Massive wildfires cost billions of dollars and burn millions of acres in the U.S. every year, but we know surprisingly little about the basic science of how they spread. At the Fire Lab in Missoula, Montana, researchers reverse-engineer spreading fires using wind tunnels, fire-whirl generators, and giant combustion chambers. They're finding that fire is a mysterious phenomenon, and the physics behind it is often counterintuitive.
A helicopter drops water as it assists in firefighting efforts at the Taylor Creek fire 25 miles southeast of Ashland, Montana. // U.S. Fish & Wildlife Service/AP