EarthDate

Switch Energy Alliance
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EarthDate is a short-format weekly audio program delivering concise, science-based stories about the Earth: its geology, environments, and the processes that shape our planet over deep time and today. Beginning in 2026, EarthDate is managed by Switch Energy Alliance and hosted by SEA's founder Dr. Scott W. Tinker. Together, we explore earth systems, natural resources, and their relevance to everyday life, with a focus on clear, accessible science education for broad audiences. EarthDate is written and directed by Emmy-winning filmmaker Harry Lynch, and researched by Lynn Kistler. We search for captivating stories to remind listeners that science can enlighten, educate and entertain.

  1. 18H AGO

    Volcanoes and Eclipses

    Volcanic eruptions can affect global warming—or cooling. And one of the ways we measure their impact is by looking at a lunar eclipse. To understand this strange connection, we need to know a bit about Earth’s atmosphere. The lowest part, the troposphere, extends from the surface up 4 to 12 miles. It’s where Earth’s weather happens. The stratosphere, above that, is dry and less active. Dust and ash particles carried into the troposphere by volcanoes, fires, or other sources will quickly fall or be rained out. But when a large volcano erupts, it blasts ash and gas through the troposphere into the stratosphere. There, sulfur gas forms microscopic droplets of sulfuric acid. These “sulfate aerosols” can remain suspended for years. One way scientists measure them is by looking at lunar eclipses. If they’re murky and dim, the stratosphere is clouded with aerosols. If they’re bright and defined, the stratosphere is clear. Large volcanoes in the past have put up enough aerosols to reflect the sun’s heat and cool the surface of Earth by as much as 1°F. But in the last two decades, the stratosphere has been remarkably clear, which has allowed more solar energy to reach Earth. Some scientists estimate this has caused half the global temperature increase seen during this period. Another example of how Earth’s processes are linked in surprising and complex ways.

    2 min

  2. 18H AGO

    Winter Solstice Celebrations

    The winter solstice is the shortest day, and the longest night, of the year. It’s been celebrated by cultures around the world since our earliest history. The winter solstice comes on or around December 21st—and 6 months later in the Southern Hemisphere. Leading up to it, the days appear to be dying. The dawn comes later, the sunset earlier. Nights get longer and colder. In far northern and southern latitudes, this is very keenly felt. Then on the solstice, things turn around. The day after is a little longer, and they keep getting lighter and brighter. So the solstice has always been associated with rebirth—of the sun and of a new year. Asian, Middle Eastern, North and South American cultures all had, and still have, festivals marking the rebirth of the sun. The Romans, too, celebrated Saturnalia, dedicated to the sun god Saturn, characterized by charity and gift-giving. In the 4th century when they converted to Christianity, they turned their festival of the sun’s rebirth into a celebration of a different son’s birth. This gave us Christmas, on December 25. Later, when the Vikings became Christians, they brought Nordic solstice traditions: evergreen trees, holly, and mistletoe, all symbols of life in the dark winter. So this holiday season, you might consider a solstice party. It’s the astronomically correct way to ring out the old year and welcome the birth of the new.

    2 min

  3. 18H AGO

    Powering the World

    Though our electricity system is highly complex, its basic principle is simple: 99 percent of our electricity comes from turning a generator. We do that mostly by burning a resource like coal or natural gas to boil water, which makes steam, which turns a turbine, connected to a generator. Heat from a nuclear reaction or a geothermal well are other ways to make steam and turn a generator. Water held behind a dam, then released to flow through turbines, turns generators without having to produce steam. All these generation systems produce emissions—like water vapor, CO2 or other gases, particulates, or a small amount of nuclear waste. And all of them are available on demand, which is very important, because we can’t store electricity very well at scale. So it must be made when we need it. Wind, too, turns a generator. It makes up about 1 percent of global power generation. Solar, the only one to produce electricity without a generator, makes up another 1 percent. Wind and solar produce no emissions. But they have other environmental impacts, in mining materials, manufacturing, the large amounts of land they occupy, and eventual disposal. And because they make electricity only when the sun shines or the wind blows, we have to back them up with other power sources. The modern world depends on our electricity system, and it’s something we’ll talk more about.

    2 min

  4. 18H AGO

    The Iceman Goeth

    One June, a man climbed into the Ötzal Alps, on today’s Austrian–Italian border. Dressed in leather and fur, he was mid-40s and extremely fit. He carried a wooden bow, flint-tipped arrows, and a copper axe. He had no way of knowing that in an hour he’d be dead. 5,300 years later, some hikers discovered his body, melting out of a glacier. Local police called in forensic experts, and so began a 30-year investigation into the best-preserved mummy from pre-modern history. They traced the minerals in his teeth to a nearby groundwater source, to determine where he lived. They looked at food and pollen in his gut to re-create his last day of meals and where he ate them. Ötzi the Iceman, as they called him, had walked from his mountain home to the valley floor. That night, judging from a telltale slash on his hand, he got into a knife fight. The wound had begun to heal by the time he died, suggesting he won it. What had not healed were a fatal arrow wound to his back and a cracked skull. Someone had tracked him into the mountains and ambushed him. His valuable copper axe was not taken, suggesting a revenge killing. Perhaps the killers buried him in snow, beginning his mummification. Today, Ötzi rests in a museum freezer near where he was discovered. A model of him in life stands in the same building, while 3D printings of his body are studied around the world.

    2 min

  5. 18H AGO

    Ice Age Brexit

    Today you can take a train, in a tunnel beneath the English Channel called the Chunnel, from London to Paris in 2 hours. But half a million years ago, the English Channel didn’t exist: Britain was attached to Europe. At that time, Earth alternated between glacial and interglacial periods, as it still does today. During glacial periods, some of Earth’s water is held in vast glaciers, on top of continents rather than in oceans, which causes ocean levels to drop hundreds of feet. Toward the end of one of these glacials, as the ice sheets started to melt, an enormous lake formed in the North Sea—dammed in the north by a massive wall of ice and in the south by a rock land bridge. Eventually water levels rose so high that the lake began pouring over the British land bridge in gargantuan waterfalls. Engineers planning the path of the Chunnel discovered this. Using seismic studies, they found huge, deep pits in the seafloor filled with rubble and sediment, and designed the Chunnel to avoid them. Eventually scientists collected enough data to recognize the pits as plunge pools that those giant waterfalls would have made from millions of tons of water, pounding down on the seafloor over centuries. The waterfalls began to erode the land bridge, but it held—until, a couple of glacial and interglacial cycles later, another flood finished the job. The channel formed—causing a natural Brexit thousands of years ago.

    2 min

  6. 18H AGO

    So Cheap Yet So Valuable

    Alchemists in the Middle Ages were fixated on turning lead into gold. Both are soft, heavy metals. If they could make the dull one into the shiny one, they’d be rich. Right? Maybe not. Thousands of years before them, another metal, iron, was eight times more valuable than gold. It could only be found in its pure metal form in iron meteorites. Assyrians and Egyptians made prized iron jewelry, which we find in ancient tombs. Then some alchemist of their time figured out how to smelt iron from common iron ore, like hematite and magnetite. When supply boomed, the price plummeted. Iron eventually became the least expensive metal on Earth. That’s because iron, as found in ores, is our most plentiful element by mass. Iron makes up most of Earth’s core, which produces Earth’s magnetic field, protecting us from cosmic rays and solar wind. Iron is the main ingredient in steel, an alloy of iron and carbon. We make a billion tons a year, and use it in everything, especially large buildings—which might be impossible without steel. Iron is also abundant in the human body; it carries oxygen in the blood and gives blood its signature color…along with many other red things on Earth, from rocks and soil to farmers’ barns, painted with iron oxide pigments. Iron is common and cheap and incredibly useful, so in some ways, that still makes it a lot more valuable than gold.

    2 min

  7. 18H AGO

    Ripples in Earth’s Crust

    Previously, we talked about how scientists discovered the asteroid that brought down the dinosaurs. But what exactly happened when a rock twice the size of Manhattan smashed into our planet— with the force of 10 billion atomic bombs? It punched a hole in Earth’s crust 50 miles wide and 20 miles deep, causing nearly a million cubic miles of solid rock to behave like liquid. Like when a rock lands in a pond, the sides of the crater splashed outward, up, then collapsed. The center of the crater rebounded, rocketing up higher than Mount Everest; then it, too, collapsed. Earth’s crust rippled like the surface of water. A ring of ridges spread out from the impact site. This giant “splash” on Earth’s surface happened in a matter of minutes. Then, the rocks froze into their new positions and were protected from erosion by layers of marine sediment. A 2016 mission drilled into the ridges circling the crater floor. The explorers found large sections of melted rock. Below that, they found granites so badly pulverized that they were less dense than normal granite. And, as often happens in science, one insight leads to another. A recent space mission had discovered that the moon’s crust is less dense than it should be, and scientists wondered why. The crater on Earth suggests it’s due to 4 billion of years of impacts on the moon’s famously cratered surface.

    2 min

  8. 18H AGO

    Ripples in Earth’s Crust

    Previously, we talked about how scientists discovered the asteroid that brought down the dinosaurs. But what exactly happened when a rock twice the size of Manhattan smashed into our planet— with the force of 10 billion atomic bombs? It punched a hole in Earth’s crust 50 miles wide and 20 miles deep, causing nearly a million cubic miles of solid rock to behave like liquid. Like when a rock lands in a pond, the sides of the crater splashed outward, up, then collapsed. The center of the crater rebounded, rocketing up higher than Mount Everest; then it, too, collapsed. Earth’s crust rippled like the surface of water. A ring of ridges spread out from the impact site. This giant “splash” on Earth’s surface happened in a matter of minutes. Then, the rocks froze into their new positions and were protected from erosion by layers of marine sediment. A 2016 mission drilled into the ridges circling the crater floor. The explorers found large sections of melted rock. Below that, they found granites so badly pulverized that they were less dense than normal granite. And, as often happens in science, one insight leads to another. A recent space mission had discovered that the moon’s crust is less dense than it should be, and scientists wondered why. The crater on Earth suggests it’s due to 4 billion of years of impacts on the moon’s famously cratered surface.

    2 min
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About

EarthDate is a short-format weekly audio program delivering concise, science-based stories about the Earth: its geology, environments, and the processes that shape our planet over deep time and today. Beginning in 2026, EarthDate is managed by Switch Energy Alliance and hosted by SEA's founder Dr. Scott W. Tinker. Together, we explore earth systems, natural resources, and their relevance to everyday life, with a focus on clear, accessible science education for broad audiences. EarthDate is written and directed by Emmy-winning filmmaker Harry Lynch, and researched by Lynn Kistler. We search for captivating stories to remind listeners that science can enlighten, educate and entertain.

Information

  • Creator
    Switch Energy Alliance
  • Years Active
    2K
  • Episodes
    88
  • Rating
    Clean
  • Copyright
    © Copyright 2026 EarthDate
  • Show Website
    EarthDate