We live in time like fish in the water. Time flows. This seems unquestionably true and universal. But “reality is often very different from what it seems”. This is the idea with which Rovelli opens “The order of time”.

In the introduction he explains the book’s structure, and how it is divided into three “unequal” parts. 

The first part is a summary of what modern physics knows about time so far. The author highlights the complexity of time’s nature, in fact it remains a mystery. “Is like holding a snowflake in your hands: gradually, as you study it, it melts between your fingers and vanishes”. When we think about time, we consider it as a simple thing, that it goes on and never comes back, from past to future, never vice versa. But physics debunks the unity of time and its unidirectionality. This first part ends by considering the ramifications of quantum mechanics—granularity, indeterminacy, and the relational aspect of physical variables—each one destroying “further the little that was left of our idea of time”. 

The structure of time is not what it seems to be: it is different from this uniform, universal flowing”.

The second part describes what remains in the end: a world without time. An essential world, full of beauty and clearness. For those reasons, this part is more philosophical, full of metaphysics. Rovelli tries to understand this world with the help of quantum mechanics, that is his field of study.

The third part is the most difficult one. It is the return journey. The writer becomes a detective who wants to find who’s guilty for creating time. But what happens if the detective himself is the guilty one? Rovelli tries to reconstruct the idea of time with a human perspective, which is full of mistakes and approximations. The mystery of time is about what we are in the world, in the universe.

This book is a wonderful voyage from what physics has discovered throughout history about time to the huge mysterious ocean of what we don’t know yet.