Particles of light

摘要

Bose-Einstein condensation, which demonstrates the wave nature of material particles, now offers further illumination of wave-particle duality: it has been observed in light itself. See Letter p. 545rn"Art is the Tree of Life. Science is the Tree of Death." So wrote the vision-ary English poet and artist William Blake in 1826, contrasting the limitless creativity of art with the limiting rigidity of science. Blake understood the science of his day - well enough, for instance, to lump together "The Atoms of Democritus And Newton's Particles of Light", and compare them both to sand. In Blake's time, both were conceived of as indivisible and indestructible, their motion governed by Newtonian mechanics.