Episodes

In a few rare places in the world, there are salt lakes that are flamingo pink. To understand what gives them their bright color, we should first understand what makes flamingos pink. The birds spend much of their lives wading and feeding in shallow lakes that aren’t pink but are salty and hold the flamingo’s favorite food: brine shrimp. These shrimp are pink, colored by high concentrations of beta-carotene—the same pigment that makes carrots orange. After a couple years of eating shrimp, fla...

Throughout the Apollo missions, NASA believed there was no water on the Moon. In the nearly one thousand pounds of rock and soil samples that these missions brought back, they did find traces of water. But they assumed these were contamination from gathering and transport. Then in 2008, the Indian space agency launched a Moon orbiter carrying NASA’s Moon Mineralogy Mapper—or M3—which was designed to search for minerals, like water. The tilt of the Moon’s axis prevents sunlight from reaching i...

Some of the loudest sounds in the ocean are air guns, fired by ships doing seismic studies of the seafloor. The blasts can interfere with the communication of whales for a thousand miles around. So, scientists thought, what if they could use whales to do the studies instead? In a seismic study, sound waves from a ship travel down through the water, through the ocean floor and into the geologic layers below. They reflect off these layers and bounce back to other ships, where powerful computers...

Here’s a fun experiment you can try at home to make miniature cold lightning using rocks from your yard, or candy. First, look for some quartz pebbles. Preferably milky white ones. Next, find some wintergreen Life Savers—or white sugar candies will do. Then grab some safety glasses, because you’ll be smashing things. Now go to a darkened room, let your eyes adjust, and rub the pebbles together. Try different levels of friction and speed. You should see a flash of light in one or both pebbles...

For billions of years, there was no fire on Earth. There was heat to ignite it, like volcanic eruptions and lighting strikes. But fire lacked two very crucial ingredients: fuel to burn, and oxygen to feed the flames. Ironically, plants would provide both. Fire is a chemical reaction where fuel oxidizes to produce heat and light energy, carbon dioxide, water vapor and other gases. Fire can start when there’s about 13% oxygen in the air, but it won’t stay lit. It will burn steadily at 16% oxy...

In another EarthDate, we talked about Earth’s magnetic polarity reversing. But sometimes the poles don’t flip, they just go on an excursion—with potentially drastic consequences. A polar excursion happens when the pole moves more than 45 degrees from Earth’s rotational axis. This happened 12 times in the last million years. Forty-two thousand years ago, there was a particularly wayward North Pole. It wandered down to New York, then all the way to Antarctica, before rising back up to its orig...

If your birthday is in August, your birthstone is peridot. And if you have one, you can be sure it came from deep within the Earth—or deep in outer space! Peridot is the gem name for a gem-quality example of olivine. Olivine is very common inside the Earth, where it makes up an astonishing 50 percent of Earth’s upper mantle. But it’s much less common on the surface. It’s found where tectonic forces push mantle up and over Earth’s crust, or where volcanic activity brings up mantle in the form ...

For decades, Death Valley held a mystery that scientists could not solve. Large rocks were slithering across the valley floor, traveling hundreds of meters, leaving long tracks behind them. But no one had seen them do it or could figure out how it happened. So, scientists fitted rocks with GPS trackers and set up remote cameras to try to capture the rocks in motion. Because the movements could be separated by decades, they expected this to be “the most boring experiment ever.” But just two ...

In the Stone Age, the most important tool was, yes, the stone. But what was second? Well, we’ll spin a yarn about that on this EarthDate, because it was … yarn, or string. String is just plant fibers like cotton or hemp, or animal hair like sheep or llama wool, twisted together. This simple invention allowed early humans to turn short fibers into long cords with many uses. String tied stone points to spears and arrows. It strung a bow to shoot those arrows. It tied fishhooks made of shell to ...

How would medical researchers build the perfect needle, for sensitive injections or brain-tissue sampling? Of course, they’d look to nature. And where in nature would they find the perfect needle? On the sharp end of a mosquito! Mosquitoes are the most dangerous creatures on Earth, carrying diseases that infect 700 million people a year and kill 2 million. This is because, for millions of years, they’ve been so good at sticking their beaks into us. They do this with a special six-part probos...

Compasses point north. Until one day, they’ll all point south—as they have before. In 1905, a French geologist discovered a lava field with some very strange properties. Iron within it was magnetized in reverse. What should have been north was south. After much pondering, he realized this could only be possible if Earth’s magnetic poles were reversed at the time the lava was flowing. When it solidified, it preserved that reversed magnetic orientation. It took 50 years for other scientists to ...

The Maya ruled central America for 1200 years, creating written language, mathematics, and spectacular architecture. Then, in AD 900, they mysteriously abandoned their cities, and their empire crumbled. Contaminated water may have played a role. At their ancient capital of Tikal, 60,000 citizens relied completely on rainwater trapped in reservoirs. But the rain also washed red mercury paint, which the Maya used to decorate the city, into the reservoirs. They recognized the problem and devise...

Here’s a riddle for you: What animal behaves like a plant? The answer is coral. These tiny, transparent organisms live mostly in colonies, connected by living tissue through which they share nutrients. But they often can’t consume enough nutrients to live. So, they rely on special symbiotic algae in their tissues—meaning most corals require sunlight, like a plant. The algae take in sun and carbon dioxide and produce oxygen and sugars, which the corals consume to grow and produce the hard exos...

At the start of the 20th century, Serbian mathematician and physicist Milutin Milanković decided to use math to determine how Earth’s ice ages had occurred. First, he calculated how the amount of sun that Earth receives—its insolation—determines its temperature. Then, he identified and explained Earth’s different climate zones based on their insolation. Finally, he built a mathematical model to discover if Earth’s insolation is affected by three variations: a changing elliptical path around t...

Earth is like an onion. The layer we live on, the crust, is like the onion skin. It represents less than 1 percent of the distance between Earth’s surface and its center. Below the crust is the more malleable mantle, making up nearly half of Earth’s volume. Below that are the metal inner and outer cores. In the late 1950’s, at the start of the Space Race, the U.S. and Soviet Union began a different contest: to see who could go deeper into the Earth, perhaps even all the way to the mantle. The...

Just over 30 years ago, the Loma Prieta earthquake shook Northern California, killing 63 people and injuring almost 4,000 more. It got Californians dreaming about an earthquake early warning system. Even a few seconds of lead time would allow people to stop what they’re doing, drop to the ground, and take cover, or pull over if driving. To build this system, three large technological challenges had to be overcome. First, the state installed hundreds more seismometers and electronically connec...

In 1957, the Russians launched Sputnik, the first satellite to orbit Earth. The U.S. responded by forming NASA, and the Space Race had begun. The Russians took the lead 4 years later when they sent a cosmonaut into orbit. President Kennedy conferred with U.S. experts; several were leading German rocket scientists who had emigrated after the war. They designed a program around U.S. strengths. In May of 1961, Kennedy announced their bold ambition: “before this decade is out, of landing a man o...

On another EarthDate, we talked about the Space Race to the Moon. NASA recruited its Gemini and Apollo astronauts from the fighter pilot program. They had nerves of steel and could make split-second decisions. But they also needed a strong scientific background for their missions. So NASA trained them in aerodynamics, rocket propulsion, celestial navigation, spacecraft guidance, and ultra-long-distance communication. Most of these were about getting to the Moon. But what would they do once t...

It’s easy to imagine Earth’s orbit as a circle around the Sun. But in truth, its path is more complicated. In AD 127, the Greek astronomer Hipparchus compared star maps made centuries before to his own maps–and found the stars were in different places. He realized that Earth must be slowly wobbling on its axis like a top wobbles as it spins, causing it to be oriented differently to the stars. He called this precession, which happens on a 26,000-year cycle. In 1500, Copernicus put forth the i...

In another EarthDate, we talked about kelp: 100-foot-tall seaweed that grows near shore. Asian cultures have farmed kelp and other large seaweeds for centuries. If you’ve had Japanese food, you’ve probably eaten it sliced in seaweed salad, dried to flavor soup, or wrapped around sushi. Seaweed is nutritious, easy to grow and harvest, and requires no irrigation or fertilizer. It thrives in cool- and cold-water bays, including those that have become barren from overfishing, mismanagement, or agric...

The world’s tallest mountain just had a couple of feet added to it. Mount Everest sits on the Nepal–Tibet border. In Nepalese, it’s called Sagarmatha, meaning “the head of the sky.” In Tibetan, it’s called Chomolungma, “goddess earth mother.” It got its English name to honor George Everest, who led the survey to map and measure the peaks of India and Nepal in the mid-1800s. His team used triangulation to sight from point to point, thousands of times, to work out elevations. In 1856, they determi...

In other episodes, we talked about solar storms: electromagnetic radiation that flows from the Sun to Earth. In severe cases, they can disrupt our electricity and communication systems. One very severe event happened a hundred years ago, in 1921, and lasted for 3 days when a large group of sunspots emitted bursts of plasma called coronal mass ejections. Traveling a million miles an hour, these can take 1 to 3 days to reach Earth. Once here, their energy can create electrical currents that flow...

It might surprise you to hear that there are forests underwater. In temperate oceans near the shore, kelp grows. It’s technically not a plant, but algae–specifically, a brown macroalgae. And macro it is. The largest species of kelp can reach 130 feet. They stretch from the dark ocean floor, where they anchor to rocks. A long stem grows upward to where the kelp can reach light. There, it produces long leaf-life blades that conduct photosynthesis. The stalk and fronds are held upright by gas-fille...

We’ve talked about some weird animals on EarthDate, but the platypus may be the strangest. They’re famous for having a duckbill and a beaver tail. But that’s just the start of it. Platypuses are monotremes, one of just three mammals—all in Australia—that lay eggs. But they also produce milk to nurse their young once hatched. And they’re one of the few venomous mammals. Males have sharp spurs on their back legs that can inject poison potent enough to send a human to the hospital. They spend much ...