In each of these cases, whether writing the value of pi or shooting at a target, you achieve accuracy when the accumulation of results is close to the desired value, which in these examples is either the true value of the constant or the center of the target. Precision, by contrast, is attained when the accumulated results are similar to one another, when the shooting attempt is achieved many times with exactly the same outcome—even though that outcome may not necessarily reflect the true value of the desired end. In summary, accuracy is true to the intention; precision is true to itself.

By allowing ships to know their positions and plot their voyages with efficiency, accuracy, and precision, these clocks and their successors enabled the making of untold trading fortunes. ... Precise-running clockwork made for precise navigation; precise navigation made for maritime knowledge, control, and power.

H1, H2, and H3, each clock a subtle improvement upon its predecessor, each the work of years of patient experimentation—H3 took Harrison fully nineteen years to build—employ essentially the same bar balance principle, and when they are working, they are machines of an astonishing, hypnotic beauty and seemingly bewildering complexity.

Yet, for reasons that have much to do with what is euphemistically called the “culture” of that particular facility within Rolls-Royce’s immense engineering establishment, the stub pipe passed all its inspections. A potentially weakened engine component made its way all along the supply chain until it was placed into the engine, and there to await its inevitable breakage—and the equally inevitable destruction of the entire engine. It should have failed inspection, but it didn’t. It just failed in real life.