Why are horses so big? Why do horses have tails and manes? How do their legs move? Are their bones in their hooves? What do they eat and how do they run and jump? We tackle those questions and more in this episode all about horses. We’ll also learn a little bit more about the unique horses in Iceland, where there’s a strict ban on horses coming in from other countries. But Why visited riding instructor Sonja Noack at Hestasnild, a riding school in Iceland, to get answers to all your equine questions.

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Volcanoes have been erupting on Earth for BILLIONS of years, and they’re still creating new landscapes today! Volcanoes can seem mysterious and scary, but people all over the world have learned to live in close proximity to active volcanoes. Today we answer questions you’ve sent us about how they form, how they erupt, what magma/lava is, and how volcanologists work to predict when they might erupt. Our guest is Freysteinn Sigmundsson, a volcanologist and professor at the University of Iceland.

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But Why went somewhere really cool - literally - and we’re taking you along! We visited Sólheimajökull, a glacier in southern Iceland and then talked with University of Iceland glaciologist Guðfinna Aðalgeirsdóttir to discover how glaciers are formed, why they can be different colors, and how they shape the land. (Do you know the difference between a V-shaped valley and a U-shaped valley? Glaciers!) Plus we’ll talk a little bit about why glaciers around the world are retreating at such a fast pace.

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Have you noticed especially hazy skies where you live over the last few summers? While many parts of the world are experiencing more frequent and intense wildfires, even places that are nowhere near the fires are being impacted by the smoke from fires hundreds or thousands of miles away. Wildfire smoke gets so high in the atmosphere, it can be blown across a continent in a matter of days. In this special bonus episode, we’re going to learn the how and why of wildfire smoke that drifts around the world. And we’ll talk a little bit about how to stay safe when air quality goes down. Our guests are Professor Joel Thornton of the University of Washington and Dr. Gregg Furie of Brigham and Women's Hospital in Boston.

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Have you ever seen a puffin? With their bright beaks, orange feet and black and white coloring, these birds are very cool to look at. And we’ve gotten a lot of questions about them! In this episode, we talk with Don Lyons, an educator and avian ecologist with the Seabird Institute in Maine. What are puffins? Why are puffin beaks so colorful? Why do puffins dig burrows? How do puffins learn to fly? How can you tell if a puffin is male or female? How long can puffins hold their breath? Why do they have red feet?

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Where did the English language come from? Why do words have silent letters? Why do some people have accents? Why do some words sound similar? Answers to all of your questions about English and words with sociolinguist Erica Brozovsky, host of a PBS digital show called Otherwords.

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For today’s episode, we’re doing something a little different! We’re going to be listening to our video series, But Why Bites! (Even without the video part, they’re really cool!) Every other week over on our YouTube channel, we answer one kid question in a short and sweet little video. You can find all of them at the But Why Kids channel while you enjoy this compilation of episodes that we’re calling a Big Bite.

Who created math problems? Why does one plus one equal 2 and not 11? Why do numbers go on forever? Why are numbers for counting? Why do you need math?

If you love math, this is the episode for you. And if you hate math…this is the episode for you! We’re answering all kinds of questions and demystifying the science and beauty of the discipline of mathematics with Dr. Melania Alvarez, outreach coordinator for the Department of Mathematics at the University of British Columbia in Canada. She’s also education coordinator for the Pacific Institute for the Mathematical Sciences. And she loves all your mathematical questions!

Stay tuned for a math puzzle you can solve during the episode!

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Math Question: There's a farmer who sells live chickens. He goes to three markets to sell them.

At the first market, he sells half of his chickens, plus half a chicken.

Then he goes to the second market, where he sells half of his remaining chickens, plus half a chicken.

At the third market, he sells half of all his remaining chickens, plus half a chicken. And he is left with no chickens.

How many chickens did he have at the start?

(HINT: No chickens were harmed at any of the markets, and they were all fully alive when they were sold.)

(Answer: 7 chickens)