Radio waves aren’t sound. They’re electromagnetic radiation and essentially a type of invisible light. Radio astronomer Nicole Gugliucci joins us to explain how it's used to observe the formation of galaxies, black holes and other objects in outer space. Then, Gillian and Diona go on a field trip to see a meteor shower! It’s pretty much a disaster, but kind of hilarious and most definitely a blast. Stick around until the very end for an important announcement.

Birds are simply captivating. We take a deep dive into their relationship dynamics, parenting habits and other behaviors with biologist and conservationist Wenfei Tong. Then, actress Olivia Scott Welch (Fear Street) stops by to help us share an incredible story from the Apollo Era. We also get a voice memo from Gillian’s co-star on Community, Joel McHale!

Cities aren’t meant to last, according to writer Annalee Newitz. In their book “Four Lost Cities: A Secret History of the Urban Age,” they explore the rise and fall of ancient sites. What can architecture tell us about how we live? What can urban planning tell us about our changing values? And ultimately, why are cities abandoned? Later, we also dive into the story of a scientist who helped us understand the very structure of our DNA. Plus, we get a voice message from actress Sarah Ramos (Parenthood).

We’re off this week, but we wanted to share a bonus behind the scenes exclusive: Creating the sound for our show. We’re joined by senior audio engineer and musician Brendan Byrnes, who walks us through initial concepts and building the music you hear every week!

This exclusive is part of a series of bonus episodes, which includes peeks behind the scenes and extended guest conversations. You can hear more bonus episodes by signing up for Stitcher Premium. Just subscribe through the Stitcher app, use the promo code PERIODIC and then you can listen to the rest of our bonus content for free for 30 days!

Can you imagine hearing music all day, every day? Mary Steenburgen says that’s her reality. The Oscar-winning actress and songwriter joins us to share a mysterious, fascinating and moving story. How do you re-adjust to life when your brain plays music nonstop? Also, in a completely separate conversation, we learn about the functions and mysteries of the brain by talking to neurosurgeon Dr. Alfredo Quiñones-Hinojosa.

A roughly 1-million pound space station orbits our planet every day. Wanna know how they keep the lights on? Battery Subsystem’s Manager Penni Dalton breaks down how it gets its power. Then, NASA engineer Tracy Drain returns to answer listener questions. We even get a question from actor Joel McHale! Plus, director Mikey Alfred sends us a math fact.

Astronaut Victor Glover joins us after an extended stay on the International Space Station. He gets personal, sharing his launch day music playlist and what it's like being a dad in space. Then, actor Jack Black and his brother Neil Siegel do their first joint interview. In a one-of-a-kind conversation, they reminisce about the life and career of their late mother, aerospace engineer Judith Love Cohen. We hear unbelievable stories, like the day Judith left for work, went into labor, delivered Jack and still finished the problem she was working on. And yep, she also worked on a system that helped get Apollo 13 astronauts home.

This week, we’re immersed into the world of sound. First, we’re deep in the ocean with acoustic ecologist Michelle Fournet. She shares some truly mind-blowing audio of humpback whales and bearded seals, and then analyzes what they’re probably saying. Later, we have an extended conversation with Roman Mars, host and creator of the show 99% Invisible. He breaks down telling visual design stories through sound, and how to teach yourself to see stories everywhere. Also, actor Pedro Pascal (Game of Thrones, The Mandalorian) leaves us a voice memo that has us wishing he’d work on a nature documentary.

Humans are about 99.9% the same genetic material. The little that makes us different tells fascinating stories about our ancestors and histories, according to geneticist Dr. Janina Jeff. She joins us to share some basics about our genes, and to have a critical conversation about race and facing the harmful history of genetics. Then, New York Times best selling author Mary H.K. Choi helps share the story of a man who built the precursor to our modern day traffic signal. We also get a fun voice message from actor Danny Pudi (Community, Mythic Quest) and his daughter that has us smiling from ear to ear.

We need to talk about volcanoes. Seriously. From the Pacific Ring of Fire to Mount Erebus, which holds an active lava lake, volcanoes have altered the very landscape of our planet, according to volcanologist Kayla Iacovino. Then, actress Zazie Beetz (Atlanta, Joker) helps share the story of severe storm researcher Dr. Tetsuya ‘Ted’ Fujita, aka Mr. Tornado. We also get a delightful voice memo from actress Robin Tunney (The Mentalist, The Craft) about raindrops.

Stick around until the very end for a post-credit treat!