Asking what is meant by motion in space, Einstein says we “cannot form the slightest conception” of what ‘space’ means, since it seems to have two quite different values according to the person on the train and the pedestrian. Instead, he reconstructs the description of the stone’s trajectory in terms of two systems of coordinates – the moving train and the footpath. He concludes:
“there is no such thing as an independently existing trajectory but
only a trajectory relative to a particular body of reference.”
Therefore, in popular terminology, the motion of the stone dropped from the train must always be described according to some ‘observer’ – a particular body of reference – the earth, the train, the sun, etc, to have any meaning.
This is what Woods considers to be subjective idealism. But Engels also understood that there was no such thing as an independently existing trajectory. When Engels first conceived of writing about the dialectics of nature, in 1873, he began by noting the following:
“1. The first, simplest form of motion is the mechanical form,
pure change of place:
a) Motion of a single body does not exist – [it can be spoken of]
only in a relative sense…”
Dialectics of Nature, p329
In words, Woods sometimes denies and sometimes echoes the idea that time and space are bound up with matter. But when he argues that, “Time and space are properties of matter, and cannot be conceived of separately from matter” (p146), it becomes clear from the context that Woods is not embracing Einstein’s theory of relativity, but essentially arguing that if a body is travelling at a certain speed, this motion through space and time is an inherent property of that body, without reference to any other body, in other words, not relative to it. In this sense, it is an expression of absolute space and time.
The earth’s motion must be judged in relation to other bodies, such as the sun. Taken as a single body, the earth’s motion “does not exist”, as Engels puts it. We may treat the earth, in accordance with our day-to-day earthbound experience, as stationary. The earth’s creatures do not experience its motion because space is relative. Remember that all we are discussing here is Galileo’s principle of relativity and Einstein’s discussion of it. But Woods rejects this, thinking he is rejecting Einstein’s “subjective idealism”.
Clocks, twins and time
Despite the fact that he calls Einstein’s special relativity “one of the greatest achievements of science” (p160), Woods proceeds, sometimes insidiously and sometimes openly, to attempt to denigrate Einstein’s relativity, particularly in the sections Problem Not Resolved, and Idealist Interpretations. (Einstein’s ‘special relativity’ deals only with the special case of motion unaffected by gravity or acceleration. His ‘general relativity’ includes gravity.)
Woods discusses the famous ‘twins’ example, where one twin goes on a high-speed intergalactic journey and returns having aged less than her earthbound twin. Woods’ treatment is impeded by his failure to grasp Galileo’s principle of relativity. Let us see how Galileo’s science contradicts Reason in Revolt.
“A controversial idea here is the prediction that a clock in motion will
keep time more slowly than one that is stationary. However it is
important to understand that this effect becomes noticeable at
extraordinarily high speeds, approaching the speed of light.” (p163)
There is much that is wrong here but, above all, the effect of motion on the timekeeping of clocks is not “controversial”, it is incontrovertibly proved (as Woods admits elsewhere). For instance, navigation systems using the Global Positioning System (GPS) constantly make use Einstein’s special and general theory of relativity in about a dozen distinct types of calculations, in order to ensure the accuracy of their results, twenty-four hours a day. It is quite misleading for Woods to witheringly assert: “Unlike special relativity, experimental tests which have been carried out on [the general theory of relativity] are not very many.” (p172) Fifty years ago Woods’ assertions were true. The reader may have noticed already that Reason in Revolt is trapped in a kind of fifty-year-old time warp. (This is true for the second half of the book also, which we do not discuss in this review.)
In Einstein’s Universe, Nigel Calder describes the definitive experiment on this question, carried out in 1971 using four robust atomic clocks, which were placed aboard regularly scheduled commercial passenger jet aircrafts which took them right around the world. “One circumnavigation was made eastwards and one westwards, both journeys taking about three days. The result of the experiment was that the clocks no longer agreed about the time of day.” The clocks were compared to similarly highly accurate atomic clocks which remained at the US Naval Observatory in Washington DC. (Einstein’s Universe, p60)
The two experimenters, JC Hafele and Richard Keating, had predicted a loss of 40 nanoseconds eastbound, and the clocks did indeed lose time, although it was slightly larger, at 59 nanoseconds. Westbound the experimenters predicted a gain of 275 nanoseconds and the clocks gained 273 nanoseconds, a very close agreement indeed.
“In Newton’s universe, there would be no accounting for the discrepancies in such highly reliable instruments,” Calder remarks. Since then, subsequent experiments have tested the theory to far greater precision.
Woods proceeds to admit that this ‘time dilation’ effect, as it is called, has indeed been observed, and now objects: “The whole question hinges upon whether the changes, observed in rates of atomic clocks, also apply to the rate of life itself.” (p164) Woods’ line of argument could only arise if he has not grasped Galileo’s principle of relativity, since it does not matter in the least what is moving – living organisms or mechanical clocks – the point is their steady motion is measured relative to a stationary observer (another frame of reference, an earthbound twin, etc). It is only relative to earthbound clocks that the clocks on the spaceship run slow.
In the section Idealist interpretations, Woods says, “it is not easy to see” how “the process of aging” of the astronaut twin can be “fundamentally affected either by velocity or gravitation, except that extremes of either can cause material damage to living organisms.” He continues:
“If it were possible to slow down the rate of metabolism in the way
predicted, so that, for example, the heart-beat would slow to one
every twenty minutes, the process of aging would presumably be
correspondingly slower. It is, in fact, possible to slow down the
metabolism, for example, by freezing. Whether this would be the
effect of travelling at very high speeds, without killing the organism,
is open to doubt.” (p165)
Relativity, of course, makes no prediction about slowing down a person’s metabolism. It is not a biological science. But can extremes of velocity “cause material damage to living organisms” as Woods appears to believe? The followers of Aristotle’s orthodoxy in the early seventeenth century thought that if the earth was “travelling at very high speed” it would cause very visible effects, and ridiculed the idea mercilessly. Yet the entire earth’s population is going round the sun at roughly thirty kilometres a second, or one ten-thousandth of the speed of light.
Woods feels that the time dilation effect on “life itself” is “open to doubt” because he is convinced that travelling at very high speeds is injurious to life. Would not this very high speed “kill the organism” or at least cause some “material damage to living organisms” just as Woods ponders it might? Does our metabolism slow down? It does not, no matter how fast we travel at a steady velocity, because space is relative, as Galileo explained.
We must emphasis here another point that Woods fails to grasp. What is being discussed here is constant velocity or steady motion in a straight line. Woods also uses this term: “From the standpoint of relativity, steady motion on a straight line is indistinguishable from being at rest.” (p161) Einstein’s special theory of relativity, written in 1905, takes the special case of steady motion in a straight line (velocity), and excludes acceleration. Acceleration is quite different to steady motion. An accelerating jet fighter plane can generate enough g-forces to swiftly kill the pilot. Einstein’s later general theory of relativity, published in 1916, deals with acceleration, and he showed that acceleration too can affect time and space.
The entire point in the twins example is that the clocks and heart-beat of the space traveller moving at high speed are slow only relative to her twin on the earth. The motion of the spaceship is not an absolute motion, a spaceship which has the “property” of moving at high speed. Although it must have accelerated to its current speed, now it is cruising in steady motion it is only moving at its current high speed relative to the earth from which it departed. Relative to her frame of reference, the astronaut is stationary, and her life processes are unaffected by her relative motion as she floats weightlessly inside her craft. She could “survive thousands of years into the future” (p164) but only as measured from the earth, only into the future of the earth, not as measured from the spaceship, where she will live a normal life span – disappointing as that may be. It is clear that Woods cannot consistently grasp Galileo’s principle of relativity here, let alone the ‘twins’ example itself in relation to Einstein’s relativity (which is more involved than can be adequately discussed here).
The discussion of Einstein’s relativity in Reason in Revolt never grasps the seventeenth century scientific debate between Galileo and Aristotle’s supporters, and at no point clearly recognises the validity of Galileo’s arguments (as Engels certainly did) or of Newton’s first law of motion. Essentially, in this respect, Reason in Revolt sides with those who supported Aristotle’s views of a stationary earth, at the centre of the celestial spheres.
Woods makes a further error when, as discussed above, he asked whether “the changes, observed in rates of atomic clocks, also apply to the rate of life itself”. Woods tries to draw a distinction between processes taking place in humans or other living things and those in inanimate objects moving at high speeds. This is an unintentional departure from materialism, since it suggests humans or living things have a special, non-physical (and by implication therefore spiritual) essence which does not necessarily always obey the laws of physics by which material things are bound.
Criticising modern cosmological applications of Einstein’s relativity, Woods intones, “Here the study of philosophy becomes indispensable” (p216) but he has not grasped the problem, the most basic, elementary physics and, in fact, cannot escape from Aristotelian or Newtonian concepts of absolute space and time, on which his philosophical criticism of modern science is based. Philosophy is no use when you have no grasp of your subject.
Einstein applied the same relativity principle to time, but these considerations still do not yet depart, in essence, from classical Newtonian laws of motion. The issues that Einstein addressed which brought about an entirely new understanding of the universe will be briefly touched on later.2
1 For those familiar with these concepts: according to the satellite COBE’s 1996 measurements, our solar system is moving at roughly one thousandth the speed of light (about 300 kilometres per second) in the direction of the constellation Leo, relative to the cosmic background radiation. http://arxiv.org/PS_cache/astroph/pdf/9601/9601151.pdf. Our local cluster of galaxies is travelling at twice this speed in the direction of the constellation Crater. http://www.arxiv.org/abs/astroph/0210165 (NB: Incidentally, unlike velocity, rotational movement can be determined by experiment.)
But we are justified in considering so closely Galileo’s contribution since, as the physicist Hermann Bondi once said, “I always say that Einstein’s contribution has a name for being difficult, but it is quite wrong. Einstein’s contribution is very easy to understand, but unfortunately it rests on the theories of Galileo and Newton which are very difficult to understand!” (Quoted by Gleik, Issac Newton, p 200)