In the Prologue to Act 4.4, Gower, urging the audience to follow the movements of the play's characters, says:
"Like motes and shadows see them move awhile;"
Comment: Editors show no sign of understanding why Shake-Speare couples motes (specks of dust in a sunbeam) with shadows. But a Bacon passage explains it. In his Natural History he wrote:
Bacon: "The utmost parts of the shadows seem ever to tremble. The cause is for that the little motes do ever stir, though there be no wind, and therefore those moving in the meeting of light and shadow, from the light to the shadow and from the shadow to the light, do show the shadow to move because the medium moveth."
Comment: A most telling parallel. Shake-speare could not have borrowed from Bacon whose Natural History was not published till years later. And Bacon could not have found in the play his theory as to why shadows tremble.