“The most incomprehensible thing in the universe is that it is clear”, once said albert Einstein. These days, however, the Universe is difficult to call a clear or even unique. Fundamental physics is experiencing a crisis associated with the two popular concepts that is often called the “multiverse” and the “uglyverse”, which literally stands for “multiple universe” and “the universe is ugly”.
How the universe works?
Proponents of multiple universe defend the idea of the existence of innumerable other universes, some of which have completely different physics and the number of spatial dimensions; in these universes, you, I and everyone else can exist in countless copies. “The multiverse may be the most dangerous idea in physics”, said the South African cosmologist George Ellis.
From the earliest days of science the discovery of unlikely coincidences led to the need to explain it, to seek the hidden reason and a motive. Among the modern examples is this: the laws of physics, apparently, precisely tuned to allow the existence of intelligent beings that can detect these laws is a coincidence that requires explanation.
With the advent of the multiverse, everything has changed: no matter how incredible of a coincidence, in billions of billions of universes constituting a multiverse, anything — it will be. And if the match seems to be contributing to the emergence of complex structures, life or consciousness, we should not even be surprised that we find ourselves in a universe that allows us to exist in the first place. But this “anthropic reasoning”, in turn, implies that we are unable to predict anything. There are no obvious principles for physicists at CERN to search for new particles. And there is no fundamental law which can be detected over the random properties of the universe.
A completely different but no less dangerous was another problem — “the universe is ugly”. Says theoretical physicist Sabine Hossenfelder, modern physics was baffled by his attraction to “beautiful”, which led to the emergence of mathematically elegant, speculative fantasy without any ties with the experiments. The physics of “lost mathematics,” she said. And what physicists call “beauty”, it’s structure and symmetry. If we can’t rely on such concepts more, the difference between understanding and simple according to experimental data will be blurred.
Both problems have the soil under themselves. “Why are the laws of nature care about what I think is beautiful?”, fair asks Hossenfelder. And the answer is: they do not care. Of course, nature could be complex, confusing and incomprehensible — if she was a classic. But nature is not like that. Nature is quantum-mechanical. Although classical physics is the science of our everyday lives in which the objects are separable from each other, quantum mechanics is different. The condition of your car not related to the color of the dress your wife. But in quantum mechanics all things are causally dependent on each other, what Einstein called “spooky action at a distance”. Such correlations form the structure, and the structure is beautiful.
In contrast, the multiverse, it seems difficult to deny. Quantum mechanics, in particular, perfectly applies to it. Shot individual electrons in a screen with two slits leads to interference pattern on the detector behind the screen. In each case, it turns out that the electron passes both slits every time.
Quantum physics is the science behind nuclear explosions, and collisions between the particles and it is known for its eccentricities, like schrödinger’s cat, existing in a limbo between life and death. In quantum mechanics, different realities could overlap (like “a particle here and a particle there” or “cat alive” and “dead cat”), just like the waves on the lake surface. The particle can be half here and half there. This is called superposition, and it leads to the appearance of the interference pattern.
Originally developed to describe the microscopic world, quantum mechanics in recent years have shown that it controls all the larger object if they are sufficiently isolated from the environment. But somehow our daily lives are somehow protected from too much quantum weirdness. No one has ever seen a half-dead cat, and whenever you measure the position of a particle, you get a certain result.
Direct interpretation presupposes that all possible options are implemented, albeit in a different, but parallel realities “Everett branches” — named after Hugh Everett, who first championed this view, known as the many-worlds interpretation of quantum mechanics. “Many worlds” of Everett actually represent only one example of a multiverse — one of the four. The other two are not so interesting, and the third is the “landscape of string theory”, to which we will return later.
Turning to quantum mechanics to justify the beauty of physics, and we seem to sacrifice the uniqueness of the universe. However, this conclusion rests only on the surface. In this picture usually overlooked the fact that Everett’s multiverse is not fundamental. It is only apparent or “emergent”, as the philosopher David Wallace from the University of southern California.
To understand this point, you need to understand the principle lying in the basis of quantum measurement, as well as “spooky action at a distance”. The key for both phenomena is the concept of “entanglement”, which in 1935 was pointed out by Einstein, Boris Podolsky, and Nathaniel Rosen: in quantum mechanics a system of two entangled spins with a zero amount may consist of a superposition of pairs of spins with opposite direction of rotation with an absolute uncertainty of the directions of rotation of the individual spins. Confusion is a natural way of combining parts into a whole; the individual properties of the constituents cease to exist in favor of a much tied total system.
Whenever the quantum system is measured and associated with the environment, manifested the important role of entanglement: the quantum system, the observer and the rest of the universe are intertwined. From the point of view of local observer information is scattered in an unknown environment and begins the process of “decoherence”. Decoherence is the agent of classicality: it describes the loss of quantum properties when the quantum system interacts with the environment. Decoherence works like a zipper between the parallel realities of quantum physics. From the point of view of an observer, the universe “splits” into different branches of Everett. The observer observes a live cat or a dead cat, but nothing in between. For him the world seems classical, although from the global point of view, it is still quantum mechanical. In fact, from this point of view, the whole universe is a quantum object.
And here we attract an interesting concept of “quantum monism” proposed by the philosopher Jonathan Schaffer. Shaffer pondered the question, what is in the universe. Under quantum monism, the fundamental layer of reality is not made up of particles or strings, but of the universe itself, understood not as the sum of its things, but rather as a single entangled quantum state.
Similar thoughts have been expressed before, for example, physicist and philosopher Carl Friedrich von Weizsacker: taking quantum mechanics seriously predicts a unique single quantum reality underlying the multiverse. The homogeneity and the tiny temperature fluctuations of the cosmic microwave background, which indicate that the observable universe can be traced back to a single quantum state, normally associated with quantum field of the primary inflation, support this view.
Moreover, this conclusion applies equally to other concepts of the multiverse theory. Since entanglement is universal, it is not limited to our cosmic bubble. Whatever the multiverse, if you take the quantum monism, everything will be part of a whole: there will always be more fundamental layer of reality that underlies many of the universe inside the multiverse, and this layer will be unique.
And quantum monism, and muratovska many-worlds interpretation are the predictions of quantum mechanics. Distinguishes them only the prospect that what from the point of view of a local observer would be like “many worlds” actually is a single unique universe with a global perspective (for example, creatures that can see the whole universe from the outside).
In other words, many worlds is a quantum monism the eyes of an observer with limited information about the universe. In fact, the original motivation for Everett was to develop a quantum description of the universe in terms of “universal wave function”. Look at it as through a smudged window: nature is divided into many pieces, but this is just perspective distortion.
Monism and multiple worlds can be avoided, but only if someone will change the formalism of quantum mechanics — usually this is in conflict with the special theory of relativity — or someone will introduce quantum mechanics as a theory not about science, but about knowledge: human ideas, but not science.
In its current form, quantum monism should be regarded as a key concept in modern physics: it explains why “beauty” is perceived in a structure, correlation and symmetry between apparently independent realms of nature, is not distorted aesthetic ideal, but a result of the splitting of nature from a single quantum state. In addition, the quantum monism also eliminates the need for multiple universe because it predicts correlations that are implemented not only in the individual born of the universe, but in every separate branch of the multiverse.
Finally, the quantum monism can resolve the crisis in experimental fundamental physics that relies on larger and larger colliders to study smaller and smaller components of nature. Because the smaller components will not be a fundamental layer of reality. The study of the foundations of quantum mechanics, new areas of quantum field theory or large-scale structures in cosmology can be just as useful.
All this means that we should not stop looking. In the end, this desire we have not to take. Somewhere, deep down, there is a unique, clear and fundamental reality.
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