Science and Marxism

Galileo and the relativity of space

Some elementary scientific errors appear in Reason in Revolt, which quite undermine the authority of the author.

Some elementary scientific errors appear in Reason in Revolt, which quite undermine the authority of the author.

One is an inability to grasp Galileo’s ‘principle of relativity’, confusing it with Einstein’s relativity. In this chapter we will attempt to disentangle this confusion by discussing this principle of relativity as presented by Copernicus, Galileo, Newton – and more profoundly by Einstein.

Another error Woods makes is to proceed from this failure to the conclusion that modern physics is saturated with “subjective idealism” since, Woods argues, Einstein was always concerned with “the observer” rather than the physical processes taking place independently of any observer in what he believes to be absolute space and time.

Woods misunderstands the term “the observer”, as if Einstein means the particular, subjective viewpoint of an individual, rather than a location from which an objective measurement can be taken.

Copernicus’ revolution

Galileo Galilei (1564-1642)

Aristotle’s heavens appeared incorruptible to western astronomers until the seventeenth century when, in 1609, Galileo constructed his telescope. Galileo discovered that there was change in the spheres, because moons orbited Jupiter, and the Earth’s moon was pitted with craters and not perfect. This gave rise to a new consciousness among the most advanced thinkers in the Renaissance.

Stars seemed to some to stretch to infinity. But Galileo did not see infinity through his telescope, nor has it ever been seen – only inferred by extrapolation, by the quantitative extension of finite observations.

Galileo defended the Copernican system, which redrew the map of the universe by rearranging the ‘perfect spheres’ so that the sun rather than the earth was at the centre of the solar system.

Nicolaus Copernicus’ famous On the Revolution of the Heavenly Spheres, published in 1543, is thought to have invested the word ‘revolution’ with its ‘revolutionary’ connotations, in the sense of a complete change or an overthrowing of the old conditions.

In his opening remarks, Copernicus briefly contrasted his revolutionary alternative of an immobile universe in which the earth rotates with the old Aristotelian idea of immense but finite heavens which rotate daily round an immobile earth. Ptolemy of Alexandria (87-150 CE), Copernicus tells us, had asserted that if the earth rotated, “this movement, which would traverse the total circuit of the earth in twenty-four hours, would necessarily be very headlong and of an unsurpassable velocity.” This rotational velocity, Ptolemy says, would have violently torn apart the earth long ago and all the pieces would have “passed beyond the heavens, as is certainly ridiculous”. (On the Revolution of the Heavenly Spheres, book one, Introduction, point eight, pp22-3)

Ptolemy assumes that if the earth is rotating we would certainly experience it. In fact a point on the equator of the earth is moving, in round numbers, at an astonishing 1000 miles an hour as part of our 24 hour daily rotation. Yet we do not experience this motion. Ptolemy finds the idea ridiculous.

Copernicus replies: “Why didn’t [Ptolemy] feel anxiety about the world instead, whose movement must necessarily be of greater velocity?” In other words,  Copernicus argues, in this seminal work: Would not the much greater rotational movement of the heavenly spheres around the earth, as defended by Ptolemy, have torn them apart and thrown them outwards? But this objection was not meaningful to the ancient philosophers, since they believed the “heavenly spheres” to be “incorruptible” and unchanging, incapable of any disturbance.

Copernicus then asks the reader a quite remarkable question: Have “the heavens become so immense, because an unspeakably vehement motion has pulled them away from the centre, and because the heavens would fall if they came to rest anywhere else?”

This remarkable question bears comparison with two aspects of the Big Bang theory. Copernicus asks whether the universe is so large because it has expanded from the centre and whether this expansion has prevented the collapse, under the pull of gravity, of the heavens, which if they came to rest would be bound to fall back to the centre. These tentative suggestions remarkably anticipate modern theory. Copernicus seems to present in one brief remark essentially an explanation to the problem of why gravity has not caused the supposedly static universe (the model of the universe which Woods defends) to collapse in on itself – because it is expanding outwards rapidly. This problem of gravitational collapse is a problem for supporters of the static universe which Woods had not fully grasped 450 years later. Needless to say, this problem is naturally resolved by the Big Bang theory. It will be touched on further in the next chapter. 

Copernicus ponders: “[I]f this reasoning were tenable, the magnitude of the heavens would extend infinitely.” Perhaps Copernicus has in mind Aristotle’s potential infinity – that in this scenario, the heavens would go on expanding indefinitely. But if Copernicus means “infinitely” in the sense Woods presents it (Aristotle’s actual infinity), this could only be true if the universe had existed for an infinite period of time. Yet if the universe is expanding “from the centre”, it must have began at some finite point in the past.

Galileo’s defence of Copernicus

What were Galileo’s views on an infinite universe? Just nine years before Galileo began looking through his telescope, in 1600, Giordano Bruno was burned at the stake by the Inquisition, after being tortured for nine years for preaching that the universe was infinite. He refused to recant. So, perhaps not surprisingly, Galileo did not express, or at least did not publish, any views on whether the universe was infinite or not. But he did discover additional contradictions which the idea of infinity leads to, (anticipating some of the concepts of the late nineteenth century mathematician George Cantor, who we discuss very briefly below) and elsewhere notes that infinities “transcend our finite understanding… In spite of this, men cannot refrain from discussing them… we attempt, with our finite minds, to discuss the infinite, assigning to it properties which we give to the finite and limited; but I think this is wrong…” (Galileo, Dialogues Concerning Two Sciences, First day, p418)

The ‘corruptible heavens’ which Galileo viewed through his telescope implied – by Aristotle’s own admission – a beginning and end to the universe, and this was bound to disturb all accepted dogmas.

Motion is relative, not absolute

Galileo set out to defend the theory of Copernicus that the sun, not the earth, was the centre of the solar system. This meant that, in addition to its “violent” rotational motion, the earth must move with incredible speed round the sun. To prove this, Galileo needed to demonstrate the rather surprising fact that steady motion in a straight line, such as the earth’s motion approximated to, cannot be readily detected by someone experiencing this motion (unless by reference to external evidence). 

Now the bumps and jolts we often experience when in motion are little accelerations – changes in motion from one speed to another. Acceleration is not steady motion. This is critical to our understanding of Galileo’s argument, since our most common experience of motion will consist of increasing and decreasing acceleration, and this misleads us, as it did in Galileo’s time, that we can tell, without external reference, if we are in motion. 

Steady motion in a straight line cannot be intrinsically experienced – such motion is not an “absolute” property of an object, as Aristotle had taught. Let’s see how Galileo does this. 

In the section, Problem Not Resolved, Woods says:

Einstein was determined to re-write the laws of physics in such a way that the predictions would always be correct, irrespective of the motions of different bodies, or the ‘points of view’ which derive from them. From the standpoint of relativity, steady motion on a straight line is indistinguishable from being at rest. (p161)

The law that steady motion in a straight line “is indistinguishable from being at rest”, as Woods puts it, when properly understood, is an essential feature of Newton’s first law of motion. As mentioned earlier, Galileo argued that the earth moved, but despite this “violent motion”, people on earth should not experience that motion at all – that, in this particular sense, we find our “state of rest” indistinguishable from being in motion.

So this was no “re-write” of the laws of physics by Einstein. Here are Newton’s words, published in 1687:

Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon. (Principia, Axioms or Laws of Motion, Law I, p743)

It may be subtle, but the use of the little word “or” sets up an equivalence between the state of rest and the state of steady motion. As stated above, the bumps and jolts we generally associate with motion arise from accelerations, and acceleration is not steady motion. It was another of Newton’s laws that clearly distinguished acceleration from steady velocity, correctly termed, meaning steady motion in a straight line. To reach a steady speed we must first accelerate to that speed. Hence Galileo must pick an example where motion is very steady. Today we might imagine a person floating in a spacecraft with its thrusters turned off. Despite travelling at enormous speed, once the thrusters which accelerate the spaceship are turned off and the rocket is in steady motion, the objects and the astronaut experience weightlessness rather than any impression of the speed of the craft. A person on the earth experiences gravity rather than weightlessness, but no sense of the 30km per second speed of  the earth through space. We will return to this shortly.

Perhaps Newton had in mind our planet earth, or some other planet, when he set down his epoch making first law. Every “body”, such as, for instance, the earth, would continue in its “state of rest, or of uniform motion in a straight line” if it were not for a force such as that of gravity, which, as Newton understood it, pulls the earth round the sun. Similarly, a person sitting on the earth, in a state of rest, will continue in that state of rest, despite the steady motion of the earth, unless pushed, pulled or otherwise constrained to get up and do some work.

The influence that Galileo had on this law will perhaps becomes clear as we discuss how Galileo argued that it is impossible to tell if the earth is stationary, as the followers of Aristotle maintained, or moving — with reference only to observations confined to objects on earth — since the two states of a body, either in uniform motion or rest, are “indistinguishable” as Woods terms it, within the frame of reference of that body. (Admittedly our planet does not travel in a straight line, but, disregarding Einstein’s contribution to this question here, the earth’s path round the sun is so huge that it can be treated as if it is going in a straight line, and Galileo does so.)

So Newton’s law begins with Galileo’s physics and ends with a denial of Aristotle’s physics. Newton’s law predicted that a rock travelling along in space, (or one at rest in space with respect to some observer) will continue to travel along unless acted on by a force – such as gravity. This is indeed what we observe. By contrast, Aristotle believed that no force need be applied to a rock travelling along in space (or at rest) to send it hurtling to earth. Rather, for Aristotle and his followers, the rock’s place is down at the centre of the universe where earth is, and it will fall to the earth if unimpeded, for that reason.

As we shall show, Woods mistakes what became known as Galileo’s principle of relativity, enshrined in Newton’s first law of motion, for a supposed ‘re-write’ of the laws of physics by Einstein in his theory of relativity, which in fact takes Galileo’s principle of relativity as its starting point. Woods even uses the same terms, “rest” “motion” and “line” and yet does not recognise this elementary physics.

Furthermore, Woods seeks to undermine this law of motion, Galileo’s principle of relativity, all the time believing it to be a facet of Einstein’s relativity, asserting instead the existence of absolute space and time – meaning, that if an object is in motion, that motion is a property intrinsic to itself – and this means that it “experiences” that motion in the way that Aristotle conceived. Thus a person on earth should experience the earth’s 30km per second motion.

We must untangle this in what follows. This error leads Woods to take essentially the same position as the supporters of Aristotle in their dispute with Galileo in his defence of Copernicus. Copernicus, we should add in passing, briefly anticipates Galileo’s arguments. (On the Revolution of the Heavenly Spheres, book one, Introduction, point five, p23)

What is this fundamental law of physics, the principle of relativity, on which Newton based his first law of motion, and from which Einstein took the name ‘relativity’? Let us take a glimpse at what Galileo and Einstein said.

Galileo’s thought experiment

The followers of Aristotle’s orthodoxy in the early seventeenth century thought that if the earth was travelling round the sun, or rotating, this would cause many very visible effects:

How would birds find their nest again after they had flown from them? Why does a stone thrown up come straight down if the earth underneath it is rotating rapidly to the east? (The Galileo Project,

Aristotle himself provided arguments against the notion that the earth moved, since one school of ancient Greek philosophers, led by Pythagoras, proposed that the earth did move. For instance, Aristotle asks, why do “heavy bodies forcibly thrown quite straight upward return to the point from which they started” if the earth has moved in the meantime? (On The Heavens, book II, chapter 14)

In the same passage Aristotle also argued that if the earth moved, one would surely see the stars pass by: “… there would have to be passings and turnings of the fixed stars. Yet no such thing is observed. The same stars always rise and set in the same parts of the earth.” This was a very powerful argument, not experimentally refuted until stellar parallax was measured by powerful telescopes in the 1800s. (Stellar parallax is the apparent movement of a star caused by viewing it from different positions, for instance, when the earth has moved a sufficient distance in its orbit round the sun.) Galileo could only suppose (correctly) that the stars were at too great a distance for parallax to be observed with the naked eye.

Galileo suggested experiments to prove the followers of Aristotle wrong. Adopting a popular, accessible style and writing in the native language rather than the scholars’ Latin, Galileo begins by asking his audience to imagine they are shut up “with some friend in the main cabin below decks on some large ship”. While the ship is stationary, Galileo suggests conducting a number of experiments designed to test motion in space, such as throwing and jumping, and setting a bottle to drip into a jar below. Then, he suggests:

… have the ship proceed with any speed you like, so long as the motion is uniform and not fluctuating this way and that. You will discover not the least change in all the effects named, nor could you tell from any of them whether the ship was moving or standing still.  (Dialogue Concerning the Two Chief World Systems)

The ship, of course, represents the earth. Galileo is at pains to show that motion is “indistinguishable” from rest under these conditions, the accusation Woods levels at Einstein. 

The water still drips directly into the jar below – it does not fall behind the jar as the ship moves forward steadily. Many people have been below decks on a ship or car ferry, where you cannot see out, and experienced something similar: you cannot be sure if the ferry is moving or not, so long as it is going at a constant velocity. Galileo’s point is that a scientist, conducting experiments, could not determine by any experiment whether the ferry or, of course, the earth, was in constant motion or stationary either.

Einstein calls this Galileo’s principle of relativity.

ScientistMotion Universe
Table 2. Schematic summary of the views of Galileo added to table 1.

Einstein’s railway carriage

Thus far, the matter is quite clear. Einstein deepens this understanding, by discussing the trajectory of an object as seen from the two different standpoints – one at rest, and one in motion. And he truly deepens our grasp of precisely what it means to see the equivalence of these two.

Einstein discusses Galileo’s principle of relativity, which he calls “the fundamental law of the mechanics of [Galileo] Galilei-Newton” at the very beginning of his short popular primer, Relativity (first written in 1916 and still in print). He poses two questions:

I stand at the window of a railway carriage which is travelling uniformly, and drop a stone on the embankment, without throwing it. Then, disregarding the influence of the air resistance, I see the stone descend in a straight line. A pedestrian who observes the misdeed from the footpath notices that the stone falls in a parabolic curve. I now ask: Do the ‘positions’ traversed by the stone lie ‘in reality’ on a straight line or on a parabola? Moreover, what is meant here by motion ‘in space’? (Einstein, Relativity, p9)

Dropped from the train, as seen from the footpath, the stone will continue moving forward as well as downwards, because before its release it is already set in motion forward by the forward motion of the train. Its downwards motion is accelerating under gravity. It will therefore cut out a curve (a parabola) in space as viewed from the footpath. You can plot this motion out on a piece of paper. But the train passenger, since he or she is also moving forward at the same speed as the stone, only observes the downward movement, so the stone appears to fall straight down to the passenger. If you find it difficult to visualise the effect of the stone falling without air resistance, on a fast moving train, imagine that the stone is dropped inside the carriage rather than out. It drops straight down. So it would outside the train, if it were not for air resistance, from the point of view of the train passenger.

Einstein reminds us that Galileo and Newton (in respect of his first law of motion) have shown that in reality both views, the one from the train, and the one from the footpath, are equally valid. Both views of the trajectory of the “misdeed” of dropping the stone, whether falling in a parabola or a straight line, furthermore, are objective descriptions of reality. This is quite a striking fact which we will explore further. But neither views are merely subjective impressions. Despite what Woods maintains, the subjective thoughts or impressions of individuals do not come into it.

Woods argues: “Einstein regretted his earlier subjective idealism, or ‘operationalism’, which demanded the presence of an observer to determine natural processes.” (p167) Einstein never demanded the presence of an observer to determine natural processes. It is a “complete misinterpretation of Einstein’s ideas” as Woods himself says slightly earlier (p163), without appearing to understand what he says. Einstein proceeds to re-phrase his own words this way:

The stone traverses a straight line relative to a system of coordinates rigidly attached to the carriage, but relative to a system of coordinates rigidly attached to the ground (embankment) it describes a parabola. (Relativity, p10)

It helps to consider the train to be a substitute for the earth. When we drop a stone on the earth it falls straight down despite the earth moving. What concerns us is the relative positions of the stone, as measured according to two different system of coordinates, or frames of reference, one moving and one stationary – the train and the footpath.

But does one frame of reference offer a correct description, while the other is merely secondary? No, they are both correct. At first, we may be tempted to say that the pedestrian on the footpath has the correct view or, to put the same thing another way, that the stone, as measured according to the frame of reference of the earth, is the correct measurement, because the pedestrian is the ‘stationary’ one, standing on the ‘stationary’ earth.

But the earth is not stationary. We must keep in mind that in the few seconds it took for the stone to fall, the earth and the stone have travelled perhaps sixty kilometres or more around the sun. Why take the earth as the correct or absolute reference point? In addition, the sun itself travels round our galaxy, and our galaxy is moving in a complex gravitational dance with our local cluster of galaxies. And all independent clusters of galaxies in the universe are moving away from us at great speed, in proportion to their distance from us.[1]

Whose space is the correct space? From the point of view of physics, each view, each measurement, whether from the railway carriage, the footpath, or the Andromeda galaxy, is equally valid. According to the Newtonian laws of motion which begin with Galileo’s insight (and which Newton acknowledged), the view from Andromeda is just as valid as the view from the train. Hence motion and space are relative to the observer (whether that observer is a person or a scientific instrument is irrelevant), meaning, relative to the frame of reference you choose to take – the train or the embankment in this case. 

Einstein’s universe

Now, according to classical Newtonian physics, we have no trouble at all translating the measurements of one frame of reference into that of another. They have a very simple, physical relationship. Suppose the train is moving at twenty miles an hour and a passenger is walking towards the front of the train at three miles an hour in the railway carriage. To put it another way, relative to the railway carriage frame of reference, the passenger is moving at three miles an hour. By simple addition, we say that the passenger is moving at twenty-three miles an hour relative to the footpath frame of reference – the speed of the train plus the speed of the passenger in the carriage.

We make this rather obvious point to make clear that no-one, whether Galileo, Newton or Einstein, is suggesting that, because the measurements are, in the common idiom, relative to the observer, these measurements are “subjective” in some way, or that physics has wallowed in subjective idealism ever since Galileo, which is the unintended essence of Woods’ claim.

However, Einstein realised that these calculations fail to take into consideration the speed of light. When we observed the train moving, we did so with the aid of light. But light does not travel instantaneously as our Newtonian calculation above assumed but at a definite speed. Furthermore, light has very unexpected properties. It is only once we have learnt about the strange qualities of light and have taken them into account that we can start to discuss Einstein’s universe. (In order to calculate the real transformation of the speed of the passenger relative to the carriage into his or her speed as measured from the platform, an equation associated with the physicist Hendrik Lorenz must be used, which takes the strange properties of light into account: the Lorenz transformation.)

What is space?

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. (Relativity, p10)

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 Woods cannot claim to have the authority of Marxism on this question (even if it were correct to use Marxism in this way). In fact, 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. And thus, as we will very shortly see, Woods expects that a person travelling very fast (such as someone sitting on the fast-moving earth) would experience that motion in “material damage” to their internal organs.

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.

This is the deeper understanding of the meaning of the statement that steady motion and rest are “indistinguishable”, as expressed by the fact that you do not experience the motion of the earth while sitting reading this page of text. 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 calling 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 commonly used ‘twins’ example of the effect of motion according to the theory of relativity. Here, one twin goes on a high-speed intergalactic journey and returns. The effect is that she will have aged less than her earthbound twin – the amount depending on what fraction of the speed of light she travelled. 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.

Woods begins:

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, such as the earthbound twin). 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.” (Page 165, My emphasis)

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 today can generate enough g-forces to kill the pilot if sustained for long enough. Einstein’s later general theory of relativity, published in 1916, deals with acceleration, and he showed that acceleration too can affect time and space.

But 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 a frame of reference confined purely to the spaceship, the astronaut feels herself to be 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).

It is perhaps necessary to add that currently no spaceship can remotely approach the kind of speeds that would be necessary to observe a twin “time travel” years into the future in the way that Einstein’s theory of relatively revealed. These speeds must be a sizable fraction of the speed of light. Space flight currently renders astronauts imperceptible fractions of a second younger any earthbound twin, as measured by atomic clocks. Scott Kelly, who spent 520 days in orbit travelling at 28,000km an hour round the earth, is now 5 milliseconds younger than his twin Mark Kelly, reported (Einstein’s ‘Time Dilation’ Spread Age Gap For Astronaut Scott Kelly & his Twin, 13 July 2016).

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]

Next: Newton: belief and contradiction

[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. Our local cluster of galaxies is travelling at twice this speed in the direction of the constellation Crater. (NB: Incidentally, unlike velocity, rotational movement can be determined by experiment.)

[2] 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)

This chapter was revised for the 2022 WordPress edition.