In the traditional accounts it is the first and finest of the four ages. In this book it is a definition, and the definition is testable in a single day.
Traditional descriptions of Satyayuga speak of an age in which dharma stands complete, lifespans are long, and truth requires no enforcement because deception has not yet become useful. That is the tradition, reported as such. This book does not claim it as history and does not need it to be.
What I want from the concept is its structure. Strip away the golden cities and what remains is a precise proposal: SatyaYuga is the condition in which inner state, speech and action are the same thing. Nothing is being performed. Nothing must be maintained. The energy that a divided life spends on managing the gap between appearance and reality is simply not being spent, and is available for something else.
Read that way, the idea becomes immediately practical, because it can be checked. Where today did what I said match what I thought? Where did what I did match what I said? The distance between those three is measurable by anyone honest enough to look, and it is the only measurement of an age this book proposes.