James Clerk Maxwell, in 1861–1864, published his theory of electromagnetic fields and radiation, which shows that light has momentum and thus can exert pressure on objects. Maxwell's equations provide the theoretical foundation for sailing with light pressure. So by 1864, the physics community and beyond knew sunlight carried momentum that would exert a pressure on objects.
james clerk maxwell in 1861–1864 published his theory of electromagnetic fields and radiation which shows that light has momentum and thus can exert pressure on objects maxwell's equations provide the theoretical foundation for sailing with light pressure so by 1864 the physics community and beyond knew sunlight carried momentum that would exert a pressure on objects