While theoretical physics delves into the basics nature of realityWe’re left to deal with the questions he leaves us. For example, some physicists claim that we have The universe is an illusionthe product of quantum machinations occurring in a low-dimensional environment—in other words, a hologram.
But do these latest theoretical insights make discoveries in reality, themselves, or are they just mathematical tools that help us solve thorny problems? When it comes to the most advanced theories of physics, what is the product of our imagination, and what is the product of the universe?
Black holes may be a clue
The problem began with these pranksters in the universe, the black holes. Ostensibly (and bright readers will later be rewarded with the realization that this is a pun), black holes Simple things fall in and never get out. All information about these objects is locked away beyond the event horizon, never to be seen again. But in the 1970s, the famous astrophysicist Stephen Hawking realized that black holes are not entirely black. It is a little gray and a little leaky, emitting a tiny amount of radiation, which is causing black holes To slowly, but inevitably, evaporate completely out of existence.
However, this radiation does not carry any information with it, which leads to a nasty paradox: Information It enters, but does not exit, and then the black hole disappears. So what happened to all the information?
✅ In this context, Information It is a list of all the properties of all the particles that fell into the black hole – in other words, everything you need to reconstruct the original objects that fell into it. Instead, what comes out of the black hole, due to Hawking radiation, is just a collection of random particles. You can’t tell what happened based on the outgoing radiation.
The main evidence has come in the decades since Hawking’s extraordinary discovery. One way to measure the amount of information is through Entropy, a thermodynamic concept which are closely related to the amount of disturbance in the system. Black holes have a surprising property: they are entropy It is proportional to its surface area, not its volume. In other words, the amount of information in a black hole is related to its two-dimensional surface, not its three-dimensional volume.
The concept of entropy It describes the tendency of a system to transition from order to disorder, because there are many more ways for a disordered state to exist than there is for an ordered state. For example, you can clean your room, there is only one way to clean the room. However, there are countless ways to make it not clean, or get messy, like adding a smear of dirt or a stray sock stuck in a corner. So over time, the entropy should increase. This applies to any system in the universe, not just your room.
This is very different from any other object in the entire universe, and naturally a lot of physicists became very interested in black holes, with top-notch physicists like Leonard Susskind leading the charge to this new Earth from The principle of holography. The name comes from holography itself. ever seen a hologram In real life, the image seems to jump out at you? That’s because the hologram encodes all three-dimensional information into a two-dimensional surface.
So, there seems to be something funny about black holes, as their information seems to be encoded on their two-dimensional surfaces. Perhaps the same applies to the entire universe.
A two-dimensional universe?
This idea isn’t as crazy as it first appears, because we may already have a working example of the hologram principle in action. It’s known by the somewhat embarrassing name of the AdS/CFT correspondence, and was developed in 1997 by physicist Juan Maldacena.
To understand, let’s build a special kind of universe with some strange properties. First, this universe has five spatial dimensions. Secondly, it is completely devoid of matter and radiation. Third, it contains a constant cosmic force that bends you inward. This type of Free time It is called counterspace (five-dimensional).
Now, suppose you’re trying to solve a very complex problem within this universe, like how Quantum gravity He works. We’ve been trying to solve quantum gravity for nearly a century, and although we don’t have any answers yet, we do have a host of tools that we hope will one day lead us to one. This set of tools is known as string theory.
✅ Let’s break down some of the more complex concepts.
Quantum gravity is an understanding of gravity applied to the smallest things in the universe, such as subatomic particles. We can understand the behavior of these particles using quantum mechanics, but when gravity becomes strong, as it does inside black holes, our theories fall apart. Quantum gravity is an attempt to fix these broken theories.
quantum fields They are entities that permeate the entire universe. When patches of fields are activated, we see the formation of particles or the exchange of forces.
Corresponding field theory It is a type of quantum field theory with certain special mathematical properties. These kinds of theories have limited applications in some high energy physics experiments, but aren’t very useful outside of that.
Maldacena discovered that you could turn this problem—the problem of how to solve quantum gravity in this strange universe—into an entirely different problem that lived on its four-dimensional frontier. After this transformation is made, all gravity disappears, and is replaced by a special kind of quantum theory known as conformational field theory (it’s the CFT part of congruence). So far, we’ve become very good at solving quantum field theory problems, and we have a whole bunch of well-tested tools for working through those kinds of math.
Maldacena performed the theoretical physics equivalent of a magic trick: he was able to solve a problem we don’t know how to solve (quantum gravity with string theory) and turn it into a problem we Can Solve (field theory corresponding to quantum fields).
Is this the origin of spacetime?
This is where things get really wild. Some physicists have developed this idea and extended it away from just a tool for solving headache-inducing gravity problems to Explain gravity itself. They claim to have discovered congruences where the quantum nature of all fields that live at the boundary of this Free time Cause general relativity to emerge within it. General relativity is our description of the force of gravity, where we look at gravity in terms of the bends and wrinkles in space and time. In other words, the hologram principle may tell us that quantum interactions live at the frontiers of our universe Literally clear space-time within it.
If this is true, then what we perceive as a three-dimensional universe, filled with interesting, interesting objects that interact through gravity, is really a two-dimensional surface filled with strange quantum shapes from which everything else emerges.
That’s big if.
Despite decades of work along these lines, the holographic principle has some shortcomings. First, her theoretical darling, the AdS/CFT reporter, is at this point just a guess as to what may be be correct based on certain observed mathematical relationships; No one has actually proven the authenticity of the correspondence. In addition, even if we did, the universe described through correspondence looks nothing like the one we live in. Our universe has three spatial dimensions, not five, and it has a time dimension. It is not empty, nor does it close in on itself, but instead is filled with matter and radiation, which it is It is currently going through a phase of accelerated expansion. Most importantly, our universe does not have well-defined boundaries, so the entire raison d’être of the holographic principle is dead in the water.
Second, the vast majority of physical theories that apply to real-life problems in being definitely no Matching domain theories, and so the usefulness of the AdS/CFT correspondence is not foolproof (although it has been put to work in some interesting cases).
And while the nature of black hole information is interesting, no one has been able to use the principle of holography to describe exactly what happens to real black holes in reality. being. Not to mention that everything weird about entropy about black holes doesn’t apply to other things: if you stuff information into you, for example, the entropy goes up proportionately to your size.
But hey, it’s a young field. It took physicists and chemists more than a century to finally determine that atoms exist, so it’s a bit unfair to rush to judgment on entirely new insights into reality. But what if their wildest dreams come true? What if we found a close relationship between the physics of our three-dimensional universe and physics at the frontier?
So, is our universe a hologram? Or a mathematical illusion?
The implications of the hologram theory are murky at best. Some physicists have already gone all the way, saying that our reality is an illusion, that what we perceive as space, time, and gravity are merely manifestations of a deeper reality that exists in lower dimensions—that our universe is, quite literally, a hologram.
But mathematical solutions to physical theories do not necessarily dictate reality. One could easily argue that if the hologram principle turns out to be useful, then we would have discovered a powerful—and even vital—mathematical tool for understanding our universe. But that doesn’t mean that what the math tells us is true.
For example, physicists routinely use countless Sports Games To solve the problems. Sometimes problems are cast in higher or lower dimensions; Sometimes they turn into the realm of imaginary numbers; Sometimes we move processes back and forth in time. We perceive these tools for what they are: methods for solving difficult problems, not new formulations of the basic components of reality.
On the other hand, mathematical tricks are sometimes lifted and grounded in our understanding of the physical universe. Take general relativity. Before Einstein’s work, we conceived of gravity as a force like any other, a set of invisible strings that bind every object to mass. But now we see gravity as distortions in the fabric of space-time. We judge the view provided by general relativity as more “realistic” than the pre-Einstein understanding, by virtue of providing greater precision and insight into the force of gravity. But you can easily tell that it’s all a mathematical invention developed by our meager human brains to help us organize and make sense of the world, which is, after all, a fantasy. Indeed, the universe does what the universe does.
If the holographic principle truly leads to a new and revolutionary conception of our universe, it will ultimately be up to us to decide whether our reality as we understand it is an illusion, or whether physicists need to get back to work.
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