Example from CERN

confusion (YOU ARE HERE)

Example from CERN

This example from Speakable and Unspeakable in Quantum Mechanics, by John Bell (page 67) shows the confusion and controversy associated with relativity theory. Although relativity theory fits with observed phenomena, the causes of the phenomena are not apparent, which results in confusion.
Do you agree with Bell that the thread will break?

Speakable and unspeakable in quantum mechanics

Three small spaceships, A, B, and C, drift freely in a region of space remote from other matter, without rotation and without relative motion, with B and C equidistant from A (Fig. 1).

Fig. 1.

On reception of a signal from A the motors of B and C are ignited and they accelerate gently (Fig. 2).

     Let ships B and C be identical, and have identical acceleration programmes. Then (as reckoned by an observer in A) they will have at every moment the same velocity, and so remain displaced one from the other by a fixed distance. Suppose that a fragile thread is tied initially between projections from B and C (Fig. 3). If it is just long enough to span the required distance initially, then as the rockets speed up, it will become too short, because of its need to Fitzgerald contract, and must finally break. It must break when, at a sufficiently high velocity, the artificial prevention of the natural contraction imposes intolerable stress.
     Is it really so? This old problem came up for discussion once in the CERN canteen. A distinguished experimental physicist refused to accept that the thread would break, and regarded my assertion, that indeed it would, as a personal misinterpretation of special relativity. We decided to appeal to the CERN Theory Division for arbitration, and made a (not very systematic) canvas of opinion in it. There emerged a clear consensus that the thread would not break!
     Of course many people who give this wrong answer at first get the right answer on further reflection.

The reader will find that the quantum medium view permits a clear and unambiguous explanation of the above problem. It shows why the thread will break, as Bell states, and that there is an underlying complexity to this problem that is obscured by relativity theory.

(Thanks to Philip Pearle of Hamilton College for this example.)

Return