Why does the moon change shape? How much does the moon weigh? What color is the moon? Why does the Earth only have one moon? Why does the moon have holes? Where does the moon go when we can't see it? Why do we sometimes see the moon in the daytime? Why does the moon look like it's following you when you're in the car? Answers to your moon questions with John O'Meara, chief scientist at the W.M. Keck Observatory.

What is it like to be an adult? It's a big question from a young mind! We invited adults who listen to share their perspectives and Nora McInerny, host of the podcast Terrible, Thanks for Asking, helps guide us through that and a few other questions about the strange world of adults: Why can adults do things that kids can't do? Why don't adults play pretend like they used to when they were kids? What happens when you don't listen to your boss? And why do people cry when they're happy?

How does your body make poop? How many germs are in an ounce of poop? Why do people fart and why are farts stinky? Look, everybody does it, so today we're going to tackle one of the areas kids seem to find fascinating: why and how we poop! Plus, we get some help from Chicago public radio station WBEZ's Curious City to learn about what happens after you flush the toilet.

This week, instead of a normal episode, we're bringing you an episode from one of our podcast friends, Circle Round, from WBUR in Boston. Circle Round features folk tales from around the world, and we've selected one we think you'll really enjoy. French comedian Gad Elmaleh stars in "Armadillo's Song," a story about achieving goals and proving naysayers wrong!

Why don't spiders stick to their own webs? How do spiders walk up walls and on ceilings without falling? Why do spiders have eight legs and eight eyes? How do they make webs? And silk? What's a cobweb? How do spiders eat? And why are daddy long legs called daddy long legs when they have to have a female to produce babies?! We're talking spiders today with arachnologist Catherine Scott. Download our learning guides: Transcript| Coloring Page

Why do we celebrate Halloween? Who created this holiday? Where do pumpkins come from and why do we carve them? This week we're answering your Halloween questions with a professor of all kinds of scary and creepy things, Regina Hansen of Boston University.

In today's episode we're not answering any questions. Instead, we're going to talk with 11-year-old twins Isabelle and Sophie Posner-Brown. When Sophie was two, she was diagnosed with a malignant brain tumor. She's had three surgeries and lots of chemotherapy, but she's been on a break from chemo for the last four years. The twins talked with But Why about what it's like to live with Sophie's illness.

A cancer diagnosis can be scary, and for kids it can be bewildering. We've gotten some questions about cancer and in this episode we answer them with Dr. Donald Small, director of pediatric oncology at Johns Hopkins School of Medicine. We answer how people get sick when it's not caused by germs, how people get cancer, and why cancer "does not have a cure." There's nothing graphic or scary in this episode, but adults may want to give this episode a listen if cancer is something your littles have been dealing with.

We'll learn about the kinds of animals that live in urban environments and the challenges they face! One young Australian listener wants to know why wombats, kangaroos and koalas hang out in the countryside rather than the city. Dr. Mark Eldridge from the Australian Museum Research Institute tackles that one. And we turn our focus to one particular urban dweller, the raccoon, with York University raccoon expert Suzanne MacDonald. She lives in Toronto, which has one of the most dense populations of raccoons in the world. She helps answer why raccoons eat garbage, how long they live and why they look like they're wearing masks.

We visit Fireman's Hall Museum in Philadelphia and get answers to a dozen questions about fire from Philly firefighter Lisa Desamour. She tells us what fire is, why matches work to start fires, and why fire is often orange. Plus: how does water put out fire? How do smoke alarms work? Why do firefighters have Dalmations?