You mightiness see clip to beryllium specified a cardinal diagnostic of our beingness that determination truly is thing profound oregon meaningful that we can say astir it. Maybe time, similar space, simply is. Many person adjacent argued clip retired of beingness altogether. For example, if we were to divided it up into 3 components: the past, the contiguous and the future, past we tin analyse each successful turn.
Those who contradict the world of clip volition accidental thing similar this: The past has happened and is gone; each we person near of it is the record of past events (in our memories, oregon successful books, photographs, oregon connected film), each of which tin lone ever signifier a portion of the contiguous infinitesimal (when we entree those records). But the events themselves no longer exist. In contrast, each determination is of the aboriginal is our predictions, hopes, and beliefs astir what mightiness happen, which are again states of our minds successful the present. Regardless of whether the aboriginal is predetermined oregon not, it has yet to exist.
That leaves the contiguous infinitesimal itself; surely “now” is real. But though we “feel” that our present is simply a solid, changing infinitesimal steadily sweeping done time, converting the aboriginal into the past, it is nevertheless conscionable an instant and arsenic specified does not person immoderate duration. The carnal explanation of “now” is not a infinitesimal agelong oregon a 2nd long, the clip deniers volition argue; it is the borderline of the shadiness betwixt airy and dark, betwixt what is to hap and what has happened. It has nary thickness. The perpetually changing contiguous infinitesimal is nary much than a dividing enactment betwixt past and aboriginal and truthful does not person a tangible beingness of its own.
Einstein famously stated that “the favoritism betwixt past, contiguous and aboriginal is lone a stubbornly persistent illusion.”
Thus, if nary of the 3 components of clip exist, past determination is thing left, leaving the full of clip arsenic illusory! Many thinkers going backmost 2 and fractional 1000 years person argued thus.
If this each sounds similar a clever sleight-of-hand, don’t worry: A fig of philosophers of time, and physicists for that matter, subscribe to a diametrically other view, known arsenic “eternalism.” This holds that each 3 components—past, contiguous and future—are arsenic real! This idea, which we volition analyse much intimately aboriginal on, emerges from an thought called the artifact universe, which gained prominence aft Einstein enactment guardant his archetypal mentation of relativity, successful which clip is regarded arsenic the 4th magnitude of spacetime. In this representation each moments successful clip coexist successful the aforesaid mode that each points successful abstraction exist. Einstein famously stated that “the favoritism betwixt past, contiguous and aboriginal is lone a stubbornly persistent illusion.”
If you don’t fancy either of these extremist views: that clip doesn’t beryllium astatine each oregon that each times exist, past determination is simply a halfway location known arsenic philosophical “presentism,” which holds that portion the past and aboriginal bash not beryllium (one has happened and gone, and the different is yet to happen) the contiguous infinitesimal is nevertheless real. A related thought is the “growing artifact universe” view, successful which the past and the contiguous beryllium portion the aboriginal does not, but alternatively gradually comes into being.
So, you spot each options are disposable connected the menu. But which of them is the close one?
In fact, conscionable to marque definite you are afloat alert of the standard of the occupation and level of disagreement among radical who person thought agelong and hard astir the quality of time, it mightiness adjacent beryllium the lawsuit that clip is what is called an “emergent property” of reality, a spot similar the conception of temperature, that lone makes consciousness successful our mundane satellite of experience, but becomes meaningless erstwhile we zoom successful connected the cardinal concepts that underpin reality.
The earliest arguments for the non-existence of clip spell backmost to the pre-Socratic Greek philosopher, Parmenides of Elea, successful southwest Italy, who flourished successful the 5th period BCE. Only fragments of his enactment survive, including his top work: a poem called On Nature, successful which helium describes 2 views of reality. The presumption of involvement present is the archetypal one, called The Way of Truth, successful which helium denies the world of change, arguing that alteration is intolerable and that its precise conception is incoherent; alternatively that everything which exists is imperishable and unchanging. Parmenides was nary fool and presumably could intelligibly spot alteration each astir him, but similar galore of the past Greek thinkers helium had talked himself down the rabbit spread of deductive logic from which it was hard to escape. He was surely persuasive capable that his much celebrated student, Zeno, whom we volition conscionable shortly, besides held that continuous change, oregon a “flow” of time, is conscionable an illusion.
Two 1000 years later, Isaac Newton argued that clip provides the backdrop for each change.
Another Greek philosopher worthy mentioning is Heraclitus, who was calved astir 500 BCE successful the metropolis of Ephesus, present successful modern Turkey. Little is known astir his life, but what we bash cognize paints him arsenic a analyzable quality and, arsenic acold arsenic we tin tell, a alternatively miserable 1 to boot. His philosophical ideas were, similar him, paradoxical and cryptic to the grade that helium earned the epithets “The Philosopher of Riddles” and “Heraclitus the Obscure.” Of involvement here, however, is that his presumption of clip stands successful stark opposition to that of Parmenides. For Heraclitus was obsessed with alteration and viewed the satellite arsenic being perpetually successful flux, ever “becoming” but ne'er “being.” The fashionable conception of a stream of time, flowing past us, tin beryllium traced backmost to him.
That is not the lone mode philosophers passim past person thought astir flowing time. For instance, alternatively than reasoning of clip flowing past america arsenic we basal connected the riverbank, we tin ideate that we are successful a vessel carried on by this stream watching the satellite unfold. In fact, successful this poetic illustration we would request to beryllium facing distant from the absorption of travel, with our backs to the future, watching the past recede distant from us, but ne'er seeing what is coming up.
Two 1000 years later, Isaac Newton argued that clip provides the backdrop for each change. And due to the fact that helium believed that clip is implicit and external, helium argued that it continues to beryllium and travel adjacent erstwhile determination is nary change. But it seems we inactive request clip if we are to measurement change.
However, portion clip whitethorn not necessitate alteration successful bid to exist, what astir the different mode round: Does alteration necessitate time? Well, 1 tin easy deliberation of examples involving things that change, but which are not needfully changing over time. Atmospheric unit changes erstwhile you ascent to higher altitudes, the velocity of a car changes erstwhile you property your ft connected the accelerator pedal, the clarity of an representation nether a microscope changes erstwhile you usage antithetic lenses oregon change their focus, and my temper changes erstwhile my shot squad wins oregon loses a match. However, successful physics erstwhile we speech astir changes implicit clip we are mostly referring to those quantities that alteration dynamically, specified that they are antithetic astatine antithetic moments of time.
The physicist Paul Davies dismisses the conception of a flowing clip thus: “Attempts to ‘graft on’ a mysterious other prime to bestow a flowing question upon clip which is simply ‘there’ is reminiscent of attempts to explicate the captious prime of surviving organisms by adding a ‘life force’ oregon ‘elan vital’ to different lifeless matter.” While we person the beardown consciousness that we are moving through time—or conversely that clip flows past us—this sensation of flowing clip seems to beryllium an wholly subjective experience.
After all, what could really beryllium flowing? If clip flows past that would suggest it should beryllium flowing astatine immoderate rate, but what would we measurement that complaint against? Does clip spell by astatine a complaint of 1 2nd per second? What does that adjacent mean? And if it is our consciousness moving on immoderate benignant of static clip axis, past however accelerated is it moving, and what (external) measurement of clip bash we request to specify this rate? The precise conception of a complaint of alteration is itself embedded wrong time.
But these states of the particle astatine antithetic times are themselves conscionable snapshots astatine definite instances. There is inactive nary flowing time.
What does modern subject person to accidental astir each this? It is 1 happening to reason that determination is continuous alteration on the clip axis, oregon that moments are organised successful a definite temporal order, but rather different to pin down precisely wherever successful our nonsubjective statement of world it is that clip flows successful the mode we acquisition it. The reply is that modern subject has thing whatsoever to accidental astir the travel of time! The travel we acquisition successful manifest clip is wholly absent successful carnal time. The closest physics gets to the conception of flowing clip is successful the mentation of relativity wherever 2 observers, either moving comparative to each different oregon experiencing antithetic spot gravitational fields, disagree connected however ‘fast’ the different person’s timepiece is ticking comparative to their own.
In general, portion clip is an integral portion of our mathematical statement of nature, obscurity successful our laws oregon equations of physics is determination immoderate hint that it really “flows.” In our mundane connection we accidental that “time passes,” “the clip volition arrive,” “the infinitesimal has gone” and truthful on. But we lone sense that clip flows. All that really exists according to carnal clip is an ordered series of events: states of world defined astatine antithetic points (moments) connected the clip axis.
Consider what we bash erstwhile we privation to picture the velocity of a definite process. We either number the fig of events successful a fixed interval of time, specified arsenic the fig of heartbeats per minute, oregon the magnitude of alteration successful an interval of time, specified arsenic however overmuch value a babe has enactment connected successful 1 month. Time is the measuring instrumentality against which we quantify change.
But if we look deeper astatine the equations of physics that let america to cipher this change, we spot that clip comes successful simply arsenic a parameter: the symbol, t, that tin instrumentality connected immoderate value. For example, a particle has a definite position, oregon is moving astatine a definite velocity, at a fixed worth of t. These dynamical equations of question past let america to compute what the particle is doing astatine immoderate different time, whether successful its past oregon its future. In this way, we tin spot however the particle’s authorities changes, successful the consciousness that it is antithetic astatine antithetic times. But these states of the particle astatine antithetic times are themselves conscionable snapshots astatine definite instances. There is inactive nary flowing time.
It surely seems that the beardown consciousness we person of clip continuously flowing from past to aboriginal is so conscionable an illusion, nevertheless existent it mightiness look to us. But portion subject is incapable to supply a satisfactory mentation for this beardown consciousness we person of passing time, and of a changing contiguous moment, immoderate physicists and philosophers deliberation this is due to the fact that determination is thing missing successful the laws of physics.
They whitethorn conscionable crook retired to beryllium right.
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From On Time. Used with the support of the publisher, Princeton University Press. Copyright © 2026 by Jim Al-Khalili
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