This article was originally published in the Spring 2026 Print edition.
Time governs everything we do, but physics still struggles to pin down what it actually is.
In everyday experience (and in classical physics), time appears universal and uniform; however, relativity dismantled that assumption. We know from Einstein that time depends on motion and gravity – clocks moving at high speeds or sitting in strong gravitational fields tick slower relative to others. Take, for instance, GPS satellites, which require relativistic corrections to function. So, time is not a neutral background per se; it is physical, local and observer-dependent.
Science fiction often exaggerates these ideas, with talk of time travel, reversible time loops and so on. Christopher Nolan’s Interstellar is a rare exception worth treating seriously. Near the black hole Gargantua, the film depicts extreme gravitational time dilation: hours for the astronauts correspond to years for observers on Earth. This effect is a direct prediction of general relativity, calculated for the film by physicist Kip Thorne.
But the deeper uncertainty lies not in Hollywood; it’s right at the heart of physics itself. At the intersection of general relativity and quantum mechanics, there is still no complete theory, a tension often referred to as the Problem of Time. In fact, in some approaches to quantum gravity, time does not appear as a fundamental variable at all. The Wheeler–DeWitt equation, for example, contains no explicit time parameter, describing a universe without a preferred temporal evolution. Other frameworks treat change relationally, with time emerging from correlations between physical systems rather than existing as a universal clock.
This does not mean physics has concluded that time is unreal. Some theories, such as canonical quantum mechanics, treat time as a fundamental parameter against which systems evolve. Others, including loop quantum gravity and relational approaches, suggest time may be emergent, with temporal order arising from the relationships between systems. What matters is that there is no consensus.
Meanwhile, psychology and neuroscience show that our experience of time is largely constructed. Attention, memory and emotion shape duration judgments; the brain infers time from change rather than measuring it directly. The feeling of time passing may reflect cognition tracking motion, causality and entropy.
Thinking about time – how it bends, how we perceive it, how it runs out – can be unsettling. But it’s also exactly the kind of thing worth thinking about, because it shapes how we live, learn and try to make sense of the world.
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