{"id":336063,"date":"2025-12-08T01:18:11","date_gmt":"2025-12-08T01:18:11","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/336063\/"},"modified":"2025-12-08T01:18:11","modified_gmt":"2025-12-08T01:18:11","slug":"time-might-not-exist-and-were-starting-to-understand-why","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/336063\/","title":{"rendered":"Time might not exist \u2013 and we’re starting to understand why"},"content":{"rendered":"

The nature of time<\/a> is one of the most profound and longstanding problems in physics \u2013 one that no one can agree on<\/a>. From our perspective, time seems to steadily progress forward with each tick of the clock.<\/p>\n

But the closer we look, the more bizarre time becomes \u2013 from equations that state time should flow as freely backwards<\/a> as it does forwards, to the strange quantum realm where cause and effect can flip on their heads.<\/p>\n

Could it even be that time itself is an illusion<\/a>?<\/p>\n

What makes time so confounding is that we have three very different ways of defining it, which don\u2019t easily fit together.<\/p>\n

The first definition comes from the equations that describe how things change over time.<\/p>\n

We have many such equations describing everything from the motion of tennis balls to the decay of atomic nuclei. In all these equations, time is a quantity, referred to as \u2018coordinate time<\/a>\u2019.<\/p>\n

Time is no more than a mathematical label to which we can assign a particular value.<\/p>\n

The second definition of time comes from Einstein\u2019s theories of relativity, where it\u2019s a dimension<\/a> in addition to the three we\u2019re familiar with. It\u2019s a direction in four-dimensional spacetime.<\/p>\n

Our picture of reality then becomes one in which all times \u2013 past, present and future \u2013 are equally real and co-exist, just as all points in space are equally real.<\/p>\n

More than that; time has a deep connection with gravity<\/a> according to General Relativity, where the shape of spacetime is influenced by gravity.<\/p>\n

Much of the effort at the forefront of theoretical physics over the past half-century has been devoted to unifying General Relativity with the strange world of quantum mechanics.<\/p>\n

Mathematical frameworks that attempt to do this are known as theories of quantum gravity.<\/p>\n

But how do we reconcile these two notions of time \u2013 the quantum mechanical idea, in which time is a mere parameter, versus the relativistic idea that time is a dimension in spacetime?<\/p>\n

I call this \u2018the first problem of physical time\u2019.<\/p>\n

Time in quantum gravity<\/p>\n

The reason it\u2019s so difficult to reconcile quantum mechanics with General Relativity is that their mathematics are fundamentally incompatible.<\/p>\n

Not only that, but quantum effects primarily govern very small scales such as subatomic particles, while gravity impacts much larger scales such as planets and galaxies, so trying to create an experiment where both scales are not only relevant, but can be accurately measured, has proved exceedingly difficult.<\/p>\n

Early attempts at unifying a quantum description of reality with the 4D spacetime of General Relativity led John Wheeler and Bryce DeWitt to come up with an equation \u2013 the Wheeler-DeWitt equation<\/a> \u2013 in 1967, in which time no longer appears at all.<\/p>\n

What they were attempting to describe is the quantum state of the entire Universe, independent of time. This, many physicists have suggested, means that time might just be an illusion.<\/p>\n

But should we be so radical or dismissive about time? We\u2019ve come a long way since then, so how does time enter current attempts to develop a theory of quantum gravity?<\/p>\n

Here, things get very murky.<\/p>\n

Some approaches still start from something like traditional coordinate time, but then add time again as part of a spacetime with more dimensions than the four we\u2019re used to.<\/p>\n

In other approaches, time emerges from more fundamental concepts about the Universe.<\/p>\n

Time might even turn out to be \u2018quantised\u2019, meaning that if we were to zoom down to small enough scales, we would see both time and space as lumpy. So, we end up with quanta (atoms) of spacetime.<\/p>\n

Combining quantum mechanics and General Relativity is all well and good, but there\u2018s one key mystery it doesn\u2019t address: why does time only seem to flow in one direction?<\/p>\n

\"IllustrationSuperstring theory, which views the constituents of the Universe as vibrating strings rather than points in space, is an attempt to unify quantum mechanics and General Relativity, but requires a wholly different understanding of time – Image credit: Science Photo Library<\/p>\n

This brings us to the third definition of time, stemming from thermodynamics, which describes the properties of large numbers of particles treated in terms of macro quantities like heat, temperature and pressure.<\/p>\n

Here, time is neither a dimension nor a label, but a direction \u2013 pointing from the past to the future.<\/p>\n

This is typically phrased as being in the direction of increasing entropy: our unwinding Universe, balls rolling downhill, ice cubes melting in a glass of water and so on.<\/p>\n

However, despite all the irreversible processes we see around us, the fact is that, in all the fundamental equations of physics, reversing the direction of time doesn\u2019t prevent the equations from working.<\/p>\n

That is, time could point either way and we wouldn\u2019t be able to tell the future from the past. Yet we see a clear difference between the past and the future.<\/p>\n

This is \u2018the second problem of physical time\u2019. How do we reconcile the fact that our equations work just as well whichever way time is running with the irreversibility of time that we experience in the world?<\/p>\n

For this, we might have to look towards the quantum domain and the strange phenomena of entanglement.<\/p>\n

Read more:<\/p>\n

Quantum entanglement<\/p>\n

Quantum objects like electrons or photons can have properties that are not fixed before they\u2019re measured, such as location, momentum, energy or spin direction.<\/p>\n

That is, they can exist in a \u2018quantum superposition<\/a>\u2019 of having a range of values at once, such as being spread out in space or spinning in two directions at the same time.<\/p>\n

Only when we choose to observe a property do we force the quantum system to decide on one of the many options of that property it was co-existing in.<\/p>\n

But if, before our measurement, an electron interacts with a second one, then this second electron can be \u2018infected\u2019 by the superposition of the first. It\u2019ll also find itself in a limbo state prior to measurement.<\/p>\n

We say the two electrons are quantum entangled<\/a> and we have to describe them as a single quantum entity.<\/p>\n

\"QuantumQuantum entanglement (illustrated here) is a theory that links two particles across time and space. Changes to one particle will be reflected in the other – Image credit: Science Photo Library<\/p>\n

The strange feature of entanglement is that observing just one of the two electrons also forces the second to snap into one of the available options in its superposition. This will happen at the same time, however far apart they are.<\/p>\n

And it\u2019s not even the entanglement between two electrons that needs to be considered. The entire Universe can become \u2013 indeed will inevitably become \u2013 quantum entangled with its surroundings.<\/p>\n

In fact, we should stop thinking of quantum entanglement as some sort of bizarre phenomenon that only rarely happens in nature, or that it\u2019s \u2018spooky\u2019, as Einstein once said.<\/p>\n

Rather, it\u2019s one of the most, if not the most prevalent process in the Universe. So, how can it help us demystify the nature of time?<\/p>\n

In 1983, Don Page and William Wootters first suggested<\/a> a link between time and quantum entanglement, rescuing time from the timeless Wheeler-DeWitt equation.<\/p>\n

Imagine that some hypothetical quantum clock is entangled with its environment.<\/p>\n

Instead of thinking of the clock being in a superposition of two locations in space, we can combine them into an entangled clock+environment system in a superposition of states at different times.<\/p>\n

Now, when we measure the clock by reading the time, it forces the clock\u2019s environment to snap into what it was doing at that time only.<\/p>\n

So, what if we think of the overall state of the Universe, which might be timeless, as being composed of two parts: (1) a clock and (2) everything else?<\/p>\n

For us, embedded within the \u2018everything else\u2019, perceiving a particular time amounts to measuring the clock at that time, so we perceive reality \u2013 the clock\u2019s environment, aka the Universe \u2013 at that moment.<\/p>\n

But, viewed from \u2018outside\u2019 the Universe, all times co-exist and there\u2019s no \u2018passage\u2019 of time, as Wheeler and DeWitt argued.<\/p>\n

Quantum causality<\/p>\n

If quantum mechanics tells us that a system can be in a superposition of states at two different times, then this has an even more fascinating consequence when we consider the ordering of cause and effect.<\/p>\n

That is, for something to occur, the cause must come before the effect.<\/p>\n

Consider two events, A and B, such as flashes of light<\/a> made by two sources in different places.<\/p>\n

Cause and effect means there are three possibilities: 1) Flash A happened before flash B, and via some mechanism, could have triggered B; 2) Flash B happened before Flash A and could have triggered it; 3) Neither one could have triggered the other because they are too far apart in space and too close in time for a triggering signal to have been sent from one location to the other.<\/p>\n

\"IllustrationEntropy, the idea that the order of a system breaks down as time moves forwards, is perceived as being inevitable and irreversible. But our theories appear to suggest otherwise – Image credit: Science Photo Library<\/p>\n

Now, Einstein\u2019s Special Theory of Relativity states that all observers, no matter how fast they\u2019re moving relative to each other, see light travelling at the same constant speed.<\/p>\n

This strange but simple fact can lead to observers seeing events happening in different orders.<\/p>\n

For option (3) above, two observers moving relative to each other close to the speed of light might disagree on the ordering of flashes.<\/p>\n

Thankfully, there\u2019s no danger of an effect coming before its cause (known as a \u2018violation of causality\u2019) since the events are too far apart for either to cause the other.<\/p>\n

However, what if options (1) and (2) coexisted in a quantum superposition? The causal order of the two events would no longer be fixed.<\/p>\n

They would exist in a combined state of Flash A happening before and triggering Flash B, and of B happening first. We see then that cause and effect can become blurred when we bring quantum mechanics and relativity together.<\/p>\n

It gets even weirder when we introduce gravity via General Relativity.<\/p>\n

Here\u2019s an interesting thought experiment. Imagine two quantum entangled clocks, each in a superposition of different heights above Earth\u2019s surface.<\/p>\n

According to General Relativity, this would mean the two clocks tick at slightly different rates, due to the slight difference in the gravitational field.<\/p>\n

The superposition here is a combination of State 1 in which clock A is higher than clock B, and so ticking a little faster, and State 2 in which the clocks are swapped over.<\/p>\n

Until this combined entangled state is measured by reading the time on one of the clocks, it\u2019s not possible to determine the ordering of any events recorded by the two clocks.<\/p>\n

And if we can\u2019t determine which events are in the future and which are in the past, we arrive at the possibility of events acting backwards in time to cause events in their past.<\/p>\n

If, at the quantum level, events in the past can be affected by events in the future, then all bets are off.<\/p>\n

While some physicists argue that causality is sacred and must be preserved at all costs, others have argued in favour of the idea of retrocausality (the future affecting the past) and even of quantum time travel.<\/p>\n

It may well be the case that even if we find our true theory of quantum gravity, time will turn out not to be one single concept, but rather a multi-faceted, complex thing.<\/p>\n

Perhaps it really does retain its different properties depending on how we\u2019re using it: a dimension of spacetime, a coordinate to be measured against, and an irreversible arrow<\/a>.<\/p>\n

All of these are only meaningful in the approximate, zoomed-out way we subjectively perceive time. Maybe that\u2019s the best we can hope for.<\/p>\n

Or maybe, just maybe, we need to dig even deeper into the mysteries of time.<\/p>\n

Read more:<\/p>\n","protected":false},"excerpt":{"rendered":"The nature of time is one of the most profound and longstanding problems in physics \u2013 one that…\n","protected":false},"author":2,"featured_media":336064,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[199,79],"class_list":{"0":"post-336063","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/336063","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=336063"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/336063\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/336064"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=336063"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=336063"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=336063"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}