This week, we bring you the best bits of technology from the world of engineering including a guiding light into the workings of a retroreflector, the dual life of bi-stable structures, and a new way to harness energy from our rivers. Plus, we unearth the workings of a copper mine, discover how Barnes Wallis designed his famous bouncing bomb and bring you an atomic insight into the art of metalworking! Like this podcast? Please help us by supporting the Naked Scientists