Hurricane Danny is seen in a NOAA image taken by the GOES-East satellite taken at 10:15 ET on Thursday. The storm, now a Category 2, is expected to lose strength over the next day or two. NOAA/Reuters/Landov hide caption

itoggle caption NOAA/Reuters/Landov

United has purchased 15 million gallons of renewable jet fuel made from beef tallow, or fat, by Alt Air Fuels and plans to use the fuel this year for Los Angeles-to-San Francisco flights. Tony Ruppe/United hide caption

itoggle caption Tony Ruppe/United

After the Animas River spill, rancher Irving Shaggy is forced to travel a 70-mile round trip to get water for his livestock. "It's going to be a long struggle," he says. Laurel Morales/KJZZ hide caption

itoggle caption Laurel Morales/KJZZ

UC Berkeley tree biologist Wendy Baxter is about to begin her ascent of a giant sequoia. Ezra David Romero/Valley Public Radio hide caption

itoggle caption Ezra David Romero/Valley Public Radio

"Physics tells you what you can and can't do. If you know the physics anything else is possible." — Taylor Wilson James Duncan Davidson/TED hide caption

itoggle caption James Duncan Davidson/TED