Benjamin Hopkins talks about the concept of the frontier: how it exists not merely as a place on a map but as a set of practices used by colonial states around the world. Hopkins is an associate professor of history at George Washington University. He's the author of Ruling the Savage Periphery: Frontier Governance and the Making of the Modern State.

Claire Isabel Webb talks about the search for extraterrestrial life and the different strategies used by astronomers and exobiologists to look for it. Webb is a PhD candidate at MIT's History, Anthropology, Science, Technology, and Society Program. Her dissertation project, "Technologies of Perception: The Search for Life and Intelligence Beyond Earth" won the HSS/NASA Fellowship in Aerospace History.

Al Zambone talks with me about American polar exploration, the origin of Time to Eat the Dogs, and the history of science as an academic discipline. Zambone is the host of the podcast Historically Thinking. He's the author of Daniel Morgan: A Revolutionary Life. You can hear an extended version of this interview on the Historically Thinking podcast, available on most podcast platforms as well as online at historicallythinking.org.

Lukas Rieppel talks about dinosaur fossils in the Gilded Age – from the discovery and excavation of fossils in the American West to the re-construction of fabulous creatures in museums that were the darlings of wealthy philanthropists. Rieppel is an assistant professor of history at Brown University. He's the author of Assembling the Dinosaur: Fossil Hunters, Tycoons, and the Making of a Spectacle.

Annette Joseph-Gabriel speaks to Jessica Nabongo about her quest to be the first black woman to travel to all of the countries of the world. Joseph-Gabriel is an Assistant Professor of French and Francophone Studies at the University of Michigan, Ann Arbor. Nabongo is a writer, entrepreneur, and the founder of Jet Black, a boutique luxury travel company that promotes tourism to Africa, the Caribbean, and Central and South America.

Lisa Ruth Rand talks about the Starlink satellite program. She also talks about Project West Ford, which attempted to create an artificial ionosphere in 1961 by launching millions of copper needles into orbit. Rand is the Haas Postdoctoral Fellow at the Science History Institute in Philadelphia. Her op-ed on Starlink and Project West Ford appeared in the July 8th 2019 edition of Scientific American.

Lachlan Fleetwood talks about debates about altitude sickness in the Himalaya and the ways these debates became tied up with ideas about the physiology of Europeans and Himalayans in the 1800s. Fleetwood is the author of "Bodies in High Places: Exploration, Altitude Sickness, and the Problem of Bodily Comparison in the Himalaya, 1800-50," published in the journal Itinerario 43, no. 3 (2019): 489-515.

Fiona Vernal talks about the migration stories of Hartford Connecticut's many communities. Vernal is an associate professor of history at the University of Connecticut and the creator of the exhibition "From Human Rights to Civil Rights: African American, Puerto Rican, and West Indian Housing Struggles in Hartford County Connecticut, 1940-2019" now open at the Hartford Public Library.

Kate Hollander talks about Bertolt Brecht's life and work. She also talks about the community of artists who were his friends, lovers, and collaborators. Hollander is a historian of modern Europe. She's also the author of a book of poems, My German Dictionary, which was awarded the Anthony Hecht Poetry Prize by USA Poet Laureate Charles Wright.

David Woodman talks about his quest to find the missing wrecks of the Franklin Expedition, a mission that led him to the journals of the Arctic explorer Charles Hall who lived with the Inuit for four years and recorded their encounters with British explorers. Woodman is the author of Unravelling the Franklin Mystery: Inuit Testimony, a book that correctly predicted the site of HMS Erebus discovered by Parks Canada in 2014.