Episodes

Have you ever wondered how squirrels find the nuts they hid months before? A typical squirrel can store 3,000 of them in a fall season, in dozens of locations. It seems almost impossible that they could remember them. But they do. There are 200 species of ground squirrel, tree squirrel and flying squirrel that rely on stored seeds and nuts. To do that, they need to return to them even after leaves fall and snow covers the ground. How do they do it? Smell plays a role. But sight and memory ar...

LEDs are everywhere today. But what does L. E. D. stand for anyway? Luminous Efficiency Device? Less Electricity Demanded? Not quite – though both correctly describe Light Emitting Diodes. They make more light, from less electricity, than any other technology. Incandescent bulbs of the 20th century heat a metal filament until it glows white hot. They produce light, but much more electricity is converted into, and wasted as, heat. Fluorescent tubes pass energy through a gas that glows. They c...

Rust is common on Earth. It shouldn’t exist on the moon. But somehow, it does. Rust is just the common name for iron oxide. Iron that has bonded to oxygen. The moon, however, has no oxygen. Yet lunar rovers have recovered grains of iron oxide in lunar soil. How could they have gotten there? One possibility is from Earth. Or rather, from our atmosphere. The magnetic field of our planet, called its magnetosphere, surrounds Earth like an invisible force field. The sun produces a solar wind of ...

Imagine there was not one species of human…but many. One stronger. One smaller. All different, but closely related. Around 40,000 years ago, that’s exactly how it was. Homo sapiens – us – shared Earth with several other Homo species. Then those other ones went extinct, and we carried on. The sole survivors. Why? Because we could better adapt to changing climates. And that’s because of a few key qualities. First, we had more flexible diets. We could eat large animals or small. Fish, fowl, or f...

Gold is rare. Except in one place on Earth that it’s incredibly plentiful. But we’ll probably never get to it. Over the course of human civilization, people have searched for gold. Still, we haven’t found much – 220,000 tons across all those centuries. By comparison, we’ve mined seven times as much silver. And 3,000 times more copper. But we now know there’s much, much more gold on Earth. When the planet formed, more than 4 billion years ago, many metals swirled together in Earth’s molten mag...

Is there life on Mars? That’s the question NASA wanted its first Mars mission to answer – in 1976. They designed their remarkable Viking rover -- well before modern computers -- to collect and test soil samples, 140 million miles from Earth. First, Viking added a nutrient solution to the soil, looking for carbon dioxide that microbes would produce if they consumed it. And the test showed a small amount! Next, Viking incubated the sample to see if microbes, if present, could produce organic ma...

A large manatee can top 1000 pounds and eat 15% of its weight in seagrass each day. That may sound hardy, but manatees are actually very sensitive. There are three species, all adapted only to the constant warm waters of the tropics. But the West Indian manatee has found a way to survive Florida winters by taking advantage of the state’s geology. As temperatures drop, manatees leave coastal waters and swim up rivers toward headwater springs. Florida has hundreds of springs, more than any oth...

In the mid-1800s, London’s SoHo neighborhood was a terrible smelling place to live, as raw sewage ran through the gutters into open cesspools. When a cholera epidemic broke out, 600 people died and many remaining residents fled, fearing – as was common then – that foul air spread the disease. Local physician John Snow didn’t buy it. Ten years earlier, he had proposed that cholera spread through contaminated water. But lacking proof, he was ignored. With an outbreak on his doorstep, he saw an ...

Plastic has remarkable value to humans. But it’s also a major source of ocean plastic pollution. Most of it is nets and rope from fishing boats, or municipal garbage that’s carried down rivers into the ocean. There it accumulates in spinning gyres of plastic, twice the size of Texas. Large pieces eventually break down into fragments and microplastics. But because plastic is made to be durable, it won’t degrade any farther than that. Wouldn’t it be great if we could clean it up? That’s what a...

Sand is incredibly common. There are oceans of it – in oceans, and deserts too. But, for our purposes, that’s not the right kind of sand. We use sand in concrete, to make bridges and roads, buildings, houses and power plants. We use it in glassmaking, for windows, computer chips, solar panels and much more. We use it for hydraulic fracturing, to prop open cracks in shale deposits so oil and gas can flow. In all, we use billions of tons of sand every year. But only a certain kind will do. Beac...

In 1985, a passenger jet landing at DFW airport was forced to the ground by an unusual downward blast of wind called a downburst. The plane struck cars on the highway and a water tank, then crashed on the airfield, killing more than 100 people. It was the third such fatal crash in a decade. So, the FAA set out to invent a new warning system for these dangerous wind events. A downburst is a sinking column of air within a thunder cloud that accelerates toward Earth, reaching speeds over 100 miles...

Before modern energy gave us modern air conditioning, we had sweat to keep us cool. And shade. And maybe a jump in a lake. Animals still rely on those today to beat the heat. Horses, like humans, sweat. When the sweat evaporates, it cools the skin. Dogs, antelopes and some birds pant, drawing breath rapidly across their tongues and throats, where evaporative cooling brings down the temperature of blood near the skin surface. Other birds vibrate the flaps of skin on their throats to circulate ai...

If you’ve been on a boat, pretty much anywhere in the tropics, you’ve seen mangrove forests. There are at least 75 species of these small trees, evolved to live in harsh tidal conditions, their roots in sand, their trunks often submerged in saltwater. There, they can form dense thickets that protect the coast from ravaging waves and storm surges. And that’s just one of their benefits. Mangroves’ arching root networks trap and stabilize sediment to help build up the coast. In the process, they...

On another episode, we told you about urban heat islands. Buildings and asphalt absorb summer heat -- from sun and air, cars and trucks, power plants and air conditioning -- and hold it, driving city temperatures far higher than surrounding areas, sometimes to devastating effect. Urban heat islands have killed thousands. But new studies of over 3,000 cities around the world show they’ve saved many more! That’s because heat islands also hold heat in winter, as buildings, transportation and indus...

Summer in the city. It’s sweltering. The sun beats down all day. Its heat is absorbed by concrete buildings and blacktop, which hold that heat at night -- and into the next day. The heat builds over weeks and months, keeping summer city temperatures much higher than their surrounding suburban and rural areas. Cities can be 10 degrees Fahrenheit hotter, or more! That’s what’s called an urban heat island. People respond by turning down the thermostat on their air conditioning. Exhaust from AC u...

Today we make stuff in three ways. Plants and animals make our food, wood and fiber. Oil and gas make plastic, fuels, chemicals and clothing. And rocks, dug out of a mine, become metal, concrete and stone – which make our buildings and roads, planes, trains and automobiles, energy infrastructure and much more. By weight and value, our most important mined product is coal – which makes about 1/3 of global electricity. Coal was also the first thing humans mined at scale, 20,000 years ago in Sou...

In another EarthDate, we talk about how mining provides the materials to build the modern world. But new technology is changing that world. We’re building huge new data centers for AI; batteries to power EVs, and stabilize the power grid; and enormous volumes of solar panels and wind turbines. All these will require a lot more mining. And all mining impacts the environment. So engineers are working to make the process cleaner and safer. Mine tailings – the waste rock – are today kept in huge...

On another episode, we talk about how mines have a large environmental footprint. Think of a giant pit, with huge machines digging out ore. By contrast, think of your old smart phone. In one ton of discarded phones there’s 80 times more gold than in one ton of ore. Electronic waste, like phones and computers, contains gold, silver, palladium and rare earth elements. Old batteries contain lithium, cadmium and other heavy metals. Construction and demolition debris contains copper from piping a...

Our modern supplies of water and energy are miraculous – and tightly interlinked. Only 3% of Earth’s water is fresh. And 99% of that is frozen in glaciers or stuck underground. That means just 1% of fresh water is on the surface where we can easily access it – for agriculture, mining, industry and our consumption. To get that water to us requires energy. First it’s pumped, sometimes over long distances, from a reservoir or river to a water treatment plant. There, it’s filtered, purified and ch...

Charles Darwin proposed that life on Earth may have started in bodies of highly alkaline water called soda lakes. New research suggests he may have been right. You might remember from a prior EarthDate that phosphorus is an essential building block for DNA, RNA, and the energy carrier for cells, ATP. Without phosphorus, there is no life. Soda lakes are some of the few places on Earth where phosphorus is readily available, rather than bound up in rocks. Nearly all these lakes around the world ...

In 1858, Queen Victoria sent a telegraph to U.S. President Buchanan, via the first undersea cable. The cable worked for just a few weeks, but it launched an international cable network that still dominates global communication. We think we live in a wireless world. But it’s just the short hop from our phones and wifi to a receiving antenna. Nearly everything after that is transmitted by cable, on land and undersea. Undersea cables made of copper served the world for more than a hundred years....

After the Chernobyl nuclear accident, the Russian government declared a thousand square miles around it an exclusion zone. The hundred thousand people evacuated could never return to their homes. The wildlife, however, could. European bison, which had vanished from the area, returned and populations grew. So did native deer. These large herbivores brought large predators, like lynx, bear and especially wolves, which had been hunted to near extinction. Large birds of prey came back too – gold...

The giant bogong moth has a brain one-tenth the size of a grain of rice. And eyes the diameter of a human hair. Yet it can navigate by sensing the magnetic field of Earth. Or by gazing at the stars, reading a mental map that it was somehow born with. Each spring in Australia, they leave the lowlands by the millions, and fly at night over terrain they’ve never seen before, following their internal compass, and that inherited star map. They’re the only insects we know of that can navigate this ...

During World War 2, an American pilot flying over the Canadian arctic saw something extraordinary. A midnight blue lake, 2 miles across, shaped in a perfect circle. The Allies kept it a secret, using the lake as a navigation landmark during the war. But in 1950, photos hit the media, and the lake became a sensation…because it shouldn’t exist. There were no rivers leading into it, and none leading out. There was not enough liquid groundwater in this frozen landscape to fill it. It was as if th...