Pyotr Lebedev and the pressure of light

Today we celebrate the birthday of the Russian physicist Pyotr Nikolayevich Lebedev (8 Mar 1866 – 1 Apr 1912).

Working in the field of electromagnetism, Lebedev was responsible for a rather famous physics experiment in 1899 – measuring the pressure a beam of light exerts on a solid body. By doing this, he was the first to quantitatively confirm James Clark Maxwell’s theory of electromagnetism. Not only did he prove that the pressure exerted by light, although minute, is very real – he also proved that the pressure of light on a reflective surface is twice as great as on absorbent surfaces.

Lebedev’s discoveries led him to postulate that it was the pressure exerted by sunlight on tiny particles of cosmic dust that made the tail of a comet point away from the Sun. However, it is now generally accepted that solar wind has more effect than light pressure in determining the direction of a comet’s tail.

Lebedev died quite young, yet his achievements was significant enough that the Lebedev Physical Institute in Moscow and the lunar crater Lebedev are named after him.