The history of Bideford and the Torridge is inextricably linked to tides, which are dictated by the moon’s gravity. Early civilisations recognised the correlation between tides and the phase of the moon but could not accurately predict tidal behaviour. It was Eudoxus of Cnidus, an ancient Greek astronomer, who as early as 356 BCE explained the apparently irregular motions of the planets by combinations of uniform circular motions. Around 400 BCE the Greek scholar Pytheus noticed the link between lunar phases and tides. The earliest tide tables date back to 1543.

In our area, local people and seafarers will have been observing the tides and tidal currents for centuries. They used their observations and practical knowledge in a variety of ways to their advantage. For example, it helped them schedule the sailing of ships to and from port. It aided shell fishermen to know when to work the mudflats and fishery activities in the inter-tidal zone in the Rivers Taw and Torridge. 

Early civilisations primarily predicted tides through tracking recurring patterns linked to the lunar cycle. By noticing that tides matched the moons orbit, shifting about 50 minutes later each day, and peaking during new or full moons, ancient coastal cultures and seafarers compiled reliable, cyclical timetables. Seventeenth century astronomers eventually incorporated tide cycles into complex astronomical clocks. The Gravitational Revolution came in 1687 when Sir Isaac Newton laid the scientific foundation by demonstrating how the gravitational pull of the sun and moon drives the tides. Pierre-Simon Laplace later refined this in 1775 with his dynamic theory, applying advanced fluid-motion equations.

Up to 1884, all tide predictions for tide tables were computed by means of auxiliary tables and curves constructed from the results of tide observations at different ports. After that, Tide-Predicting Machines were used, which cut down on labour. 

Predicting machines were superseded in 1966 by digital electronic computers, initially of the large main-frame type but by the late 1980s they were replaced by increasingly sophisticated desktop computers. These are now used exclusively by the National Ocean Service in making predictions for the standard ports of this country and at other locations where sufficient observational data exists.

The Newlyn Tidal Observatory in Cornwall – no more than a hut really – is used for continuous logging of sea levels and, since 1921, has been the reference point calculating the altitude of locations ‘above sea level’ across England, Scotland, and Wales.