations, up its sides. For...

Many animals have a sixth sense that we humans do not. It’s called magnetoreception, and it allows them to read Earth’s magnetic field to navigate. The magnetic field comes out of the ground at the South Magnetic Pole, flows parallel to the surface across the equator, then dives back into the ground at the North Magnetic Pole. Many bacteria, earthworms, and blind mole rats can sense the direction of this magnetic field and orient to it. We call this compass sense. Migrating animals like butterfl...

From an earlier EarthDate, you may remember John Wesley Powell, who mapped the Grand Canyon and became one of America’s leading geologists. After his trip, he studied the American West—then called the Great American Desert. Powell realized its dryness—with rainfall below 20 inches a year—made it fundamentally different than the rest of the country. He predicted that farming and settlement methods used in the East and Midwest would fail, and proposed to Congress a much different approach: Don’t d...

In 2018, wildfires burned an unusually high 8.5 million acres. Conversely, 2017 was a very wet year—but that was part of the problem. Heavy rain brings more foliage, which the next year becomes fuel. Wet years are often followed by high-fire years. Wildfires are a natural process, and in many ways can be beneficial: they clear out dead plant matter, control insects and plant disease, return nutrients to the soil, and make way for new growth. It’s even thought that, in the geologic past, fires re...

In another EarthDate, we talked about ways to prevent wildfires. Now, we’ll talk about what’s encouraging them. In a warming climate, the air holds more moisture. It draws more water from plants, making them drier and more combustible. Summers become longer, which extends the fire season and gives fire-prone lands more chances to burn. Expanding development also puts more people in fire zones. Human activity starts four out of five fires, which increases burned areas sevenfold. Drought across th...

Here’s a great story to read on the beach, but it’s not on your summer book list. Every beach is a mystery. Read the clues right and they’ll tell you about the area’s ocean floor, sea life, and geology. You can start with the usual suspects: waves. They make or break a beach. Gentle slopes and slow-rolling waves produce wide beaches and shallow, sand-rich bottoms extending way off shore. Steep slopes and tall, angular waves that crash hard rob the beach of sand, keeping it narrow and rocky. Now ...