This document outlines the key themes and topics covered in a course called Physics 155 Physics Behind the Internet. The course aims to teach physics concepts in the context of communications technology and networks. It will cover topics such as how information is encoded and transmitted, the physics of devices like computers and cameras, photon and electron communication, internet routing, and social issues related to technology and society's control of networks. Overall, the course uses physics concepts to explain the internet and related technologies, and examines the societal impacts of communications networks.