EASTHAMPTON — For Amy Christenson, a formative memory involving her son, an escalator and a kind stranger is driving a mission to change the world. Christenson’s son Ben, now 9 years old, has autism.

Every step you take makes these old, worn-out planks creak. Is this bridge about to give out with you suspended 100 m (330 ft) above a raging river? Hang in there, help is on its way. Oh, and whatever ...

Andy Nguyen receives funding from the Queensland government, through the Advance Queensland fellowship. He is on the executive committee of Australian Network of Structural Health Monitoring. The ...

Editor’s Note: Call to Earth is a CNN editorial series committed to reporting on the environmental challenges facing our planet, together with the solutions. Rolex’s Perpetual Planet Initiative has ...