This is a survey article on two topics. The Energy E of knots can
be obtained by generalizing an electrostatic energy of charged knots
in order to produce optimal knots. It turns out to be invariant under
Möbius transformations. We show that it can be expressed in terms
of the infinitesimal cross ratio, which is a conformal invariant of a
pair of 1–jets, and give two kinds of interpretations of the real
part of the infinitesimal cross ratio.
