The following is an excerpt from Hasok Chang's "Who Cares about the History of Science?"
Complete paper: https://royalsocietypublishing.org/doi/10.1098/rsnr.2016.0042 ****************** In addition to teaching us about the general contingency of the present, the study of the past also serves to expand our conceptual horizons more specifically. It is said that truth is stranger than fiction, and actual past science can go beyond our imagination because our imagination is usually heavily constrained by our present situation. The motto here is provided by the novelist L. P. Hartley, who opened The Go-Between thus: ‘The past is a foreign country; they do things differently there.’ Learning history is broadening like travelling is meant to be broadening. It is a common occurrence for those of us who delve into old scientific texts to slap our knees and exclaim: yes, one could think like that! One quick example will illustrate this point well. The astronomer William Herschel, the discoverer of Uranus, is also known for his discovery of infrared light in 1800. However, that is not how Herschel himself and many of his contemporaries conceived the latter achievement; for them, what Herschel had done was to separate out, by means of the prism, rays of caloric (heat) from rays of light in the sunbeam.18 Herschel had probed the solar spectrum by placing a thermometer in various parts of it. Noting that the heating power increased as he moved towards the red end of the visible spectrum, Herschel tested whether it might continue into the dark space beyond the red, and indeed detected a great heating effect there. Joseph Banks, the long-time President of the Royal Society, wrote to Herschel in appreciation of his account of this discovery submitted to the Royal Society: ‘I have shown your second paper to Mr. Cavendish and to some other of my friends … and all are struck with the discovery, of Radiant Heat being separable from Radiant Light.’ Figure 3 shows Herschel's own representation of this interpretation, showing the distributions of ‘heat making rays’ and the light rays as clearly distinct entities. link to Figure 3. https://royalsocietypublishing.org/cms/asset/8b29db6a-d006-4768-aa63-8309f42e4393/rsnr20160042f03.jpg Recovery In addition to serving the role of opening our minds, past systems of science are valuable in themselves. This brings us to the function of history that consists in the recovery of lost scientific knowledge. Kuhn famously argued that when a scientific revolution happens, some knowledge that had been established in the old paradigm is liable to become lost. He accepted this as part of the normal course of scientific development, but there is no reason why historians should not contemplate with real appreciation what we dig up from the past. If the chemistry of phlogiston, and Antoine-Laurent Lavoisier's chemistry of oxygen and caloric, each once gave valid understanding of nature to the practitioners of those systems, then they can still provide that same understanding concerning the domains of phenomena in which they remain valid. This is how orthodox scientists in fact treat venerable old theories of physics such as geometric optics and Newtonian mechanics, which they still teach to every student of physics. That same appreciative attitude could be extended with benefit to some of the theories that orthodox science has now rejected. This agenda of recovery may be quite difficult to accept when it comes to theories. It is difficult to go against the confidence of present experts that the old theories were rejected for good reasons, and deserve to be forgotten. This is why experimental work is so valuable in this context, because our own judgement can more easily be independent when we come face-to-face with phenomena themselves. Let me illustrate this point with a few examples. In a study published in 1791, Marc-Auguste Pictet made a striking experiment in Geneva demonstrating the reality of radiant heat. He set up two concave metallic mirrors facing each other and placed a sensitive thermometer at the focus of one mirror; then he brought a hot but not glowing object into the focus of the other mirror, and observed that the thermometer reading began to rise immediately. The really surprising result came when Pictet made the same experiment with a cold object (a flask filled with snow): this time the temperature at the other focus began to sink immediately! Count Rumford, well-known to historians of science as a pioneer of the kinetic theory of heat (and the founder of the Royal Institution in London), unleashed a controversy by interpreting Pictet's result as a genuine action of ‘frigorific rays’, and performed striking new experiments to support his view.22 When faced with such reports from the past that seem alien to modern science, historians may try to confirm if the alleged phenomena can be reproduced; if so, then we will have recovered a piece of forgotten scientific knowledge. In this case, Pictet's experiment was duly replicated by two modern physicist–historians, James Evans and Brian Popp, though that replication itself seems to have been largely neglected. *************************
