Dutch mathematician, physicist, engineer, astronomer, & inventor who is regarded as a key figure in the Scientific Revolution Christiaan Huygens was born #OTD in 1629.
He developed the wave theory of light, proposing that light propagates as a wave rather than a stream of particles, which was a revolutionary idea at the time. Huygens also invented the pendulum clock, which greatly improved timekeeping accuracy and became widely used in scientific experiments and everyday life.