The Direction of Time

This paper investigates the question whether we could have reason to believe that time is two-dimensional. I connect discussion of this question to discussion of the question whether we could have reason to believe that there has been a global time freeze.

That we find the idea of travelling in time, and in particular travelling backwards in time, fascinating, is evidenced by the plethora of new science fictions shows depicting time travel that hit our TV screens in 2016. I love time travel shows, and I can hardly keep up. In almost all cases these shows depict what philosophers call inconsistent time travel stories: stories that commit what my colleague Nick Smith (The University of Sydney) calls the second time around fallacy. These (...) stories depict individuals travelling back in time (or in some cases sending a signal back in time) in order to change some past event (or, in some cases, to try and mitigate the changes brought about by some other time travellers). -/- It’s easy to see why these storylines are captivating. They ask us to imaginatively entertain questions about the robustness of the present. We are asked to ponder to what extent the way things are now is the product of fluky events, so that had the past been ever so slightly different, the present would be very different indeed. These questions are intriguing because we all wonder to what extent our present selves are the result of choices we made, where we could so easily have made others, and to what extent who we are is most robust, resilient under small changes in our past decisions. (shrink)

The Simulation Hypothesis proposes that all of reality is an artificial simulation, analogous to a computer simulation. Outlined here is a low computational cost method for programming cosmic microwave background parameters in Planck time Simulation Hypothesis Universe. The model initializes `micro Planck-size black-holes' as entities that embed the Planck units. For each incremental unit of Planck time, the universe expands by adding 1 micro black-hole, a dark energy is not required. The mass-space parameters increment linearly, the electric parameters in a (...) sqrt-progression, thus for electric parameters the early black-hole transforms most rapidly. The velocity of expansion is constant and is the origin of the speed of light, the Hubble constant becomes a measure of the black-hole radius and the CMB radiation energy density correlates to the Casimir force. A peak frequency of 160.2GHz correlates to a 14.624 billion year old black-hole. The cosmological constant, being the age when the simulation reaches the limit, approximates $t$ = 10$^{123} t_p$. (shrink)

The principle of Information Conservation or Determinism is a governing assumption of physical theory. Determinism has counterfactual consequences. It entails that if the present were different, then the future would be different. But determinism is temporally symmetric: it entails that if the present were different, the past would also have to be different. This runs contrary to our commonsense intuition that what has happened in the future depends on the past in a way the past does not depend on the (...) future. To understand how this can be so we observe that while the truth of some counterfactuals is guaranteed by the laws of logic or the laws of nature, some are not. It is among the latter contingent, counterfactuals that we find temporal asymmetry. It is this asymmetry that gives causation a temporal direction. The temporal asymmetry of these counterfactuals is explained by the fact that the dynamical laws of nature are logically irreversible functions from partial states of the world onto other partial states. (Logical reversibility is not to be confused, though it too often is, with time-reversal invariance). Though these irreversible laws are locally indeterministic, they can sum to give a globally deterministic description of the world. This combination of global determinism and local indeterminism gives rise to contingent counterfactual dependence and gives that dependence a direction. That direction is independent of the direction of entropy. The direction of contingent counterfactual dependence is time's arrow. (shrink)

The central motivating idea behind the development of this work is the concept of prespace, a hypothetical structure that is postulated by some physicists to underlie the fabric of space or space-time. I consider how such a structure could relate to space and space-time, and the rest of reality as we know it, and the implications of the existence of this structure for quantum theory. Understanding how this structure could relate to space and to the rest of reality requires, I (...) believe, that we consider how space itself relates to reality, and how other so-called "spaces" used in physics relate to reality. In chapter 2, I compare space and space-time to other spaces used in physics, such as configuration space, phase space and Hilbert space. I support what is known as the "property view" of space, opposing both the traditional views of space and space-time, substantivalism and relationism. I argue that all these spaces are property spaces. After examining the relationships of these spaces to causality, I argue that configuration space has, due to its role in quantum mechanics, a special status in the microscopic world similar to the status of position space in the macroscopic world. In chapter 3, prespace itself is considered. One way of approaching this structure is through the comparison of the prespace structure with a computational system, in particular to a cellular automaton, in which space or space-time and all other physical quantities are broken down into discrete units. I suggest that one way open for a prespace metaphysics can be found if physics is made fully discrete in this way. I suggest as a heuristic principle that the physical laws of our world are such that the computational cost of implementing those laws on an arbitrary computational system is minimized, adapting a heuristic principle of this type proposed by Feynman. In chapter 4, some of the ideas of the previous chapters are applied in an examination of the physics and metaphysics of quantum theory. I first discuss the "measurement problem" of quantum mechanics: this problem and its proposed solution are the primary subjects of chapter 4. It turns out that considering how quantum theory could be made fully discrete leads naturally to a suggestion of how standard linear quantum mechanics could be modified to give rise to a solution to the measurement problem. The computational heuristic principle reinforces the same solution. I call the modified quantum mechanics Critical Complexity Quantum Mechanics (CCQM). I compare CCQM with some of the other proposed solutions to the measurement problem, in particular the spontaneous localization model of Ghirardi, Rimini and Weber. Finally, in chapters 5 and 6, I argue that the measure of complexity of quantum mechanical states I introduce in CCQM also provides a new definition of entropy for quantum mechanics, and suggests a solution to the problem of providing an objective foundation for statistical mechanics, thermodynamics, and the arrow of time. (shrink)

Symmetries have a crucial role in today’s physics. In this thesis, we are mostly concerned with time reversal invariance (T-symmetry). A physical system is time reversal invariant if its underlying laws are not sensitive to the direction of time. There are various accounts of time reversal transformation resulting in different views on whether or not a given theory in physics is time reversal invariant. With a focus on quantum mechanics, I describe the standard account of time reversal and compare it (...) with my alternative account, arguing why it deserves serious attention. Then, I review three known ways to T-violation in quantum mechanics, and explain two unique experiments made to detect it in the neutral K and B mesons. (shrink)

Skow ([2007]), and much more recently Callender ([2017]), argue that time can be distinguished from space due to the special role it plays in our laws of nature: our laws determine the behaviour of physical systems across time, but not across space. In this work we assess the claim that the laws of nature might provide the basis for distinguishing time from space. We find that there is an obvious reason to be sceptical of the argument Skow submits for distinguishing (...) time from space: Skow fails to pay sufficient attention to the relationship between the dynamical laws and the antecedent conditions required to establish a complete solution from the laws. Callender’s more sophisticated arguments in favour of distinguishing time from space by virtue of the laws of nature presents a much stronger basis to draw the distinction. By developing a radical reading of Callender’s view we propose a novel approach to differentiating time and space that we call temporal perspectivalism. This is the view according to which the difference between time and space is a function of the agentive perspective. (shrink)

This thesis is a study of the notion of time in modern physics, consisting of two parts. Part I takes seriously the doctrine that modern physics should be treated as the primary guide to the nature of time. To this end, it offers an analysis of the various conceptions of time that emerge in the context of various physical theories and, furthermore, an analysis of the relation between these conceptions of time and the more orthodox philosophical views on the nature (...) of time. In Part II I explore the interpretation of nonrelativistic quantum mechanics in light of the suggestion that an overly Newtonian conception of time might be contributing to some of the difficulties that we face in interpreting the quantum mechanical formalism. In particular, I argue in favour of introducing backwards-in-time causal influences as part of an alternative conception of time that is consistent with the picture of reality that arises in the context of the quantum formalism. Moreover, I demonstrate that this conception of time can already be found in a particular formulation of classical mechanics. One might see that one of the central themes of Part II originates from a failure to heed properly the doctrine of Part I: study into the nature of time should be guided by modern physics and thus we should be careful not to insert a preconceived Newtonian conception of time unwittingly into our interpretation of the quantum mechanical formalism. Thus, whereas Part I is intended as a demonstration of methodology with respect to the study of time, Part II in a sense explores a confusion that can be seen as arising in the absence of this methodology. (shrink)

Temporal non-dynamists hold that there is no temporal passage, but concede that many of us judge that it seems as though time passes. Phenomenal Illusionists suppose that things do seem this way, even though things are not this way. They attempt to explain how it is that we are subject to a pervasive phenomenal illusion. More recently, Cognitive Error Theorists have argued that our experiences do not seem that way; rather, we are subject to an error that leads us mistakenly (...) to believe that our experiences seem that way. Cognitive Error Theory is a relatively new view and little has been said to explain why we make such an error, or where, in the cognitive architecture, such an error might creep in. In this paper we remedy this by offering a number of hypotheses about the source of error. In so doing we aim to show that Cognitive Error Theory is a plausible competitor to Phenomenal Illusion Theory. (shrink)

For millennia people have speculated about the nature of time—without success. Time plays a role with all processes and events studied by all the disciplines. It is reported here that the existence of time is a direct consequence of the existence of space. Space exists, and it continues to exist. Space is there, and it continues to be there. Space exists as place, the three-dimensional place that matter can occupy. The three-dimensional extension of spatial-place is measured with a ruler of (...) some kind. Place, three-dimensionality, and extension are intrinsic-qualities of space itself. The continuing-existence of space is a direct consequence of the existence of space. The continuing-existence of space is measured with a clock. Spatial continuing-existence also has intrinsic-qualities. A list of the qualities of the continuing-existence of space appears to be the same as a list of the qualities of time. Seventeen qualities of the continuing-existence of space are compared to the equivalent qualities of time. There is an exact match between the qualities of time and the qualities of spatial continuing-existence. The qualities and roles of the continuing-existence of space fulfill all the known qualities and roles of time. Realizing that spatial continuing-existence is time makes time understandable, and clarifies the relations of time to matter, change, and process. (shrink)

What would it be for a process to happen backwards in time? Would such a process involve different causal relations? It is common to understand the time reversal invariance of a physical theory in causal terms, such that whatever can happen forwards in time (according to the theory) can also happen backwards in time. This has led many to hold that time reversal symmetry is incompatible with the asymmetry of cause and effect. This paper critiques the causal reading of time (...) reversal. First, I argue that the causal reading requires time-reversal-related models to be understood as representing distinct possible worlds, and on such a reading causal relations are compatible with time reversal symmetry. Second, I argue that the former approach does however raise serious sceptical problems regarding the causal relations of paradigm causal processes, and as a consequence there are overwhelming reasons to prefer a non-causal reading of time reversal whereby time reversal leaves causal relations invariant. On the non-causal reading, time reversal symmetry poses no significant conceptual nor epistemological problems for causation. -/- . (shrink)

Time travel and superluminal travel are two of mankind's dreams. They inspire our imagination and provide material for bizarre stories. -/- A work on the subject of time travel and superluminal travel forces us to re-examine our concept of "time". The complexity and the contradictory nature this subject makes it difficult to be more precise about "time". On its deepest subjective side, time is a means of perception, a biological rhythm, a social phenomenon in terms of our collective understanding of (...) time. But it is also a physical parameter. -/- Albert Einstein's Theory of Relativity revolutionised our idea of space and time by freeing us from the Newtonian concept of absolute space and absolute time. The "problem of time travel", a subject that Herbert George Wells wrote about just ten years before as mere fiction, was now a discussion worthy of physics. Albert Einstein's Special Theory of Relativity (1905), by predicting the effects of time dilation, allowed for "travels into the future" and Albert Einstein's Theory of Gravity used closed time-like lines for solutions to calculations about time travel (for example, the Gödel Universe and the Anti-de Sitter Universe). However, a trip to a time warp would immediately involve a whole set of paradoxes (for example, the grandfather paradox and the information paradox) and semantic inconsistencies. -/- Surprisingly, the fundamental laws of physics (apart from extremely rare and non-emergent macroscopic quantum mechanical effects) are not violated by the concept of time reversal. Yet, in nature, there still seems to be a fundamental prohibition against time travel to the past. Physicist Dieter Zeh, whose position is more closely presented in the final chapter of this work, supports the view that science fiction literature on the subject of "time travel" is overwhelmingly based on simple conceptual errors. The processes used in this literature, which are based on the General Theory of Relativity, at best, are just as "theoretically possible" as a gas which gathers itself into the corner of a container. -/- This work discusses approaches for "time machines" and superluminal travel which are consistent with modern physics. Some of the discussions that will be presented are the tachyon hypothesis, Frank J. Tipler's rotating cylinder, the Gödel Universe, the Anti-de Sitter Universe, so-called "wormholes" and the Alcubierre-metric. At the same time, approaches will be presented (for example, Eternalism, the Many-Worlds Interpretation and the Consistent Histories Approach) that will provide attempts to find a solution for paradoxes regarding time travel to the past. -/- Questions about time travel to the past and superluminal travel are like the questions asked on Radio Yerevan. The answer is always, "In principle yes, but…" But the fascination about time travel will continue to provide material for "fiction". (shrink)

This paper examines the problem of the basis of time’s asymmetry. I hold the view that there is an objective temporal asymmetry in Leibniz’s philosophy of time. I closely examine various asymmetrical phenomena, which can be candidates as an explanation of time’s asymmetry: (1) causation; (2) the flow of time; (3) the modal difference between past and present; (4) counterfactual dependence; and, finally (5) the asymmetry of the world’s progress and its direction and (6) of the progress of rational creatures. (...) I conclude that time’s asymmetry involves an irreducibly pragmatic aspect: the asymmetry of agency itself on which all other asymmetrical phenomena rely. (shrink)

Simple partial logic (=SPL) is, broadly speaking, an extensional logic which allows for the truth-value gap. First I give a system of propositional SPL by partializing classical logic, as well as extending it with several non-classical truth-functional operators. Second I show a way based on SPL to construct a system of tensed ontology, by representing tensed statements as two kinds of necessary statements in a linear model that consists of the present and future worlds. Finally I compare that way with (...) other two ways based on Łukasiewicz’s three-valued logic and branching temporal logic. (shrink)

In this paper I give consideration to some apparent impossibilities for the time travelers to the past. After criticizing the views of D. Lewis and K. Vihvelin, I will show in what sense they are really impossible.

The conventional claims and concepts of 5* - 8* are a hang-over from the classical theory of thermodynamics – i.e. thermodynamics based on a fully deterministic micro-theory, developed in the time of Boltzmann, Loschmidt and Gibbs in the late C19th. The classical theory has well-known ‘reversibility paradoxes’ when applied to the universe as a whole. But the introduction of intrinsic probabilities in quantum mechanics, and its consequent time asymmetry, fundamentally changes the picture.

These are the first two chapters from a monograph (The Time Flow Manifesto, Holster, 2013-14; unpublished), defending the concepts of time directionality and time flow in physics and naturalistic metaphysics, against long-standing attacks from the ‘conventional philosophy of physical time’. This monograph sets out to disprove twelve specific “fallacies of the conventional philosophy”, stated in the first section below. These are the foundational principles of the conventional philosophy, which developed in the mid-C20th from positivist-inspired studies. The first chapter begins by (...) re-presenting the basic analysis of time reversal symmetry in the context of probabilistic or non-deterministic processes, removing the first critical error in the conventional account. The second chapter argues for a law-like explanation of physical time asymmetry and irreversibility, and shows how the ‘reversibility paradoxes’ are explained. (shrink)

The inevitability of arising in equations of kinetics and hydrodynamics irreversibility not contained in original equations of classic mechanics is substantiated. It is established that transfer of information about the direction of system evolution from initial conditions to resulting equations is the consequence of losing information about the position of an individual particle in space, which takes place at roughening description. It is shown that the roughening with respect to impact parameters of colliding particles is responsible for appearance of the (...) irreversibility in resulting equations. Direct equations of kinetics and hydrodynamics are the result of roughening distribution functions with respect to impact parameters of particles, which have not yet reached the domain of their interaction. The direct equations are valid for the progressive direction of timing on the time axis pointing from the past to the future. Reverse equations of kinetics and hydrodynamics are the result of roughening distribution functions with respect to impact parameters of particles, which have already left the domain of their interaction. The reverse equations are valid for the progressive direction of timing on the time axis pointing from the future to the past. (shrink)

Bertrand Russell famously argued that causation is not part of the fundamental physical description of the world, describing the notion of cause as “a relic of a bygone age”. This paper assesses one of Russell’s arguments for this conclusion: the ‘Directionality Argument’, which holds that the time symmetry of fundamental physics is inconsistent with the time asymmetry of causation. We claim that the coherence and success of the Directionality Argument crucially depends on the proper interpretation of the ‘ time symmetry’ (...) of fundamental physics as it appears in the argument, and offer two alternative interpretations. We argue that: if ‘ time symmetry’ is understood as the time -reversal invariance of physical theories, then the crucial premise of the Directionality Argument should be rejected; and if ‘ time symmetry’ is understood as the temporally bidirectional nomic dependence relations of physical laws, then the crucial premise of the Directionality Argument is far more plausible. We defend the second reading as continuous with Russell’s writings, and consider the consequences of the bidirectionality of nomic dependence relations in physics for the metaphysics of causation. (shrink)

Statistical physics cannot explain why a thermodynamic arrow of time exists, unless one postulates very special and unnatural initial conditions. Yet, we argue that statistical physics can explain why the thermodynamic arrow of time is universal, i.e., why the arrow points in the same direction everywhere. Namely, if two subsystems have opposite arrow-directions at a particular time, the interaction between them makes the configuration statistically unstable and causes a decay towards a system with a universal direction of the arrow of (...) time. We present general qualitative arguments for that claim and support them by a detailed analysis of a toy model based on the baker’s map. (shrink)

Backtracking influence is influence that zigzags in time. For example, backtracking influence exists when an event E_1 makes an event E_2 more likely by way of a nomic connection that goes from E_1 back in time to an event C and then forward in time to E_2. I contend that in our local region of spacetime, at least, backtracking influence is redundant in the sense that any existing backtracking influence exerted by E_1 on E_2 is equivalent to E_1's temporally direct (...) influence on E_2. I prove the redundancy of backtracking influence using several plausible physical principles without assuming any fundamental temporal or causal asymmetry. This explanation can play a prominent role in an account of why causation appears to be objectively asymmetric regardless of whether the fundamental laws are symmetric. (shrink)

This volume sets the agenda for future work on time and chance, which are central to theemerging sub-field of metaphysics of science.

I conduct an empirical analysis of the temporally asymmetric character of our epistemic access to the world by providing an experimental scheme whose results represent the core empirical content of the epistemic asymmetry. I augment this empirical content by formulating a gedanken experiment inspired by a proposal from David Albert. This second experiment cannot be conducted using any technology that is likely to be developed in the foreseeable future, but the expected results help us to state an important constraint on (...) our ability to know the future. Finally, I show that a third experiment concerning precognition, described by Michael Scriven and John Mackie, does not characterize any additional empirical content but does help to illustrate why it is unlikely that any precognition exists. (shrink)

I provide a comprehensive metaphysics of causation based on the idea that fundamentally things are governed by the laws of physics, and that derivatively difference-making can be assessed in terms of what fundamental laws of physics imply for hypothesized events. Highlights include a general philosophical methodology, the fundamental/derivative distinction, and my mature account of causal asymmetry.

An explanation of our seeming inability to influence the past.

Why is our knowledge of the past so much more ‘expansive’ (to pick a suitably vague term) than our knowledge of the future, and what is the best way to capture the difference(s) (i.e., in what sense is knowledge of the past more ‘expansive’)? One could reasonably approach these questions by giving necessary conditions for different kinds of knowledge, and showing how some were satisfied by certain propositions about the past, and not by corresponding propositions about the future. I take (...) it that such is the approach of Chapter 6 of Time and Chance (T&C). Here’s another such a proposal, similar to that of, but significantly different from T&C; my purpose in this section is to highlight the differences, by showing how this account fails. (shrink)

This paper assesses branching spacetime theories in light of metaphysical considerations concerning time. I present the A, B, and C series in terms of the temporal structure they impose on sets of events, and raise problems for two elements of extant branching spacetime theories—McCall’s ‘branch attrition’, and the ‘no backward branching’ feature of Belnap’s ‘branching space-time’—in terms of their respective A- and B-theoretic nature. I argue that McCall’s presentation of branch attrition can only be coherently formulated on a model with (...) at least two temporal dimensions, and that this results in severing the link between branch attrition and the flow of time. I argue that ‘no backward branching’ prohibits Belnap’s theory from capturing the modal content of indeterministic physical theories, and results in it ascribing to the world a time-asymmetric modal structure that lacks physical justification. (shrink)

This paper defends Aristotle’s project of deriving the order of time from the order of change in Physics 4.11, against the objection that it contains a vicious circularity arising from the assumption that we cannot specify the direction of a change without invoking the temporal relations of its stages. It considers and rejects a solution to this objection proposed by Ursula Coope, and proposes an alternative solution. It also considers the related problem of how the temporal orders and directions derived (...) from individual changes can together constitute a single, globally consistent order and direction of time. (shrink)

Is it conceptually possible for an event, L, to be the cause of an earlier event, E? Some writers have employed the so-called bilking argument to attempt to show that the idea of such backwards causation is incoherent . According to this argument, if we are presented with what someone claims to be a case of backwards causation, it would be possible in principle to wait for E to occur, and then intervene to prevent the occurrence of L, thus demonstrating (...) that E could not have been caused by L after all. Moreover, if our attempts to bilk L-type events having observed E-type events always fail, we have grounds to argue that any causal relationship between the two is not one of backwards causation, but of ordinary, forwards, earlier-to-later causation.Does the bilking argument succeed in showing backwards causation to be incoherent? Before answering this question, let us deal with a far simpler reason for deeming backwards causation incoherent, whose elucidation now will be useful later. To those attracted to the view that temporal order is determined by causal order, 1 backwards causation may seem incoherent because on this view a cause is by definition earlier than its effect. I do not take issue with this view, and wish my conception of backwards causation to be compatible with it. 2 By ‘backwards causation’, I mean causation that runs in the opposite direction to some other causal processes, such that the temporal order entailed by such backwards causation is the reverse of that entailed by those other causal processes. In most philosophical discussions of backwards causation, we are at least implicitly given reasons to believe that these other causal processes dictate the …. (shrink)