Preface: One Ruler, Five Measurable Questions

The royal cubit of ancient Egypt was a ruler about half a metre long, divided into seven palms and twenty-eight fingers. It laid out temples and pyramids for more than two thousand years. In the last century it has also gathered a second life: as a “sacred” length said to carry special harmonic or energetic properties, and as the measure for copper rings and coils sold with promises about health and well-being.

This book takes the cubit seriously in a different way. It asks five questions that can be answered with a ruler, a calculator and an inexpensive measuring instrument.

1. How long is a royal cubit? What do the surviving rods in Turin, Paris and London measure, how much do they vary, and why does this book use 523.5 mm? (Chapter 1)
2. What does a cubit resonate with? Any length resonates with waves whose wavelength fits it. Using $\lambda = c/f$, which sounds and which radio waves “fit” one cubit? (Chapter 2)
3. What does a twisted copper ring do? When two strands of copper carry current in opposite directions, their magnetic fields largely cancel. When does a cubit ring actually do this, and how can it be measured, including with the standing-wave ratio (SWR) used by radio engineers? (Chapter 3)
4. What happens when rings are combined? Three rings at right angles form a spherical octahedron. How do their fields add, and why do they not disturb one another? (Chapter 4)
5. How can a reader check all this at home? With an open-source vector network analyser and a software-defined radio receiver, each costing less than a family dinner, every measurement in this book can be repeated. (Chapter 5)

The answers are physics, not mysticism, and that is the point. A length does not need to be sacred to be beautiful, and the measurements in this book are ones anyone can repeat.