The single, most important technological problem of the seventeenth century was to discover a practicable method of finding longitude at sea. The word ‘technological’ is used here with care. Other critical technical problems existed, of course, but a solution to the problem of longitude was deliberately sought through developments in science or natural philosophy. Both the educated navigator and the Baconian natural philosopher expected that a solution, when it came, would develop from an application of some scientific principle. In this sense, the problem was understood to be one of technology.

Most proposed solutions relied on some method for finding the time at a standard meridian, distant from the observer. This might be done by carrying a timepiece set to the standard time, or by observing the progress of some celestial phenomenon such as the motion of the Moon or of the satellites of Jupiter, and consulting tables constructed for time at the standard meridian. The longitude difference could then be found merely by comparing standard time with local time – readily discovered from Sun or stars – an hour's difference in time being equivalent to 15 degrees of longitude. Alternatively, improvements might be made in the traditional methods of keeping an account of the voyage in bearings and distances (so-called ‘dead reckoning’), or an absolute measure of position on the Earth's surface might be found from some terrestrial phenomenon such as magnetic variation.