Time Is an Illusion—Meaning the Past, Present, and Future Exist Simultaneously

Our everyday lives operate on the notion that time is real, with every second slipping by uncontrollably. Rush hour traffic, lunch breaks, dinnertime—it’s all fixed around a set, 24-hour schedule. But what if it was all just an illusion, and time doesn’t exist? As a physicist, I’d like to explain how quantum physics leads us to this startling conclusion and speculate on how that could possibly change the laws of physics.

Photo by Sasun Bughdaryan on Unsplash

For starters—whether or not time is real—we never measure it directly. Instead, we use another physical system called a clock, whose positions actually indicate different moments in time. For early humans, the sun and the moon served as natural clocks, with their positions in the sky telling the time. Astronomers still use distant stars for the same purpose (“distant” so that Earth’s motion doesn’t significantly distort the time-keeping). However, scientists have since developed even more sophisticated methods, such as atomic clocks; these measure how many times an electron shifts its position within an atom. Typically, this occurs one hundred million billion times per second, providing a reliable tick of about 10 to the power of -16 seconds.

All of the above illustrate the point that we always use the change of state of one system and call this a time measurement. Because time is ultimately a measurement of changes in other systems, rather than a separate entity in its own right, we can eliminate it from all fundamental equations of change in physics.

Think about a race car doing laps around a track. Exactly as it completes the first lap, the hand on the stopwatch points at one. At the end of the second lap, the hand points at two and so on. We see that all we need here is a correlated table of the car’s positions relative to the stopwatch. This clearly shows that we do not need the variable “t” (standing for time) anywhere in the equations. There is no time, nor is there any flow of it. Everything can be encapsulated by questions of the form: when the hand of the stopwatch is in the position 57, where is the car? And the table will tell us that the car has just completed lap number 57.

The same “trick” applies in quantum mechanics. Quantum physics—or the study of matter and energy at the finest level—is all about the states of physical systems and how they change in time (dynamics). In order to eliminate time, we need to assign a correlated state between the system’s positions and the corresponding positions of the clock. In fact, this kind of correlation is called entanglement in quantum mechanics, and it says that once we look at the state of the clock, we immediately know the state of the system.

This approach is known as the Page–Wootters picture, named after Don Page and Bill Wootters, who authored a paper titled “Evolution without evolution” in 1983, proposing this entangled state. They aimed to describe how dynamics arises from the entangled state between the system and the clock, which itself (the entangled state) remains unchanged over time. This is exactly like the correlated table of positions of the race car and the hand of the stopwatch, since that table also doesn’t “change in time.” The dynamics that emerges at the system level are described by the usual Schrödinger equation (the same Schrödinger of the cat fame, who suggested that, according to quantum mechanics, both dead and alive version of a cat should be able to exist), which is regarded as the most fundamental law of dynamics in physics.

This magical property of quantum timelessness is that different instances of time now become different universes! Time emerges out of entanglement in the same way that the dead and alive cat emerge through entanglement with the decaying atom and the poison in Schrödinger experiment. This is fascinating because the property of being in another universe (say, seeing a living cat instead of a dead one) now becomes equivalent to existing at another time (which, incidentally, we do routinely by just waiting a bit).

What are the main consequences of this extraordinary fact? First of all, it implies that the past and the future exist “at the same time” as the present. In fact, there is nothing special about the moment we call “now” since every instant is a now instant. Likewise, time does not flow; the river of time is not carrying us from the present to the future. Even more interestingly, entering another time just means that your conscious perception is now correlated with the universe’s new state. This means that the “now” could be randomly hopping between different worlds in the quantum entangled state of the universe and we would still perceive the same apparent Schrödinger dynamics as we normally do.

In that sense, Saint Augustine—a fourth-century Christian theologian and philosopher—was correct to say that the past exists in our memories and the future in our anticipations. Time travel is, therefore, entirely consistent with the timeless concept, although it can be dull because, if we were to jump to a previous time, our memories in that state would only correspond to “earlier times.” We simply would not remember (and there would be no other record of it elsewhere) that we came from the future. Likewise, if we traveled from the past directly into the future, our future state would include all the memories of the intervening periods, so we would never be able to tell that we came directly from a distant past.

Einstein’s view of the universe aligned with this, and he found great comfort in it. He wrote to the wife of his closest friend, Michele Besso: “Now he has departed from this strange world a little ahead of me. That means nothing. For us believing physicists, the distinction between past, present and future is only a stubbornly persistent illusion.”

However, an even more intriguing question for a physicist is: what new possibilities could we explore if the universe truly is timeless?

Being a physicist, the most fantastical possibility is this: by performing measurements on the universal clock in a suitable way, we might be able to alter the dynamics of the rest of the universe. Instead of the Schrödinger equation, we could derive a different law of dynamics. That, quite astonishingly, would suggest that the laws of physics are perhaps not fixed but can be shaped through our actions. When we speak of mastering nature, it does not get any better than being able to reprogram its laws—and this might only be possible because time itself does not truly exist.