Is Time An Illusion?

It’s pithy, and not really all that accurate, but it does get across an important truth: that time, or at least our perception of it, is more fluid than we often assume. We can stretch time, spend it, make it, kill it; if we go fast enough, or get too close to the wrong black hole, we can slow it down to almost an infinite degree. At the same time, it’s stubbornly inscrutable – always half-hidden, and defying any attempt to fully nail it down as a concept.

“As so often in philosophy, there’s not really an agreement with respect to what time is,” says Giuliano Torrengo, an Associate Professor of Philosophy at the University of Milan and founder and coordinator of the Centre for Philosophy of Time (CPT). “And so there’s not really an agreement [on] a definition of time.”

“There’s a bunch of things that we can discuss” about the concept, he added. “And within each aspect there’s usually no real agreement either.”

What’s the time?

The quest to unravel the mystery of time has been around for a long – well, a long time. “It started, really, with two philosophers which you probably have heard about,” explains Giuseppe Spolaore, an associate professor of the philosophy of language at the University of Padua, and senior member of the CPT.

It’s not just that there is not a common definition – you first have to agree what you aim to define.

Giuliano Torrengo

“There was Heraclitus, the one who said panta rhei – everything flows, or everything changes; you cannot bathe twice in the same river, stuff like that,” Spolaore tells IFLScience. “And there was Parmenides, who told us – in the few fragments we have – that ‘Being’ is completely uniform, [and] that everything, every kind of change, every kind of variety, only emerges from the fact that you have different perspectives [of that].”

Like math or language, time is one of those weird conceptual things where we all know it exists – we all experience it, and use it every day, after all – but we’re not necessarily all in agreement about what “exists” means. Ask a philosopher for a definition of time, and you’re likely to give them quite a headache: “with time, the situation might be in a sense worse […] than with other concepts,” Torrengo says. “It’s not just that there is not a common definition – you first have to agree what you aim to define.”

Are you asking about the physical reality of time? Its extrinsic versus intrinsic properties? The distinction between past, present, and future? All of the above? None of them? 

“‘Time’ is a bit of an umbrella term,” Torrengo tells IFLScience. “Nobody would just take ‘time’ as the object of investigation, without pointing out that there’s a lot of objects there.”

The question is perhaps easier for those in the hard sciences – even if the answer seems somehow even more vague. “Time as it appears in our equations is – well, it’s the master variable, under which the world unfolds,” explained Frank Wilczek, winner of the 2004 Nobel Prize in Physics and the 2022 Templeton Prize and Herman Feshbach Professor of Physics at MIT, among many other accolades, in Quanta’s Joy of Why podcast last year. 

“So, it’s a symbol, t, that appears in our equations,” he said. “And by following the equations, we get hints about what t is.”

Here’s the problem, though: time isn’t just a variable, is it? It’s not like space, or speed, or mass – more-or-less static quantities that we get to stand completely apart from as we study them. It’s not even totally clear that it exists outside of our own experience – to misquote George Berkeley and various others, if a universe exists and there’s no consciousness around to witness it, does any time pass?

The time of our lives

There are, basically, two points of view here. Well, as with any topic in philosophy, there are innumerable points of view – but they more or less boil down to this: either time exists, with events happening “within” it in some way, or else it doesn’t, and what we know as “time” is really just a way of describing the order in which things occur.

“I’d say that the most common position is probably the Aristotelian one,” says Spolaore. “[That] says, more or less, that time is just an emergent reality; [it] emerges from the fact that there is change – that there are different things at different times.”

It’s perhaps not the most intuitive idea outside of philosophy classrooms – but it has the weight of physics behind it. “It’s probably the received view among physicists,” Spolaore tells IFLScience. “That the ‘arrow of time’ emerges from the distribution of events.”

It’s an idea that leads to some pretty mind-bending conclusions. If “time” is just defined by things happening – and we can get pretty technical here, invoking concepts like entropy and thermodynamics – then, well, what happens if they occur in the other direction? 

You can draw this analogy and say also, time has a direction in a way, but it is only because we are in the proximity of a very large event – the Big Bang.

Giuseppe Spolaore

It’s not as nonsensical as it sounds. After all, ask a Dark Ages scholar whether it’s always true that objects fall down, and they would answer of course: that’s a fundamental law of nature. Enter Kepler and Newton, however, and the frame changes; now we know that gravity just draws things toward any large object – the fact that “everything” falls down here is due only to our position on top of such a massive ball of rock.

Similarly, the law that “entropy increases” may just be an artifact of some other massive influence on our perspective, Spolaore suggests. “You can draw this analogy and say also, time has a direction in a way, but it is only because we are in the proximity of a very large event – the Big Bang,” he tells IFLScience. 

That was “an event having very, very low entropy,” he adds. “And so, this entropy is only bound to increase from that event. And the direction of time is just the direction of entropy.”

Time to give up?

It goes without saying that none of these ideas are universally accepted – this is philosophy, for goodness’ sake. Some people think time exists outside of external events; that the direction of the arrow of time is a fundamental truth – and there’s nothing to say that’s wrong: “You can construct solutions of the basic laws of physics – so, consistent with all the basic principles we know – where nothing happens,” Wilczek pointed out, “and t is still an ingredient of those equations.”

Equally, there are those who reject the concept of time entirely – or at least, the idea of it “passing” in any real sense. It’s a “radical position,” Torrengo says, but one with some surprisingly big names attached: “Emmanuel Kant is not very so far away from that,” he tells IFLScience, pointing to the enlightenment thinker’s view of time not as any feature of the real world, but as a kind of inescapable perceptual prison of our own creation.

And here’s the thing: maybe that’s the closest we’re going to get to a real answer on the reality of time. It may exist; it may not – but either way, we’re kind of stuck with it. And it’s stuck with us.

“Even if we assume that there is an objective flow of time, it’s not clear that would make any difference for our experience,” Torrengo tells IFLScience. “And regardless of whether you think there is an objective passage of time or not, you need an explanation of the passage of time in terms of what happens in your mind.”

Asked whether he thinks time is an illusion, Torrengo removes his glasses. Time, he says, is akin to the blurriness of the world seen without spectacles: “an experience of something that elicits a certain belief not in virtue of what is presented, but in virtue of how it is presented.” 

Time, in other words, may be real, and may not be – but either way, we can’t really exist without it. It’s the only way we know how to perceive the world; a result of our place in the universe, our brains, and the necessary limits both impose on our understanding of reality. 

So, is time an illusion? Perhaps, as with so many of life’s big questions, the answer is somewhere in the middle.

“‘Illusion’ is a very heavy word,” cautions Spolaore. “It’s a very loaded word.” 

“I don’t think time is an illusion,” he says, “but I think that our constructive contribution is much larger than we tend to think.”