EarthDate

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 foraged plants.

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 magma, gold am...

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 matter. A tiny amount was dete...

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 ot...

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 opportunity to test his hypo...

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?

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.<...

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 an hour. 

W...

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 air around blood vessels found there.

...

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 filter and clea...

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 industry ‘leak’ heat into the environment.

The result, just as in summer...

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 units and heat f...

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 South Africa. 

Around 6...

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 pond...

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 and air conditioning, and stee...

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 chlorinated.  

It then flows to our h...

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 are closed basi...

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. Then, in 198...

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 – golden eagles, white tail eagles, black storks and owls...

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 t...

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 the lake had b...

Horses changed human history. But first we had to change horses.  

The horse evolved in North America 50 million years ago, and migrated across the Bering land bridge into Eurasia. Then, during the last Ice Age, it went extinct in the Americas. 

Around 5,000 years ago, humans began taming horses in the Eurasian Steppe, in what is today Kazakhstan, Russia and Ukraine. 

There, archaeologists have found residue of mare’s milk in drinking vessels. Some horse skeletons show wear on their teeth suggesting they held bits in their mouth.  

Two hundred million years ago, the ginkgo tree evolved to be very stinky, because there was a creature that loved it. 

The ginkgo is unlike any other tree; not a conifer, not a flowering deciduous.  

When pollen from the male ginkgo fertilizes an ovule of the female, it produces a round yellow fruit full of butyric acid, which smells -- especially when it falls and rots on the ground – like, well, vomit. 

But there must have been a dinosaur or other creature that found this smell appetizing. So it...

The Chernobyl nuclear powerplant, in Ukraine, was designed and operated so badly, it was practically destined for disaster.  

First, the Soviet plant design was fatally flawed. It didn’t include a containment vessel, the massive concrete structure that encloses other nuclear reactors. Adding one, of course, would have been very expensive. But, it would have contained the accident.  

It occurred when unqualified engineers ran the reactor at very low power during a test – which made the reaction unstable. To keep the test running, they pulled nearly all the safety control rods from the...

Famous early scientists, like Leonardo da Vinci, would not have called themselves scientists, or practiced science as we do today.  

They were then more commonly called ‘natural philosophers,’ and based their work on observing the natural world, then inferring principles.  

Until Sir Isaac Newton, and his colleague Sir Francis Bacon, moved to standardize the scientific method.  

They wanted proof; knowledge based on evidence, not speculation.  

So they argued that scientists should put forth a hypothesis, often an if-then statement: “If this happens, then that will be t...

Just eight percent of Earth’s surface is covered in topsoil -- but that grows 95 percent of our crops.

And healthy plant growth depends on healthy soil. Which depends on a healthy population of soil life.

As noted in an earlier EarthDate, a single handful of healthy soil contains more microbes than the human population of Earth. 

And more biodiversity than the entire Amazon. One handful.

Along with microbes, there are fungi, worms, insects, plant roots, and much more. And they all make noi...

In 2024, Spanish oceanographers studying the deep seafloor west of the Canary Islands discovered an enormous seamount -- 

A mile-high, 70-mile long mountain on the bottom of the ocean, formed of three inter-linked ancient volcanoes.

At its summit, just 200 feet beneath the water’s surface, they found sand dunes and cliff faces that could only have been formed if it had once been above water.

During the last Ice Age, when Earth’s water was locked up in continental ice sheets, sea level was over 300 feet lower. 

There are many kinds of floods.

River floods develop slowly, water gradually rising over days, providing ample time to evacuate.

Coastal floods come mostly from storm surges, when a hurricane or tsunami makes landfall. 

Coastal communities also have evacuation warnings. But when not, these can be catastrophic.

Urban flooding happens increasingly as paved areas expand, preventing the land from absorbing rainfall.

Flash floods, though often localized, can be the deadliest for their size, simply because they are sudden. 

...

Greenhouse gases trap heat in the atmosphere and keep Earth warm. Without them it would be a frozen iceball – as it once was before.

There are many greenhouse gases. Water vapor is by far the largest by volume, and does most of the warming.

Carbon dioxide is the weakest greenhouse gas in warming potential, but the second most abundant.

Carbon is always moving between Earth and sky in what’s called the carbon cycle. 

But since humans have industrialized, we’re transferring carbon that wa...

Billions of years ago, the globe spun twice as fast as today; a complete rotation took just 6 hours. 

Then Earth’s rotation slowed, and that’s why you’re here listening to this episode. Let me explain.

The atmosphere of early Earth was made up of methane, CO2 and sulfur gases. But no oxygen.

Eventually, as noted on a prior EarthDate, cyanobacteria, blue-green algae, began to produce oxygen through photosynthesis.

At first, the amount of oxygen they released was so small that it was abs...

Each year, U.S. drivers collide with 1 to 2 million large animals, often killing them and endangering the drivers.

Add in smaller creatures, and studies estimate up to 300 million animals die on U.S. roads annually. An astounding number.

This is because wildlife must roam, and always has -- to find food and water, breed and raise young, and migrate seasonally.

They often follow ecological corridors dictated by geography and natural resources. 

These pathways could be millennia old. But in the last century, they’ve...

Sand dunes are dynamic, always changing.

They occur wherever there’s sand, even thousands of miles from the sea. Even on the shores of freshwater lakes.

And the largest freshwater dunes in the world, more than 400 feet high, are in Michigan, on the shores of the Great Lakes.

They’re made of sand formed during the last Ice Age. 

Continental glaciers ground up rock as they moved, and deposited sand in the basins that would become the Great Lakes.

Dunes...

Around the world, a small group of secluded libraries contain some of the rarest and most fragile objects on Earth. 

They’re staffed by scientists, equipped with redundant power supplies… and kept very, very cold.

That’s because the ‘books’ in these libraries are ice cores. 

They’re collected in some of Earth’s harshest environments, like Antarctica and Greenland, at great cost, then transported frozen to these libraries.

Each core is one of a kind. And once it’s been read – small samples melted to re...

We often think of rivers as mostly straight or gently bending waterways. 

If they are, it’s because we’ve made them that way, guiding them with levees or dredging them for navigation.

When viewed from the air, natural rivers, especially across nearly flat landscapes, bend dramatically, sometimes folding back on themselves. 

Rivers meander, constantly changing their paths.

Rivers have several sources: lakes, springs, drainage plains, and melting snow or glaciers. 

When they originate in steep areas, gravity moves the wat...

Five centuries ago, the last emperor of the Aztecs drank a full gallon each day of a coveted beverage, rich in vitamins and caffeine. 

The Aztec word for it: xocolatl Chocolate.

Just like today’s chocolate drinks, his was made from the ground seeds of the cacao fruit. 

The Olmecs and Mayans before him domesticated the cacao, an understory tree from Ecuador.

There and in Mexico, it thrived – under very specific conditions: 

Steady warm temperatures. Abundant rainfall. Well drained volcanic...

In 1984, an engineer walked into a nuclear power plant under construction and set off radiation alarms. 

But there was no nuclear material yet on site. Where was the radiation coming from?

Testing revealed the man was carrying it, on his clothes. 

Where did he become so contaminated? Turns out, at home.

Scientists visited his house and found levels of radon gas 600 times higher than normal – the highest level ever measured inside a building.

They immediately moved the man and his...

Volcanoes often form where tectonic plates collide or pull apart. But sometimes they’ll form in the middle of plates, due to geologic hotspots.

A hotspot is a plume of hot mantle that rises from within Earth, and heats, expands and deforms the crust above it, to create mountains, volcanoes or volcanic islands.

The classic example is the chain of Hawaiian Islands, which formed as the Pacific plate traveled across a hotspot.

Scientists always thought hotspots were stationary, while tectonic plates moved over them. But new research fr...

Geothermal energy, the heat of the earth, can be found under our feet everywhere on Earth.

Historically, we’ve only been able to access it in a few places, commonly in hot springs. 

Much less commonly, in far fewer places, we find more intense heat, so close to the surface that it can be used to heat cities or generate electricity.

That intense heat could be developed anywhere… if we could go deep enough, cheaply enough. And that’s always been the challenge: 

How to r...

Humans have lost most of our body hair, but the beard has stubbornly remained – though anthropologists can find no function for it.

Perhaps that’s why men have been grooming it, or removing it, for thousands of years.

Early cave paintings show men with smooth faces. 

Archeologists have found flint ‘razors’ they may have used to shave. And shell ‘tweezers’ they may have used to pluck off their beards. Ouch!

The Egyptians were first to engage in elaborate shaving rituals. 

Facial hair...

Birds have very large brains for their body size. New research is helping scientists understand how they work, and came to be.

One part of a bird’s brain, the cerebellum, controls their amazing flight capabilities – their spatial awareness, allowing sudden direction changes through tree branches, or their ability to chart migration over thousands of miles.

PET scans taken pre- and post-flight have shown very high brain activity in the cerebellum, especially the neural pathways connected to the eyes.

CT scans of the skulls of modern birds and...