Fleas, lice, tapeworms and ticks - these are all examples of parasites, living organisms that live on or in a host species and need this other organism to complete their complex life cycles. Sounds bad, but parasites are essential to a healthy ecosystem! And our guest for this episode says they’re also fascinating and even beautiful. Parasite ecologist Chelsea L. Wood, author of Power to the Parasites, tackles all your parasitic questions in this episode! They include: Why are there worms in our stomachs? Why do fleas bite cats and dogs? Where did head lice come from? Why do lice make you itch? Why do ticks suck our blood?

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How do trains work? We went to Union Station in Washington, DC to answer a whole wagonload of questions with Amtrak's Patrick Kidd.

A few years ago, we left our studio in Vermont to hop on the Amtrak Acela train that runs multiple trips per day between Washington, DC, New York City and Boston. But don't worry; we got off before the train departed! It was so much fun, we wanted to bring you that journey again!

Questions we're answering in this episode: How do trains work? What about electric trains? Steam trains? Bullet trains? Why do they have to go on tracks? How can trains go so fast even though they're so heavy? And why don’t trains have seat belts?

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How do people whistle? How does whistling make a sound? Why does your tongue change a whistle higher or lower? Can you get a trophy for whistling? Can people with laryngitis whistle? Get ready, we learn all about whistling with musician and champion whistler Emily Eagen and musician Yuki Takeda. And who whistles our theme song? We'll hear from musician Luke Reynolds, and a kid whistling chorus from our listeners!

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