Nature can be different for different people. Nature can be wonderful. Nature can be weird. Nature has laws. Nature continues to amaze scientists who are trying to understand these laws. Over the past few decades, the scientific community has come to accept the concept of “naturalness,” a term coined by Einstein to describe the delicately complex laws of nature. Scientists believe that if the universe is natural, then it can be explained mathematically. But if its nature is unnatural, then some of the laws of physics are arbitrary and seem extremely fine-tuned to allow life (as we know it) to arise and exist. And yet, scientists are striving for a unified description of reality. But modern physics allows many different descriptions, many of which are equivalent to each other and bound by a landscape of mathematical possibilities.
Secrets of the Universe
In a series of ordinary everyday life, it may seem that we know enough about the world and the Universe to answer in the affirmative the question of whether all known laws of physics exist. However, scientists studying the quantum world may disagree. According to Quanta Magazine , physicists have found many examples of two completely different descriptions of the same physical system.
So, if physical ingredients are particles and forces, then recipes are mathematical formulas that encode their interactions. In this case, the very process of cooking is the quantization procedure that turns equations into probabilities of physical phenomena. This is why quantum physicists are wondering how different “recipes” lead to the same results.
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Albert Einstein famously believed that given some general principles, there was a unique way to build a coherent, functioning universe. From Einstein's point of view, if we explored the essence of physics deeply enough, there would be one and only one way in which all the components – matter, radiation, forces, space and time – would fit together to make reality work, just as uniquely the combination of gears, springs, dials and wheels of mechanical watches.
The modern Standard Model of Particle Physics is indeed a tightly constructed mechanism with only a few components. However, instead of being unique, the universe appears to be one of an infinite number of possible worlds. We have no idea why this particular combination of particles and forces underlies the structure of nature.
In addition, the Standard Model contains 19 constants of nature – numbers such as the mass and charge of an electron that must be measured in experiments. The values of these "free parameters" seem to have no deeper meaning.
If our world is just one of many, then how can we exist simultaneously with alternative universes? The current point of view can be seen as the polar opposite of Einstein's dream of a unique space. Modern physicists embrace a huge space of possibilities and try to understand its overarching logic and interconnection. From gold prospectors, they have evolved into geographers and geologists, detailing the landscape and studying the forces that shaped it.
Вам будет интересно: Почему физики считают, что мы живем в Мультивселенной?
String theory has become a watershed moment for modern physics. At the moment, it is the only theory that comes closest to the very "theory of everything" – Albert Ensten's dream, capable of describing all particles and forces, including gravity, as well as obeying the strict logical rules of quantum mechanics and the theory of relativity.
The good news about this whole story is that string theory doesn't have a dial (like a mechanical watch). It doesn't make sense to ask which string theory describes our universe, because there is only one. The absence of any additional signs leads scientists to the conclusion that all numbers in nature must be determined by physics itself. They are not "constants of nature", but only variables fixed by equations (possibly insoluble complex).
However, it is important to understand that there are complex, overwhelming number of solutions to string theory. In physics, this is not unusual. We traditionally distinguish between fundamental laws given by mathematical equations and solutions to these equations. Typically, there are only a few laws, but an infinite number of solutions. Let's take Newton's laws. They are clear and elegant, but describe an incredibly wide range of phenomena, from a falling apple to the orbit of the moon.
Если вы знаете начальные условия конкретной системы, то сила этих законов позволяет решать уравнения и предсказывать, что произойдет дальше. Мы не ожидаем и не требуем априори уникального решения, которое описывает все.
In string theory, some features of physics that we usually think of as laws of nature – such as specific particles and forces – are actually solutions. They are determined by the shape and size of the hidden extra dimensions. The space of all of these solutions is often referred to as the "landscape," but that's an understatement. Even the most impressive mountain landscapes pale in comparison to the vastness of this space.
Landscape of the universe
But how do scientists study the vast landscape of physical models of the universe, which could easily have hundreds of dimensions? To understand this, let's imagine the landscape as a largely undeveloped desert, much of which is hidden under thick layers of unsolvable complexity. Only on the very outskirts do we find habitable places. Here we find basic models that we fully understand. They are of little value for describing the real world, but serve as a convenient starting point for exploring the local area.
A good example is the theory of quantum electrodynamics (QFT), which describes the interaction of matter and light. This model has a single parameter, called the fine structure constant, α, which measures the strength of the force between two electrons. In the theory of quantum electrodynamics, all processes can be viewed as arising from elementary interactions. For example, the repulsive force between two electrons can be represented as an exchange of photons. The QFT asks us to consider all the possible ways in which two electrons could exchange a photon, which in practice would mean that physicists must solve a very complex problem, with an infinite number of solutions.
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Why is all this so exciting for physics? First of all, the conclusion that many, if not all, of the models are part of one huge interconnected space is one of the most surprising results of modern quantum physics. This is a change in perspective worthy of the term "paradigm shift." He tells us that instead of exploring the archipelago from separate islands, we discovered one huge continent.
In a sense, by studying one model deeply enough, we can study them all. We can explore how these patterns are related by highlighting their common structures. It is important to emphasize that this phenomenon is largely independent of whether string theory describes the real world or not. This is an inherent property of quantum physics that will remain here, whatever the future "theory of everything" turns out to be.