Light is made up of individual particles called photons. A photon is a discrete quantum of electromagnetic energy. Photons are special because they have properties of both a particle and a wave. Photons have mass and can interact with physical matter. The phenomenon of "solar pressure" is caused by photons bombarding a surface and exerting force. (This force actually has to be accounted for in orbital mechanics.) However, light also has a wavelength and frequency, similar to sound or other wave
