A commentary on “Physical Time Within Human Time”

In: Timing & Time Perception
Paolo Di Sia School of Science & School of Engineering, University of Padova, 35122 Padova, Italy
School of Medicine, Applied Technical Sciences, University of Verona, 37124 Verona, Italy
Primordial Dynamic Space Research, Verona, Italy

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This work underlines the importance of studying time and its connections with real life and with disciplines such as physics, mathematics and neuroscience. The problem of time is a very important issue from a transdisciplinary point of view and should be better supported by research and funds.

1. Introduction

The ancient Greek philosophers initiated the great debate of whether or not time is an illusion. Currently, many physicists opt for Einstein’s view that the past/present/future are illusions. A line of thinking holds that time does not exist at the fundamental level, but at a derivative level. There are many philosophical speculations, which, however, must also be connected to the concrete facts of neuroscience and experimental psychology.

Works have been (and are being) written on the current disagreements between neuroscience and physics about the problem of time, which involves its ‘flow’, and physical concepts as the entropy and various models of the universe, such as the block universe. The interesting work of Gruber and colleagues fits into this context: it is full of connections, stimulating ideas and supported by an extensive bibliography (Gruber et al., 2022).

2. The ‘Two-Times Problem’

The ‘two-times’ problem is treated with a unified theory of manifest time, which considers human temporal experiences, with the use of IGUS (information-gathering and -utilizing system)-type systems in Hartle’s original proposal and modified with more ‘gadgets’ to take into account various other phenomena. Hartle proposed a means of trying to reconcile the ‘physical now’ with the ‘experiential now’.

Past, present and future wouldn’t be properties of 4D spacetime, but notions describing how individual IGUSes manipulate information, linking the subjectivity of the past/present/future with the physics of time. ‘Manifest time’ is also considered, as the sum of human temporal experiences suddenly perceived and recognized by the mind, and connected to ‘subjective time’ and to the flow (passage) of time.

3. Connecting Neuroscience with the Physics of Time

Many current cosmological theories of spacetime consider the block universe as a basis, with modifications to allow its growth and to show an objective basis for the ‘time flow’. It is emphasized that to date there is no empirical evidence for the block universe; it can be misleading as it suggests a static reality. Furthermore, the various cosmological models do not agree with each other and it is necessary to investigate which ones can be considered correct and therefore supported.

The distinction between past and future requires thermodynamics, so it is statistical in nature. Physics believes that it is a task of neuroscience to account for the subjective experience of the flow of time, since it can be a collateral effect of how the brain uses information about the past to predict the future.

Neuroscience asks to physics to try to explain how the sense of the flow of time considers the reality and involves the theories of brain function and evolution (Buonomano, 2017). The ‘time inversion’ invariance of the fundamental physical laws and relativity create discrepancies. The ‘arrow of time’ appears to be a complex probabilistic macroscopic phenomenon, a consequence of the increase in entropy relating to the second law of thermodynamics and the low initial entropy of the universe (Rovelli, 2020).

The idea of a preferred oriented temporal variable allowing irreversible processes is well defined in the domain in which the biosphere develops, even if it is not universally defined. From relativity follows that the distinction between past, present and future must be finer than in the common-sense view of temporality. Compared to the ‘here and now’, many events in the universe are neither past nor future.

Time plays a special role also in neuroscience; the brain is an intrinsically temporal organ because for many aspects its primary function is to learn from the past in order to better predict the future.

Two extreme formulations on the nature of time are related to ‘presentism’ and ‘eternalism’. These are not accurate names that are interpreted in a distinct way by the various authors. It seems that both of these extreme views of time are not appropriate for describing nature. Physics does not describe static entities, but processes; it concerns events and change. Neuroscience has historically taken presentism as its starting point, considering that the subjective experiences of human being are consistent with it.

A possible solution key concerns considering time as a multi-layered concept. Normally, humans interact with a small number of dynamic variables relative to the number of dynamically correlated degrees of freedom; moreover, the entropy defined by these variables was low in the past universe. From that it follows that physical phenomenology on the human scale is well described by thermodynamics and undoubtedly time-oriented. In this sense we can say that the distinction between past and future is objective.

It should also be emphasized that it is not easy (nor perhaps possible) to develop an adequate perception of temporality in the domains which are outside the nonrelativistic and thermodynamic approximations, as well as outside the approximation that does not consider quantum gravitational effects. To date, there are no scientifically accepted empirical observations in contradiction with relativity, but this is not necessarily the case in the future. All the more, there remain evident (and perhaps insurmountable) empirical holes in unified theories (even at higher dimensions than 4) involving quantum aspects and very high energies.

Fundamental physics, with its development and discoveries, does not doubt about the congruence of the conceptual tools used in neurosciences; it believes that they are appropriate and well founded, but in certain limited domains and based on approximations.

4. Discussion

The deep understanding of the phenomenology of experiential time requires a careful interaction between physics and neuroscience. It is constructive to assign portions of sovereignty to the two fields and determine the issues that benefit from a bridge between neuroscience and physics. The basis concerns principles established by both disciplines (physics and cognitive sciences) and from there developing a more complete view through theories that explain and hopefully predict. As a system for collecting and using information (IGUS), humans have a past/present/future experience that is consistent with physical laws.

The human being needs to feel a persistence and that they are not just a union of impermanent events, as indicated by the main cosmological theories of spacetime. The human being in the present in motion needs to believe that they are a single individual and not a multiplicity of momentary individuals that extend backward in time. The human experience rests on the sensation of a flow of time, with the present moment constantly moving into the past and introducing the future, over which the human being seeks control.

The experiential past, present and future do not fit to be properties of 4D spacetime, but notions describing how humans process information. A line of thought concerns the possibility that, through the natural selection, the veridical system generated the illusory system to obtain a globally better temporal system in relation to the general functionality of the human being.

The dialogue between neuroscience and physics allows us to examine and clarify the common points and discrepancies regarding the nature of time, separating the different problems and not considering time as a single mono-layer concept. It remains therefore opportune and fruitful to separate the aspects of temporality explained by physics from those that can be explained by neuroscience (Buonomano & Rovelli, forthcoming).

The phenomenology of human experiential time is closely connected with the problem of consciousness; its understanding concerns in particular neuroscience and psychology, not physics, even if the boundary between the competences of the two disciplines remains unclear and dark in some parts. It is therefore essential on the one hand to perfect our understanding of fundamental physics in relation to time, and on the other the way in which our brain deals with and manages time and allows us to experience its flow.

There are two types of descriptions of the universe: (a) the description in the ‘first person’, that is what human, individually and collectively, observes the universe; (b) the description in the ‘third person’, that is, the universe as it is, what it contains, how it is organized and how it changes over time. These two different modes of description are linked to the concept of ‘observer’.

Science is interested in developing theories in the third person, since they are objective; but with the development of quantum mechanics and, in particular, with the Copenhagen interpretation of the quantum world, the situation has changed, suggesting that the observer can influence the experiments. Quantum mechanics does not describe reality as it really is, but as it is perceived by an observer. Seeking a possible solution to this counterintuitive and strange aspect of reality (for classical macroscopic observers), alternative interpretations of quantum physics have been proposed (and are being proposed), including the Everett’s interpretation, or ‘many worlds interpretation’.

There is still a lot to understand about why we remember the past and not the future, and why we can influence the future but not the past. The paper by Gruber and colleagues is undoubtedly a stimulus for discussion and a help in addressing the problem of time by aiming for ever better clarity. It is certainly constructive to think and carry out future experiments and mental experiments. However, it should be remembered that the so-called ‘hard science’ has inevitable limits; a global understanding of the human being and the ultimate meaning of life seems to have to go through the development of holistic theories, concerning not only ordinary matter and energy (Di Sia, 2021a, b, c, 2022).

The problem of time is a very important issue from a transdisciplinary point of view and should be better supported by research funds.

The inter/transdisciplinarity in the research on time is essential; every scientific, phenomenological and metaphysical investigation on time is important, contributing decisively to the complex picture of the nature of temporality.

Our daily experience of temporality is also important; analyzing the ways in which time enters in the everyday ordinary practices and language provides insights that are as crucial to the end goal as those that derive from cosmology and metaphysics.

All this constitutes an important background for the current growing interest in creating artificial devices that follow human behavior. In such designs it seems that devices need to be equipped with temporal experience capabilities similar to ours. Advances in this direction will depend on an analysis of time that considers its multiple manifestations.


All claims expressed in this article are solely those of the author and do not necessarily represent those of his affiliated organizations, or those of the publisher, the editors and the reviewers.

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


This research received no external funding.


  • Buonomano, D., & Rovelli, C. (forthcoming). Bridging the neuroscience and physics of time. In P. Harris and R. Lestienne (Eds), Time and science. Singapore: World Scientific. arXiv preprint arXiv:2110.01976.

    • Search Google Scholar
    • Export Citation
  • Buonomano, D. V. (2017). Your brain is a time machine: the neuroscience and physics of time. New York, NY, USA: W.W. Norton.

  • Di Sia, P. (2021a). Interdisciplinary insights about the concept of time. Int. J. Sci. Res. Mod. Educ., 6, 1416. doi: 10.5281/zenodo.4727049.

    • Search Google Scholar
    • Export Citation
  • Di Sia, P. (2021b). On the concept of time in everyday life and between physics and mathematics. Ergon. Int. J., 5, 268. doi: 10.23880/eoij-16000268.

    • Search Google Scholar
    • Export Citation
  • Di Sia, P. (2021c). On advances of contemporary physics about totality. Int. J. Sci. Res. Mod. Educ., 7, 812. doi: 10.5281/zenodo.4642485.

    • Search Google Scholar
    • Export Citation
  • Di Sia, P. The Primordial Dynamic Space (Introduction 1). OSFPreprint [Preprint] (2022). Available at:

  • Gruber, R. P., Block, R. A., & Montemayor, C. (2022). Physical time within human time. Front. Psychol., 13, 718505. doi: 10.3389/fpsyg.2022.718505.

    • Search Google Scholar
    • Export Citation
  • Rovelli, C. (2020). Memory and Entropy. ArXiv preprint doi: 10.48550/arXiv.2003.06687.

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