The best case for thinking that quantum mechanics is nonlocal rests on Bell's Theorem, and later results of the same kind. However, the correlations characteristic of EPR-Bell (EPRB) experiments also arise in familiar cases elsewhere in QM, where the two measurements involved are timelike rather than spacelike separated; and in which the correlations are usually assumed to have a local causal explanation, requiring no action-ata-distance. It is interesting to ask how this is possible, in the light of Bell's Theorem. We investigate this question, and present two options. Either (i) the new cases are nonlocal, too, in which case action-at-a-distance is more widespread in QM than has previously been appreciated (and does not depend on entanglement, as usually construed); or (ii) the means of avoiding action-at-a-distance in the new cases extends in a natural way to EPRB, removing action-at-a-distance in these cases, too. There is a third option, viz., that the new cases are strongly disanalogous to EPRB. But this option requires an argument, so far missing, that the physical world breaks the symmetries which otherwise support the analogy. In the absence of such an argument, the orthodox combination of viewsaction-at-a-distance in EPRB, but local causality in its timelike analogue -is less well established than it is usually assumed to be. "Our intuition, going back forever, is that to move, say, a rock, one has to touch that rock, or touch a stick that touches the rock, or give an order that travels via vibrations through the air to the ear of a man with a stick that can then push the rock-or some such sequence. This intuition, more generally, is that things can only directly affect other things that are right next to them. If A affects B without being right next to it, then the effect in question must be indirect-the effect in question must be something that gets transmitted by means of a chain of events in which each event brings about the next one directly, in a manner that smoothly spans the distance from A to B. . . .We term this intuition 'locality.' Quantum mechanics has upended many an intuition, but none deeper than this one. And this particular upending carries with it a threat, as yet unresolved, to special relativity-a foundation stone of our 21st-century physics." ([1], p. 32.) 1 See, e.g., [36] and [10] for the former viewpoint, and [17] for an introduction to the latter.
To demarcate the limits of experimental knowledge, we probe the limits of what might be called an experiment. By appeal to examples of scientific practice from astrophysics and analogue gravity, we demonstrate that the reliability of knowledge regarding certain phenomena gained from an experiment is not circumscribed by the manipulability or accessibility of the target phenomena. Rather, the limits of experimental knowledge are set by the extent to which strategies for what we call ‘inductive triangulation’ are available: that is, the validation of the mode of inductive reasoning involved in the source-target inference via appeal to one or more distinct and independent modes of inductive reasoning. When such strategies are able to partially mitigate reasonable doubt, we can take a theory regarding the phenomena to be well supported by experiment. When such strategies are able to fully mitigate reasonable doubt, we can take a theory regarding the phenomena to be established by experiment. There are good reasons to expect the next generation of analogue experiments to provide genuine knowledge of unmanipulable and inaccessible phenomena such that the relevant theories can be understood as well supported. This article is part of a discussion meeting issue ‘The next generation of analogue gravity experiments’.
Childhood obesity is a complex problem that warrants early intervention. General recommendations for obesity prevention and nutrition counseling exist. However, these are notably imprecise with regard to early and targeted interventions to prevent and treat obesity in pediatric populations. This study examines family medicine primary care providers' (PCPs) perceived barriers for preventing and treating pediatric obesity and their related practice behavior during well-child visits. Methods. A written survey addressing perceived barriers and current practices addressing obesity at well-child visits were administered to PCPs at eleven family medicine clinics in the Duke University Health System. Results. The most common perceived barriers identified by PCPs to prevention or treatment of obesity in children were families not getting enough exercise (93%) and families too often having fast food meals (86%). Most PCPs do not discuss fast foods at or prior to the twelve-month well-child visit. The two-year visit is the first well-child visit at which a majority of PCPs (68%) discuss fast food. Conclusion. No clear consensus exists as to when PCPs should discuss fast food in early well-child checks. Previous research has shown a profound shift in children's dietary habits toward fast foods, such as French fries, that occurs between the one- and two-year well-child checks. Consideration should be given to having a “French Fry Discussion” at every twelve-month well-child care visit.
One obstacle faced by proposals of retrocausal influences in quantum mechanics is the perceived high conceptual cost of making such a proposal. I assemble here a metaphysical picture consistent with the possibility of retrocausality and not precluded by the known physical structure of our reality. This picture employs two relatively well-established positions-the block universe model of time and the interventionist account of causation-and requires the dismantling of our ordinary asymmetric causal intuition and our ordinary intuition about epistemic access to the past. The picture is then built upon an existing model of agent deliberation that permits us to strike a harmony between our causal intuitions and the fixity of the block universe view. I conclude that given the right mix of these reasonable metaphysical and epistemological ingredients there is no conceptual cost to such a retrocausal picture of quantum mechanics.
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