Parallel universes - is it theory or reality? Many physicists have been struggling to resolve this issue for many years.
Are there parallel universes?
Is our universe one of the many? The idea of parallel universes, previously attributed solely to science fiction, is now becoming more and more respected among scientists - at least among physicists, who usually take any idea to the very limits of what can be assumed. In reality, there are a huge number of potential parallel universes. Physicists have proposed several possible forms of the "multiverse", each of which is possible according to one or another aspect of the laws of physics. The problem that follows directly from the definition itself is that humans can never visit these universes to make sure they exist. Thus, the question is how to use other methods to verify the existence of parallel universes that cannot be seen or touched?
The origin of the idea
It is assumed that at least some of these universes live human counterparts who live similar or even identical lives with people from our world. This idea touches your ego and awakens your fantasies - which is why the multiverse, no matter how distant and unprovable they may be, have always been so popular. Most clearly, you have seen multiverse ideas in books such as The Man in the High Castle by Philip K. Dick, and in films such as Watch Out The Doors Are Closing. In fact, there is nothing new in the idea of multiverse - this is clearly demonstrated by the religious philosopher Mary-Jane Rubenstein in her book Worlds Without End. In the mid-sixteenth century, Copernicus argued that the earth was not the center of the universe. Decades later, Galileo's telescope showed him stars out of reach,this is how humanity got its first idea of the immensity of space. Thus, at the end of the sixteenth century, the Italian philosopher Giordano Bruno reasoned that the universe could be infinite and contain an infinite number of inhabited worlds.
Promotional video:
Universe matryoshka
The idea that the universe contains many solar systems became quite common in the eighteenth century. In the early twentieth century, the Irish physicist Edmund Fournier D'Alba even suggested that there could be an infinite regression of nested universes of varying sizes, both large and small. From this point of view, a single atom can be considered as a real inhabited solar system. Modern scientists deny the assumption of the existence of a multiverse-matryoshka, but instead they have proposed several other options in which multiverse could exist. Here are the most popular ones.
Patchwork universe
The simplest of these theories stems from the idea of the infinity of the universe. It is impossible to know for sure whether it is infinite, but it is impossible to deny it. If it is nevertheless infinite, then it should be divided into "patches" - regions that are not visible to each other. Why? The fact is that these regions are so far from each other that light cannot cover such a distance. The universe is only 13.8 billion years old, so any regions 13.8 billion light years apart are completely cut off from each other. According to all the data, these regions can be considered separate universes. But they do not stay in this state forever - eventually the light crosses the border between them, and they expand. And if the Universe actually consists of an infinite number of "island universes" containing matter, stars and planets, then somewhere there must be worlds identical to the Earth.
Inflationary multiverse
The second theory grows out of ideas about how the universe began. According to the dominant Big Bang theory, it began as an infinitesimal point that expanded incredibly quickly in a red-hot fireball. A fraction of a second after the start of the expansion, acceleration had already reached such a tremendous speed, which was much faster than the speed of light. And this process is called "inflation". Inflationary theory explains why the universe is relatively homogeneous at any given point. Inflation has expanded this fireball to cosmic proportions. However, the original state also had a large number of different random variations, which were also subject to inflation. And now they are saved as relic radiation, the faint afterglow of the Big Bang. And this radiation permeates the entire Universe,making it less uniform.
Cosmic natural selection
This theory was formulated by Lee Smolin from Canada. In 1992, he suggested that universes could evolve and reproduce in the same way as living things. On Earth, natural selection contributes to the emergence of "useful" traits, such as a fast running speed or a special position of the thumbs. There must also be a certain pressure in the multiverse that makes some universes better than others. Smolin called this theory "cosmic natural selection." Smolin's idea is that the "mother" universe can give life to the "daughters" that are formed within it. The parent universe can only do this if it has black holes. A black hole forms when a large star collapses under its own gravitational force, pushing all atoms together to the point whereuntil they reach infinite density.
Brane multiverse
When Albert Einstein's theory of general relativity began to gain popularity in the twenties, many people discussed the "fourth dimension." What could be there? A hidden universe perhaps? It was nonsense, Einstein did not assume the existence of a new universe. All he said was that time is the same dimension, which is similar to the three dimensions of space. All four are intertwined, forming a space-time continuum, the matter of which is distorted - and gravity is obtained. Despite this, other scientists began to discuss the possibility of other dimensions in space. For the first time, hints of hidden dimensions appeared in the works of the theoretical physicist Theodor Kaluza. In 1921, he demonstrated that by adding new dimensions to the equation of Einstein's general theory of relativity,an additional equation can be obtained to predict the existence of light.
Multi-Worlds Interpretation (Quantum Multiverse)
The theory of quantum mechanics is one of the most successful in all of science. She discusses the behavior of the smallest objects, such as atoms and their constituent elementary particles. It can predict all kinds of phenomena, from the shape of molecules to how light and matter interact, all with incredible precision. Quantum mechanics looks at particles in the form of waves and describes them in a mathematical expression called the wave function. Perhaps the strangest feature of the wave function is that it allows a particle to exist in multiple states simultaneously. This is called superposition. But superpositions are destroyed as soon as the object is measured in any way, since the measurements force the object to choose a specific position. In 1957, American physicist Hugh Everett suggested that we stop complaining about the strange nature of this approach and just live with it. He also suggested that objects do not switch to a specific position when they are measured - instead, he believed that all possible positions embedded in the wave function are equally real. Therefore, when an object is measured, a person sees only one of many realities, but all other realities also exist.