Metascience DOI 10.1007/s11016-013-9752-z BOOK REVIEW

Science or mathematical fiction? Helge Kragh: Higher speculations. Grand theories and failed revolutions in physics and cosmology. Oxford: Oxford University Press, 2011, 411pp, $63 HB Jan Faye

 Springer Science+Business Media Dordrecht 2013

In the summer of 2012, the first reports ticked in that the Large Hadron Collider in CERN had produced some events in the range of 125–126 GeV that might indicate the existence of the Higgs boson. This particle, whose discovery still has to be confirmed, is the last particle predicted by the non-supersymmetrical Standard Model. At present, LHC operates at 4 TeV per beam and no supersymmetrical particle below 1 TeV has been discovered although the most common Supersymmetrical Standard Models suggest the existence of some supersymmetrical partners with masses in the range of 100–800 GeV. As if this was not bad enough for the idea of supersymmetry, the lack of discovery of any physics between the Higgs mass and 1 TeV also affects more exotic ideas of superstrings, theories of everything, landscapes and multiverses. This alarming situation has ignited some reflection in the mind of at least one eminent particle physicist, Mikhail Shifman (2012), who warns his colleagues against continuing down a blind alley. Speaking about the community of particle theorists, he summarized his discussion in the following way: During their careers many of them never worked on any issues beyond supersymmetry-based phenomenology or string theory. Given the crises (or, at least, huge question marks) in these two areas we currently face, there seems to be a serious problem in the community. Usually such times of uncertainty as to the direction of future research offer wide opportunities to young people, in the prime of their careers. To grab these opportunities a certain reorientation and reeducation are apparently needed. Will this happen? These remarks illustrate quite well, I think, the status of much current high energy physics as being a subject of high theoretical speculation. It goes astray J. Faye (&) Section of Philosophy, Department of Media, Cognition and Communication, University of Copenhagen, Njalsgade 80, 2300 Copenhagen S, Denmark e-mail: [email protected]

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without empirical support. Mathematics alone cannot save particle physics and cosmology. Nevertheless, Helge Kragh, an esteemed historian of science, tells us in Higher Speculations that there have been many times in the history of physics in which physicists alone have had high hopes to sagacity and mathematics as they were dealing with rational cosmology and a unifying theory of electromagnetism and gravitation. Not only does this book present cases from the past, but also scenes from the present. The author gives us a detailed and conscientious account of ideas developed by Gustav Mie, Edward Milne, Arthur Eddington, Paul Dirac, Albert Einstein, Brandon Carter, Alan Guth, Martin Rees, Andrei Linde, Leonard Susskind, and many others. Most of the book is dedicated to the current discussion in physics and cosmology, and the author elaborates on issues concerning cyclical universes, the anthropic principle, landscapes of vacuum, string theories and multiverses. In general, Kragh does not take sides in these debates, for example, by mentioning physicists like Max Tegmark and Susskind who believe that cosmologists and particle physics can completely dispense with experience since nature is nothing but mathematics in disguise, and physicists who strongly object to theories that cannot be falsified because they do not predict any experimental results. Kragh clearly respects the intellectual integrity of both camps even though one may sense from his comments that he himself is closer to the empiricists than the Platonists. Indeed, some of these discussions are more philosophical than physical. They revolve around problems like what happened before the big bang, why there is something rather than nothing, the reality of many universes and what science is and what it ought to be. One such philosophical problem is Brandon Carter’s introduction of the strong anthropic principle as an explanatory principle in cosmology. Sometimes it is called the ‘‘new paradigm of explanation’’ in physical discussions though it has been much contested ever since its appearance. The proponents of the anthropic principle claim to offer explanations of certain quantities and phenomena ranging from the neutron–proton mass difference to the age of the universe by a reference to our presence. But the discussion between the protagonists of the principle and its antagonists focus on whether it is scientific or not without knowing what they are talking about. For instance, as Kragh points out, when Barry Collin and Hawking in 1973 suggested that the answer to a question like ‘‘why is the universe isotropic?’’ is ‘‘because we are here’’, the authors definitely did not mean that human beings cause the universe to be isotropic. Nor did they take such an explanation to be teleological in the sense that an isotropic universe exists for the sake of human life (246). What then did they have in mind? Little of this was said. John Leslie has suggested that it should be understood in a logical sense like ‘‘saying that being a woman is a logical consequence of being a wife’’ (246). Personally, I see the anthropic principle in a different light. There is nothing conceptual that links ‘‘isotropic’’ and ‘‘human beings’’. Instead, Collin and Hawking appealed to the effect of an isotropic universe, namely the existence of human being, and used it to explain one of the functions of an isotropic universe which is to support biological evolution and human beings. Thus, I would say that anthropic explanations are a kind of functional explanations which has been reintroduced into physics. The idea behind the anthropic principle seems to be that physical quantities

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are fine-tuned by being adapted to the environment and that this fine-tuning has a function of preparing for life. If this interpretation is true, physicists and philosophers can begin to discuss on a more solid basis whether or not it makes sense to introduce anthropic explanations into physics and to consider different universes as if they were different organisms. Kragh is very mindful about the nature of these high speculations. Says he, ‘‘Directly or indirectly, many of the questions discussed in the multiverse controversy are of a philosophical nature, not least when it comes to the proper standards of science on which the multiverse scenarios should be evaluated. Interestingly, the questions are discussed mostly within the scientific community, whereas philosophers so far have shown little interest in them’’ (280). Why this is so is not something Kragh attempts to answer. But let me suggest a reply. Part of the answer is that modern philosophers of science are no longer lofty people who just speculate freely and wildly but they bind their thinking by rational and empirical commitments. The growing interest in the naturalization of human knowledge and philosophical reasoning goes against much thinking that is over-speculative. Moreover, I think that philosophers often consider some cosmologists and particle theorists quite naı¨ve with respect to philosophical matters in the sense that their views build more on fiat than arguments. They can do it by themselves, thank you very much. This is also a point Kragh is aware of: ‘‘In a situation where the very standards of science are at stake one might expect the scientists to appeal to philosophical notions and demarcation criteria of science. Although this has happened in the modern cosmological debate, it is only on rare occasions and without much effect. Generally speaking, physicists have little respect for or are plainly uninterested in the opinion of philosophers …. They see it as part of their job to expand the domain of physics at the expense of philosophy and other branches of knowledge, to turn vague philosophical doctrines into precise operational concepts’’ (281). And he adds, ‘‘For instance, the semiphilosophical anthropic principle has now moved into physics and thus, because it is no longer philosophical, becomes scientifically acceptable’’ (282). But all science builds upon metaphysical presuppositions whose validity neither empirical discovery nor mathematical skills can demonstrate. For instance, why should one be an empiricist or a Platonist in the first place? However, from what I have seen and read about physicists’ understanding of the anthropic principle, I think that they could still need profit from a philosophical perspective when it comes to distinguishing the logical consequences. Current physics is a highly technical enterprise, but so is philosophy of science. Therefore, physics and philosophy should be able to benefit from one another. Kragh has written an inspiring and informative book about the contemporary history of the most conspicuous development of the most spectacular fields of modern physics. It stands as the culmination of Kragh’s long-time occupation with the history of cosmology and quantum mechanics and deserves to be read by physicists and all philosophers of science. Not only does it describe the theoretical creativity of the human mind, but also the strong resistance within the physics community towards this kind of a new physics where the anthropic principle and mathematical consistency are thought sufficient. This physics, however, may be in

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for a big change. As part of a possible change I believe that philosophers of science should look at the methodological side of the present discussion and take actively part in the debate in order to move it forward. But this will not happen without firing a short. Although one leading string theorist, Edward Witten, claim that supersymmetry ‘‘is a genuine prediction of string theory’’ (310), another important colleague, John Schwarz, maintains that string theory is almost certainly correct and even though he expects supersymmetry to be found, he ‘‘would not abandon this theory if supersymmetry turns out to be absent’’ because string theory is such a ‘‘unique mathematical structure that combines quantum mechanics and general relativity’’ (311). Perhaps, future developments within particle physics will confirm Imre Lakatos’s suggestion that a research programme is given up not so much because it is falsified but because it increasingly draws on ad hoc hypotheses to protect itself against empirical discoveries and therefore becomes dragged into a reactionary decline.

Reference Mikhail, Shifman. 2012. Reflections and impressionistic portrait at the conference frontiers beyond the standard model, FTPI, Oct 2012. http://arxiv.org/abs/1211.0004v1.

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