The Day the Universe Changed - James Burke [165]
Ten years later the science of oceanography had altered the accepted view of the sea-bed. An extensive system of mid-ocean ridges had been discovered throughout the world. Running through the ridges were rift valleys with associated narrow earthquake zones. The ridges were also shown to have unusually high heat flows along their crests. They were obviously related to some kind of continuous activity in the ocean floor.
In 1960 magnetic analysis of the areas parallel to some of the ridges showed alternating strips of high and low residual magnetic intensity. At the same time oceanographers were shocked to discover that the sediments on the sea-bed were extremely thin, especially at the ridges. Moreover, no sediments older than the relatively young cretaceous period were found in core samples. The sea-bed was both younger and thinner than expected.
In June 1963 it was established that the polarity of the earth’s magnetic field had undergone periodic reversals throughout history. Two researchers, Vine and Matthews, proposed that if the evidence showed that hot material was coming to the surface at the sea-bed ridges and spreading outwards, which would explain everything so far observed, the flow, as it started and stopped, ought to be characterised by strips on either side of the ridge which would have emerged during periods when the earth’s magnetic field alternated. The strips should therefore have alternately polarised residual magnetism.
The position of the continents 60-100 million years ago, based on the evidence of residual magnetism. Note how India lies off the coast of Africa.
In 1966 several magnetic profiles were made of the Pacific-Antarctic ridge. They confirmed the new view. The ocean floor was spreading outward from the ridges, and it was this mechanism which had slowly pushed the continents apart. This was the only structure that could accommodate all the new data. What is more, it explained other anomalies. If the sea-bed were spreading it would encounter the continent edges and be forced back downwards. This would account for the earthquake zones along the Californian coastline and the mountain-building activity in the north-west of the United States.
The new structure presupposed that the earth’s surface was composed of a number of tectonic plates, floating on a spherical, molten subsurface. The emergence of plate tectonics revolutionised the entire field of geophysics, and opened the door to a new set of structures and controls by which research is now to be conducted in the new version of how the earth functions. The old structure has been replaced.
Each structure must, by definition, be a complete version of what reality, or one aspect of it, is supposed to be. It is the contemporary truth. But as has been seen, structures are replaced. Aristotle gives way to Copernicus who gives way to Newton who is replaced by Einstein. Lavoisier and Priestley destroy the concept of pneumatic chemistry and the mystery ‘quality’, phlogiston, in order to replace it with a chemistry based on combustion. The use of perspective geometry challenges the theological rules for interaction with the intangible physical world by making it measurable. Nineteenth-century geology does away with the biblical record of history.
A composite computer map of the world showing the mountainous mid-ocean ridges (red) rising from the seabed.
In most cases, each structure is generated by circumstances that are not directly related to the scientific field itself. Often the pressure for change will come from outside the discipline. Whatever the cause, however, it will be seen that the initial cosmological structure sets the overall pattern of reality within which other structures work. They, in turn, define the areas of research to be covered. These areas demand specialist forms of investigation that then discover anomalies which the overall structure cannot accommodate, and so change occurs. But the theories, discoveries, equations, laws, procedures, instruments, as well as the judgemental systems used to assess the