Short Wave

Some weapons used by the U.S. military are so powerful they can pose a threat to the people who fire them. Today, we meet two Marines, William Wilcox and Michael Lozano, who spent years firing missiles and rockets, then developed the same rare brain condition: arteriovenous malformation, or AVM. The condition sends high pressure blood from a tangle of abnormal blood vessels directly into fragile veins, which can leak or burst. Most AVMs are caused by genetic changes that affect the growth of blood vessels, so the connection between weapon blasts and AVM isn't always immediately clear. But NPR's brain correspondent Jon Hamilton reports that recent research suggests that blast waves can alter genes in the brain — and that the evidence is even stronger for less extreme blood vessel changes.Have questions or story ideas? Let us know by emailing [email protected]!Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

There are hundreds of atomic clocks in orbit right now, perched on satellites all over Earth. We depend on them for GPS location, Internet timing, stock trading ... and space navigation?Today on the show, hosts Emily Kwong and Regina G. Barber learn how to build a better clock. In order to do that, they ask: How do atomic clocks really work, anyway? What makes a clock precise? And how could that process be improved for even greater accuracy?For more about Holly's Optical Atomic Strontium Ion Clock, check out the OASIC project on NASA's website.For more about the Longitude Problem, check out Dava Sobel's book, Longitude. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Have questions or story ideas? Let us know by emailing [email protected]!Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

Funeral services begin today for former President Jimmy Carter. He died Sunday, at 100-years-old. Carter brought attention to global health challenges, particularly "neglected" tropical diseases like Guinea worm. With reporter Jason Beaubien, we look at that decades-long effort and how science was central to Carter's drive for a better world. Questions or comments for us at Short Wave? Let us know by emailing [email protected] — we'd love to hear from you! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

Snowflakes. These intricate, whimsical crystals are a staple of magical wintry scenes, but how big can they really get? Well, according to the Guinness World Record keepers, the "largest snowflake" ever recorded was a whopping 15 inches in diameter. It was spotted near Missoula, Montana in 1887. But Kenneth Libbrecht, a physicist at Caltech, has long been skeptical of that record. So he set out to find what makes a snowflake a snowflake and whether that 1887 record is scientifically possible. You can read more about what he discovered here. (encore)Want to share the snowflakes you've spotted this winter? Email us a photo at [email protected] more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy