The Day the Universe Changed - James Burke [160]
Sometimes, too, evidence is deliberately rejected because its source or style does not conform to accepted standards. In 1769 three ‘thunderstones’were submitted by three different sources for examination by the French Academy of Sciences. They were reputed to have fallen from the sky. Chemical analysis revealed them to be surprisingly similar, but the account of their origin was rejected. This was because of the prevailing view of meteors, whose composition was disputed by scientists although their existence was not. Meteors were seen by scientists. Falling stones were seen by peasants, or at best local clerics. In the days before the French Revolution such sources of evidence were to be ignored.
Scientific proof during the Enlightenment had been uniquely established by observation and experiment on the part of a scientific community which had chosen to isolate itself from the rest of society. Disorganised and for the most part amateur, it was jealous of its dilettante status. The acceptance of evidence from members of the lower classes would endanger that status.
Meteorites, or falling stones, were also part of folklore and as such to be discredited, even when they occurred in conjunction with the appearance of a well-observed meteor. When a large meteorite fall occurred near La Grange de la Juliac, in southern France, it was witnessed by over three hundred people including the mayor and the town’s lawyer, but because no scientists were present their report was dismissed as fiction. The usual objection was that the observers had suffered from an optical illusion.
By 1801, however, enough ‘stones’were being chemically examined for the French scientific community to feel that the matter was in reliable professional hands. Then, and only then, were new reports of meteorite falls taken seriously. In 1803 a giant fall at L’Aigle, near Paris, was examined by Jean-Baptiste Biot, of the Institut de France, and declared to be celestial in origin. The revolution had enhanced the position of the common man in France, and with scientists controlling the means of finding and examining the evidence, meteorites could now be accepted as a genuine phenomenon. Final proof of the meteorites’origin came when scientific analysis of the stones revealed a composition of nickel and iron not found anywhere on earth.
By the time the structure had changed sufficiently for meteorites to be accepted for what they were, the same structure also dictated the use of scientific analysis using specific instruments in specific ways in order to establish whether or not the stones were of earthly or unearthly composition. The researchers were looking for the presence or absence of predicted data.
When evidence has been accepted or rejected and the existence of a phenomenon established, the structure again dictates the next step. It provides the means for examining the phenomenon and a guide to expected data. Any data presented in this way will be acceptable, since the instruments used will have been designed to find only those data which, according to the structure, are needed for confirmation. Any data considered to be extraneous to the event will be disregarded.
In England in the late nineteenth century, for instance, a time when it was thought that electromagnetic radiation exerted pressure, William Crookes constructed a radiometer to measure the pressure. He pivoted a number of tiny vanes on a vertical axis in a glass bulb from which all the air had been extracted. The side of the vanes facing the radiation sources was painted black, because it was known that radiation affected dark surfaces more than bright ones. Sure enough, when the device was exposed to sunlight, the vanes spun away from the light. The more intense the light, the faster the spin. The radiation was evidently causing pressure on the vanes, as predicted. The instrument was so sensitive that it was used in turn to detect and measure stellar