the.com/lightsail

means A propulsion method where a large, thin, reflective sheet is pushed through space by the pressure of light (sunlight or a beamed laser), letting a craft accelerate without carrying propellant.

from A 20th-century coinage built straight from its job: a 'sail' that catches 'light' instead of wind. The physics idea traces to early 1900s thinkers like Tsiolkovsky and others who realized light carries momentum and can shove on a mirror-like surface. The word itself emerged as the engineering concept matured mid-to-late 20th century, especially as scientists and writers popularized designs using sunlight, and later concentrated laser beams, as the 'wind' for interstellar-scale sailing.