EarthDate

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...

You might have heard of your microbiome, but did you know you also have a virome? That’s right, there are more than a trillion active viruses within you right now. Viruses exist in every organism, in every environment. There are at least ten times more viruses on Earth than all other biological entities combined. A virus is a tiny packet of RNA or DNA, about 1500 times smaller than a grain of salt...

To Egyptians and ancient Greeks, amethysts were as precious as diamonds, rubies, and sapphires. The stone was thought to cool tempers and prevent drunkenness, so it was cut into jewelry for wise kings and crafted into wine goblets for those who hoped to stay sober. In the Middle Ages, it adorned the rings of religious leaders and the scepters of royalty. Since then, huge finds in many places, espe...

Dr. Gene Shoemaker mapped the moon, trained astronauts and discovered more than 800 asteroids. He was also the first person to go to the moon… and stay there. Shoemaker started his career with a bang, proving with his Princeton dissertation that the mile-wide Barringer Crater in Arizona, previously attributed to volcanic activity, was in fact the result of a meteorite impact. Soon after, he founde...

When scientists mapped the human genome, they found that just 2% of it controlled our own functioning. Fully 8% was the DNA of fossil viruses. Paleovirologists who study fossil viruses have found that all viruses share a common single-cell ancestor from more than 3 billion years ago. About 1.5 billion years ago, viruses changed their protein coating, allowing them to penetrate the cells of their h...

In earlier episodes, you heard that trillions of viruses live peacefully, even beneficially, within each of us today. And that our ancestors battled now-extinct “fossil viruses,” which are preserved in our own genetic code. Turns out, that’s been beneficial too. For instance, viruses helped drive our evolution. 100 million years ago, proto-mammals were infected with a virus that encoded into their...

Mt. Everest, at just over 29,000 feet above sea level, may be the highest point on Earth’s surface—but what’s the lowest? Well, the deepest part of the deep sea is the Mariana Trench in the Pacific, off the island of Guam, about halfway between Japan and Australia. It’s five times as long as the Grand Canyon and more than a mile deeper than Everest is tall. And the deepest point in the trench is c...

In another EarthDate, we talked about Challenger Deep, the deepest point in all the oceans, at almost 7 miles down. The first humans to explore it were a Swiss oceanographer and U.S. Navy Lieutenant. They built a special deepwater submarine called a bathyscaphe, and in 1960, headed for the bottom. It took them 3 hours to reach the western pool of Challenger Deep at 35,000 feet. But they stirred up...

You may have heard that bumblebees shouldn’t be able to fly. That’s a myth actually, as any flying bumblebee will tell you. The science of their flight is now understood. But the bees hold another mystery that could affect human agriculture. Bumblebees hibernate over winter, and when they emerge in the spring, they’re hungry. But what if the plants they rely on for pollen and nectar aren’t yet pro...

What if you’re a fish in freezing water? Well, a free-swimming ocean fish can migrate to a warmer part of the sea. But if you’re a lake fish, you don’t have that option. Luckily, the properties of water make its solid form—ice—less dense than its liquid form. As a lake freezes, the ice floats on the surface, insulating the water below and keeping most lakes—and the fish within them—from freezing s...

The horseshoe crab is a living fossil—sometimes called a stabilomorph, a body design that evolution got so right, it hasn’t had to change. They’ve been roaming the coastal shelves and brackish bays of Earth for more than 400 million years in nearly the identical form as today, having survived all five great extinction events we’ve discussed on EarthDate—including the asteroid that wiped out the di...