In the 18th century, while the scientific revolution was in full swing and the age of great discoveries was at its peak, the most pressing scientific problem that dominated the scientific and political circles of Britain, and not only, had clear practical significance: it was the calculation of geographical longitude.

The inability to measure it had cost thousands of lives lost at sea for centuries, while it posed serious obstacles to the commercial expansion and defensive fortification of the island nation. The top astronomers of the time tackled this specific problem, but a persistent craftsman, John Harrison, devised a mechanical solution.

Devoting 40 years of his life, he managed to create a clock that accurately measured the passage of time at sea, something that the clocks of the era could not achieve even on land. This perfect clock, now known as the chronometer, was the culmination of a heroic effort that faced endless difficulties, challenges, and setbacks, to finally receive official recognition and universal acceptance.

“Those who are unaware of this unique episode in human history will enjoy an exciting narrative about an amazing achievement in the fields of time measurement and navigation.” Neil Armstrong (2005), the first man to set foot on the Moon (and who introduces the edition).