EarthDate

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...

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 lay...

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. Tr...

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 wh...

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....

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 force...

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...

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...

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, t...

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 solid...

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...

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...

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 di...

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 differen...

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 ha...

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 Ma...

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-dis...

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 c...

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- an...

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 triangula...

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...

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 l...

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 th...

If you live in or visit the mountains, you can look at the snow-covered hills as nature’s water towers. As that snow melts, it could provide 75 percent or more of the area’s freshwater each year. That’s true far downstream from the mountains too, and even in snowy flat areas. Around the world, snow provides 50 percent of our total annual freshwater supply. And it does more than that: snow reflects...

In another episode, we talked about the horseshoe crab, which has existed on Earth nearly unchanged for more than 400 million years. In the last 40 years, it’s become a vital player in our medical industry. Why? It’s in their blood. Horseshoe crab blood is copper based, not iron based like ours, which makes it blue. It coagulates so rapidly and completely around invading pathogens, that medical re...