Who has seen the wind? A Poem by Christina Rossetti www.poetryfoundation.org Who has seen the wind? Neither I nor you: But when the leaves hang trembling, The wind is passing through. Who has seen the wind? Neither you nor I: But when the trees bow down their heads, The wind is passing by. The Wind Rises windtreesseeing
Caustic (optics) Caustics made by the surface of water. In optics, a caustic is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light. Wikipedia en.wikipedia.org Architectural CausticsCaustic Engineering caustics