Relax as you learn about the historical pioneers who developed and tested the first hot air balloons & hydrogen gas balloons (all the older episodes are on the Calm History-Bonus & Archives Podcast for Silk+ Members).* Become a Silk+ Member (FREE for a limited time) & enjoy 500+ episodes from these 8 Silk+ Podcasts: * Calm History-Bonus & Archives Podcast * Sleep Whispers-Bonus Podcast * Sleep Whispers-Archive Podcast * ASMR University-Bonus Podcast * ASMR Sleep Station-Revived Podcast * Counselor Curt ASMR-Exclusive Podcast  * Sleep With Silk: 8-Hour Nature Sounds * Sleep with Silk: 8-Hour Background Sounds ************************************* Become a Silk+ Member, FREE for a limited time [silkpodcasts.com/plus] FREE alerts of new episodes. Tap “Follow“ on [Apple or Spotify] Shape the future of Calm History [Vote Now] Rate & review Calm History on [Apple Podcasts] Website, Contact, & All My Podcasts [silkpodcasts.com] Bored?  Explore my Favorite Goodies! [silkpodcasts.com/faves]   *Content adapted, remixed, edited, and produced by Harris from materials in the public domain and from Wikipedia. Calm History is part of the Airwave Media podcast network: AirwaveMedia.com Contact [email protected] if you would like to advertise on this podcast.