Light travels at different speeds based on the medium it passes through. For example, in a vacuum, it travels at 3.0 × 10^8 m/s in a straight line. But when directed towards glass, air, diamond, water ...

Negative refraction achieved at visible wavelengths. Can visible light ever be manipulated so that it bends the wrong way? If it could, a range of futuristic devices would be tantalizingly close to ...