Homage to Maxwell in Edinburgh

Imagine my joy on coming upon this statue of James Clerk Maxwell in the middle of Edinburgh. I'm so impressed that they have put his equations into the pavement like a work of art. The upside down triangle is called del or nabla. It is a method of differentiating a vector field (ie a series of arrows like a map of wind speeds) that exists in three dimensions. The differentiation means finding a gradient. The dot means finding the gradient along the line of one of the vectors. The cross means in a direction perpendicular to both of the vectors. These four equations sum up all of electromagnetism and he used them to predict the existence of electromagnetic waves, figuring out that light must be one when his theoretically derived speed turned out to be the speed of light.