The friendship of Michele Besso and the “stubbornly persistent illusion”
Michele Besso was Albert Einstein’s closest friend since their student days in Zurich. They shared intense conversations at the Bern Patent Office while Einstein was developing Special Relativity. In fact, the landmark 1905 article, Zur Elektrodynamik bewegter Körper (On the Electrical Dynamics of Moving Bodies ), ends with an acknowledgment unusual in scientific literature: “I wish to note that my friend and colleague Michele Besso has rendered me a valuable service with several suggestions.”
When Besso died in Geneva in March 1955, an already ill Einstein wrote the family a letter of condolence that has become famous for one of its sentences: “Now he has left this strange world a little before me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is nothing but a stubbornly persistent illusion.” [1]
Einstein would die just a month later, on April 18, 1955. With that phrase he set in motion a debate that still runs through physics, philosophy and neuroscience today.
Time according to Einstein: the universe block
Special Relativity, particularly through the relativity of simultaneity, implies that there is no universal “now.” From this idea arises the concept of the block universe: a static, four-dimensional spacetime in which all events—past, present, and future—exist permanently and equally.
In this view, time does not flow; it simply is . All moments coexist within the geometric structure of spacetime. From this perspective, Besso’s death “meant nothing” because his life continued to exist eternally at some coordinate within the block. The fundamental laws of physics, from Newton to relativity, are largely symmetrical with respect to time (reversible), which reinforces the idea that “time flow” could be a mere subjective construct.
Einstein himself seemed to accept that the human experience of the present was a psychological illusion. However, he was not entirely comfortable with this conclusion. Rudolf Carnap recounts a revealing conversation in his memoirs: “Einstein stated that the problem of the ‘now’ troubled him deeply. The experience of the present has a special significance for human beings, but that difference cannot be expressed within physics. For Einstein, this limitation was unavoidable, but also unsettling: science describes the world, but does not fully capture the experience of lived time.” [2]
Criticism of the block universe
In recent decades, this interpretation has been strongly challenged. Philosophers such as Tim Maudlin have pointed out that calling the block universe “static” creates a contradiction: if nothing changes, how is it possible that we experience change? Causality and scientific explanation depend on a real temporal direction: earlier states explain later ones, but not vice versa. [3]
From the field of physics, Ilya Prigogine (Nobel Prize in Chemistry 1977) harshly criticized Einstein’s timeless vision. Classical and reversible laws explain the movement of the planets well, but they fail to account for the irreversible processes that dominate the real world: heat conduction, diffusion, vortex formation, or biological evolution.
Prigogine demonstrated, through non-equilibrium thermodynamics, that systems far from equilibrium can generate dissipative structures: order and complexity emerge thanks to irreversibility. For him, time is not an illusion, but a fundamental ingredient of creative reality.
George Ellis: The Evolving Block Universe
George Ellis, a South African cosmologist and physicist, offers one of the most consistent proposals for overcoming the static block without abandoning general relativity. [4]
Ellis argues that at its most basic level, reality is composed of quantum interactions. In quantum mechanics, a system exists in a superposition of states (many possibilities) until a measurement or decoherence process occurs. At that instant, the multiple options “collapse” into a single, definitive reality—an intrinsically irreversible process. This constant transformation of uncertain futures into a fixed and immutable past is the passage of time.
He defends the evolving block universe model in which the past exists in a fixed way and has causal power; the future does not yet exist: it is indeterminate and is full of quantum possibilities; the present is the moving boundary of space-time, where quantum uncertainty (superposition of states) becomes a defined reality through processes of decoherence and measurement.
Ellis also integrates top-down causation (from higher to lower levels) and the emergence of complexity, showing that time is necessary for both physics and biology.
Mind and time: the Bayesian brain
The physics of the universe and the biology of the mind converge in the “now.” Ellis states that the present is where quantum possibilities become fixed facts. Every time the brain processes a stimulus, it is participating in the physical process of “building” the past. Our perception of the “now” is the subjective experience of that process of reality-making. We feel that time flows because our biology is physically present at the “boundary” where spacetime is being fabricated.
We know that a sensory lag exists because light travels faster than sound, and tactile signals from the feet take longer to reach the brain than those from the nose. If the brain were a passive mirror, we would perceive a fragmented and desynchronized reality. Therefore, the brain retains the fastest signals and waits for the slowest ones to form a single, simultaneous event. This integration window lasts about 80 to 100 milliseconds; the brain doesn’t process reality as a continuous flow, but in time-dimensioned chunks.
In this sensory process, we don’t perceive what has just happened, nor even what the sensory signals indicate about it, but rather what the brain concludes is most likely occurring at that precise moment. This functioning, akin to statistical inference [5] , has given rise to the concept of the “Bayesian brain” [6] . That is, the brain continuously generates predictions about the world, compares them with sensory data, and minimizes prediction error. It actively integrates memory (past experience), attention (present information), and expectation (future predictions). This dynamic process generates the sensation of temporal flow and a unified “now.”
The proximity of current neuroscience to the thinking of Saint Augustine from fifteen centuries ago is striking, as he already located time within the interiority of the mind [7] . In the Confessions , he defines time as distentio animi : a distension of the soul that simultaneously unites memory of the past, attention to the present, and expectation of the future. The time we experience is not a mere appearance, but the way in which a conscious predictive system participates in the continuous construction of reality. [8]
How to understand time today
George Ellis’s evolving block universe offers a framework where quantum physics, relativity, thermodynamics, biology, and conscious experience converge.
From this perspective, time is neither a mere illusion (as Einstein suggested) nor simply a subjective experience. It is a real process that manifests itself on multiple levels: in quantum decoherence; in thermodynamic irreversibility; in the emergence of complex structures and life; in the predictive dynamics of the mind.
From this perspective, Augustine of Hippo’s intuition takes on a new meaning: the time we experience is not a mere appearance, but the expression of a universe that, instead of being given all at once, is continually being made.
Manuel Ribes . Institute of Life Sciences. Bioethics Observatory. Catholic University of Valencia
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[1] Einstein, A. (1905), Zur Elektrodynamik bewegter Körper. Ann. Phys., 322: 891-921. https://doi.org/10.1002/andp.19053221004
[2] The philosophy of Rudolf Carnap EDITED BY PAUL ARTHUR SCHILPP NORTHWESTERN UNIVERSITY LA SALLE, ILLINOIS Open Court Publishing Company 1963
[3] George Musser A Defense of the Reality of Time Quanta Magazine May 16, 2017
[4] George FR Ellis On the Flow of Time arXiv:0812.0240v1 [gr-qc] 1 Dec 2008
[5] Bayesian inference is a type of statistical inference in which evidence or observations are used to update or infer the probability that a hypothesis may be true.
[6] The term Bayesian brain has been consolidated from the article Knill, DC, & Pouget, A. (2004). The Bayesian brain: The role of uncertainty in neural coding and computation . Trends in Neurosciences , 27(12), 712–719.
[7] M. Ribes Time… do we carry it within us? UCV Bioethics Observatory April 22, 2022
[8] Saint Augustine Confessions Editorial Gredos SA ISBN: 978-84-249-1505-6