Is time a fundamental reality or a trick of the brain?

Science · Published 24 October 2026 Swipe more like this →

In short: We experience time as a river flowing from past to future, but modern physics suggests this might be a mental shortcut. From the equations of relativity to the mysteries of quantum mechanics, science is increasingly finding that the "now" we feel might not exist in the physical world at all.

While Isaac Newton viewed time as an absolute constant, Albert Einstein revolutionized our understanding by showing that time is intertwined with space to form "space-time." In this framework, time can stretch and compress. This led to the concept of the "block universe," where time functions like a spatial dimension. In this model, every event has its own fixed coordinates, making the future no more "open" than the past is fixed.

However, quantum mechanics presents a different challenge. Unlike general relativity, quantum equations often do not include time as a built-in property. For instance, the Wheeler-DeWitt equation—a quantum description of gravity—describes the universe purely in terms of events and relationships without requiring time to pass. Rather than being a basic property of existence, time is viewed by certain thinkers, such as Carlo Rovelli, as a secondary phenomenon. They suggest that "events," rather than objects, are the basic building blocks of reality, similar to individual still frames in a movie.

If time isn't fundamental, why do we perceive it so vividly? Physicists suggest this may be due to our limited perspective and the laws of thermodynamics. Because we cannot see the world in microscopic detail, our brains simplify the steady increase of entropy—the march toward disorder—into a linear "arrow of time." Furthermore, recent research into quantum entanglement suggests that time might emerge only for objects entangled with a "clock" system; for unentangled systems, time may simply not exist. Ultimately, because we cannot currently test whether time is non-existent, the debate remains one of science's greatest mysteries.

Isaac Newton maintained that time was universal and moved uniformly for all observers, whereas Albert Einstein demonstrated that space and time are linked to create space-time.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Time might not be a fundamental feature of our universe
• Physicists may not actually know what time is
• Gravity can literally stretch and slow the flow of time
• Is the future already real, or is time just a persistent human illusion?
• Does time actually flow, or is our perception of the present just an illusion?
• Can we finally develop a universal flu vaccine that targets every single strain?
• Could a cubic planet like the one in Minecraft actually exist in our universe?
• Could human hibernation be the key to surviving long-duration space travel to Mars?
• Could fungal intelligence hold the secret to human survival?
• Could a simple blood test spot Alzheimer’s decades before symptoms?
• Could a bottle of eye drops finally make reading glasses obsolete?
• The science of doppelgängers and the possibility of hidden kinship

More in Science · Latest · A–Z · All topics