What the universe reveals about time

By Marta Kuhn

Like the heartbeat of our universe, time seems to tick away with every passing second. In Western cultures, we perceive time as flowing along an imaginary arrow, from past to future. It’s hard to imagine our universe without it – but what is time, and where does it come from?

These fundamental questions lie at the heart of the ERC-funded PROTEUS project, led by Silvia De Bianchi, which brought together physicists, philosophers and historians to rethink the nature of time across disciplines.

While it is generally believed that the universe began with a hot Big Bang around 13.8 billion years ago, some theories – particularly in quantum gravity and quantum cosmology – suggest that the universe had no beginning in time. Time, as we know it, may simply not have existed at the very origin. As Stephen Hawking once famously put it, asking what came ‘before’ the Big Bang may be as meaningless as asking what is south of the South Pole. But if time itself had not yet begun, how can we even think about a ‘beginning’? To say that time is an illusion or that it does not exist do not represent suitable solutions.

The problem of time

Modern physics rests on two equally important but seemingly incompatible pillars.

The first is Albert Einstein’s theory of general relativity – our best explanation of gravity and the universe at the large scales, from planetary orbits to the structure of galaxies. ‘On the one hand, we have a four-dimensional continuum – spacetime – that is ubiquitous in the description of the geometric structure of the universe,’ explains Silvia De Bianchi. Warped and curved by mass and energy, time forms part of this dynamic, continuous structure. In this sense, time is not fixed or static; it passes differently depending on where you are and how fast you move.

The second pillar is quantum mechanics – our leading theory of matter at the small scales, ruling the discrete quantum world of atoms and particles. Here, the picture looks strikingly different: ‘We don’t find this continuous structure in quantum physics,’ De Bianchi notes. ‘Time is associated with an external parameter – a clock, if you wish.’ Rather than being woven into the fabric of the universe, time in quantum mechanics is simply assumed to be there, like a fixed background against which events unfold.

‘For more than 70 years, physics has been trying to produce a unitary picture of phenomena that concern both the early universe and the microcosmos,’ says De Bianchi. Yet this has proven notoriously difficult. When physicists attempt to reconcile general relativity with quantum mechanics into a unified theory of quantum gravity, their two radically different conceptions of time clash head-on. 

In some approaches, it is suggested that what we experience as time and space would not be basic ingredients of reality, but something emergent: spacetime arising from relational patterns at a deeper level, much like temperature emerges from the collective motion of molecules. 

However, as De Bianchi points out, this hypothesis comes with its own conceptual problem: it implies a transition in time – even though time is meant to emerge. To address this, PROTEUS turned not only to physics, but also to the long history of philosophy.

Like the shape-shifting Proteus 

The idea that time could have emerged from a deeper, more fundamental reality is not new at all. ‘It has been discussed in the history of philosophy since Plato’s Timaeus,’ says De Bianchi, referring to the ancient Greek philosopher’s dialogue about the formation of the universe. ‘If we look back, we see that the answers to the cosmological problem were different, but the questions that Plato asked were structurally very similar.’

This observation is also what inspired the project’s name: Proteus, the Greek sea god known for evading capture by constantly changing shape. Like the mythical Proteus, the problem of time has recurred throughout history in different guises, reflecting a persistent tension between viewing time as fundamental or emergent.

‘It’s a tension between philosophers like Plato, who thought that time was generated and not fundamental, and philosophers like Kant, who believed that we must consider time as pure form of intuition,’ De Bianchi explains. ‘Time is always presupposed in our representation – as a condition of human thought and experience.’

Revitalising an ancient idea

But how could past concepts of time help untangle current cosmological paradoxes?

The PROTEUS team found a crucial clue in the Platonic dialogues – one that had been neglected for centuries: ‘Plato had a very complex view of what we can call atemporality’, De Bianchi says. ‘He reasoned that even if temporality dominates the physical world, this fact did not necessarily exclude that its contrary could have assumed different forms. Due to Aristotle’s influence, we often conflate atemporal with eternal or to a mere negation of time.

But Plato proposed different notions of atemporality: the ‘Now’ and the instant. ‘The absolute present is, for Plato, not a dimension of time; the present is out of time.’

The same holds for the instant. What may sound rather counterintuitive is, in fact, a powerful theoretical move: it allows us to think of transitions that have no duration, such as a sudden switch between opposite states. ‘Through this definition of atemporality, you can solve paradoxes associated with time,’ De Bianchi explains.

This proves useful in scenarios proposed by quantum gravity, such as geometrogenesis, which suggest that spacetime emerged as a phase transition from a non-geometric to a geometric phase. ‘Is it possible to find a transition that can, at least conceptually or mathematically, be understood in atemporal terms? Yes, we found it, but another thing is to attribute physical meaning to it’ says De Bianchi.

The PI has also shown that by associating atemporality to the modern notion of imaginary time even in relativistic contexts important results are obtained: atemporality can be applied to black holes – without leading to mathematical breakdowns, or singularities, predicted by general relativity. 

Three disciplines in one room

With philosophers of science, historians of philosophy and theoretical physicists working side by side, the PROTEUS team’s set-up was in itself an experiment. ‘It’s a multidisciplinary project in the actual practice,’ says De Bianchi. ‘I put the historians of philosophy literally in the same room as the physicists, so they were forced to think differently.’ 

PROTEUS shows that the conceptual tools of philosophy remain relevant for cutting-edge physics and cosmology. De Bianchi suggests that this fruitful exchange is partly due to the current state of theory-building in quantum gravity. ‘If it had been a different historical period, I’m not sure that a project like PROTEUS could have been so successful.’

Building a digital legacy

An all-female team of PROTEUS researchers played a key role in translating these ideas into tangible outputs. Drawing on more than 100 works, they developed an AI-powered search engine capable of analysing philosophical texts in both ancient and modern languages.

They also created Timaeus and Its Legacy, a digital archive with nearly 500 sources -from antiquity to the 20th century - that reference or were inspired by Plato’s work on time and the universe.

‘Someone who wants to do research on the impact of Plato’s Timaeus throughout the history of Western culture can rely on this tool,’ says De Bianchi.

Biography

Silvia De Bianchi is Associate Professor of Logic and Philosophy of Science at the University of Milan and currently leading the COSMOS Project (2021-2026), working at the intersection of the foundations of physics, philosophy and cosmology. As PI of the ERC project PROTEUS (2018-2024), she worked on the conceptualisation of a new notion of atemporality that can solve inconsistencies in fundamental physics and philosophy of time. Recent publications include Time and Timelessness in Fundamental Physics and Cosmology, Achronotopic Interpretation of Quantum Mechanics, Atemporality from Conservation Laws of Physics in Lorentzian-Euclidean Black Holes, Building universes: the philosophical and mathematical underpinnings of cosmology (eighteenth-twentieth centuries).