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Epistemology of Experimental Gravity - Scientific Rationality

By Sfetcu, Nicolae

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Book Id: WPLBN0100303996
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Reproduction Date: 11/2/2019

Title: Epistemology of Experimental Gravity - Scientific Rationality  
Author: Sfetcu, Nicolae
Language: English
Subject: Non Fiction, Science, gravity
Collections: Authors Community, Philosophy
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Publisher: MultiMedia Publishing
Member Page: Nicolae Sfetcu


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Sfetcu, B. N. (2019). Epistemology of Experimental Gravity - Scientific Rationality. Retrieved from

The evolution of gravitational tests from an epistemological perspective framed in the concept of rational reconstruction of Imre Lakatos, based on his methodology of research programmes. Unlike other works on the same subject, the evaluated period is very extensive, starting with Newton's natural philosophy and up to the quantum gravity theories of today. In order to explain in a more rational way the complex evolution of the gravity concept of the last century, I propose a natural extension of the methodology of the research programmes of Lakatos that I then use during the paper. I believe that this approach offers a new perspective on how evolved over time the concept of gravity and the methods of testing each theory of gravity, through observations and experiments. I argue, based on the methodology of the research programmes and the studies of scientists and philosophers, that the current theories of quantum gravity are degenerative, due to the lack of experimental evidence over a long period of time and of self-immunization against the possibility of falsification. Moreover, a methodological current is being developed that assigns a secondary, unimportant role to verification through observations and/or experiments. For this reason, it will not be possible to have a complete theory of quantum gravity in its current form, which to include to the limit the general relativity, since physical theories have always been adjusted, during their evolution, based on observational or experimental tests, and verified by the predictions made. Also, contrary to a widespread opinion and current active programs regarding the unification of all the fundamental forces of physics in a single final theory, based on string theory, I argue that this unification is generally unlikely, and it is not possible anyway for a unification to be developed based on current theories of quantum gravity, including string theory. In addition, I support the views of some scientists and philosophers that currently too much resources are being consumed on the idea of developing quantum gravity theories, and in particular string theory, to include general relativity and to unify gravity with other forces, as long as science does not impose such research programs.

The evolution of gravitational tests from an epistemological perspective framed in the concept of rational reconstruction of Imre Lakatos, based on his methodology of research programmes.

Allan Franklin and Slobodan Perovic, in Experiment in Physics[7], state that theories in science in general, and in physics in particular, are confirmed (temporarily) by experiments that verify the assertions and predictions of theories, thus laying the groundwork for scientific knowledge. Francis Bacon was the first to support the concept of a crucial experiment, which can decide the validity of a hypothesis or theory. Later, Newton argued that scientific theories are directly induced by experimental results and observations, excluding untested hypotheses. Hobbes stated, on the contrary, that human reason preceded experimental techniques, criticizing Boyle's optimism about the role of the experimental method[8]. In the 20th century, logical positivism separates observational deductions from theoretical ones. Thomas Kuhn and Paul Feyerabend criticized this view, saying that all experiments are based on a theoretical framework and therefore cannot independently confirm a theory[9]. Ian Hacking agreed with this idea, but says the comments remain reliable through independent confirmations. In the case of a single viable experimental system, Allan Franklin and Slobodan Perovic propose specific strategies for validating the observation, which, together with Hacking's strategy, constitute an epistemology of the experiment: Experimental verification and calibration, with the help of known phenomena. Reproduction of previously known artifacts. Elimination of plausible sources of error and alternative explanations of the result ("Sherlock Holmes strategy"). Using the results to argue their validity. Using a well-corroborated independent theory of phenomena to explain the results. Using an apparatus based on a well-corroborated theory. Use of statistical arguments. [10] But applying these strategies does not guarantee the correctness of the results. Because of this, physicists use several strategies, depending on the experiment. Peter Galison, in How Experiments End (1987), states that experiments end in a subjective way, when experts believe they have reached a valid result[11]. Most experiments are based on the traditions in the field and the personal experience of the researcher (including his theoretical assumptions), both in designing the experiment and in accepting a theory that "allows" the conduct of experiments. The theoretical assumptions of the experimenters are accepted. Harry Collins has developed an argument called "experimenters’ regress[12]," according to which there are no formal criteria that you can apply to decide whether an experimental device works properly or not. What actually matters is negotiation within the scientific community, which depends on factors such as the career, social and cognitive interests of scientists and perceived usefulness for future work, but which is not decided by what we may call epistemological criteria or rationalized judgment[13]. Pickering also argues that the reasons for accepting the results are their subsequent usefulness in scientific practice, and their agreement with existing community commitments[14]. He states that an experimental system rarely produces valid experimental results unless it is adjusted accordingly, and that the theory of apparatus, as well as the theory of phenomena, determines the production of a valid experimental result[15]. Later, he concludes that "the outcomes depend on how the world is"[16]: "In this way, then, how the material world is leaks into and infects our representations of it in a nontrivial and consequential fashion. My analysis thus displays an intimate and responsive engagement between scientific knowledge and the material world that is integral to scientific practice.” [17] Hacking claims that, despite appearances, constructivists, such as Collins, Pickering or Latour, do not believe that facts do not exist or that there is no reality. He cites Latour and Woolgar that the result is a consequence of scientific work rather than its cause[18] [19], in a relative consensus with the scientific community. Franklin and Perovic state that the accumulation of a large amount of data in an experiment may require a selection, by the technique of reduction used by physicists, of the data that will be used. This may be an important epistemological concern regarding the selection of data considered useful, minimizing the probability of unexplored results[20]. In such cases, physicists apply a robustness analysis in testing hypotheses, checking the equipment used, and establishing working algorithms. In the case of the solutions of Einstein's equations of general relativity and of the modeling of quantum gravity theories, due to the complexity of these approaches, simulations of computer experiments are attempted. Currently, there is an ongoing dispute to what extent these simulations are experiments, theories or some kind of hybrid methods of doing science. [21] Between 1965 and 1990 many experiments were developed for testing gravitational theories, including[22] High precision measurements of the effects of electromagnetic radiation in the gravitational field, confirming the GR for the weak gravitational field. Detection of the non-linear gravitational interaction of the masses at a pulsar in the gravitational field of a neutron star. Indirect confirmation of gravitational radiation by observing two nearby neutron stars, confirming GR. Attempts, so far failed, to ascertain the violation of the principle of equivalence or the existence of a fifth force. During this period most experiments confirmed the general relativity with the help of the newly developed technologies. A technological basis for gravitational wave astronomy has been created. Cryogenic barogenic antennas and laser interferometric antennas were built, associated with the theoretical analysis of the experiments with the test masses, resulting in the sensitivity of the experiments depending on the thermal insulation, if the device continuously records the coordinates the antenna sensitivity is limited, and the sensitivity can be increased if there are used quantum procedures[23]. The antennas can help in observing the gravitational background radiation and testing the general relativity in the ultra-nonlinear case. Regarding the sensitivity of gravitational measuring devices, Vladimir B Braginsky states that the current level of knowledge allows us to hope that the sensitivity of the antennas can increase, and no limit of sensitivity has been set in the gravitational experiments, it depends on the knowledge of the scientists. [24] Currently, experimental gravity is an emerging field, characterized by continuous efforts to test the predictions of gravity theories. The classical limit or the limit of correspondence is the ability of a physical theory to approximate the classical version when it is taken into account by the special values of its parameters[25]. The principle of correspondence formulated by Niels Bohr in 1920[26] states that the behavior of systems described by quantum mechanics reproduces classical physics within the limits of large quantum numbers[27]. This principle has two basic requirements: the reproduction of the Poisson brackets, and the specification of a complete set of classical observables whose operators, when acting through appropriate semiclassical states, reproduce the same classical variables with small quantum corrections[28].

Table of Contents
Introduction    Gravity    Gravitational tests    Methodology of Lakatos - Scientific rationality    The natural extension of the Lakatos methodology       Bifurcated programs       Unifying programs 1. Newtonian gravity    1.1 Heuristics of Newtonian gravity    1.2 Proliferation of post-Newtonian theories    1.3 Tests of post-Newtonian theories       1.3.1 Newton's proposed tests       1.3.2 Tests of post-Newtonian theories    1.4 Newtonian gravity anomalies    1.5 Saturation point in Newtonian gravity 2. General relativity    2.1 Heuristics of the general relativity    2.2 Proliferation of post-Einsteinian gravitational theories    2.3 Post-Newtonian parameterized formalism (PPN)    2.4 Tests of general relativity and post-Einsteinian theories       2.4.1 Tests proposed by Einstein       2.4.2 Tests of post-Einsteinian theories       2.4.3 Classic tests Precision of Mercury's perihelion Light deflection Gravitational redshift       2.4.4 Modern tests Shapiro Delay Gravitational dilation of time Frame dragging and geodetic effect Testing of the principle of equivalence Solar system tests       2.4.5 Strong field gravitational tests Gravitational lenses Gravitational waves Synchronization binary pulsars Extreme environments       2.4.6 Cosmological tests The expanding universe Cosmological observations Monitoring of weak gravitational lenses    2.5 Anomalies of general relativity    2.6 The saturation point of general relativity 3. Quantum gravity    3.1 Heuristics of quantum gravity    3.2 The tests of quantum gravity    3.3 Canonical quantum gravity       3.3.1 Tests proposed for the CQG       3.3.2. Loop quantum gravity    3.4 String theory       3.4.1 Heuristics of string theory       3.4.2. Anomalies of string theory    3.5 Other theories of quantum gravity    3.6 Unification (The Final Theory) 4. Cosmology Conclusions Notes Bibliography


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