Time is an object

Fernando Kaskais

May 30

Red-eyed tree frog, near Arenal Volcano, Costa Rica. Photo by Ben Roberts/Panos Pictures

Not a backdrop, an illusion or an emergent phenomenon, time has a physical size that can be measured in laboratories

Sara Walker is an astrobiologist and theoretical physicist at Arizona State University, where she is deputy director of the Beyond Center for Fundamental Concepts in Science and professor in the School of Earth and Space Exploration. She is also external professor at the Santa Fe Institute and a fellow at the Berggruen Institute.

Lee Cronin is Regius Chair of Chemistry at the University of Glasgow in Scotland and CEO of Chemify.

Atimeless universe is hard to imagine, but not because time is a technically complex or philosophically elusive concept. There is a more structural reason: imagining timelessness requires time to pass. Even when you try to imagine its absence, you sense it moving as your thoughts shift, your heart pumps blood to your brain, and images, sounds and smells move around you. The thing that is time never seems to stop. You may even feel woven into its ever-moving fabric as you experience the Universe coming together and apart. But is that how time really works?

According to Albert Einstein, our experience of the past, present and future is nothing more than 'a stubbornly persistent illusion'. According to Isaac Newton, time is nothing more than backdrop, outside of life. And according to the laws of thermodynamics, time is nothing more than entropy and heat. In the history of modern physics, there has never been a widely accepted theory in which a moving, directional sense of time is fundamental. Many of our most basic descriptions of nature – from the laws of movement to the properties of molecules and matter – seem to exist in a universe where time doesn't really pass. However, recent research across a variety of fields suggests that the movement of time might be more important than most physicists had once assumed.

A new form of physics called assembly theory suggests that a moving, directional sense of time is real and fundamental. It suggests that the complex objects in our Universe that have been made by life, including microbes, computers and cities, do not exist outside of time: they are impossible without the movement of time. From this perspective, the passing of time is not only intrinsic to the evolution of life or our experience of the Universe. It is also the ever-moving material fabric of the Universe itself. Time is an object. It has a physical size, like space. And it can be measured at a molecular level in laboratories.

The unification of time and space radically changed the trajectory of physics in the 20th century. It opened new possibilities for how we think about reality. What could the unification of time and matter do in our century? What happens when time is an object?

For Newton, time was fixed. In his laws of motion and gravity, which describe how objects change their position in space, time is an absolute backdrop. Newtonian time passes, but never changes. And it's a view of time that endures in modern physics – even in the wave functions of quantum mechanics time is a backdrop, not a fundamental feature. For Einstein, however, time was not absolute. It was relative to each observer. He described our experience of time passing as 'a stubbornly persistent illusion'. Einsteinian time is what is measured by the ticking of clocks; space is measured by the ticks on rulers that record distances. By studying the relative motions of ticking clocks and ticks on rulers, Einstein was able to combine the concepts of how we measure both space and time into a unified structure we now call 'spacetime'. In this structure, space is infinite and all points exist at once. But time, as Einstein described it, also has this property, which means that all times – past, present and future – are equally real. The result is sometimes called a 'block universe', which contains everything that has and will happen in space and time. Today, most physicists support the notion of the block universe.

But the block universe was cracked before it even arrived. In the early 1800s, nearly a century before Einstein developed the concept of spacetime, Nicolas Léonard Sadi Carnot and other physicists were already questioning the notion that time was either a backdrop or an illusion. These questions would continue into the 19th century as physicists such as Ludwig Boltzmann also began to turn their minds to the problems that came with a new kind of technology: the engine.

Though engines could be mechanically reproduced, physicists didn't know exactly how they functioned. Newtonian mechanics were reversible; engines were not. Newton's solar system ran equally well moving forward or backward in time...

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https://aeon.co/essays/time-is-not-an-illusion-its-an-object-with-physical-size