Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Relativity: The Primacy of Light
The Special Theory of Relativity was born ("On the Electrodynamics of Moving Bodies", 1905) out of Albert Einstein’s belief that the laws of nature must be uniform, whether they describe the motion of bodies or the motion of electrons. Therefore, Newton’s equations for the dynamics of bodies and Maxwell’s equations for the dynamics of electromagnetic waves had to be unified in one set of equations. In addition, they must be the same in all frames of reference that are "inertial", i.e. whose relative speed is constant. Galileo had shown this to be true for Newton's mechanics, and Einstein wanted it to be true for Maxwell's electromagnetism as well. In order to do that, one must modify Newton’s equations, as the Dutch physicist Hendrik Lorentz had already pointed out in 1892. The implications of this unification are momentous.
Relativity conceives all motion as "relative" to something. Newton's absolute motion, as the Moravian physicist Ernst Mach had pointed out over and over, is an oxymoron. Motion is always measured relative to something. Best case, one can single out a privileged frame of reference by using the stars as a meta-frame of reference. But even this privileged frame of reference (the "inertial" one) is still measured relative to something, i.e. to the stars. There is no frame of reference that is at rest, there is no "absolute" frame of reference. While this is what gave Relativity its name, much more "relativity" was hidden in the theory.
In Relativity, space and time are simply different dimensions of the same space-time continuum, as shown by the Russian mathematician Hermann Minkowski ("The Basic Equations for Electromagnetic Processes in Moving Bodies", 1908). Einstein showed that the length of an object and the duration of an event are relative to the observer. This is equivalent to calculating a trajectory in a four-dimensional spacetime that is absolute. The spacetime is the same for all reference frames and what changes is the component of time and space that is visible from your perspective. One person’s time is another person’s mixture of time and space.
All quantities are redefined in space-time and must have four dimensions. For example, energy is no longer a simple (mono-dimensional) value, and momentum is no longer a three-dimensional quantity: energy and momentum are one space-time quantity which has four dimensions. Which part of this quantity is energy and which part is momentum depends on the observer: different observers see different things depending on their state of motion, because, based on their state of motion, a four-dimensional quantity gets divided in different ways into an energy component and a momentum component. All quantities are decomposed into a time component and a space component, but how that occurs depends on the observer’s state of motion.
This phenomenon is similar to looking at a building from one perspective or another: what we perceive as depth, width or height, depends on where we are looking from. An observer situated somewhere else will have a different perspective and will measure different depth, width and height. The same idea holds in space-time, except that now time is also one of the quantities that changes with “perspective” and the motion of the observer (rather than her position) determines what the “perspective” is. This accounts for bizarre distortions of space and time: as speed increases, lengths contract and time slows down (the first to propose that lengths must contract was, in 1889, the Irish physicist George Fitzgerald, but he was thinking of a physical contraction of the object, and Lorentz endorsed it because it gave Maxwell's equations a particularly elegant form, whether the observer was at rest or in motion). This phenomenon is negligible at slow speeds, but becomes very visible at speeds close to the speed of light.
An observer who travels away from a clock-tower at the speed of light, would always observe the same time, as if the clock's hands never moved and time was still. If the observer traveled at a speed slightly less than the speed of light, the observer would see the hands of the clock moving very slowly over the years as the light would take a long time to travel that distance. On the other hand an observer who travels very slowly away from the same clock-tower (all of us on human-made vehicles), would observe the clock's hands moving. Therefore time depends on the speed of the observer relative to the clock (or viceversa). A moment of time is slower at higher speed. Time intervals are dilated by higher speeds.
A further implication is that "now" becomes a meaningless concept: one observer's "now" is not another observer's "now". Two events may be simultaneous for one observer, while they may occur at different times for another observer: again, their perspective in space-time determines what they see. The traditional law of causality is an illusion. Two events that follow each other from an observer's point of view may be simultaneous from the point of view of another observer who is moving at a different speed. The present is a concept that depends on the observer. Each observer has a different set of contemporary events that constitute its present.
Even the very concept of the flow of time is questionable. There appears to be a fixed space-time, and the past determines the future. Actually, there seems to be no difference between past and future: again, it is just a matter of perspective.
Time and space complement each other: as one dilates, the other contracts. The traditional law of causality had ceased to exist, but a new sort of causality was introduced because any warping of space corresponded to a warping of time.
The speed of light is the same in every frame of reference. What changes in each frame of reference is the very notion of distance and duration. That's why the speed of light remains the same regardless of what the frame of reference is doing: what it is doing alters its space and time in such a way that the speed of light remains the same for everybody.
Mass and energy are not exempted from "relativity". The mass and the energy of an object increase as the object speeds up. This principle violates the traditional principle of conservation, which held that nothing can be destroyed or created, but Einstein proved that mass and energy can transform into each other according to his famous formula E=mc2: a particle at rest has an energy equal to its mass times the speed of light squared. (Note that the equation does not apply to things like photons that are not quite "objects" and that are never "at rest"). A very tiny piece of matter can release huge amounts of energy. Scientists were already familiar with a phenomenon in which mass seemed to disappear and correspondingly energy seemed to appear: radioactivity, discovered in 1896. But Einstein's conclusion that all matter is energy was far more reaching.
Light has a privileged status in Relativity Theory. The reason is that the speed of light is always the same, no matter what. If one runs at the speed of a train, one sees the train as standing still. On the contrary, if one could run at the speed of light, one would still see light moving at the speed of light. Most of Relativity's bizarre properties are actually consequences of this postulate. Einstein had to adopt the Lorentz transformations of coordinates, which leave the speed of light constant in all frames of reference, regardless of the speed it is moving at, but, in order to achieve this result, one must postulate that moving bodies contract and moving clocks slow down by an amount that depends on their speed.
If all this sounds unrealistic, remember that according to traditional Physics the bomb dropped on Hiroshima should have simply bounced, whereas according to Einstein’s Relativity it had to explode and generate a lot of energy. That bomb remains the most remarkable proof of Einstein’s Relativity.
Note that most of the equations in Einstein’s Relativity had already been derived by others (Lorentz, Fitzgerald, Poincare) but they were merely attempts at explaining experimental data. Einstein introduced the principle of relativity (that the laws of physics must be the same in all inertial systems), and those equations became natural consequences. De facto, Einstein made a metaphysical choice: he decided that space and time are not absolute. Once the metaphysics changed, the oddities of the experimental data went away, or, better, became the natural consequences of a bigger oddity.
Back to the beginning of the chapter "The New Physics" | Back to the index of all chapters