Solar Impulse, the world’s most advanced solar aircraft, is trekking across the United States. It’s already made it from the Bay Area to Phoenix, Ariz. Check out photos from its U.S. flights, and read more about the all-solar plane’s journey.
Osha Gray Davidson has been an investigative reporter for 25 years and is the author of six books of nonfiction. He publishes the online journal The Phoenix Sun covering solar power.