Ho citato piu' volte in passato il lavoro di Eberhard del 1989 (si puo'
scaricare alla pagina
http://mio.discoremoto.alice.it/brunodisco/) nel quale
viene presentato il modello che io ho poi riproposto nel 2005. All'epoca non
conoscevo quel lavoro, quindi nel 2005 non ho potuto fare alcun confronto
fra il mio lavoro e quello di Eberhard. In post recenti (sia qua che su
free.it.scienza.fisica) ho sottolineato quale e' quello che a me pare essere
l'unico punto essenziale nel quale quanto ho detto io si distingue da quanto
detto da Eberhard.
Oggi ho rapidamente sfogliato un altro articolo di Eberhard, scritto nel
1993,
(
http://www.osti.gov/bridge/servlets/purl/10191801-vaC5R6/10191801.PDF)
sullo stesso argomento.
A parte il fatto che cominciano a venirmi alcuni dubbi su quanto siano
effettivamente rilevanti le differenze fra quanto dice Eberhard e quanto
dico io (dubbi che non potro' dissolvere finche' non decidero' di studiarmi
per bene i dettagli dei lavori di Eberhard), quello che posso intanto notare
come decisamente interessante nel lavoro del 1993 e' il primo paragrafo, dal
titolo "A Historical Precedent".
Sotto riporto il paragrafo per intero; si potra' notare che Eberhard dice
esattamente le stesse identiche cose che dicevo qualche giorno fa nel thread
"Paradosso del gatto di Schr�dinger".
"It is the contention of this paper that loophole free EPR experiments [1]
would not rule out all forms of "locality per say," i.e. would not
necessarily imply that influences can be exerted at a distance
instantaneously without the mediation of an ether. The argument is inspired
by a historical precedent, from Newton's times, when the principle of
locality was threatened already. In Newton's theory of gravitation,
celestial bodies exert attractive forces on each other, instantaneously at a
distance and through vacuum, i.e. without an apparent material support to
mediate that action at a distance. However, in a letter, Newton expressed
himself in the following terms [2]:
...That gravity should be innate, inherent, and essential to matter, so that
one body may act upon another at a distance through a *vacuum*, without the
mediation of anything else, by and through which their action and force may
be conveyed from one to another, is to me so great an absurdity that I
believe no man who has in philosophical matters a competent faculty of
thinking can ever fall into it ....
That quote shows that, in Newton's times, the existence of "something" to
mediate actions at a distance was not an idea that could be disposed of
easily, even though the theory of gravity at the time seemed to point in
another direction. Today, because predictions of quantum theory concerning
the EPR-paradox [3] have been shown to imply instantaneous actions at a
distance [4], that locality principle is in jeopardy again, but, now as in
Newton's time, it is natural that one look for possibilities to hang on to
that principle.
There was a remarkable development of gravitation theory, long after
Newton's letter, when that theory was modified and did not involve
instantaneous actions at a distance anymore. In "general relativity" indeed,
gravitational effects propagate in gravitational waves at the finite
velocity c. General relativity is in agreement with experimental results of
today, but it is also compatible with astronomical observations that
justified Newton's gravitation theory, because the latter observations had
measurement errors which made the difference between instantaneous and
finite-speed actions at a distance unnoticeable.
In this paper, it is suggested that the same circumstances may apply again
to the present interpretation of EPR experiments [5] against locality and
that this can be true even if and when a loophole free EPR experiment [1] is
performed, if and when it demonstrates the existence of actions propagating
faster than c. Then experiments that have confirmed Lorentz invariance and
restricted relativity can be reinterpreted in order for the theory to cope
with those superluminal velocities. To demonstrate this point, it is
sufficient to construct one model that accounts for all experimental data to
date and is local. Such a model exists [6]. It is not claimed to yield the
correct description of phenomena in nature but it is an example to prove the
argument."
[1] N.D. Mermin, "The EPR experiment - thoughts about the 'Loophole,' " New
Techniques and and Ideas in Quantum Measurement Theory, edited by D.M.
Greenberger (New York Academy of Science, New York, 1986) pp. 422-428.
[2] I. Newton in a letter to R. Bentley, 1692/3, quoted in Theories of the
Universe. M.K. Munitz, ed., The Free Press, New York, (1957) 217.
[3] A. Einstein, B. Podolsky and N. Rosen, Phys. Rev. 47 (1935) 777.
[4] J S. Bell, Physics 1 (1964) 195; followed by generalizations : J.F.
Clauser, M.A. Home, A. Shimony and R.A. Holt, Phys. Rev. Lett. 23 (1969)
880; H.P. Stapp, Phys. Rev. D 3 (1971) 1303; J.F. Clauser and M.A. Horne,
Phys. Rev. D. 10 (1974) 526; J.S. Bell, CERN preprint Th 2053, reproduced in
Epistem. Lett. (Assoc. F. Gonseth CP 1081, CH-205 Bienne) 9 (1975) 11.
[5] S.J. Freedman and J.F. Clauser, Phys. Rev. Lett. 28 (1972) 938; J.F.
Clauser, Phys. Rev. Lett. 37 (1976) 1223; E.S. Fry and R.C. Thompson, Phys.
Rev. Lett. 37 (1976) 465; A. Aspect, P. Grangier, and G. Roger, Phys. Rev.
Lett. 47 (1981) 460; ibid. 49 (1982) 91; A. Aspect, J. Dalibard, G. Roger,
Phys. Rev. Lett. 49 (1982) 1804; and many others.
[6] P.H. Eberhard, in Quantum Theory and Pictures of Reality, W. Schommers,
ed., Springer Verlag, Heidelberg (1989) 169.
Chiudo ricordando che anche in questo articolo Eberhard sostiene che il
realismo locale ha assicurato il "pareggio come minimo" con la stessa
intransigenza con la quale lo sostengo io. La pagina 6 si chiude con queste
parole:
"Therefore the model is compatible with any *tested* prediction of quantum
theory and the model cannot be ruled out by any past or future experiment
where the predictions of quantum theory are verified. The experiment can
only set a lower limit for V [le misure del gruppo di Gisin, mi pare del
2001, danno V>10^4 c, pero' quell'esperimento ha dei problemi riguardanti
l'orientazione dell'apparato sperimentale. Potrebbe quindi anche essere
V<10^4 c (se il riferimento privilegiato per la propagazione dei tachioni
non fosse, come ipotizzato dal gruppo di Gisin, il Microwave Backgroung
Reference). L'esperimento di cui parlavo giorni fa, che vorrei tanto poter
riprendere, non ha i problemi di orientazione suddetti, per quanto ne abbia
altri]".
L'articolo si chiude cosi':
"In addition, before any violation is found [individuare sperimentalmente
delle violazioni (e, naturalmente, individuarle nel senso indicato dal
modello) equivarrebbe alla vittoria per il realismo locale], the model can
be used by anyone agreeing with Newton's above quoted statement and wanting
to justify his belief in "locality." "
--
Bruno Cocciaro
--- Li portammo sull'orlo del baratro e ordinammo loro di volare.
--- Resistevano. Volate, dicemmo. Continuavano a opporre resistenza.
--- Li spingemmo oltre il bordo. E volarono. (G. Apollinaire)
Received on Tue Nov 04 2008 - 20:13:27 CET