Q&A: Following the debate – action at a distance
Following the debate – action at a distance
Question
You argued in the debate that in physics, “action at a distance” has no observational basis.
But we do in fact see that a change in one particle necessarily affects another. That is the observation.
The fact that we do not understand the interaction between the two particles, or that it contradicts clear foundations in physics, does not mean it cannot be regarded as something observed.
By your logic, one could say that until a few decades ago heredity was something non-empirical just because we didn’t know about DNA . . .
But clearly certain principles of heredity were evident even before the discovery of how it works, and that was considered something we observe
Answer
You see that there is an interaction, but not that it is carried out at a distance or not at a distance. The physicists’ assumption is that the action is not carried out at a distance (rather, there is mediation), and that has no empirical basis.
Discussion on Answer
I’m glad that such a genius physicist as yourself has appeared in our midst. A few comments, if I may nevertheless be permitted:
1. Bell’s theorem is not taught in first-year physics, and usually not in an undergraduate degree at all. So I do not recommend asking first-year students. But geniuses like me, of course.
2. Reading comprehension. I didn’t write that there is no action at a distance, but that this is a common assumption in physics even though it has no observational basis. And indeed, in physics they assume, without observational basis, that there is no action at a distance. That is why everyone is convinced there are gravitons, for example (even after Bell). True, in quantum theory Bell’s inequality challenges this (see below), but the very fact that everyone is agitated and looking for explanations, and that this is an exceptional result, shows that this really is the assumption in physics.
3. Not all interpretations of Bell’s inequality hang on locality. See Wikipedia there (or in the first-year course where you learned about Bell). By the way, the reason people look for another explanation is precisely because of that assumption. EPR is considered a paradox (though not a logical one) mainly because it contradicts locality. Well, Einstein and Rosen probably didn’t make it through first year.
4. Even if the inequality violates locality, that still does not mean there is action at a distance. Bell’s inequality does not deal with a force that one body exerts on another. In other words, not with interaction but with correlation (about the difference, ask first-year students).
5. And even if everything were correct, it is still possible that there is a medium that carries this correlation/influence. The fact that the correlation is fast does not mean it is carried out at a distance and without mediation. It may contradict the relativistic speed-of-light limit, but in any case one of the fundamental principles of physics has to break here.
6. Not for nothing, there is not a single physicist I know (at least after first year) who, בעקבות Bell’s inequality, gave up the assumption that there is no physical interaction at a distance. Except for you, of course.
Good luck in second year.
What does it mean that the assumption has no empirical basis? All the swans we’ve seen so far are white, so our assumption is that all swans are white—how is that not an empirical basis? Did I misunderstand?
Bell’s experiment is of course the swan whose color we still don’t really know.
What does that have to do with the principle of causality?
I wasn’t talking about the principle of causality. You wrote, “The physicists’ assumption is that the action is not carried out at a distance, and that has no empirical basis.”
That too has no empirical basis at all. On the contrary, empirically it seems that there is action at a distance (gravity, electric field).
Rabbi Michi’s example was completely mistaken. Every first-year physics student knows there are cases in which the principle of action at a distance is ruled out; look up Bell’s theorem on Wikipedia.