What did Newton call the particles of light?

Newton called the particles of light corpuscles. The word comes from the Latin corpusculum, meaning a small body or little particle, and it described his influential corpuscular theory of light.

Newton proposed that light consisted of tiny bodies emitted by luminous objects and traveling in straight lines. This model helped him account for familiar effects such as rectilinear propagation, reflection, and refraction. He also tried to explain colors by suggesting that different kinds of corpuscles produced different sensations and were refracted by different amounts.

Corpuscles should not be confused with modern photons. Newton’s idea was a seventeenth-century mechanical theory, while photons are quantum excitations of the electromagnetic field. The later wave theory of light, supported by experiments on interference, diffraction, and polarization, displaced Newton’s corpuscular model during the nineteenth century. Modern physics combines wave-like and particle-like descriptions through wave-particle duality, but “corpuscles” remains the historically correct term for Newton’s proposed light particles.