Sir

Gottfried and Wilson1 criticize the Edinburgh school of sociology's contention that scientific knowledge is a communal belief system with a dubious grip on reality. The assessment is based on two points: (a) the neglect of a large body of experimental evidence that constrains scientific knowledge and guides theory and (b) the predictive power of science.

There is another powerful element that exposes the faulty logic of the ‘Edinburgh’ school: technology. Science constrains possible technology. When the latter (a new device, instrument or system) becomes reality, it validates the specific theories on which it is founded. If scientific knowledge was not an objective description of reality, but merely a social construct, we would not have technological realities such as transistors, microprocessors, personal computers and the Internet, or semiconductor lasers, fibre optics and compact disc players in addition to radios, cars and jets.

It is instructive to examine a few of the thousands of ‘food chains’ connecting scientific knowledge (the product of hypotheses and experiments converging into a theory) to technology.

Consider lasers and in particular semiconductor lasers, an essential element of long-distance fibre-optic communications. Without the concepts of energy levels and energy bands, created by quantum mechanics, we would not have these lasers, modern telecommunications, CD players, CD-ROMs and much more. Similarly, integrated circuits, microprocessors and personal computers (used by sociologists in writing papers on science as a social construct!) would not have become a reality without quantum mechanics and its quantitative description of chemical bonds and energy bands in silicon and of the statistical behaviour of electrons in doped semiconductors (Fermi levels and Fermi statistics), transistors and the subsequent elements of the ‘food chain’. Of course much more (electronics, chemistry, optics and so on) than quantum mechanics, a necessary but not sufficient element, was needed for all of this to happen.

Another recent and wonderful but less known example is the Global Positioning System (GPS). This system, based on 24 orbiting satellites, allows anyone equipped with a suitable portable receiver to find almost instantaneously his/her position anywhere on the Earth with a precision of roughly 100 feet. Its applications also include navigation systems (from ships to jet aircraft and cars), surveys of the Earth and earthquake monitoring, synchronization of telecommunication networks, tracking of satellites and so on. This technology is based on atomic clocks, accurate to within one second in 100,000 years, which would not have been possible without the understanding of hyperfine transitions in caesium and rubidium atoms, made possible by quantum mechanics and atomic theory. In addition, general relativity and its effects on the timing of these clocks must be taken into account in the design of the GPS!

Some of these paths from science to technology and others in chemistry, biology and medicine have been analysed in a project of the US National Academy of Sciences, “Beyond discovery: the path from research to human benefit”. It can be accessed via the academy's home page on the World Wide Web ( http://www.nas.edu).

In summary, the reality of successful technologies helps to validate science as an objective system of knowledge, with a firm grip on reality, as much as reproducible experiments and predictions do. In addition, through a fascinating feedback loop, technologies often open up new frontiers of scientific knowledge.