Épisodes

  • The Star of India

    The Star of India
    Feb 27 2026
    In October 1964, three young thieves cased the American Museum of Natural History in New York City. They returned that night to scale the museum wall, climb through a bathroom window, and steal 22 of the most precious jewels in the world. Among them were the Eagle Diamond, the DeLong Star Ruby, and, most famous of all, the Star of India sapphire. Sapphires are a variety of corundum, the third-hardest mineral. Pure corundum is clear, but when colored blue by titanium impurities, it’s called a sapphire. When colored red by chromium, it’s a ruby. Mineral inclusions in a sapphire sometimes line up along its crystal lattice to reflect light in a six-pointed star. The Star of India, besides being huge and nearly flawless, has stars that are visible from top and bottom. The thieves didn’t go far with it, renting a luxury apartment near the museum. An informant tipped off the police, who raided the place and captured one of them. The other two fled to Florida; the cops pursued and, a few days later, apprehended them, too—but not before they dispersed the jewels. The Eagle Diamond was never recovered, probably cut into several smaller stones. The philanthropist John D. MacArthur, paid a ransom to have the DeLong Ruby returned to the museum. One of the thieves finally led detectives to the Star of India, which they found with several smaller gems in a wet leather bag in a bus-station locker. It’s Earth’s near-flawless creations that humans still value the most…
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    2 min
  • Green Iceland/Icy Greenland

    Green Iceland/Icy Greenland
    Feb 27 2026
    If you’ve been to Iceland, you know it doesn’t have much ice. In fact, there’s so much grass that on maps it’s colored green. On the other hand, you probably know that Greenland is covered in glaciers. So why is the green one Iceland and the white one Greenland? Legend has it that the Vikings who discovered Iceland wanted to protect it from settlement, so gave it an unflattering name. But it was actually a matter of perspective. The first explorer to Iceland had a terrible trip. His daughter died on the long voyage. He arrived in winter and his livestock froze. That spring, his ship was nearly sunk by icebergs. Fed up, he called it as he saw it: Iceland. And the name stuck. A century later, another Viking explorer was visiting Iceland when he got in a fight with the settlers and was run off the island. He sailed west and found Greenland, which was warmer than today, and the coastal areas were indeed green. Wanting to attract settlers, he called it Greenland. They came, and built farms and grazing operations—which lasted until around 1400, when the climate cooled. Greenland’s glaciers expanded, leaving less green land. Today the Arctic is warming, which means Greenland’s glaciers are melting, and it may one day be greener again. Conversely, cold glacial meltwater entering the ocean from Greenland could blunt the Gulf Stream that warms Iceland, making it icier.
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    2 min
  • Tuskless Elephants

    Tuskless Elephants
    Feb 27 2026
    We often think that evolution takes thousands of years. But in rare cases where humans impact small populations, adaptation can work much faster. Take the case of the tuskless elephant. Nearly all male elephants and most females have tusks. These are just elongated lateral incisors that grow outward once the elephant loses its baby teeth. But a small percentage of elephants are born without these teeth and never develop tusks. In 1919, the South African government brought trophy hunters to the East Cape to exterminate elephants that were eating crops and trampling farms. By 1931, only eight females survived, and half were tuskless—perhaps because they made the least attractive trophies. Instead of natural selection, this was human selection. Fortunately, public opinion forced a change of heart and a preserve was established to protect the elephants. The tuskless matriarchs had tuskless offspring, and today nearly all female elephants in the park lack tusks. A similar thing happened in Mozambique. During a 15-year civil war, soldiers poached elephants for their meat to feed the troops and for their ivory to sell to buy more weapons. Again, elephants with tusks were killed, and by the end of the war, half the females were tuskless. As the population has rebounded, a large portion of females remain without tusks. But with the hunting pressure off, experts think natural selection may again favor animals with tusks—and both groups may eventually become tusked again.
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    2 min
  • The Geology of Fireworks

    The Geology of Fireworks
    Feb 27 2026
    This 4th of July, try regaling your fellow revelers with some firework history and, yes, geology. They’ll probably know that fireworks originated in China. But they likely won’t know they started as simple bamboo sticks thrown into a fire. The air inside the hollow stalks expanded, then exploded, making a “crack” that the ancient Chinese used to ward off evil spirits. A few centuries later, legend has it that a kitchen recipe gone awry combined charcoal, saltpeter, and sulfur. Who knows what food they were trying to make…but they created gunpowder. Warlords quickly recognized its military potential. Luckily, firecracker enthusiasts pursued its celebration potential. They filled those same bamboo tubes with gunpowder, to make a far bigger noise, then used more gunpowder to launch ever-larger firecrackers into the air. And fireworks were born. When Marco Polo came to China, he was so impressed that he took fireworks back to Italy, where they’ve been a hit for over 700 years. The Italians were the first to add common minerals like gypsum and calcite to produce colored explosions. The science has come a long way since, now blending in a variety of metal salts and exotic minerals to make better fuels and to add deeper colors and special effects. So when you see a brilliant finale of red, white, and blue, you can shout, “Wow! Celestine, barium oxide, and copper ore!” Then you can blame EarthDate for making you the science nerd at the party.
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    2 min
  • Cooler in the Mountains

    Cooler in the Mountains
    Feb 26 2026
    Here’s a riddle: If heat rises, and mountains are closer to the sun, why are they always colder? The answer may surprise you. The heat of the sun can’t actually radiate through space. There would need to be particles of some element to conduct its heat; but space is a vacuum. Instead, the sun emits electromagnetic energy: ultraviolet, visible and infrared light, X-rays, and radio waves. When this solar radiation finally meets Earth’s surface, it warms it. And that radiates heat back upward, warming the atmosphere from the bottom up. So is that why it’s warmer lower and cooler higher? Not exactly. It has more to do with air pressure. Like all gases, the air in our atmosphere is a poor conductor—because it’s not dense with particles. However, the atmosphere does have mass. And its weight bearing down on the air at the surface compresses it more than the air at altitude. The compressed air is denser with molecules, which are more likely to collide, and these collisions produce heat. That means the air near the surface is not only better able to conduct Earth’s reflected heat but generates its own heat because it’s dense. This hot air can indeed rise. But as it does, the atmospheric pressure decreases, the air expands, and it cools. So, even though they’re closer to the sun, thin air in the mountains keeps them colder than the thicker air in the lowlands surrounding them.
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    2 min
  • Pterosaurs

    Pterosaurs
    Feb 26 2026
    If things had worked out differently, you might see a tiny pterodactyl on your windowsill instead of a modern bird. That’s because pterosaurs evolved more than 80 million years before the earliest birds, with many of the same characteristics. Pterosaurs had hollow bones, some with an even more sophisticated structure than birds; it’s one of the things that allowed them to grow to such immense size: the largest pterosaur was bigger than an F-16 fighter jet, with a wingspan of 33 ft. These gigantic beasts were able to launch themselves because they were quadrupeds, which allowed them to run to get airborne. Pterosaurs may also have been warm-blooded like birds, as suggested by pelts of hair-like bristles found in the fossil record. They appear to have had similar social structures to birds: they reared young in nests, and some species appear to have traveled in flocks. Many pterosaurs sported eye-catching crests like today’s birds. Theirs were made of bones and skin, but are thought to have served the same purpose of attracting mates. Sharp-toothed predators, peg-toothed clam crackers, filter feeders living on lakes, pelican-like ocean fishers. Insectivores the size of today’s cardinal. Swoopers, stalkers, and scavengers. They did it all, they did it well, and they did it first! Why did more than 200 species of pterosaurs perish when the Chicxulub asteroid struck, allowing birds to take their place? It’s a mystery that scientists are still working to solve.
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    2 min
  • Beach Reading

    Beach Reading
    Feb 26 2026
    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 scoop up some sand for a closer look. Fine, rounded grains that look mostly alike mean the beach is made of rocks and minerals from far away, broken down over long time frames as they traveled in rivers or ocean currents. Pebbly, angular sand grains with lots of diversity come from nearby coastal headlands or fast-moving rivers. White sand could be quartz, or limestone from nearby cliffs, or ground-up seashells, suggesting an ocean healthy with mollusks and snails. Pink sand could be ground-up coral, indicating offshore reefs Black sand is made of obsidian or basalt, like on some beaches in Spain. Green beaches mean volcanic rocks are eroding, concentrating olivine in the sand, as you can find in Hawaii. With a keen eye, there’s a great deal to uncover on the beach. For more clues, visit EarthDate.org.
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    2 min
  • Fire Weather

    Fire Weather
    Feb 26 2026
    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 the West, intensified by development and agricultural water use, makes fires more likely. But one of the strongest contributors to fires are fires themselves. Wildfires, it turns out, can make their own weather—which causes them to spread. Two of California’s biggest fires last year produced devastating firestorms. Towering flames heat the air, creating a rapidly rising updraft, which pulls air into the base of the fire, feeding it with oxygen and increasing the intensity. These updrafts may eventually spiral into what’s called a fire whirl—essentially a tornado of flames, with winds up to 150 miles an hour. Meanwhile, smoke fills the air with particulates, on which water vapor can condense, forming thunderheads above fires that can produce lightning and start more fires. Scientists are now studying fire weather, and re-creating it in lab conditions, to better understand how to control wildfires once they begin.
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    2 min