Readers may know that 2005 is the centenary of Einstein’s seminal paper on Special Relativity. Over the next few months, Terry Longhurst, FIAP takes the opportunity to develop his distinctive, maybe unique, ideas about the theory from, as he says, an analyst’s standpoint. This month he sets the scene.
As a technical manager in a software house, I’m more used nowadays to a spreadsheet than a compiler but my approach to life is still based on the mindset acquired through years of programming in low (and high) level languages. The human mind has a wonderful capacity for fuzzy logic. This is an essential function of decision-making with insufficient data. It also has a part to play in some brilliant conceptual leaps, which are obvious only in hindsight. Such lateral thinking is a major contributor to scientific and technological progress.
However computer languages punish woolly and incoherent thinking. The acronym ‘gigo’ (garbage in, garbage out) is just as true with modern development tools as it was with assembly language. It’s just less obvious. So working in a development environment tends to imbue a rigidly logical approach to problem solving.
This is a mindset that, I believe, has benefits in other areas of human endeavour and in particular when trying to comprehend the nature of the universe. This is a very wide topic, with philosophic, spiritual, and religious, as well as scientific connotations. I think that the approach of a logician has merit in all of these fields. However, I want to focus on the scientific aspects in general and relativity in particular.
Relativity: My interest in relativity began in 1978 when I read an article in Wireless World by Dr Louis Essen, a fellow of the Royal Society and one of the foremost authorities on the measurement of time. Dr Essen was convinced that the effects on time and space proposed by Einstein’s theory would result in some of the ‘ticks’ of an atomic clock being lost. To him, that was a fatuous suggestion. Eminent physicists replied to his article pointing out errors in his logic and expounding the ‘accepted’ interpretation. He then replied to their comments, and so on.
It did not occur to me at the time to ask why Dr Essen wrote in Wireless World, instead of a scientific journal. Wireless World is a well-respected popular magazine with a world-wide readership of hobbyists and professionals alike. But it is not an academic publication. I found out later that he had become a born-again Christian and so believed in the literal truth of the Bible. However, there is such a wealth of scientific evidence that the Earth is billions of years old that it is difficult to understand how an eminent scientist could come to believe that the world was literally made in seven days some thousands of years ago. After that, scientific journals would not publish his writings.
Anyway, this discussion was an eye-opener for me. I was surprised to note that, whilst both sides appeared to successfully point out weaknesses in the other’s position, neither seemed to be able to answer the criticisms of their own. Could it be that both interpretations were, at least partially, incorrect? This idea fascinated me. Just how accurate a model of the real universe is Einstein’s theory?
So I started to research the subject. I found a book containing translations of papers by Lorentz, Minkowski and Einstein. These included Einstein’s 1905 paper on his original theory of relativity and his 1916 paper on the general theory. This is a treasured possession. I can make no better suggestion to anyone who wants to “get it from the horse’s mouth” than to seek out ISBN 0-486-60081-5. You may not understand all the mathematics, but no matter. The concepts are intelligible without them.
In his 1916 paper, Einstein presented his general theory as a logical extension of the original theory. However, careful reading of both papers reveals quite a different story. The two theories are conceptually “chalk and cheese”. To understand this, we need first to understand the conceptual environment in which Einstein developed his ideas…
The Classical View: The classical view starts with Euclid, who formalised much of geometry around 300 BC. To this, in 1687, Newton added a detailed understanding of motion. Together, these pretty well defined our understanding of the mechanics of the universe. Geometry defines the physical space and physical relationships and mechanics defines the motion of material objects in that space. It’s important to understand that the classical view assumes the existence of a material space, called the ether, in which material objects exist. And so it has largely remained. Indeed, there would be no reason to question the universal application of Newtonian mechanics, if it were not for the very strange behaviour of light.
By the nineteenth century, light was known to travel at a finite velocity and it was assumed that this velocity was constant with respect to the ether. It was realised that, as the earth was moving through space with a significant velocity, measurements of the velocity of light should be affected by the movement of the measuring instrument (which was stationary with respect to the earth) as it moved with respect to the ether. So experiments were set up to test this. The most famous was Michelson’s interferometer experiment. The results of this were published in 1887 and they showed no discernible variation at all. It appeared that the velocity of light (in a vacuum) was fixed and finite, irrespective of the motion of the source and observer.
Scientists put forward a number of proposals as to how this strange result could arise. In 1895 Lorentz proposed that the motion of Michelson’s interferometer with respect to the ether created a ‘drag’ effect that shortened the dimensions of the instrument in the direction of motion. This effect exactly counteracted the variation in the velocity of light so that it appeared to be constant. He developed this idea and published a paper in 1904 that set out the forces on the atom that would result in the orbits of the electrons becoming elliptical, hence shortening the dimensions of the whole instrument along the direction of travel. This effect became known as the Lorentz transformation.
So the apparently strange behaviour of light could be reconciled with classical mechanics and the existence of a material space. However, the experiment had been intended to prove the existence of a material space. The negative result had been explained, but it did not, of itself, prove anything.
Einstein’s Original Theory of Relativity: Just a year later, Einstein came up with a dramatically different solution. He proposed that space did not exist as a material entity. There was no absolute state of rest against which all motion could be measured. All motion was relative to the material objects themselves, hence the description ‘relativity’. This was Einstein’s original concept of relativity. To me, this is the greatest conceptual leap of all time.
However, he also proposed his principle of relativity, which states that the same rules of physics apply in all frames of reference. According to this, two objects mutually at rest share the same frame of reference, but an object moving with respect to them has its own frame of reference. The principle relates what takes place when viewed from one frame of reference to what happens when viewed from another. The important point is that they would be different. Why?
As I’ve mentioned, Lorentz proposed that the physical dimensions of a material object change when it is in motion with respect to the ether because of a ‘drag’ effect. Einstein generalised this and proposed that the dimensions changed with the frame of reference. Furthermore, it was not only the dimensions of the physical objects that changed, the spatial distances between them changed as well. And that was not all. Not only space, but also time would be relative. Two events that are simultaneous in one frame of reference would occur at different times from another frame of reference. Wow!
In September, Terry describes flaws in this edifice and takes us on to the General Theory. You can contact Terry at tlonghurst@iap.org.uk.
[Interesting project or development? Let us know at eo@iap.org.uk!]
