👉 Rigel is a German word that translates to "slip" or "warp." It is a term used in mathematics and physics, particularly in the field of fluid dynamics. The term was first introduced by Gustav Kirchhoff in his book "The Mechanical Theory of Heat," which was published in 1860. In this context, it refers to a phenomenon where heat or other forms of energy can move through a material at a speed that is slower than the speed of