The editors present a state-of-the-art overview on the Physics of Space Weather and its effects on technological and biological systems on the ground and in space. It opens with a general introduction on the subject, followed by a historical review on the major developments in the field of solar terrestrial relationships leading to its development into the up-to-date field of space weather. Specific emphasis is placed on the technological effects that have impacted society in the past century at times of major solar activity. Chapter 2 summarizes key milestones, starting from the base of solar observations with classic telescopes up to recent space observations and new mission developments with EUV and X-ray telescopes (e.g., STEREO), yielding an unprecedented view of the sun-earth system. Chapter 3 provides a scientific summary of the present understanding of the physics of the sun-earth system based on the latest results from spacecraft designed to observe the Sun, the interplanetary medium and geospace. Chapter 4 describes how the plasma and magnetic field structure of the earth's magnetosphere is impacted by the variation of the solar and interplanetary conditions, providing the necessary science and technology background for missions in low and near earth's orbit. Chapter 5 elaborates the physics of the layer of the earth's upper atmosphere that is the cause of disruptions in radio-wave communications and GPS (Global Positioning System) errors, which is of crucial importance for projects like Galileo. In Chapters 6-10, the impacts of technology used up to now in space, on earth and on life are reviewed.