For decades, Coho salmon were turning up dead in urban streams the Pacific Northwest. The salmon would stop swimming straight, and then die before they had a chance to spawn. Researchers worried that unless they figured out the cause, the species would eventually go extinct. Enter a formidable crew of biologists, modelers, community scientists, environmental chemists. After eventually ruling out the obvious suspects — things like temperature, oxygen levels and known toxins — researchers eventually zeroed in on a prime suspect: chemicals in tires. But the question remained: Which one?

If you liked this episode, check out our other episodes on satellites monitoring emissions and how air pollution could create superbugs.

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Many people are gearing up for holiday conversations with loved ones who may disagree with them — on everything from politics to religion and lifestyle choices. As the conversations unfold, these divisions are visible in our brains too. These conversations can get personal and come to a halt fast. But today on the show we get into research in neuroscience and psychology showing that as much as we disagree, there are ways to bridge these divides – and people who are actively using these strategies in their daily lives.

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Getting enough sleep regularly can be tough — and even harder when you're traveling for the holidays. "We need sleep like we need water," says Jade Wu, a behavioral sleep medicine psychologist and author of the book Hello Sleep. She and host Regina G. Barber discuss what's happening to our bodies when we get jet lag and the clocks in our body get out of whack. They also get into the science of the circadian rhythm and how to prepare for a long flight across time zones.

Check out CDC's website for tips on minimizing jet lag.

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This critter lurks in the ocean's midnight zone, has a voluminous hood, is completely see through and is bioluminescent. It's unlike any nudibranchs deep sea experts have ever seen before — and now, the researchers who spent twenty years studying them have finally published their findings.

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As global warming continues and space technology improves, there is more and more talk about the growing possibility of a sci-fi future in which humans become a multiplanetary species. Specifically, that we could live on Mars. Biologist Kelly Weinersmith and cartoonist Zach Weinersmith have spent the last four years researching what this would look like if we did this anytime soon. In their new book A City On Mars, they get into all sorts of questions: How would we have babies in space? How would we have enough food? They join host Regina G. Barber and explain why it might be best to stay on Earth.

Kelly and Zach Weinersmith's book A City On Mars is out now.

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One in four U.S. households experiences a power outage each year. Scientists at Oak Ridge National Laboratory are working on technology they hope will help fix electric grids: drones. They're betting that 2-ft. large drones connected to "smart" electric grids are a cost-effective step to a more electrified future.

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In this episode, you're invited to the fermentation party! Join us as we learn about the funk-filled process behind making sauerkraut, sourdough and sour beer. Plus, no fermentation episode is complete without a lil history of our boy, yeast.

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A pivotal week in Corey Gray's life began with a powwow in Alberta and culminated with a piece of history: The first-ever detection of gravitational waves from the collision of two neutron stars. Corey was on the graveyard shift at LIGO, the Laser Interferometer Gravitational-Wave Observatory in Hanford, Washington, when the historic signal came. This episode, Corey talks about the discovery, the "Gravitational Wave Grass Dance Special" that preceded it and how he got his Blackfoot name. (encore)

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In North-Central New Jersey, there is a backyard teeming with around 200 turtles. Many of these shelled creatures have been rescued from the smuggling trade and are now being nursed back to health in order to hopefully be returned to the wild. Science reporter Ari Daniel joins host Regina G. Barber to tell the story behind one man's efforts to care for these turtles and to ensure they have a chance at another (better) life.

Read more of Ari's reporting.

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It's Election Day in the United States. Across the nation, millions of ballots are being cast. But what would happen if the rules of our electoral system were changed? Certain states are about to find out. This year, several places have alternative voting systems up for consideration on their ballots, and those systems could set an example for voting reform throughout the rest of the country. Short Wave producer Hannah Chinn and host Emily Kwong dive into three voting methods that are representative of those systems: Where they've been implemented, how they work, and what they might mean for elections in the future.

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How did life start on Earth? The answer is a big scientific mystery scientists are actively investigating. After talking with many scientists, host Regina G. Barber found that an abundance of water on Earth is most likely key, in some way, to the origin of life — specifically, in either deep sea hydrothermal vents or in tide pools. It's for this reason some scientists are also exploring the potential for life in so-called "water worlds" elsewhere in the solar system, like some of the moons of Jupiter and Saturn. This episode, Regina digs into two water-related hypotheses for the origin on life on Earth — and what that might mean for possible alien life.

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