Bubble universe theory. Why might parallel universes be real? Playing with matter
Are parallel universes a theory or reality? Many physicists have been struggling to resolve this issue for many years.
Do parallel universes exist?
Is our Universe one of many? The idea of parallel universes, previously attributed exclusively science fiction, is now becoming increasingly respected among scientists - at least among physicists, who usually take any idea to the very limits of what can be imagined. 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 people will never be able to visit these universes to verify that they exist. So the question is, how can we use other methods to test the existence of parallel universes that cannot be seen or touched?
The birth of an idea
It is assumed that at least some of these universes are inhabited by human counterparts who live similar or even identical lives to people from our world. Such an idea touches your ego and awakens your fantasies - which is why multiverses, no matter how distant and unprovable they may be, have always received such widespread popularity. You might see ideas about multiverses most clearly in books like The Man in the High Castle by Philip K. Dick and movies like Beware the Closing Doors. In fact, there is nothing new in the idea of multiverses - as religious philosopher Mary-Jane Rubenstein clearly proves 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 stars beyond his reach, giving humanity its first glimpse of the vastness 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.
Universe-matryoshka
The idea that the universe contained many solar systems became quite common in the eighteenth century. In the early twentieth century, Irish physicist Edmund Fournier D'Alba even suggested that there might be an infinite regression of "nested" universes different sizes, both larger and smaller. 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 nesting doll multiverse, but instead they have proposed several other options in which multiverses can exist. Here are the most popular among them.
Patchwork Universe
The simplest of these theories stems from the idea that the Universe is infinite. It is impossible to know for sure whether it is infinite, but it is also impossible to deny it. If it is still infinite, then it should be divided into “flaps” - regions that are not visible to each other. Why? The fact is that these regions are so far from each other that light cannot travel such a distance. The Universe is only 13.8 billion years old, so any regions that are 13.8 billion light years apart are completely cut off from each other. According to all data, these regions can be considered separate universes. But they don't stay in this state forever - eventually the light crosses the boundary between them and they expand. And if the Universe actually consists of an infinite number of “island universes” containing matter, stars and planets, then there must be worlds identical to Earth somewhere.
Inflationary multiverse
The second theory grows out of ideas about how the universe began. According to the dominant version of the Big Bang, it began as an infinitesimal point that expanded incredibly quickly in a hot ball of fire. A fraction of a second after the expansion began, the acceleration had already reached such an enormous speed that it far exceeded the speed of light. And this process is called “inflation”. Inflationary theory explains why the Universe is relatively homogeneous at any given point. Inflation expanded this fireball to cosmic scale. However, the original state also had a large number of various random variations that were also subject to inflation. And now they are preserved as cosmic microwave background 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 proposed that universes could evolve and reproduce just like living things. On Earth, natural selection favors the emergence of “useful” traits, such as faster running speed or special placement of the thumbs. In a multiverse there must also be certain pressures that make some universes better than others. Smolin called this theory “cosmic natural selection.” Smolin's idea is that the "mother" universe can give life to "daughter" ones that form within it. The mother universe can only do this if it has black holes. A black hole is formed when a large star is destroyed by its influence. own strength attraction, pushing all atoms together until 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? Perhaps a hidden universe? This was nonsense; Einstein did not envision 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 with each other, 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 theoretical physicist Theodore Kaluza. In 1921, he demonstrated that by adding new dimensions to Einstein's equation of general relativity, an additional equation could be obtained that could be used to predict the existence of light.
Many-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 constituents elementary particles. It can predict phenomena ranging from the shape of molecules to how light and matter interact - all with incredible accuracy. Quantum mechanics considers particles in the form of waves and describes them with 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 break down as soon as an object is measured in any way, since 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 contained in 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.
- More of a “Universe” similar to ours, which came out of the same Big Bang, but is not observable.
- More Universes, similar to ours, which came out of other Big Bangs, but were born in the same inflationary state.
- Or there may be many more universes - some like ours, and some not - with different constants and even laws.
it is still finite and limited. This is our observable Universe, which began with a hot Big Bang and which contains everything that can be comprehended. And yet there is perhaps much more to this.
If we were in any other place in this Universe, we would be able to see the same amount of the Universe. On the largest scales, the Universe is more than 99.99% homogeneous, and variations in its density do not exceed 0.01%. This means that if we were lucky enough to be anywhere else, we would still see hundreds of billions of galaxies, about 10 91 particles scattered over 46 billion light years. We would simply see a different set of galaxies and particles, slightly different in detail.
From everything we can observe, and from all the theoretical guesses that the Universe throws at us about topology, shape, curvature and origin, we fully expect that there is a much larger Universe out there somewhere - identical in properties to the one we observe - but we do not see it. It is only due to the fact that the Universe existed for a certain period of time that we can see a specific part of it. This is essentially the simplest definition of a multiverse: beyond what we can see, there is much more to the unobservable universe. 
Most scientists take this for granted, because otherwise we would see the Universe being much more curved, or seeing repeating patterns in the cosmic microwave background. The lack of evidence for this clearly indicates that there is much more beyond the known universe than everything else. The lack of strong curvature indicates that we cannot see hundreds of times more of the Universe; the unobservable Universe is much larger than our own. But no matter how big it is, it probably came from a single cosmic event - that same Big Bang - billions of years ago.
But the Big Bang was not just the “beginning” of the Universe. There was a state before the Big Bang that started it all: cosmic inflation. This exponential rapid expansion of space itself in the young Universe created more and more space as it continued. And if inflation definitely came to an end where we are, something else is also possible: the rate at which inflation creates new space in almost all models is faster than the rate at which it ends and the Big Bang begins. In other words, inflation predicts unusually big number disconnected Big Bangs, each of which gave rise to its own Universe.
This multiverse is even larger than we previously thought, and if the inflationary state was eternal (and it could be), then the number of universes is infinite, not finite. Which is strange, because in these other universes, formed by other big bangs, there may be completely different physical laws and constants. In other words, there may not just be regions with worlds similar to ours, but with worlds that are completely different from ours. 
What is the multiverse? It can mean one of three things:
The multiverse can be finite in size and number of universes, or infinite. If you accept the Big Bang and modern cosmology, then the former is certainly true. If you accept cosmic inflation (and for good reason), the latter will be true. If you accept certain models of string theory or other unification theories, the third may also be true. As for the question of finitude or infinity, we don’t know for sure yet. There is a theorem that inflation could not continue forever, but there are loopholes in it that allow inflation to continue forever.
One thing is for sure: the multiverse exists, and you don't have to be a scientist to recognize it. The question is which version of the multiverse is hidden from us, and we may never know.
In cosmology, the hypothesis that our Universe is not the only one of its kind has long been considered. It may be one of the many Universes that make up the so-called Multiverse. Although this hypothesis can be considered something from the realm of science fiction, there is a fairly solid basis indicating its validity. We offer five arguments indicating that we live in the Multiverse.
1) One of the cosmological models assumes the so-called “ eternal inflation" Inflation is the very rapid expansion of the Universe after big bang. The "eternal inflation" hypothesis was first proposed by a cosmologist at Tufts University. Alexander Vilenkin. Scientists suggest that the inflationary expansion of the Universe stopped only in certain parts of space (these areas are called thermalized regions), but in some parts the expansion continues, peculiar “inflation bubbles” are born, each of which develops into a real Universe:
Inflationary theory allows for the formation of multiple daughter universes that are continuously budding from existing ones
2) Within the framework of the so-called brane theory(the term "brane" comes from the word "membrane") or M-theories, the four spatial dimensions are delimited by three-dimensional walls or three-branes. One of these walls is the space of the Universe in which we live, while there are other universe branes that are hidden from our perception. They are parallel to our brane and, under certain circumstances, they are attracted to each other by gravity. According to the theory, when the branes collide, a large amount of energy is released and thus the conditions for the Big Bang arise:
(picture from wikimedia.org)
3)Many-Worlds Interpretation of Quantum Mechanics by Hugh Everett. According to the concepts of quantum mechanics, everything in the world of particles is described only probabilistically. Everett suggested that all outcomes of a probable event are always realized, but this happens in different Universes. With each act of observation, measurement of a quantum object, the observer seems to split into several (presumably infinitely many) versions corresponding to different Universes. This can be clearly explained this way: if you are at a crossroads and you have the choice of going left or right, the existing Universe “gives birth” to two more daughter Universes: one in which you go right, and the other in which you go left:
4) As research shows, the space of our Universe is flat with a high degree of accuracy. And if space and time extend indefinitely, then at some point there must be repetition, since there is some limit to the number of combinations of particle organization in space and time. In other words, the infinity of space and time suggests that an exact copy of our Universe exists somewhere:
Space and time extend infinitely, therefore, at some point there must be a repetition of the Universe
5) Universes with different mathematics. According to some scientists, the fundamental laws of the Universe are mathematical laws. Based on this, we can assume that there are other Universes that have their own mathematical structures.
The multiverse is a paradox! It seems to me that the existence of Multiverses should not be viewed as presented in the article, as opportunities for new discoveries, but this idea should be accepted as paradoxes modern theories, indicating the incompleteness of our knowledge. And that's why.
The multiverse contradicts Occam's principle. In my opinion, the idea of the Multiverse has the following drawback: the existence of parallel ones does not physically manifest itself in our Universe in any way, except initial stages its evolution, for example, as in brane theory, otherwise this would lead to violations of the conservation law. This means that we are deprived of ways to verify this hypothesis experimentally and the only way left is to interpret observational facts using mathematical models or, even more radically, to elevate mathematical models to the absolute, as Max Tegmark suggests. Excluding the latter due to obvious controversy, it seems to me that the Multiverse, when interpreting observations, is an additional entity that, according to Ockham’s principle, should be discarded.
We do not understand enough about the structure of our Universe. But the current situation in cosmology, according to my own feelings, as a graduate student at the Institute of Cosmology, is much worse! Almost none of the cosmologists connect the construction of their theories with the analysis of observations. Mathematical models are often constructed in dimensionless quantities, so that the physical meaning is often hidden even to the theorist himself. Comes in first place mathematical analysis, and interpretation comes last. Moreover, many cosmologists are satisfied with the interpretation of the result in terms of their mathematically constructed physics, for example, it is quite normal to construct a Lagrangian in 11-dimensional space, and the real three-dimensional space is only special case, which is obtained after compactification. But few people make this important and, in fact, very difficult transition. Cosmology as a science is very young and far from perfect in its methods, and the inflationary Multiverse indicates that we do not yet fully understand the mechanism of inflation. Likewise, Everett's interpretation is likely due to our misunderstanding physical essence quantum mechanics.
“It’s great that we have encountered a paradox. Now we can hope to move forward!”, quoting Niels Bohr from What kind of misunderstanding arises from hypotheses about multiverses? There should clearly be a question here: Why is our Universe the only one and the way it is?", that is, the reasons for the fine tuning of the Universe are not yet clear. In Rosenthal's article in Uspekhi Fiz. Nauk for 1980 about physical laws and numerical values fundamental constants are well argued how their change will affect our Universe, and that these values are perhaps unique to the implementation of our life. One attempt to explain these values is to enumerate possible combinations together with the anthropic principle. But this explanation, in my opinion, is not satisfactory, because such a search is not limited by anything and is unlikely to be feasible.
Unified theory of a unified Universe. The path to creating seems more reasonable to me unified theory in one Universe that would explain the choice of such values. I think that this path lies through the search for such general mathematical properties that can have physical consequences. While they cannot be clearly named, I will give as an example the constant pi, which has a clear mathematical meaning, but is also included in physical formulas. Would a universe in which pi was different make sense? Here one can argue that the ratio of the circumference of a circle to its radius changes in curved spaces, but in the infinitesimal limit it always tends to pi and if this were not so, then space would probably lose the properties of continuity, and physical laws would become unpredictable .
leon writes:
As an example, I will give the constant pi, which has a clear mathematical meaning, but is also included in physical formulas. Would a universe in which pi was different make sense? Here one can argue that the ratio of the circumference of a circle to its radius changes in curved spaces, but in the infinitesimal limit it always tends to pi and if this were not so, then space would probably lose the properties of continuity, and physical laws would become unpredictable .
I have also been interested in this for a long time - In my opinion - this deepest problem, which is directly related to the fundamental principles of our World. Moreover, we can also say about “pi” that it is a constant obtained from experiment(through increasingly accurate measurement of the circumference of a unit diameter). But "e" is a number, speculative derived from differential calculus. That is, speculative consideration of the ideas of continuity, summation, passage to the limit leads to a very specific number. And it doesn’t matter who argues: a European, an African or a Chinese, or even, perhaps... an alien, he will come to the same thing. For me this is on the verge of a miracle. And confirmation that even the most abstract speculative constructions are related to the World, since we (and our brain) are part of the World. And therefore, looking inside ourselves, we can come to knowledge of the fundamental principles of the external (physical) World. True, you need to understand - which speculative constructions make sense? This requires powerful (physical) intuition.
Of course, Euler's number is also a wonderful mathematical constant that appears in many physical formulas.
However, the meaning of the number "pi" is much clearer to me (and historically it arose earlier). I’ll develop my idea, even if it’s like in a joke: “in war time- the value of “pi” reaches 4", then the geometry of the chessboard will correspond to it, when the smallest discrete elements of the plane correspond to square cells, and if you set the Manhattan distance metric on it, then the unit circle described around the cell will correspond to its 8 neighboring cells, then is the circumference will be equal to 8, hence pi is equal to 4. In the space of such a metric, physics can be simulated using cellular automata, which was described in the book “New kind of science” by Stephen Wolfram. However, cellular automata have a disadvantage, since their evolution. given by nearest neighbors, then they describe only local phenomena (such as wave propagation) and, in principle, they cannot be used to describe non-local phenomena, such as quantum entanglement.
This is only a special case, but it illustrates that the number “pi” determines the continuity of the geometry (space) of our world, on the basis of which modern physics is built, and therefore pi determines physics itself. Other values of “pi” most likely correspond to discrete spaces, in which it is not yet clear whether it is possible to adequately describe all physical phenomena. If it is impossible, then all such spaces are in a certain sense defective and the only physically possible one is continuous.
Ildus, hello. Happy New Year!
Write more carefully.
The geometry of a chessboard, when the smallest discrete elements of the plane correspond to square cells and if you set a metric on it with the Manhattan distance, then the unit circle described around the cell will correspond to its 8 neighboring cells, that is, the length of the circle will be equal to 8, hence pi is equal to 4.
2) We need to define the terms.
If we consider a circle to be the geometric locus of points equidistant from a given one, then the unit circle described around a cell will correspond not to 8, but only to 4 neighboring cells (east-north-west-south). The remaining four are spaced from the center at a distance of 2. Diameter D=2, circumference L=4. Therefore, pi=L/D=4/2=2.
If you define a circle in your way, through 8 neighboring cells, then the diameter is D = 4, the circumference is L = 8, pi = L/D = 8/4 = 2.
Hello, Vadim Vladimirovich! Happy New Year to you too! Thank you for understanding my reasoning and finding the error. Sorry, the link really turned out to be stupid, and besides, I mixed up the Manhattan distance and the Chebyshev distance with which I operated.
The Manhattan distance on a chessboard between squares can be described as the minimum number of moves required for a rook, and the Chebyshev distance is the minimum number of moves for a king. In the latter case, pi is equal to 4 (8 neighboring cells form an equidistant square (i.e., a unit circle), which we can continuously circle with a king, and the diameter of the unit circle is always equal to 2). But in the first one this is no longer so obvious, 4 neighboring cells cannot be continuously bypassed with the help of a rook, here moves to the center and back will be necessary and thus the length of the unit circle is 8, and pi is 4. More mathematically strictly, distances in such cases are measured by Lebesgue, then the Manhattan distance is a metric on L_1, and the Chebyshev distance on L_infinity.
For physics, the space with a metric on L_2 is important. In a world on a chessboard, where all objects move over integer distances and must somehow be physically synchronized with each other, it should theoretically be possible to set their method of movement in accordance with the metric, something like knight moves (at least Fermat’s theorem for the case 2 allows this, but for case 3 and higher it does not). But it is still difficult for me to say what pi is equal to in this case.
For the sake of mathematical warm-up, it is interesting to consider what pi is equal to depending on the tiling of the plane; surely someone has already studied this question. But for the sake of humor, for example, it can be argued that with the Chebyshev distance on a hexagonal board pi is equal to 3, and on a triangular board 1.5. However, I am inclined to believe that in a discrete space adequate physical reality cannot be described and obtained in the “demiurge” sense, so these are just mathematical puns.
Why are numbers like “pi” or “e” just like that and no others?... For me this is on the verge of a miracle.
It always felt like that. But there are also imaginary numbers, “perpendicular” "pi" and "e". Even negative numbers revolutionized mathematics.
together: $$-e^(i\pi)=1$$
Pauline writes:
But there are also imaginary numbers, “perpendicular” "pi" and "e".
Yes, that's what physical meaning the fact that the wave function of microparticles is imaginary, and the probability of detecting a particle is proportional to the square of its modulus?
Pauline writes:
The most amazing thing for me is that together speculative numbers turn into regular number- unit : $$-e^(i\pi)=1$$
Truly a wonderful formula!
I agree about the first 3 hypotheses. But one cannot agree with 4, at least from the fact that all observational facts indicate that the Universe is not infinite. About 5...
If our current knowledge, based on our mathematics, allows us, roughly speaking, to describe the presence of other universes, then why should there be different mathematics in them?
Folko writes:
About 5... If our current knowledge, based on our mathematics, allows us, roughly speaking, to describe the presence of other universes, then why should there be different mathematics in them?
Seryozha! Hello! Comment - what facts speak about the finitude of the Universe and in what form? In general, for philosophical reasons it can be argued that the Universe (with a capital letter) is finite. But in what form this finitude is realized - this still needs to be understood.
I have no arguments against the hypotheses expressed in this article... except that the proposed judgments are not arguments, but are hypotheses, that is, assumptions that do not yet have any reliable experimental verification. And the latter is very important.
All five identified hypotheses relate to different branches of physics and, according to by and large, contradict or may contradict each other.
For example, fifth the hypothesis essentially contradicts the formulation of all the others. If the mathematics is different, then what can we actually talk about within the framework of the mathematics we are familiar with...
First two hypotheses are from the arsenal of modern cosmology, and they are one of the possible options for many similar hypotheses.
Third Everett's hypothesis was intended to rationalize or "explain" the meaning quantum laws, but there are many such ways to interpret quantum theory. On the other hand, Everett’s ideas are in no way connected with general relativity, on which the first two hypotheses are based.
Fourth The hypothesis is completely unclear. And finally, there are more advanced hypotheses that can count on argumentation in contrast to those presented.
For example, Kaluza-Klein theory about five-dimensional space. There's only one problem. The Kaluza-Klein theory is not as impressive as Everett's ideas, and is based on mathematical ideas that are difficult to express in the form of statements that everyone can understand. So there are very few arguments yet, but there is a lot of confidence in the complexity of the world...
zhvictorm writes:
The proposed judgments are not arguments, but are hypotheses, that is, assumptions that do not yet have any reliable experimental verification.
I agree, these are typical examples of “mathematical science fiction”. Therefore, I carefully changed the words “theory” from the word “hypothesis”. But the concept “M-theory”, which is, of course, more correct to be called “M-hypothesis”, remains stable in modern scientific vocabulary? Is “inflationary theory” a theory or a hypothesis? What about the Big Bang theory/hypothesis? The latter, of course, have more experimental arguments in their favor than the former. The question is - where to draw the line between hypothesis and theory? Perhaps it is better to use the more neutral (in relation to experimental arguments) terms “model”? Inflationary model, Big Bang model, superstring model, etc.
zhvictorm writes:
The fourth hypothesis is completely unclear.
I didn't understand her well either. And the fifth one too. But I decided to leave them in the article, so that maybe we can figure it out together.
zhvictorm writes:
And finally, there are more advanced hypotheses that can count on argumentation in contrast to those presented. For example, the Kaluza-Klein theory of five-dimensional space.
Does the Kaluza-Klein model assume many worlds? As far as I remember, it introduces the 5th dimension, which is then compactified to small scales (in later versions of the model - to Planckian sizes). But, the World (Universe) in this model is singular.
Yes, and most importantly - To what extent is the Kaluza-Klein model confirmed by experiment? Or maybe there is some other criteria(except for direct experimental confirmation), which allow us to consider a certain model as serious, worthy of attention and, in turn, an argument for something? What could these criteria be? Well, for example, beautytheories what Einstein wrote about.
Is “inflationary theory” a theory or a hypothesis? What about the Big Bang theory/hypothesis?
These questions can be answered differently depending on which point of view you yourself lean towards. But there are still some reasons to argue that the Big Bang theory or its modern component - the inflation model, can be considered as theories. A theory, as a rule, is distinguished from a hypothesis by the deep elaboration of consequences for many different observable phenomena at once. If checking the reliability of the conclusions is difficult to this moment time, then the theory can be considered hypothetical. General relativity can still be considered a hypothetical theory, since not everything in it has been tested. For example, gravitational waves not discovered yet. The theory of inflation explains a whole bunch of observed phenomena from various branches of physics and astrophysics. For example, the absence of monopoles and the absence of the beginning of the Big Bang in the sky. But it is not possible to verify it with direct experiments, but it contains recipes for constructing mathematical conclusions of indirect facts that can or will be verified.
...to what extent is the Kaluza-Klein model confirmed by experiment?
The Kaluza-Klein theory explains electromagnetism by the presence additional dimensions. One is enough to get started. Moreover, it is structured in such a way that it is consistent with general relativity. Therefore, its validity is largely related to the validity of these theories. But, naturally, it contains statements that have not yet been verified. In particular, this concerns the existence of additional dimensions. However, it is precisely the organic nature of the unification of general relativity and the theory of electromagnetism in it that can be considered as an argument, although it also has problems in this regard. As for the multiplicity of worlds, any theory containing additional dimensions inevitably allows for the presence of many Universes. M-theories are well developed from a mathematical point of view and from this point of view can be considered as hypothetical theories or mathematical theories. Moreover, they rely on general relativity or its generalizations, and sometimes use theories like Kaluza-Klein. In the article under discussion, without any particular reason, five hypotheses are highlighted, which are not very related to each other, and especially not highlighted against the background of any other hypotheses and hypothetical theories. It’s even difficult to understand what preferences the journalist who apparently collected them had.
zhvictorm writes:
The Big Bang theory or its modern component, the inflation model, can be considered theories. ... General relativity can still be considered a hypothetical theory, since not everything in it has been tested.
It turns out interesting: theories Big Bang and inflation, which based on hypothetical OTO. How can something that is securely established be based on something that is not securely established?
zhvictorm writes:
The Kaluza-Klein theory explains electromagnetism by the presence of extra dimensions. One is enough to get started. Moreover, it is structured in such a way that it is consistent with general relativity. Therefore, its validity is largely related to the validity of these theories.
First . The situation occurs again: “ theory Kalutsy-Klein, based on hypothetical OTO."
Second . This is where it shows interesting principle: the desire to preserve (even if applied in a new perspective, but still preserve) some idea, once successfully applied and then successfully stood the test of time and experiment. IN in this case we are talking about the idea of geometrization of matter and its interactions, which was first successfully introduced into physics by Einstein in his General Relativity (although, of course, it was previously expressed by Clifford). About ideas, eidos(according to Plato), memes(according to Dawkins) we .
zhvictorm writes:
As for the multiplicity of worlds, any theory containing additional dimensions inevitably allows for the presence of many Universes.
This is not entirely clear to me regarding the Kaluza-Klein model. 3+1-dimensional spacetime + compactified 5th dimension constitute one universe(ours). Where is the second universe (and others)?
zhvictorm writes:
It is the organic nature of the unification of general relativity and the theory of electromagnetism in it that can be considered as an argument...
This is what roughly corresponds to the principle of beauty of Einstein's theory: when a new idea-eidos-meme arises, from which, at the level of theories, everything old is suddenly organically and simply (“beautifully”) united and explained. This is indeed a powerful argument, but - purely speculative, without direct relationship to the experiment. So, for example, Copernicus was guided by the desire simplify the system of the Ptolemaic World, already overgrown with epicycles, trims and equants, but at the same time giving a very good coincidence with experience. Striking similarity of the situation with the modern Standard Model, which gives excellent agreement with experiment! And the ideas-eidos in the Ptolemaic system were maintained: 1) geocentricity, i.e. the location of the God-created Earth at the center of the World and 2) perfect circularity uniform motion divine celestial bodies - planets. All the “bells and whistles” in Ptolemy’s system were subordinated to the desire to preserve these “reliable and centuries-tested” eidos. Just like in the Standard Model - yes the idea of symmetry and its subsequent breaking and the efforts of most theoretical physicists in the second half of the 20th century and the beginning of the 21st century studying particles are aimed at preserving (even if applying from a new perspective, but still, preserve) ideas-eidos, born during the revolution in physics of the first third of the 20th century. The idea of symmetry is one of them (but not the only one, of course!). As a result, those “bells and whistles” arose that resulted in the Standard Model (particle symmetries, gauge fields, the Higgs mechanism, etc.) and further - in the model supersymmetry(symmetries already exist between fermions and bosons). And during Copernicus, as now, everything seemed to be fine... Supporters of the role of science, as the handmaidens of practice, were pleased - according to the ephemerides of the luminaries, calculated according to Ptolemy, it was possible to calmly lead ships with goods to all ends of the World. Only here, one hitch... The inquisitive mind of Copernicus (oh, these “clever guys”!) was it’s unclear what the physical ( or, more correctly, for that era - divine) meaning the fact that the planets do not move along geocentric circles, but along epicycles, and even shifted to equants? Also now it is becoming more and more unclear - what is the physical meaning supersymmetries or, for example, renormalization procedures, or why there are only 3 generations of leptons and quarks, etc., etc. Not to mention the question of the physical meaning of the complexity and probability of the psi function... Copernicus proposed as a way out of this situation new idea-eidos- heliocentricity and all organically and simply explained. True, with “correspondence to experience” he was not doing well: Ptolemy’s system gave much greater accuracy to the ephemerides. And all because Copernicus “didn’t live up to” eidos of ellipticity of orbits, which was discovered only by Kepler and explained by Newton. So, the Copernican model was, at best, a hypothesis, but the main thing in it was new eidos(strictly speaking, not entirely new: the ideas of Ptolemy and the ideas of Copernicus and the ideas of Kepler come from antiquity, but they were applied by these researchers for more high level specificity and comprehensiveness).
So Doesn’t modern particle physics need new ideas-eidos, and not an endless “expansion” of old ones?
Ilya! Actually, the meaning of my comment was exclusively about unclear choice“arguments”-hypotheses regarding the hypothesis of the plurality of worlds.
I cited the Kaluza-Klein theory as an example, which can count on the argumentation of its existence to a greater extent than those given in the article. As for the hypothetical nature of GTR and related theories, this issue is quite complex and requires a discussion of the problems in the form of some mathematical constructions. Moreover, I did not talk about the absolute reliability of such theories as the Big Bang theory (BBT) and the cosmological inflation model (CIM). However, it can be assumed that even if GTR is significantly modified, the main elements of TBT and MKI may remain unchanged. For example, Friedman's solutions also have a classical analogue - an explosion of a spherical object in flat space. Therefore, all these theories are hypothetical to one degree or another.
As for the theory Kalutsy-Klein. First, compactification is not a necessary attribute of the Kaluza-Klein theory. Compactification was introduced to explain the fact that we do not observe additional dimensions. The idea of compactification is just one option. Secondly, if the observed space is three-dimensional, and the general one has dimension n+1, then any number of three-dimensional ones can fit in this ambient space. For example, compactification can be multivalued. In any multidimensional theory there is room for a plurality of worlds. Thirdly, the organic combination of general relativity and electromagnetism in the Kaluza-Klein theory provides only an argument in favor of this theory, but does not make it true.
Now about what ideas are needed modern physics . At all times, any science needs fruitful ideas that can explain the observed phenomena to the maximum extent. You can call these ideas whatever you like. This is not important. In the time of Aristotle, the idea of epicycles was a fruitful idea, in the time of Kepler - the theory of elliptical orbits. A little later, their place was taken by celestial mechanics. Ideas of symmetry have always been useful, if not elevated to the rank of absolute. Therefore, modern physics needs new ideas, just like in any other time.
However, as Khoja Nasreddin said, no matter how much you say the word sugar, It won't make your mouth any sweeter. These ideas need to be searched and tested, searched and tested... . There are simply no other recipes other than the great idea of scientific poking. If something can be applied from old baggage, then this is just happiness, and conservatism in science, if it does not cross a certain line, is useful in the sense that it weeds out unfounded theories. Unfortunately, this is not always maintained in science, and a number of theories have waited too long to be used. Well, this is already determined by the situation in society and science as a whole.
zhvictorm writes:
Modern physics needs new ideas, just like in any other time.
However, as Khoja Nasreddin said, no matter how much you say the word sugar, your mouth will not become sweeter. These ideas need to be searched and tested, searched and tested... . There are simply no other recipes other than the great idea of scientific poking.
I agree about sugar, but the method of scientific poking (brute force) is, to put it mildly, not the most effective method search. Need to study general patterns development physical knowledge and follow them more consciously in search of new fundamental and effective ideas. However, perhaps this is precisely what is reflected in the characterization of the poke, as scientific?
I would like to express my opinion about what society, and therefore we, to some extent, can do to increase the likelihood of the emergence of new fundamental physical ideas and theories. What we can do (do) here and now, and not wait until they randomly appear.
zhvictorm writes:
If something can be applied from old baggage, then this is just happiness, and conservatism in science, if it does not cross a certain line, is useful in the sense that it weeds out unfounded theories. Unfortunately, this is not always maintained in science, and a number of theories have waited too long to be used. Well, this is already determined by the situation in society and science as a whole.
The science
The universe we live in is not unique. In fact, she is just one unit of an infinite number of universes, the totality of which is called Multiverse.
The claim that we exist in the Multiverse may seem like a fantasy, but there are reasons behind it. real scientific explanations. A huge number of physical theories independently indicate that the Multiverse really exists.
We invite you to familiarize yourself with the most famous scientific theories that confirm the fact that our Universe is just a particle of the Multiverse.
1) Infinity of universes
Scientists are not yet sure exactly what shape space-time has, but most likely this physical model has a flat shape(as opposed to spherical or donut shape) and extends indefinitely. If spacetime is infinite, it must repeat itself at some point. This is due to the fact that particles can be arranged in space and time in certain ways, and the number of these ways is limited.
So if you look far enough, you may stumble upon another version of yourself, or rather, for an infinite number of options. Some of these twins will do what you do, while others will wear different clothes, have different jobs, and make different choices in life.
The size of our universe is difficult to imagine. Particles of light travel the distance from its center to the edge in 13.7 billion years. This is exactly how many years ago the Big Bang took place. Spacetime beyond this distance can be considered a separate universe. Thus, multiple universes exist next to each other, representing an infinitely gigantic patchwork quilt.
2) Bubble Giant Universe
IN scientific world There are other theories of the development of universes, including a theory called Chaotic theory of inflation . According to this theory, the universe began to expand rapidly after the Big Bang. This process was reminiscent bloat balloon which is filled with gas.
The chaotic theory of inflation was first proposed by cosmologist Alexander Videnkin. This theory suggests that some parts of space stop while others continue to expand, thus allowing isolated "bubble universes" to form.
Our own universe is just a small bubble in the vast expanse of space, in which there are an infinite number of similar bubbles. In some of these bubble universes laws of physics and fundamental constants may differ from ours. These laws might seem more than strange to us.
3) Parallel universes
Another theory that stems from string theory is that there is the concept of parallel universes. The idea of parallel worlds stems from the possibility that there are many more dimensions than we can imagine. According to our ideas, today there are 3 spatial dimensions and 1 temporal.
Physicist Brian Greene from Columbia University describes it this way: “Our universe is one “block” of a huge number of “blocks” floating in multi-dimensional space.”
Also, according to this theory, universes are not always parallel and are not always beyond our reach. Sometimes they can wedge into each other, causing repeated Big Bangs that return the universes to initial position again and again.
4) Daughter universes - another theory of the formation of universes
The theory of quantum mechanics, which is based on the concepts of a tiny world subatomic particles, suggests another way to form multiple universes. Quart mechanics describes the world in terms of probabilities, while avoiding making definitive conclusions.
Mathematical models, according to this theory, can assume all possible outcomes of a situation. For example, at an intersection where you can turn right or left, the present universe forms two daughter universes, in one of which you can go right, and in the other - left.
5) Mathematical universes - the hypothesis of the origin of the universe
Scientists for a long time debated whether mathematics useful tool to describe the universe or is it itself a fundamental reality and our observations are only imperfect representations of the true mathematical nature.
If the latter is true, perhaps the particular mathematical structure that shapes our universe is not the only option. Other possible mathematical structures may exist independently in separate universes.
"A mathematical structure is something that you can describe completely independent of our knowledge and concepts,- speaks Max Tegmark, a professor at the Massachusetts Institute of Technology, the author of this hypothesis. – Personally, I believe that somewhere there is a universe that can exist completely independently of me and will continue to exist even if there are no people in it."
The multiverse, which Sean Carroll, a cosmologist and author of the popular book “Eternity,” recently published in Russian, writes about. In Search of a Final Theory of Time,” is a hypothesis about the structure of our Universe beyond the region accessible to our observation.
What does it mean? The speed of light is limited, and the Universe is expanding in all directions - at the same time, we can only see a certain part of space. And it is far from a fact that the world outside it is structured the same way as in the vicinity of the Earth. Hypothetically, outside the sphere accessible to observation, there may be, for example, a completely different ratio of ordinary and dark matter. Or maybe something else works? physical principles, up to increasing the number of measurements.
Common sense, of course, tells us that the properties of the Universe should be the same everywhere. However, “common sense” is not a very good thing for cosmology, the science of space-time on very large scales. The assumption that the known matter in the Universe is tens of times less than some mysterious dark matter is also completely contrary to common sense, but it is precisely in such a world, consisting mainly of dark matter, that we live today. The problem with the idea that the universe is changing dramatically in places where we can no longer see it is not that it is unusual, but that such an idea cannot be tested.
A universe with hypothetically different physical laws is called a cosmological multiverse. Such a Universe is geometrically unified - in the sense that a continuous line can be drawn between any two of its points without the construction of any portals or other exotic things. And this cosmological multiverse should not be confused with, for example, multiple universe in the many-worlds interpretation of quantum mechanics.
Many-worlds quantum mechanics
At the other end of the “scale grid of the universe” there is a microcosm, the events in which are described quantum mechanics. We already know that elementary particles: electrons, quarks, gluons and their other brothers behave in accordance with rules that are not followed in the world we are used to. Thus, each particle in quantum mechanics can be considered as a wave - and seemingly “solid” atoms, which in school course chemistry is depicted as balls; when they collide with an obstacle, they will dissipate like waves. Each quantum object is described mathematically not as a ball or point limited in space, but as a wave function - existing simultaneously at all points of the trajectory of its movement through space. We can only calculate the probability of its detection in a particular place. Quantities such as the momentum of a particle, its energy, and more exotic characteristics like spin, are also calculated from the wave function: we can say that this mathematical object covering all space is the fundamental basis of quantum mechanics and all physics of the 20th century.
Calculations made on the basis of wave functions and operators (operators allow us to obtain specific quantities from the wave function) are in excellent agreement with reality. Quantum electrodynamics, for example, today is the most accurate physical model in the history of mankind, and quantum technologies include lasers, all modern microelectronics, the fast Internet we are accustomed to, and even a number of drugs: the search for promising substances for medicine is also carried out by modeling the interactions of molecules with each other with a friend. From an applied point of view, quantum models are very good, but at the conceptual level a problem arises.
The essence of this problem is that quantum objects can be destroyed: for example, when a photon (a quantum of light) falls on a camera sensor or simply collides with an opaque surface. Until this moment, the photon was perfectly described by the wave function, and after a moment the wave, extended in space, disappears: it turns out that some change affected the entire Universe and happened faster than the speed of light (can this even happen?). This is problematic even in the case of a single photon, but what about the wave function of two photons emitted from the same source in two opposite directions? If, for example, such two photons were born near the surface of a distant star and one of them was caught by a telescope on Earth, what about the second, many light years away? Formally, it forms unified system with the first, but it is difficult to imagine a scenario where a change in one part of the system is instantly transmitted to all other parts. Another example of a quantum system for which the disappearance of the wave function leads to conceptual problems is famous cat Schrödinger, which is inside closed box with a device that, based on a probabilistic quantum process, either breaks the ampoule of poison or leaves it intact. Before opening the box, Schrödinger's cat turns out to be both alive and dead: his state reflects the wave function of the quantum system inside the mechanism with poison.
The most common interpretation of quantum mechanics, the Copenhagen one, suggests simply coming to terms with the paradoxical nature of the world - and admitting that yes, despite everything, the wave/particle disappears instantly. An alternative to it is the many-worlds interpretation. According to it, our Universe is a collection of non-interacting worlds, each of which represents one quantum state: when you open a box with a cat, two worlds appear - in one of them the cat is alive, and in the other it is dead. When a photon passes through a translucent mirror, the world is also divided into two: in one, a quantum of light is reflected from the surface, and in the other, it is not. And so each quantum process leads to the emergence of more and more new branches-worlds.
Theoretically, some of these branches may be very different from ours. One atom flying in the wrong direction shortly after the Big Bang could well have led to a different distribution of hot gas, the birth of stars in completely different places, and ultimately to the fact that the Earth did not arise in the first place. But this picture cannot be called a problem of many-worlds interpretation. The real problem is the impossibility of testing the correctness of this understanding of quantum mechanics in practice: the individual components of the multiple Universe, by definition, do not interact with each other.
Somewhere, perhaps, there is an Earth inhabited by intelligent dinosaurs, somewhere the Great Mongol Empire landed on the moons of Jupiter in 1564, but there are no portals between these worlds - they diverged as a result quantum processes in the distant past. A theory that would suggest the possibility of getting into one of these worlds, from the point of view of the philosophy of science, would be no less, but more scientific, since it could be tried to be tested.
Fake it
The idea that Eurasia will soon be captured by intelligent dinosaurs with laser rifles who came through a portal from the past is intuitively perceived as the basis for a purely science fiction film, but the philosophy of science is not built on intuition. The scientific nature of such an idea is called into question not because of its similarity to cheap fiction, but because a number of consequences from this idea contradict the actual data.
Time travel, for example, would violate a number of physical laws that so far hold very well. The law of conservation of energy works everywhere: humanity has conducted many experiments to test it, and even everyday devices, from a heating battery to a smartphone, confirm that energy does not disappear anywhere. And if so, then waiting for her to “disappear” in the “time portal” is quite strange. In addition, time travel should lead to a whole series of other paradoxes - situations for which we have not observed analogues and which contradict the logical consequences of accumulated experience. Take, for example, the “grandfather paradox”: a situation where a time traveler meets his ancestors and prevents them from having offspring is obviously possible and impossible at the same time.
The hypothesis about dinosaur invaders from the past can enter the scientific field, provided that it gives the opportunity to test itself: for example, its authors describe the diagram of the alleged time portal. And if such a portal does not work, the hypothesis will have to be rejected. If the authors of the hypothesis claim that, for example, dinosaurs were facing extinction, this can also be compared with the results of paleontological excavations and a number of other facts; a scientific hypothesis must be fundamentally testable. Finally, a statement like “the portal will open on November 4, 2018” is the easiest to verify, which is perhaps why many authors of conspiracy theories avoid such predictions or push them back further.
Scientific hypotheses must be falsifiable, that is, they must be tested for falsification. Falsification is not a manipulation of facts, as one might think. A falsifiable hypothesis in its formulation states that it is false if such and such specific experimental data are obtained. If the hypothesis says that time travel is possible and one day dinosaurs with combat lasers will come to us from the past, an expedition to the past that will record the death of dinosaurs without the appearance of laser weapons will be a falsification. Or, more realistically, the discovery of the remains of ancient lizards without what was predicted by the same hypothesis developed brain. If living and very smart dinosaurs are hiding in some other past, then it is necessary to explain how to check this other past. If it is impossible to test a hypothesis, this does not even mean that it is false. This means that we are not dealing with a scientific hypothesis, but meaningless chatter, and therefore we must treat it accordingly.
Karl Popper, who formulated the principle of falsifiability. Later his ideas were developed and supplemented, but this criterion is still popular among physicists to this day. Author: LSE library, No restrictions
From this point of view, many are completely incredible from the point of view common sense hypotheses can be regarded as completely scientific as long as they are not impossible to test and as long as there is a fundamental possibility of obtaining facts that refute these hypotheses. Both quantum mechanics and the theory of relativity offered a very unusual picture of the world, but they were tested in practice and allowed the possibility of refutation. Outside of physics, an example of a theory that has revolutionized people's understanding of the world is the concept of evolution and natural selection. The idea that all of our heredity is determined by DNA molecules, the idea that stars shine due to the fusion of atoms, the idea that continents slowly drift along the viscous surface of the Earth's mantle - all this once also sounded very, very unusual and counterintuitive, but fell into the scientific field along with other, convincing, but rejected hypotheses. The idea of falsifiability scientific knowledge was proposed by Karl Popper back in 1935 and since then has been cited by many scientists as a criterion for scientific character.
Debates around science
Many-worlds quantum mechanics and the cosmological multiverse are not fundamentally verifiable and, according to a number of scientists, should be deduced from the number scientific concepts. So, on the pages of the most authoritative Nature in 2014, a column by George Ellis and Joe Silk (both prominent cosmologists) was published calling for the abandonment of these concepts as scientific ones, and at the same time string theory, which allows for too many variants of reality. As the disgruntled authors wrote, “proponents [of string theory] will always claim that we do not see the particles they predict because we lack the energy of the accelerators.”
Sean Carroll, whose cosmological multiverse we mentioned above, submitted a paper in early 2018 proposing to abandon the falsifiability criterion and thereby continued his controversy with Ellis and Silk. According to Carroll, there are actually two other criteria behind Popper's falsifiability: a scientific theory must be definite and supported by experience. The cosmological multiverse can be described in a very specific language, and the consequences of this hypothesis apply not only to the fundamentally unobservable, but also accessible parts of the Universe. Carroll also proposed his own classification of theories: from “completely untestable in principle” to those with strict verification criteria - for example, a hypothesis can only be tested using an accelerator the size of our galaxy or tens of billions of years of continuous observations.
The astrophysicist also highlights other problems with scientific criteria. In his opinion, the requirement of falsifiability is far from the only one and not even the main one. As proof, he proposes to consider two theories of gravity: the general theory of relativity and its own, but with an additional statement stating that from 2100 gravity will change sign, replacing the attraction of masses with repulsion. Formally, such a model is quite testable, however, “any sane scientist will trust the first theory more, even if they are equally justified and equally falsifiable.” The theory in which gravity disappears in 2100 should be rejected not because it is falsifiable, but because it contains unnecessary complication, which in itself does not provide anything - neither an increase in the accuracy of predictions, nor the possibility of obtaining new results.
The theory of the multiverse is not directly testable, but, according to Carroll, it can be classified as scientific because it does not contradict existing data and makes a number of indirect predictions. Moreover, choosing a theory that rejects the existence of a multiverse and asserts that the Universe is homogeneous cannot be called scientific for exactly the same reason: if we never see the entire Universe, how can we be sure of its properties?
Carroll's opponents point out that without the support of experimental data, neither the elegance of the theory nor its irreplaceability (string theory, as we have already mentioned, today is perhaps the only candidate for the role of a unified theory of all fundamental fields, including gravity, but at the same time it has problems with falsifiability - no one has ever seen any strings, membranes or branes and it is not a fact that they ever will be able to) cannot be reliable criteria.
There is merit to Carroll's argument. Physicist Sabine Hossenfelder, discussing the “falsifiability problem” on her blog, recalls listening to the strangest talk at a conference. The speaker suggested that dark matter particles could clump into disks, similar topics, which under certain conditions form particles of ordinary matter around, for example, massive bodies. And everything, perhaps, would have been fine if the speaker had not continued that, in her opinion, the solar system periodically passes through a similar disk of dark matter and this is where we should look for the cause of mass extinctions on Earth. “But why exactly dark matter particles? Why this kind of interaction?” - they asked a question from the spot, Hossenfelder recalls. The answer was this: “ I don't know, but we can check it».
Indeed, such a theory is falsifiable. All that's left to do is wait for the next one mass extinction, armed necessary tools for detecting dark matter. All that’s left to do is get a grant for this enterprise.
Therefore, Hossenfelder herself is inclined to agree that the requirement of simplicity should be considered as another necessary condition for separating a “reasonably scientific” hypothesis from an “unscientific” one, and that is why she rejects the idea of a multiverse - for redundancy and excessive complexity.
What's the result?
As you can see, many parallel worlds is an idea that is shared by at least some scientists, and we're talking about O serious specialists in their field, who have an excellent command of the methods and are not seen in any openly pseudoscientific speeches. But even they admit that, firstly, the multiplicity of universes does not change anything on the scales accessible to us (alas, we will have to live without portals to an alternative Earth), and secondly, these hypotheses do not correspond to one of the most common criteria of scientific knowledge. In other words, they are elegant, interesting, but, apparently, do not fall into the category of pure physics Scientific research.
Alexey Timoshenko