The Illusion of Time: What’s Real?
Why is time controversial? It feels real, always there, inexorably moving forward. Time has flow, runs like a river. Time has direction, always advances. Time has order, one thing after another. Time has duration, a quantifiable period between events. Time has a privileged present, only now is real. Time seems to be the universal background through which all events proceed, such that order can be sequenced and durations measured.
The question is whether these features are actual realities of the physical world or artificial constructs of human mentality. Time may not be what time seems — this smooth unity without parts, the ever-existing stage on which all happenings happen.
Is time physical?
To appreciate time is to feel the fabric of reality. I interview physicists and philosophers on my public television series, “Closer to Truth,” and many assert that time is an illusion. What do they mean that time is “not real?”
Huw Price, professor of philosophy at Cambridge University, claims that the three basic properties of time come not from the physical world but from our mental states: A present moment that is special; some kind of flow or passage; and an absolute direction.
“What physics gives us,” Price said, “is the so-called ‘block universe,’ where time is just part of a four-dimensional space-time … and space-time itself is not fundamental but emerges out of some deeper structure.”
We sense an “arrow” or direction of time, and even of causation, he said, because our minds add a “subjective ingredient” to reality, “so that we are projecting onto the world the temporal perspective that we have as agents [in this environment].” [Alan Alda Asks: ‘What Is Time?’]
Think of the block universe, which is supported by Einstein’s theory of relativity, as a four-dimensional space-time structure where time is like space, in that every event has its own coordinates, or address, in space-time. Time is tenseless, all points equally “real,” so that future and past are no less real than the present.
Time is, was, will be?
So, are we being misled by our human perspectives? Is our sense that time flows, or passes, and has a necessary direction, false? Are we giving false import to the present moment?
“We can portray our reality as either a three-dimensional place where stuff happens over time,” said Massachusetts Institute of Technology physicist Max Tegmark, “or as a four-dimensional place where nothing happens [‘block universe’] — and if it really is the second picture, then change really is an illusion, because there’s nothing that’s changing; it’s all just there — past, present, future.
“So life is like a movie, and space-time is like the DVD,” he added; “there’s nothing about the DVD itself that is changing in any way, even though there’s all this drama unfolding in the movie. We have the illusion, at any given moment, that the past already happened and the future doesn’t yet exist, and that things are changing. But all I’m ever aware of is my brain state right now. The only reason I feel like I have a past is that my brain contains memories.”
“Time is out there,” said Andreas Albrecht, a theoretical cosmologist at the University of California, Davis. “It’s called an external parameter — the independent parameter in the [classic] equation of motion. So, time — the time we know since we learned to tell time on a clock — seems to disappear when you study physics, until you get to relativity.
“The essence of relativity is that there is no absolute time, no absolute space. Everything is relative. When you try to discuss time in the context of the universe, you need the simple idea that you isolate part of the universe and call it your clock, and time evolution is only about the relationship between some parts of the universe and that thing you called your clock.” [5 of the Most Precise Clocks Ever Made]
Julian Barbour, a British physicist, describes time as “a succession of pictures, a succession of snapshots, changing continuously one into another. I’m looking at you; you’re nodding your head. Without that change, we wouldn’t have any notion of time.”
“Isaac Newton,” Barbour noted, “insisted that even if absolutely nothing at all happened, time would be passing, and that I believe is completely wrong.”
To Barbour, change is real, but time is not. Time is only a reflection of change. From change, our brains construct a sense of time as if it were flowing. As he puts it, all the “evidence we have for time is encoded in static configurations, which we see or experience subjectively, all of them fitting together to make time seem linear.”
It’s not all illusory?
But not all physicists are ready to demote time to second-class status.
John Polkinghorne, a quantum physicist, and Anglican priest believes that the flow and direction of time are real and relentless. It is a “mistaken argument,” he said, to use relativity to assert that time is an illusion, “because no observer has knowledge of a distant event, or the simultaneity of different events, until they are unambiguously in that observer’s past. And, therefore, that argument focuses on the way observers organize their description of the past and cannot establish the reality of the awaiting future.”
Polkinghorne rejects the notion of the static block universe of space and time together. “We live in a world of unfolding and becoming,” he said.
Fotini Markopoulou-Kalamara, a theoretical physicist at the Perimeter Institute, said, “I have the distressing experience of physicists telling me that time is not real. … It confuses me, because time seems to be real. Things happen. When I clap my hands, it happened. … I would prefer to say that general relativity is not the final theory than to say that time does not exist.”
Time is a prime conflict between relativity and quantum mechanics, measured and malleable in relativity while assumed as background (and not an observable) in quantum mechanics. To many physicists, while we experience time as psychologically real, time is not fundamentally real. At the deepest foundations of nature, time is not a primitive, irreducible element or concept required to construct reality.
The idea that time is not real is counterintuitive. But many ideas about how the world works that humanity had taken for granted have required a complete rethink. As Tegmark puts it, “There’ve been so many things in physics that we thought were fundamental that turned out to be mere illusions, that we’re questioning everything — even time.”
What reality is depends on what time is. Is time irreducible, fundamental, an ultimate descriptor of bedrock reality? Or is our subjective sense of flowing time, generated by our brains that evolved for other purposes, an illusion?
Opinion is divided, but many physicists and philosophers now suspect that time is not fundamental; rather, time emerges out of something more fundamental — something nontemporal, something altogether different (perhaps something discreet, quantized, not continuous, smooth).
The alternative, of course, is our common intuition: time does flow, the present is superspecial as the only real moment, and the deep nature of reality is one of becoming.
I cannot decide.
If a tree falls in a forest and no one is there to hear it, does it make a sound? Perhaps not, some say.
And if someone is there to hear it? If you think that means it obviously did make a sound, you might need to revise that opinion.
New paradox in quantum mechanics has been found that throws doubt on some common-sense ideas about physical reality.
Quantum mechanics vs. common sense
Take a look at these three statements:
When someone observes an event happening, it really happened.
It is possible to make free choices, or at least, statistically random choices.
A choice made in one place cannot instantly affect a distant event. (Physicists call this “locality”.)
These are all intuitive ideas, and widely believed even by physicists. But research, published in Nature Physics, shows they cannot all be true — or quantum mechanics itself must break down at some level.
This is the strongest result yet in a long series of discoveries in quantum mechanics that have upended our ideas about reality. To understand why it is so important, let’s look at this history. For Niels Bohr, one of the founders of the theory a century ago, that is not because we lack information, but because physical properties like “position” do not actually exist until they are measured.
And what is more, because some properties of a particle can’t be perfectly observed simultaneously — such as position and velocity — they can’t be real simultaneously.
No less a figure than Albert Einstein found this idea untenable. In a 1935 article with fellow theorists Boris Podolsky and Nathan Rosen, he argued there must be more to reality than what quantum mechanics could describe. For example, an observer measuring the position of the first particle could perfectly predict the result of measuring the position of the distant one, without even touching it. Or the observer could choose to predict the velocity instead. This had a natural explanation, they argued, if both properties existed before being measured, contrary to Bohr’s interpretation.
However, in 1964 Northern Irish physicist John Bell found Einstein’s argument broke down if you carried out a more complicated combination of different measurements on the two particles. Bell showed that if the two observers randomly and independently choose between measuring one or another property of their particles, like position or velocity, the average results cannot be explained in any theory where both position and velocity were pre-existing local properties.
That sounds incredible, but experiments have now conclusively demonstrated Bell’s correlations do occur. For many physicists, this is evidence that Bohr was right: physical properties don’t exist until they are measured.
But that raises the crucial question: what is so special about a “measurement”?
The observer, observed
In 1961, the Hungarian-American theoretical physicist Eugene Wigner devised a thought experiment to show what’s so tricky about the idea of measurement. He considered a situation in which his friend goes into a tightly sealed lab and performs a measurement on a quantum particle — its position, say.
However, Wigner noticed that if he applied the equations of quantum mechanics to describe this situation from the outside, the result was quite different. Instead of the friend’s measurement making the particle’s position real, from Wigner’s perspective the friend becomes entangled with the particle and infected with the uncertainty that surrounds it.
This is similar to Schrödinger’s famous cat, a thought experiment in which the fate of a cat in a box becomes entangled with a random quantum event.
For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer becomes involved, the entanglement would “collapse” to make the friend’s observation definite.
But what if Wigner was wrong?
Our experiment
In our research, we built on an extended version of the Wigner’s friend paradox, first proposed by Časlav Brukner of the University of Vienna. In this scenario, there are two physicists — call them Alice and Bob — each with their own friends (Charlie and Debbie) in two distant labs.
There’s another twist: Charlie and Debbie are now measuring a pair of entangled particles, like in the Bell experiments.
As in Wigner’s argument, the equations of quantum mechanics tell us Charlie and Debbie should become entangled with their observed particles. But because those particles were already entangled with each other, Charlie and Debbie themselves should become entangled — in theory.
But what does that imply experimentally?
Our experiment goes like this: the friends enter their labs and measure their particles. Some time later, Alice and Bob each flip a coin. If it’s heads, they open the door and ask their friend what they saw. If it’s tails, they perform a different measurement.
This different measurement always gives a positive outcome for Alice if Charlie is entangled with his observed particle in the way calculated by Wigner. Likewise, for Bob and Debbie.
In any realization of this measurement, however, any record of their friend’s observation inside the lab is blocked from reaching the external world. Charlie or Debbie will not remember having seen anything inside the lab, as if waking up from total anaesthesia.
But did it really happen, even if they do not remember it?
If the three intuitive ideas at the beginning of this article are correct, each friend saw a real and unique outcome for their measurement inside the lab, independent of whether or not Alice or Bob later decided to open their door. Also, what Alice and Charlie see should not depend on how Bob’s distant coin lands, and vice versa.
We showed that if this were the case, there would be limits to the correlations Alice and Bob could expect to see between their results. We also showed that quantum mechanics predicts Alice and Bob will see correlations that go beyond those limits.
Next, we did an experiment to confirm the quantum mechanical predictions using pairs of entangled photons. The role of each friend’s measurement was played by one of two paths each photon may take in the setup, depending on a property of the photon called “polarization”. That is, the path “measures” the polarization.
Our experiment is only really a proof of principle, since the “friends” are very small and simple. But it opens the question whether the same results would hold with more complex observers.
We may never be able to do this experiment with real humans. But we argue that it may one day be possible to create a conclusive demonstration if the “friend” is a human-level artificial intelligence running in a massive quantum computer.
What does it all mean?
Although a conclusive test may be decades away, if the quantum mechanical predictions continue to hold, this has strong implications for our understanding of reality — even more so than the Bell correlations. For one, the correlations we discovered cannot be explained just by saying that physical properties don’t exist until they are measured.
Now the absolute reality of measurement outcomes themselves is called into question.
Our results force physicists to deal with the measurement problem head on: either our experiment doesn’t scale up, and quantum mechanics gives way to a so-called “objective collapse theory”, or one of our three common-sense assumptions must be rejected.
There are theories, like de Broglie-Bohm, that postulate “action at a distance”, in which actions can have instantaneous effects elsewhere in the universe. However, this is in direct conflict with Einstein’s theory of relativity.
Some search for a theory that rejects freedom of choice, but they either require backwards causality, or a seemingly conspiratorial form of fatalism called “superdeterminism”.
Another way to resolve the conflict could be to make Einstein’s theory even more relative. For Einstein, different observers could disagree about when or where something happens — but what happens was an absolute fact.
However, in some interpretations, such as relational quantum mechanics, QBism, or the many-worlds interpretation, events themselves may occur only relative to one or more observers. A fallen tree observed by one may not be a fact for everyone else.
All of this does not imply that you can choose your own reality. Firstly, you can choose what questions you ask, but the answers are given by the world. And even in a relational world, when two observers communicate, their realities are entangled. In this way a shared reality can emerge.
Which means that if we both witness the same tree falling and you say you cannot hear it, you might just need a hearing aid.
As stated earlier, at the deepest foundations of nature, time is not a primitive, irreducible element or concept required to construct reality. Opinion is divided, but many physicists and philosophers now suspect that time is not fundamental; rather, time emerges out of something more fundamental — something nontemporal, something altogether different (perhaps something discreet, quantized, not continuous, smooth). Furthermore, Physical properties do not exist until they are measured. For one, the correlations we discovered cannot be explained just by saying that physical properties do not exist until they are measured. Therefore, the conflict between physicist (those who do not believe in God) that subscribe to the Big Bang Theory of the origin of the universe dating back to thirteen and half billion years ago, and the creationist (those who believe in God and the Bible) that interpreted the Bible literarily viz a viz Creation is six to seven thousand years ago, is following the reasoning in parts of this article, thus nullified by the argument that time is an illusion.
Summing up this scientific article, which consists of latest information as of the time of publishing in September 2020, a recourse can be made to an article allegedly written at least 5000 years ago, that is the book of Job in the Christian Bible, wherein the concepts and principles mentioned above were discussed, such as Time, Space, Universe and matter including an observer and a measurer. God posed a series of questions to Job, the account of which was documented in Job 38:4-5; “Where were you[observer] when[time] I laid the earth’s foundation?[universe and space] Tell me, if you understand. Who marked off its dimensions?[observer and measurer] Surely you know! Who stretched a measuring line across it? It seems that science up till now does not have an explanation or theory of everything that explains the origin of the universe(s), including the birth and death of stars (we still do not know near enough about black holes or dark holes), so we might as well accept the explanation of God and His Book.
References:
https://www.space.com/quantum-paradox-throws-doubt-on-observed-reality.html
