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arXiv2021

The curious case of Betelgeuse

Betelgeuse is the nearest red supergiant, one of the brightest stars in our sky, and statistically speaking it would be expected to be "typical". Yet it exhibits many features that seem "curious", to say the least. For instance it has a high proper motion. It rotates fast. It has little dust. It dimmed unexpectedly. Is any of these, and other, phenomena atypical, and taken together does it make Betelgeuse atypical? This is important to know, because we need to know whether Betelgeuse might be a prototype of red supergiants in general, or certain subclasses of red supergiants, since we can study it in such great detail. It is also important to know as it may be a link to understanding other, apparently atypical cases such as supernova 1987A, and maybe even such exotica as Thorne-Żytkov objects. Studying this question in itself helps us understand how we deal with rarity and coincidence in understanding the Universe we live in.

astro-ph.SR↗
arXiv2022

Einstein and the problem of confirmation by previously known evidence: A comment on Michel Janssen and Jürgen Renn's "Einstein and the Perihelion Motion of Mercury"

In this paper, I comment on a recent paper by Michel Janssen and Jürgen Renn. In his published paper of November 18, 1915, Einstein presented a solution to the problem of the perihelion motion of Mercury and obtained the correct result of 43 seconds of arc per century. Before 1915, Einstein had established non-covariant field equations (the Entwurf field equations). But in 1915, he changed his mind and dropped these equations and was led to general covariance. In a manuscript written in 1913, Einstein and his best friend Michele Besso tried to solve the Entwurf field equations to attain the perihelion advance of Mercury. The end result arrived at by Einstein was 1821 seconds of arc per century. To make a long story short, the field of a static Sun produced an advance of the perihelion of Mercury of 18 seconds of arc per century. Einstein kept quiet about this result and continued to work on the Entwurf theory. Janssen and Renn ask: If we follow the prescriptions of Karl Popper, why did Einstein not accept that his Entwurf theory had been falsified? They further ask: Given the undeniable importance of Besso's earlier calculations, why did Einstein not invite Besso as a co-author of his November 1915 paper on the perihelion motion of Mercury? Besso did not even get an acknowledgment in Einstein's paper. After a brief review of Einstein's and Besso's early attempts at calculating the advance of the perihelion of Mercury, I discuss falsification and confirmation by previously known evidence and then propose an answer to the above two questions.

physics.hist-ph↗
arXiv2022

Time as Change

According to Aristotle "time is the number of change with respect to the before and after". That's certainly a vague concept, but at the same time it's both simple and satisfying from a philosophical point of view: things do not change along time, but they do change and the measurement of such changes is what we call time. This deprives time of any attribute of substantiality, meanwhile depriving it of all problems in defining the properties of time as a substance. With the rise of Classical Mechanics, Aristotle's view is abandoned and Newton's concept of "true" and absolute time imposes itself; time flows independently on changes of any kind. Relativity will then radically modify our concept of time, but won't actually modify the fundamental idea: things keep changing along time -- changes do not make time. This work will argue Aristotle's thesis, showing how such an approach automatically leads to the principles of Special Relativity. An interesting consequence and, at least virtually, measurable will also be highlighted: the fact that synchronizing two clocks with a precision greater than a certain scale is impossible, estimating such scale around $10^{-22}$s.

physics.hist-ph↗
arXiv2022

Solstices and Equinoxes in 1703 at the meridian line of St. Maria degli Angeli in Rome, and the stellar aberration of Sirius

The 1703 was the first year of full operation of the meridian line in the Basilica of St. Maria degli Angeli in Rome. The instants of solstices and equinoxes, the \textit{Anni Cardines}, obtained by comparing transit timings of Sun and Sirius, also in daytime, are affected either by the East deviation of the meridian line of about 5' Eastward (geometrical effect), either by the stellar aberration of Sirius (relativistic effect). Similarly the seasonal shifts of Sirius' declination observed by Bianchini are here firstly recognized as depending on the stellar aberration in ecliptic latitude. The eccentricity of the Earth's orbit and the orientation of its axis in the space can be measured, since Ptolemy, by knowing the exact timing of the solstices and the equinoxes. The dates of 1703 equinoxes and solstices have been published by Francesco Bianchini in local roman mean time, referred to the local (roman) mean noon, i.e. after the solar meridian mean transit time. By using the observations of the three lunar eclipses of 1703 we found the equation of time for that year, and the UTC corresponding timings of the beginning of the seasons. This operation lead to find the contribution of the Sirius aberration to the instant calculated by Bianchini with respect to the current celestial mechanical models of IMCCE.

physics.hist-ph↗
arXiv2022

Is thermodynamics fundamental?

It is a common view in philosophy of physics that thermodynamics is a non-fundamental theory. This is motivated in particular by the fact that thermodynamics is considered to be a paradigmatic example for a theory that can be reduced to another one, namely statistical mechanics. For instance, the statement "temperature is mean molecular kinetic energy" has become a textbook example for a successful reduction, despite the fact that this statement is not correct for a large variety of systems. In this article, we defend the view that thermodynamics is a fundamental theory, a position that we justify based on four case studies from recent physical research. We explain how entropic gravity (1) and black hole thermodynamics (2) can serve as case studies for the multiple realizability problem which blocks the reduction of thermodynamics. Moreover, we discuss the problem of the reducibility of phase transitions and argue that bifurcation theory (3) allows the modelling of "phase transitions" on a thermodynamic level even in finite systems. It is also shown that the derivation of irreversible transport equations in the Mori-Zwanzig formalism (4) does not, despite recent claims to the contrary, constitute a reduction of thermodynamics to quantum mechanics. Finally, we briefly discuss some arguments against the fundamentality of thermodynamics that are not based on reduction.

physics.hist-ph↗
arXiv2022

From locality to factorizability: a novel escape from Bell's theorem

While initial versions of Bell's theorem captured the notion of locality with the assumption of factorizability, in later presentations, Bell argued that factorizability could be derived from the more fundamental principle of local causality. Here we show that, contrary to what is commonly assumed, in order to derive factorizability from the principle of local causality, a non-trivial assumption, similar but strictly independent of settings independence, is required. Loosely speaking, such an extra assumption demands independence between the states of the measurement apparatuses. We conclude that it is possible to construct a model, satisfying both the principle of local causality and settings independence, but that, in virtue of violating this additional assumption--and thus factorizability--is able to break Bell's inequality.

quant-ph↗
arXiv2022

The Fate of Causal Structure under Time Reversal

What happens to the causal structure of a world when time is reversed? At first glance it seems there are two possible answers: the causal relations are reversed, or they are not. I argue that neither of these answers is correct: we should either deny that time-reversed worlds have causal relations at all, or deny that causal concepts developed in the actual world are reliable guides to the causal structure of time-reversed worlds. The first option is motivated by the instability under intervention of time-reversed dynamical evolutions. The second option is motivated by a recognition of how contingent structural features of the actual world shape, and license the application of, our causal concepts and reasoning strategies.

physics.hist-ph↗
arXiv2022

A Higher Dimension of Consciousness: Constructing an empirically falsifiable panpsychist model of consciousness

Panpsychism is a solution to the mind-body problem that presumes that consciousness is a fundamental aspect of reality instead of a product or consequence of physical processes (i.e., brain activity). Panpsychism is an elegant solution to the mind-body problem: it effectively rids itself of the explanatory gap materialist theories of consciousness suffer from. However, many theorists and experimentalists doubt panpsychism can ever be successful as a scientific theory, as it cannot be empirically verified or falsified. In this paper, I present a panpsychist model based on the controversial idea that consciousness may be a so called higher physical dimension. Although this notion seems outrageous, I show that the idea has surprising explanatory power, even though the model (as most models) is most likely wrong. Most importantly, though, it results in a panpsychist model that yields predictions that can be empirically verified or falsified. As such, the model's main purpose is to serve as an example how a metaphysical model of consciousness can be specified in such a way that they can be tested in a scientifically rigorous way.

q-bio.NC↗
arXiv2022

Sometimes size does not matter

Cosmological fine-tuning has traditionally been associated with the narrowness of the intervals in which the parameters of the physical models must be located to make life possible. A more thorough approach focuses on the probability of the interval, not on its size. Most attempts to measure the probability of the life-permitting interval for a given parameter rely on a Bayesian statistical approach for which the prior distribution of the parameter is uniform. However, the parameters in these models often take values in spaces of infinite size, so that a uniformity assumption is not possible. This is known as the normalization problem. This paper explains a framework to measure tuning that, among others, deals with normalization, assuming that the prior distribution belongs to a class of maximum entropy (maxent) distributions. By analyzing an upper bound of the tuning probability for this class of distributions the method solves the so-called weak anthropic principle, and offer a solution, at least in this context, to the well-known lack of invariance of maxent distributions. The implication of this approach is that, since all mathematical models need parameters, tuning is not only a question of natural science, but also a problem of mathematical modeling. Cosmological tuning is thus a particular instantiation of a more general scenario. Therefore, whenever a mathematical model is used to describe nature, not only in physics but in all of science, tuning is present. And the question of whether the tuning is fine or coarse for a given parameter -- if the interval in which the parameter is located has low or high probability, respectively -- depends crucially not only on the interval but also on the assumed class of prior distributions. Novel upper bounds for tuning probabilities are presented.

physics.hist-ph↗
arXiv2022

Quantum computers as an amplifier for existential risk

Quantum computing is expected to have a profound impact on society. In this work we discuss the potential consequences on existential risk for humanity. Even with the timeline for large-scale fault-tolerant quantum computing still unclear, it is highly likely that quantum computers will eventually realize an exponential speedup for certain practical applications. We identify quantum simulation as the most relevant application in this regard and we qualitatively outline different risk trajectories. Both amplifying and mitigating effects of quantum computing for existential risk are anticipated. In order to prevent quantum computing from being an amplifier of existential risk, we call for increased efforts by the scientific community towards reducing potential future quantum risk. This viewpoint seeks to add a new perspective to the discussion on technological risk of quantum computing.

physics.soc-ph↗
arXiv2022

A self-governing, self-regulating system for assessing scientific predictive power

I propose a method for tracking and assessing scientific progress using a prediction consensus algorithm designed for the purpose. The protocol obviates the need for centralized referees to generate scientific questions, gather predictions, and assess the accuracy or success of those predictions. It relies instead on crowd wisdom and a system of checks and balances for all tasks. It is intended to take the form of a web-based, searchable database. I describe a prototype implementation that I call Ex Quaerum. The main purpose of the present document is to motivate the project, to explain its underlying philosophy, to explain the details of the consensus protocol on which it is based, to describe plans for its future development, and ultimately to attract additional collaborators.

physics.soc-ph↗
arXiv2022

Holography, Application, and String Theory's Changing Nature

Based on string theory's framework, the gauge/gravity duality, also known as holography, has the ability to solve practical problems in low energy physical systems like metals and fluids. Holographic applications open a path for conversation and collaboration between the theory-driven, high energy culture of string theory and fields like nuclear and condensed matter physics, which in contrast place great emphasis on the empirical evidence that experiment provides. This paper takes a look at holography's history, from its roots in string theory to its present-day applications that are challenging the cultural identity of the field. I will focus on two of these applications: holographic QCD and holographic superconductivity, highlighting some of the (often incompatible) historical influences, motives, and epistemic values at play, as well as the subcultural shifts that help the collaborations work. The extent to which holographic research -- arguably string theory's most successful and prolific area -- must change its subcultural identity in order to function in fields outside of string theory reflects its changing nature and the field's uncertain future. Does string theory lose its identity in the low-energy applications that holography provides? Does holography still belong under string theory's umbrella, or is it destined to form new subcultures with each of its fields of application? I find that the answers to these questions are dynamic, interconnected, and highly dependent on string theory's relationship with its field of application. In some cases, holography can maintain the goals and values it inherited from string theory. In others, it instead adopts the goals and values of the field in which it is applied. These examples highlight a need for the STS community to expand its treatment of string theory beyond its relationship with empiricism and role as a theory of quantum gravity.

physics.hist-ph↗
arXiv2022

How and When Did Locality Become 'Local Realism'? A Historical and Critical Analysis (1963-1978)

The history of the debates on the foundational implications of the Bell non-locality theorem displayed very soon a tendency to put the theorem in a perspective that was not entirely motivated by its very assumptions, in particular in term of a 'local-realistic' narrative, according to which a major target of the theorem would be the very possibility to conceive quantum theory as a theory concerning 'real' stuff in the world out-there. I present here a historico-critical analysis of the stages, between 1963 and 1978, through which the locality condition of the original Bell theorem almost undiscernibly turned into a 'local realism' condition, a circumstance which too often has affected the analysis of how serious the consequences of the Bell theorem turn out to be. In particular, the analysis puts into focus the interpretive oscillations and inconsistencies that emerge in the very descriptions that many leading figures provided themselves of the deep work they devoted to the theorem and its consequences.

physics.hist-ph↗
arXiv2022

Are Physical Theories Incommensurable?

This paper examines the incommensurability thesis - one of the most important and controversial ideas to emerge from the simultaneous work of Kuhn and Feyerabend. In the first half, I discuss three aspects of incommensurability - methodological incommensurability (the view that each paradigm supplies different standards of evaluation), observational incommensurability (the view that the theories we accept alter how we see the world), and finally, semantic incommensurability (which claims that as paradigms change, the very meanings of central theoretical terms also change). In the latter half, I tackle the general arguments of physicists against incommensurability by primarily considering the so called unifying cube of physics. I show that the cube of physics does not get rid of incommensurability, but rather favours it.

physics.hist-ph↗
arXiv2024

A note on the notion of now and time flow in special relativity

With special relativity, we seem to be facing a conundrum. It is a very well-tested theory; in this way, the Minkowski spacetime must be "capturing" essential features of space and time. However, its geometry seems to be incompatible with any sort of global notion of time. We might only have local notions of now (present moment) and time flow, at best. In this note, we will explore the possibility that a pretty much global notion of now (and time flow) might be hiding in plain sight in the geometry of the Minkowski spacetime.

physics.hist-ph↗