How I spent the International Day of Women and Girls in Science 2019

The 11th of February every year has become a day to recognise the crucial role played by women and girls in science and technology communities, as declared by the United Nations General Assembly in 2015.

I spent the International Day of Women and Girls in Science 2019 in the company of Valerie Doodson and Sylvia Asquith, who played a vital part in the STEM (Science, Technology, Engineering and Mathematics) industry during their working lives at Bidston Observatory on the Wirral Peninsula in north west England, from 1952 to 1962 and from 1947 to 1990 respectively. We discussed at length the evolution of their work, workplace and colleagues during the years they worked there.

Bidston Observatory had national and international responsibilities during its many years of operation from 1866 to 2004 including telling the exact time with the One O’Clock Gun, carrying out oceanographic research for Liverpool Tidal Institute, predicting the tides for the British Admiralty using analogue tide prediction machines and making meteorological observations for the UK Met Office.

Bidston Observatory, Wirral, UK. Photograph: Helen Mair Rawsthorne (08/01/2019).

Valerie and Sylvia both joined the observatory as part of a team of young women known as “computers” who were employed to operate the tide prediction machines, prepare the outputted data for publication in the British Admiralty Tide Tables, and perform meteorological observations. They explained to me the process of predicting the tides for a given port, which could be anywhere in the world. It began with setting up a tide prediction machine with the correct constituents for the port and then running the machine, reading off the numbers it displayed for each high and low tide over the desired period of time. These numbers would be plotted as a curve graph, which would be checked for “smoothness”; a non-smooth graph suggested the presence of an error. These errors were corrected and the newly-smooth predictions would be typed up ready to be published in the British Admiralty Tide Tables. They recall that the machines were very noisy during operation, although the sound was not unpleasant but rather bell-like.

A reminder of the global importance of the accuracy of the work of the female “computers” at Bidston Observatory was often given, as the lives of people at sea and the efficient running of global maritime transport depended upon it.

It was a delight to see the fondness with which Valerie and Sylvia spoke about their years at Bidston Observatory and I am very grateful to them both for their time and the patience with which they answered all my questions relating to the tide prediction machines with which they are so familiar.

International Day of Women and Girls in Science. “From Dream to Reality.” Accessed February 15, 2019.
United Nations. “International Day of Women and Girls in Science: Background.” Accessed February 15, 2019.

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A propos Helen Mair Rawsthorne

Physics graduate from the University of Bristol, UK, and student of the Epistemology and History of Science and Technology Master's course at the University of Western Brittany in Brest, France. --- Diplômée en physique de l'Université de Bristol au Royaume-Uni et étudiante du Master Epistémologie et l'Histoire des Sciences et des Techniques à l'Université de Bretagne Occidentale à Brest, France.

2 réflexions sur « How I spent the International Day of Women and Girls in Science 2019 »

  1. Great article, Helen. I have a couple of questions, how accurate could these tide predictions be and were there any ways to test the accuracy at the time?

    • Hi Andrew, thanks for the questions. Tide prediction machines are analogue computing machines, which means that their output is as accurate as the calculation they are calculating allows, and also depends on the accuracy of the inputted data. Before the invention of TPMs, these harmonic calculations were done by hand. The more factors taken into account in the calculation, the better the result will be. These factors are known as constituents, and represent contributions such as the lunar semidiurnal period and the solar semidiurnal period. With the use of TPMs it became possible to perform the calculations with many more constituents than was possible by hand, increasing the accuracy of the results and reducing the opportunity for human error. Although human errors were still introduced when inputting data to the TPMs and reading off the outputted data, many checks were made on the results to ensure their quality. Arthur Doodson, who developed new methods and practices of calculation, claimed in one paper that the results “could be relied on to within about 0.01 foot” (Doodson, “To Assist Works on the Tides,” 218). Testing the accuracy of the results was relatively straightforward. Observations of the high and low tides can be made using tide gauges, which have been around for much longer than TPMs. Remember that data relating to any location in the world and any time in the past or future can, in theory, be inputted to TPMs. Therefore, tidal observations can be compared with the results given by TPMs programmed with the spatial and temporal data of the tidal gauge used. This is how the accuracy of TPMs could be verified in the past. I hope that answers your questions!

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