The Project Orion spacecraft is by common consent the craziest interstellar flight concept ever devised. Ironically, it was also the spacecraft design that received the widest support by scientists, the military and other branches of the US government, as well as by private industry. It was as if all of these people had collectively lost their minds. The basic idea was utterly simple and so intuitively obvious that it could be understood by a child. This was a craft whose propulsion system was built upon the Newtonian principle of action and reaction. The central notion was that of placing a bomb under a rocket and then detonating it to loft the rocket up and away – exactly the same process as putting a firecracker under a tin can and watching it blow sky high. To keep it going up, of course, a series of bombs detonated in sequence would be required. And so the Orion rocket would be propelled through space by a stream of bombs, in fact nuclear bombs, exploding one after another behind it, thereby continuously accelerating the craft. That was the project’s key concept, and as such it was simultaneously perfect and insane.

Weinberg takes a summer job in the Atomic Beam Group at Princeton, calculating the trajectories of beam particles through the experimental equipment. He describes the culture of close relations of graduate students in physics with the younger faculty and its emphasis on research rather than course work. He details the various courses he took, along with the personalities of the Princeton professors at the time. Sam Treiman agrees to be his PhD advisor for a thesis on strong interactions in decay processes.