I know quantum and I know gravity. Why quantum gravity? Because they have yet to be reconciled with each other. “The gravitational field is described without taking quantum mechanics into account, without accounting for the fact that fields are quantum fields—and quantum mechanics is formulated without taking into account the fact that spacetime curves and is described by Einstein’s equations.” Although the electric field is well defined at a point of space, applying the same thing to gravity shows that it is not well-defined at a point. Because we can characterize electrons as being in space, but we cannot characterize how gravity – which constitutes the space itself– exists in space. So we have to jump out of this self-referencing loop and look at the reality like it is a graph, or a bag of words – one quanta of gravity or space is only defined by what lies next to it – same as the meaning of a word is defined by what context it can be used in.
The main takeaway from this book is that: we may need to throw away the idea of “events” that happen at a certain point of time. There are only interactions that define reality. I admit that I don’t understand even the surface of it. The book threw a radical idea to me that I cannot digest easily. It’s interesting to play around with, but too abstract and hard for me to understand.