  This paper considers the possibility that abstract thinking and advanced
synthesis skills might encourage extraterrestrial civilizations to accept
communication with mankind on Earth. For this purpose, a notation not relying
upon the use of alphabet and numbers is proposed, in order to denote just some
basic geometric structures of current physical theories: vector fields,
one-form fields, and tensor fields of arbitrary order. An advanced civilization
might appreciate the way here proposed to achieve a concise description of
electromagnetism and general relativity, and hence it might accept the
challenge of responding to our signals. The abstract symbols introduced in this
paper to describe the basic structures of physical theories are encoded into
black and white bitmap images that can be easily converted into short bit
sequences and modulated on a carrier wave for radio transmission.
