The Armstrong Alert

“There are few words which are misused in physics as much as ‘observer’. Sometimes it seems to mean ‘receiver’, sometimes ‘bystander’”.(7) This trenchant remark by the late Harold L. Armstrong (1921-1985), which I for myself have dubbed the Armstrong Alert, we cannot take to heart enough when dealing with relative versus absolute cosmic motions. To neglect it – I speak from sad experience! — is to court defeat in debates and disaster in deductions. (Even when outlining this essay, however much aware of the danger, I caught myself napping). A bystander is by definition not involved with, or a partaker in, the act or process he is looking at. And the point the Alert impresses on us is that relative to the Universe as a whole we can only be “inside” observers, not bystanders surveying that Universe in its entirety and determining its manner of motion – if any – from a platform at rest against a background at rest. Yet the fact is that we ever and again unthinkingly slip into an attitude of mind that forgets this cerebral trespass. Even worse: in our ratiocinations we may jump from “inside” to “outside” and back again without realizing the fallacy of not taking this jump into account. It will sometimes, and in the present paper unavoidably, become necessary to talk “as if” we were bystanders, but only for a Bystander, Who ever was, is, and will be, is the Universe truly an “object” transcended by Him.

Two striking examples, culled from among the many that are readily available, will illustrate this ever present fallacy. When Martin Gardner, enthralled by Einstein’s theories, attempts to demolish the late Herbert Dingle’s arguments against the validity of the notorious Twin Paradox, he is forced to admit that Dingle has a point. Whether the spaceship with John aboard is supposed to move rapidly away from the Earth, or the spaceship is taken to be the fixed frame of reference and stay-at-home James is condemned to blast off into the wild blue yonder – it makes, there being no absolute motion, mathematically no difference. Yet, Gardner pontificates, Dingle is wrong when he therefore does not accept the paradox. “Why wouldn’t the same calculations, with the same equations, show that earth-time slowed down the same way? They would indeed if it were not for one gigantic fact: when the earth moves away, the entire universe moves with it” (Gardner’s italics).(8)

Restricting the argument to the motions involved, we can only say something sensible about those when we judge them against a background taken to be at rest. “Inside” the box of the Universe modern science acknowledges no absolute motion to be observable. It is hence six of one or half a dozen of the other whether John leaves James or James leaves John behind – a background against which to judge the matter is immanently not in sight, and Dingle’s conclusion can therefore kinematically not be faulted. However, our relativity apostle Gardner now plays a “jack-in-the-box” game, and by doing that snatches, he thinks, victory out of the jaws of defeat. Apropos of nothing he propels himself in his imagination out of our cosmical box to a place absolutely at rest against a background at rest “outside” our Universe, from which transcendent platform, he assures us, we shall see his “gigantic” fact. Or if we prefer to state it otherwise: from a foothold “inside” the Universe, but independent of it, taken to be at rest as observed from that extra-cosmical platform, he can show us the difference between the immanently relative motions of spaceship and Earth.

What Gardner does not realize is that by using the notion of a moving Universe he is de facto, as Russell would say, fudging a metaphysical argument into the discussion. And neither good, nor bad, nor bogus science should be allowed to get away with such statements about observations that can only be made from the inaccessible regions beyond the starry dome – they are, alas, not in the province of physical science!

Earlier in the same context Gardner still reasons soberly — scientifically. “Do the heavens revolve or does the earth rotate? The question is meaningless. A waitress might just as sensibly ask a customer if he wanted ice cream on top of his pie or the pie placed under his ice cream.”(9) But does this tally with the position he takes in the Twin Paradox controversy? If it makes a gigantic difference whether either the Earth is moving or the spaceship, is it then meaningless to ask whether from the unattainable viewpoint Gardner adopts contra Dingle there is no difference between an Earth at rest and an Earth rotating in at least a kinematic sense? Is it not inconsistent and unscientific to introduce an imaginary extramundane observer when one is logically pinned down, but to shy away from that tactic when one deems it expedient to forego a “meaningless” metaphysical view?

“Is the universe rotating?” P.Birch has asked.(10) “Yes, of course”, a Christian simpleton will answer, every day we see the stars revolve around us.” Yet too hastily, I think, all and sundry will laugh this fellow out of court. For the term “rotation”, if it is to mean anything, presupposes an axis at rest against a background at rest. But such a hold, 20th century science acclaims, we do not have. Clearly the only sense in which Birch’s question makes sense is that he is asking whether, from a rockbottom position outside” the Universe, or from a viewpoint extra-cosmologically guaranteed to be at rest “inside” it, there exists an axis around which the starry dome, carrying all celestial bodies, is seen to be rotating. This means that he is leaning on the broken reed of a metaphysical presupposition, which hence entails that, e.g. the “New Scientist”, if it wants to judge justly, should vilify him as it vilified Hoyle for the invocation of supernaturalism in the latter’s “The Intelligent Universe”. For Birch, by asking the above question, which is only extranaturally answerable, has, like Sir Fred, “betrayed the very standard which the scientific community has been built”.(11)