• How would you define physical interaction?
  • What makes for good physical interaction? 
  • Are there works from others that you would say are good examples of digital technology that are not interactive?

Chris Crawford’s The Art of Interactive Design and Bret Victor’s A Brief Rant on the Future of Interaction Design.

Chris Crawford defines the term "Interactivity" as “a cyclic process in which two actors alternately listen, think and speak.” According to his assertion, there should always be two actors, (user and computer) and both should react to the input and create an output for it. Therefore, in terms of physical interaction, users do a physical action to computer/machine. I agree in some degree to Victor's point that good interaction involves physical movements of the human. People tend to remember and engage more deeply when they actually touch things. Touch is one of our powerful senses to convey our emotions. There is a study done by Dacher Keltner, who is a psychology professor at UC Berkeley did an experiment to show the power of touch. The barrier separated two contestants from each other: one with their arm stuck out of the barrier and the other had to guess what their emotions were through one-second touch. What is interesting is that nearly half of the contestants were able to get the answers right. As we can see in this experiment, human hands, which is mainly in charge of touch, is the important tool for conveying emotions. Not only limiting to the touch screens, when we fully understand the human capabilities (all five sense), we might be able to use our devices more efficiently. 
Even though Crawford pointed out that reading a book is not interactive,  I think it only applies to the traditional form of the book. What if there is a book that connects to your brain and only shows what you haven't seen? Then would this be an interactive device? Since the technology changes every day, there might be someday in the future when people don't even have to think nor do an action. There is a time when something is regarded as interactive, but not now. When we move on to high tech future, is human-centered interaction really necessary? If we don't need to use our senses (losing the importance of human capability), then the term "physical interactivity" might change. For now, within current technologies, the key factors to make a good physical interaction would be human-participation. But we should always be open to the new possibilities. 
It is hard to strictly define whether some technology has interactivity or not. So I prefer to give a degree of interactivity since I believe every input, process, and output that gives somewhat reaction to the user are "interaction" for me. That said, it doesn't always have to be a cyclic direction. When the user manipulates the tool and the digital technologies respond to their action, it creates a unique experience to the user. (whether or not you can customize the output) Even though reading a book itself might not be interactive and you cannot change the story of it, users think (process) and respond(output) to the story in some way. (I might want to call it a low degree of interactivity though since it's passive way of doing interaction) 
Therefore, it is hard to give an example of digital technologies that are NOT interactive. Even turning on the light might seem a low interactivity, it still has that three key functions(input, process, output) and readers respond to it.