Tangency, its many facets and varied applications --------------------------------------------------------------
It all began with the notion of a line tangent to a circle, circles tangent to a line, as in the successive positions of a bicycle wheel rolling along a straight track, or circles tangent to one another. In the vocabulary of non-mathematicians, these mathematical objects “brush against each other”. The concept extended to stacks of tangent circles that one tries to fit inside a closed curve, like those with which artist Jos Leys fills his images, then to tangent curves, which can be compared to the folds in draped fabric.
Spheres tangent to a plane are the marbles that roll on the ground; a cone tangent to a sphere is a crisp wafer cone and its scoop of ice cream; spheres tangent to one another are the soap bubbles that burst as they collide…
Tangencies are all around us! This highly universal notion is what this special issue 84 of Tangente, published for the magazine’s thirty-fifth anniversary, sets out to honour.
Élisabeth Busser Issue coordinator, with Robert Ferreol