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Paper 9

Collins, H. M. (2001) `Tacit Knowledge, Trust, and the Q of Sapphire', Social Studies of Science, 31, 1, 71-85

Russian measurements of the quality factor (Q) of sapphire, made twenty years ago were not repeated in the West until the summer of 1999. The measurements we are referring to were made by `driving up' the vibrations in a small cylinder of sapphire crystal and watching to see how long they took to die away. The longer the sapphire rings when left alone, the higher its quality factor.

Part of the art is to find a support for the crystal that absorbs no energy. The best experiments done in the West could not reproduce the long `ringdown' time claimed by a group at Moscow State University.

Shortfalls in tacit knowledge were partly responsible for the failure to repeat the Russian measurements in the West. The Russians had developed esoteric techniques including supporting the crystal from a Chinese silk thread lubricated with pig grease but the exact way to do it was too subtle to describe. Success was not achieved until a group from Glasgow visited Moscow and a member of the Moscow team visited Glasgow. The development of trust was an essential pre-requisite for the transfer of tacit knowledge.

A new classification of tacit knowledge is offered and applied to the case of sapphire. The importance of personal contact between scientists is brought out and the sources of trust described.

It is suggested that the reproduction of findings could be aided by a small addition to the information contained in experimental reports. This should be a description of how long and how many trials it took to make an experiment work in the first place, and how hard it remains to repeat the experiment even after many successes.