The Day the Universe Changed - James Burke [145]
Mach and the Positivists freed physics from metaphysics and such mysteries as imperceptible substances. Their phenomenology was concerned solely with relationships. It was only at this level that descriptions could take on some permanent value. As Robert Mayer had said in mid-century:
All that can be settled are constant sets of relationships. These constants are as far as science can go in saying anything about reality. Constant relationships, governed by constant rules, of constant value, which would not change whatever happened to the thing itself.
Representations could be no more than symbols that were subjective in origin.
While all this pulled the rug out from under Newton and those trying to explain the apparent failure of Michelson and Morley to detect any ether during their experiment, it still left that failure unexplained, if indeed ether were still to be regarded as a necessary reference, even if only of local value.
Einstein, a man profoundly influenced by Mach, removed the problem by removing the ether. He began the third paper of his five essays published in 1905 thus: ‘It is known that Maxwell’s electrodynamics - as usually understood at the present time-when applied to moving bodies, leads to assymmetries which do not appear to be inherent in the phenomena.’What he was referring to was the Fitzgerald-Lorentz problem of the electrostatic generator which is motionless on earth but in motion from any other viewpoint. The decision regarding the type of current being produced is relative to the position taken by the observer. Einstein placed all observers firmly within their frame of reference. It was not possible to observe the universe except from within this frame. All properties, such as time and distance, were similarly contained.
With relativity, Newtonian simultaneity disappeared. If light took a finite time to move from one place to another, the simultaneous occurrence of events in the universe could never be established, since information about an event would always arrive after it had happened.
Moreover, within an observer’s frame of reference all means of measuring the speed of light would work in relation only to the frame. If the speed of light were constant throughout the universe, Michelson and Morley’s experiment could not have produced interference patterns because within their frame of reference their instruments would have compensated, as Fitzgerald suggested, in whatever way necessary so as to show the light to be moving at a universally constant speed.
Einstein’s ‘thought experiment’with a truck illustrated the point. Inside the truck a light flashes, as it moves along. People in the truck see the light hit the front and back walls of the truck at the same time and measure its speed as 186,000 miles per second. Outside the truck, observers see the light hit the back wall of the moving truck before it hits the front. But the speed of the light for both sets of observers is the same.
If all instruments being used to measure phenomena were thus frame-dependent, it followed that all statements about nature were about the tools and methods of science rather than about objective reality. Einstein himself echoed this: ‘Physics is an attempt to grasp reality as it is, independently of its being observed.’
Einstein’s thought experiment to illustrate how the speed of light is affected by the frame of reference of the observer.
Geissler’s tubes, showing the variety of colours produced by the discharge of electricity through different rarefied gases. Geissler tubes were first used commercially in a display commemorating Queen Victoria’s Diamond Jubilee in 1897.
These views struck at the very foundations of Newtonian physics. However, worse was to come. In the middle of the nineteenth