What is outside the universe? This question is too complex for human understanding. This is due to the fact that in the very first place it is necessary to determine its boundaries, and this is far from simple.
The generally accepted answer takes into account only the observable universe. According to him, the dimensions are determined by the speed of light, because it is possible to see only the light that objects in space emit or reflect. It is impossible to look further than the most distant light that travels all the time of the existence of the universe.
The space continues to increase, but is still finite. Its size is sometimes referred to as the Hubble volume or sphere. Man in the universe will probably never be able to know what is beyond its boundaries. So for all research, this is the only space that you will ever have to interact with. At least in the near future.
Greatness
Everyone knows that the universe is big. How many million light years does it span?
Astronomers carefully study the cosmic radiation of the microwave background - the afterglow of the Big Bang. They are looking for a connection between what is happening on one side of the sky and what is on the other. And while there is no evidence that there is something in common. This means that for 13.8 billion years in any direction the Universe does not repeat itself. This is how long it takes for light to reach at least the visible edge of this space.
We are still concerned with the question of what is beyond the observable universe. Astronomers admit that the cosmos is infinite. "Matter" in it (energy, galaxies, etc.) is distributed in exactly the same way as in the observable Universe. If this is true, then there are various anomalies of what is on the edge.
Beyond Hubble's volume lies not just more different planets. There you can find everything that can possibly exist. If you get far enough, you might even find another solar system with an Earth identical in every way except that you had porridge for breakfast instead of scrambled eggs. Or there was no breakfast at all. Or let's say you got up early and robbed a bank.
In fact, cosmologists believe that if you go far enough, you can find another Hubble sphere that is completely identical to ours. Most scientists believe that the universe as we know it has boundaries. What is beyond them remains the greatest mystery.
Cosmological principle
This concept means that regardless of the place and direction of the observer, everyone sees the same picture of the Universe. Of course, this does not apply to smaller scale studies. Such homogeneity of space is caused by the equality of all its points. This phenomenon can only be detected on the scale of a cluster of galaxies.
Something akin to this concept was first proposed by Sir Isaac Newton in 1687. And later, in the 20th century, the same was confirmed by the observations of other scientists. Logically, if everything originated from a single point in the Big Bang and then expanded into the universe, it would remain fairly uniform.
The distance at which the cosmological principle can be observed to find this apparent uniform distribution of matter is approximately 300 million light-years from Earth.
However, everything changed in 1973. Then an anomaly was discovered that violates the cosmological principle.
Great attractor
A huge concentration of mass was found at a distance of 250 million light years, near the constellations of Hydra and Centaurus. Its weight is so great that it could be compared with tens of thousands of masses of the Milky Ways. This anomaly is considered a galactic supercluster.
This object is called the Great Attractor. Its gravitational force is so strong that it affects other galaxies and their clusters for several hundred light-years. It has long been one of the biggest mysteries of the cosmos.
In 1990, it was discovered that the movement of colossal clusters of galaxies, called the Great Attractor, tends to another region of space - beyond the edge of the Universe. So far, this process can be observed, although the anomaly itself is in the “zone of avoidance”.
dark energy
According to Hubble's Law, all galaxies should move uniformly apart from each other, preserving the cosmological principle. However, in 2008 a new discovery appeared.
The Wilkinson Microwave Anisotropy Probe (WMAP) found a large group of clusters moving in the same direction at speeds up to 600 miles per second. All of them were on their way to a small area of the sky between the constellations Centaurus and Parus.
There is no obvious reason for this, and since it was an inexplicable phenomenon, it was called "dark energy". It is caused by something outside the observable universe. At present, there is only speculation about its nature.
If clusters of galaxies are drawn towards a colossal black hole, then their movement should be accelerating. Dark energy indicates a constant speed of cosmic bodies in billions of light years.
One of possible causes this process - massive structures that are outside the universe. They have a huge gravitational effect. Within the observable universe, there are no giant structures with enough gravitational gravity to cause this phenomenon. But this does not mean that they could not exist outside the observable area.
This would mean that the structure of the universe is not uniform. As for the structures themselves, they can be literally anything, from aggregates of matter to energy on a scale that can hardly be imagined. It is even possible that these are guiding gravitational forces from other Universes.
Endless Bubbles
Talking about something outside of the Hubble sphere is not entirely correct, since it still has the identical structure of the Metagalaxy. "Unknown" has the same physical laws of the Universe and constants. There is a version that the Big Bang caused the appearance of bubbles in the structure of space.
Immediately after it, before the inflation of the Universe began, a kind of "cosmic foam" arose, existing as a cluster of "bubbles". One of the objects of this substance suddenly expanded, eventually becoming the universe known today.
But what came out of the other bubbles? Alexander Kashlinsky, head of the NASA team, the organization that discovered "dark energy," said: "If you move far enough away, you can see a structure that is outside the bubble, outside the universe. These structures should cause movement.”
Thus, "dark energy" is perceived as the first evidence of the existence of another Universe, or even a "Multiverse".
Each bubble is an area that has stopped expanding along with the rest of the space. She formed her own universe with her own special laws.
In this scenario, the space is infinite and each bubble also has no boundaries. Even if it is possible to breach the boundary of one of them, the space between them is still expanding. Over time, it will be impossible to reach the next bubble. Such a phenomenon is still one of the greatest mysteries of the cosmos.
Black hole
The theory proposed by the physicist Lee Smolin assumes that each similar space object in the structure of the Metagalaxy causes the formation of a new one. One has only to imagine how many black holes there are in the Universe. Inside each, there are physical laws that are different from those of the predecessor. A similar hypothesis was first stated in 1992 in the book "The Life of the Cosmos".
Stars around the world that fall into black holes are compressed to incredibly extreme densities. Under such conditions, this space explodes and expands into a new universe of its own, different from the original. The point where time stops inside the black hole is the beginning of the Big Bang of the new Metagalaxy.
Extreme conditions inside the destroyed black hole lead to small random changes in the basic physical forces and parameters in the daughter Universe. Each of them has different characteristics and indicators from the parent.
The existence of stars is a prerequisite for the formation of life. This is because carbon and other complex molecules, providing life, are created in them. Therefore, the same conditions are needed for the formation of beings and the Universe.
A criticism of cosmic natural selection as a scientific hypothesis is the lack of direct evidence at this stage. But it should be borne in mind that, in terms of beliefs, it is no worse than the proposed scientific alternatives. There is no evidence of what is outside the universe, be it the Multiverse, string theory, or cyclic space.
Many parallel universes
This idea seems to be something that has little to do with modern theoretical physics. But the idea of the existence of the Multiverse has long been considered a scientific possibility, although it still causes active discussion and destructive debate among physicists. This option completely destroys the idea of how many universes there are in space.
It is important to keep in mind that the Multiverse is not a theory, but rather a consequence of the current understanding of theoretical physics. This distinction is of decisive importance. No one waved his hand and said: "Let there be a Multiverse!". This idea was derived from current teachings such as quantum mechanics and string theory.
Multiverse and quantum physics
Many people know the thought experiment "Schrödinger's Cat". Its essence lies in the fact that Erwin Schrödinger, an Austrian theoretical physicist, pointed out the imperfection of quantum mechanics.
The scientist proposes to imagine an animal that was placed in a closed box. If you open it, you can find out one of two states of the cat. But as long as the box is closed, the animal is either alive or dead. This proves that there is no state that combines life and death.
All this seems impossible simply because human perception cannot comprehend it.
But it is quite real according to the strange rules of quantum mechanics. The space of all possibilities in it is huge. Mathematically, a quantum mechanical state is the sum (or superposition) of all possible states. In the case of "Schrödinger's Cat", the experiment is a superposition of "dead" and "alive" positions.
But how is this to be interpreted so that it makes any practical sense? A popular way is to think of all these possibilities in such a way that the only "objectively true" state of the cat is observed. However, one can also agree that these possibilities are true and that they all exist in different Universes.
String theory
This is the most promising opportunity to combine quantum mechanics and gravity. This is difficult because gravity is just as indescribable on a small scale as atoms and subatomic particles are in quantum mechanics.
But string theory, which says that all fundamental particles are made up of monomeric elements, describes all the known forces of nature at once. These include gravity, electromagnetism and nuclear forces.
However, mathematical string theory requires at least ten physical dimensions. We can observe only four dimensions: height, width, depth and time. Therefore, additional dimensions are hidden from us.
To be able to use theory to explain physical phenomena, these additional studies are "densified" and too small on a small scale.
The problem or peculiarity of string theory is that there are many ways to perform a compactification. Each of these results in the creation of a universe with different physical laws, such as different electron masses and gravity constants. However, there are also serious objections to the compactification methodology. Therefore, the problem is not completely solved.
But the obvious question is: which of these possibilities are we living in? String theory does not provide a mechanism for determining this. It makes it useless because it is not possible to thoroughly test it. But exploring the edge of the universe turned that error into a feature.
Consequences of the Big Bang
During the earliest universe, there was a period of accelerated expansion called inflation. She originally explained why the Hubble sphere is nearly uniform in temperature. However, inflation also predicted a spectrum of temperature fluctuations around this equilibrium, which was later confirmed by several spacecraft.
Although the exact details of the theory are still hotly debated, inflation is widely accepted by physicists. However, the implication of this theory is that there must be other objects in the universe that are still accelerating. Due to the quantum fluctuations of space-time, some parts of it will never reach the final state. This means that space will expand forever.
This mechanism generates an infinite number of Universes. Combining this scenario with string theory, there is a possibility that each of them has a different compactification of extra dimensions and therefore has different physical laws of the universe.
According to the teachings of the Multiverse, predicted by string theory and inflation, all universes live in the same physical space and can overlap. They must inevitably collide, leaving traces in the cosmic sky. Their character has a wide range - from cold or hot spots on the cosmic microwave background to anomalous voids in the distribution of galaxies.
Since collision with other universes must occur in a certain direction, any interference is expected to break the homogeneity.
Some scientists look for them through anomalies in the cosmic microwave background, the afterglow of the Big Bang. Others are in gravitational waves that ripple through space-time as massive objects pass. These waves can directly prove the existence of inflation, which ultimately strengthens support for the Multiverse theory.
The theory of relativity considers space and time as a single formation, the so-called "space - time", in which the time coordinate plays an equally significant role as the spatial ones. Therefore, in the very general case we, from the point of view of the theory of relativity, can only talk about the finiteness or infinity of this particular united "space-time". But then we enter the so-called four-dimensional world, which has very special geometric properties that differ in the most essential way from the geometric properties of the three-dimensional world in which we live.
And the infinity or finiteness of the four-dimensional "space - time" still says nothing or almost nothing about the spatial infinity of the Universe that interests us.
On the other hand, the four-dimensional "space-time" of the theory of relativity is not just a convenient mathematical apparatus. It reflects well-defined properties, dependencies and regularities of the real Universe. And therefore, when solving the problem of the infinity of space from the point of view of the theory of relativity, we are forced to take into account the properties of "space-time". Back in the twenties of the current century, A. Friedman showed that, within the framework of the theory of relativity, a separate statement of the question of the spatial and temporal infinity of the Universe is not always possible, but only under certain conditions. These conditions are: homogeneity, i.e. uniform distribution of matter in the Universe, and isotropy, i.e. the same properties in any direction. Only in the case of homogeneity and isotropy does the single "space-time" split into "homogeneous space" and universal "world time".
But, as we have already noted, the real Universe is much more complicated than homogeneous and isotropic models. And this means that the four-dimensional world of the theory of relativity, corresponding to the real world in which we live, in the general case, does not split into “space” and “time”. Therefore, even if with an increase in the accuracy of observations we can calculate the average density (and hence the local curvature) for our Galaxy, for a cluster of galaxies, for a region of the Universe accessible to observations, this will not yet be a solution to the question of the spatial extent of the Universe as a whole.
It is interesting, by the way, to note that some regions of space may actually turn out to be finite in the sense of closure. And not only the space of the Metagalaxy, but also any area in which there are sufficiently powerful masses that cause strong curvature, for example, the space of quasars. But, we repeat, this still does not say anything about the finiteness or infinity of the Universe as a whole. In addition, the finiteness or infinity of space depends not only on its curvature, but also on some other properties.
Thus, at state of the art general relativity and astronomical observations we cannot get a sufficiently complete answer to the question of the spatial infinity of the Universe.
They say that the famous composer and pianist F. Liszt provided one of his piano works with such instructions for the performer: “quickly”, “even faster”, “as quickly as possible”, “even faster” ...
This story involuntarily comes to mind in connection with the study of the question of the infinity of the universe. Already from what was said above, it is quite obvious that this problem is extremely complex.
And yet it is still immeasurably more difficult ...
To explain means to reduce to the known. This technique is used in almost every scientific research. And when we try to solve the problem of the geometric properties of the Universe, we also strive to reduce these properties to familiar concepts.
The properties of the Universe are, as it were, “trying on” to those existing in this moment abstract mathematical concepts of infinity. But are these representations sufficient to describe the Universe as a whole? The trouble is that they were developed largely independently, and sometimes completely independently of the problems of studying the Universe, and in any case on the basis of the study of a limited region of space.
Thus, the solution of the question of the real infinity of the Universe turns into a kind of lottery in which the probability of winning, i.e., a random coincidence, is at least enough a large number properties of the real Universe with one of the formally derived standards of infinity is very insignificant.
The basis of modern physical ideas about the Universe is the so-called special theory relativity. According to this theory, the spatial and temporal relationships between various real objects around us are not absolute. Their character depends entirely on the state of motion of the given system. So, in a moving system, the rate of time flow slows down, and all length scales, i.e. the dimensions of extended objects are reduced. And this reduction is the stronger, the higher the speed of movement. When approaching the speed of light, which is the maximum possible speed in nature, all linear scales decrease indefinitely.
But if at least some of the geometric properties of space depend on the nature of the motion of the reference frame, i.e., are relative, we have the right to raise the question: are not the concepts of finiteness and infinity also relative? After all, they are closely related to geometry.
In recent years, the well-known Soviet cosmologist A. L. Zelmapov has been studying this curious problem. He succeeded in discovering a fact, at first glance, quite amazing. It turned out that space, which is finite in a fixed frame of reference, can at the same time be infinite with respect to a moving frame of reference.
Perhaps this conclusion will not seem so surprising if we recall the reduction of scale in moving systems.
A popular presentation of the complex problems of modern theoretical physics is very difficult because in most cases they do not allow visual explanations and analogies. Nevertheless, we will now try to give one analogy, but using it, we will try not to forget that it is very approximate.
Imagine that a spacecraft is passing by the Earth at a speed equal to, say, two-thirds of the speed of light - 200,000 km/sec. Then, according to the formulas of the theory of relativity, a halving of all scales should be observed. This means that from the point of view of the astronauts who are on the ship, all segments on Earth will become half as long.
Now let's imagine that we have a straight line, although very long, but still finite, and we measure it using some unit of length scale, for example, a meter. For an observer in spaceship rushing at a speed approaching the speed of light, our reference meter will shrink to a point. And since there are an infinite number of points even on a finite line, for an observer in a ship our line will become infinitely long. Approximately the same thing will happen with respect to the scale of areas and volumes. Consequently, finite regions of space can become infinite in a moving frame of reference.
We repeat once again - this is by no means a proof, but only a rather rough and far from complete analogy. But it gives some idea of the physical essence of the phenomenon of interest.
Let us now recall that in moving systems not only scales are reduced, but the passage of time also slows down. From this it follows that the duration of the existence of some object, which is finite in relation to a fixed (static) coordinate system, may turn out to be infinite Long in a moving frame of reference.
Thus, it follows from Zelmanov's works that the properties of "finiteness" and "infinity" of space and time are relative.
Of course, all these, at first glance, rather "extravagant" results cannot be regarded as establishing some general geometric properties of the real Universe.
But thanks to them, an extremely important conclusion can be drawn. Even from the point of view of the theory of relativity, the concept of the infinity of the Universe is much more complicated than it seemed before.
Now there is every reason to expect that if a theory more general than the theory of relativity is ever created, then within the framework of this theory the question of the infinity of the Universe will turn out to be even more complicated.
One of the main provisions of modern physics, its cornerstone is the requirement of the so-called invariance of physical statements with respect to the transformations of the frame of reference.
Invariant means "not changing". To better understand what this means, let's take some geometric invariants as an example. So circles with centers at the origin of the rectangular coordinate system are rotation invariants. With any rotation of the coordinate axes relative to the origin, such circles turn into themselves. Straight lines perpendicular to the axis "OY" are invariants of the transformations of the transfer of the coordinate system along the "OX" CRS.
But in our case we are talking about invariance in a broader sense of the word: any statement only then has physical meaning when it does not depend on the choice of reference system. In this case, the reference system should be understood not only as a coordinate system, but also as a way of description. No matter how the method of description changes, the physical content of the phenomena under study must remain unchanged, invariant.
It is easy to see that this condition has not only a purely physical, but also a fundamental, philosophical significance. It reflects the desire of science to clarify the real, true course of phenomena, and the exclusion of all distortions that can be introduced into this course by the very process of scientific research.
As we have seen, it follows from the works of A. L. Zelmanov that both infinity in space and infinity in time do not satisfy the requirement of invariance. This means that the concepts of temporal and spatial infinity that we currently use do not fully reflect the real properties of the world around us. Therefore, apparently, the very formulation of the question of the infinity of the Universe as a whole (in space and time), with the modern understanding of infinity, is devoid of physical meaning.
We have received one more convincing evidence that the "theoretical" concepts of infinity, which have been used so far by the science of the Universe, are very, very limited. Generally speaking, this could have been guessed before, since the real world is always much more complicated than any "model" and we can only talk about a more or less accurate approximation to reality. But in this case it was especially difficult to judge, so to speak, by eye how significant the approximation achieved was.
Now at least the way to go is looming. Apparently, the task is primarily to develop the very concept of infinity (mathematical and physical) based on the study of the real properties of the Universe. In other words: “trying on” not the Universe to the theoretical concepts of infinity, but vice versa, these theoretical ideas to the real world. Only such a method of research can lead science to significant success in this area. No abstract logical reasoning and theoretical conclusions can replace the facts obtained from observations.
It is probably necessary, first of all, on the basis of studying the real properties of the Universe, to develop an invariant concept of infinity.
And, in general, apparently, there is no such universal mathematical or physical standard of infinity that could reflect all the properties of the real Universe. As knowledge develops, the number of types of infinity known to us will itself grow indefinitely. Therefore, it is likely that the question of whether the universe is infinite will never be answered with a simple yes or no.
At first glance, it may seem that, in connection with this, the study of the problem of the infinity of the Universe loses any sense at all. However, firstly, this problem in one form or another confronts science on certain stages and it has to be solved, and secondly, attempts to solve it lead to a number of fruitful discoveries along the way.
Finally, it must be emphasized that the problem of the infinity of the Universe is much broader than just the question of its spatial extension. First of all, we can talk not only about infinity "in breadth", but, so to speak, and "in depth". In other words, it is necessary to get an answer to the question of whether the space is infinitely divisible, continuous, or whether there are some minimal elements in it.
At present, this problem has already arisen before physicists. The question of the possibility of the so-called quantization of space (as well as time), that is, the selection in it of certain "elementary" cells, which are extremely small, is being seriously discussed.
We must also not forget about the infinite variety of properties of the Universe. After all, the Universe is primarily a process, . characteristic features which are continuous movement and incessant transitions of matter from one state to another. Therefore, the infinity of the Universe is also an infinite variety of forms of motion, types of matter, physical processes, relationships and interactions, and even properties of specific objects.
Does infinity exist?
In connection with the problem of the infinity of the Universe, a seemingly unexpected question arises. Does the very concept of infinity have any real meaning? Isn't it just conditional? mathematical construction, which in the real world does not correspond to anything at all? A similar point of view was held by some researchers in the past, and it has supporters at the present time.
But the data of science indicate that when studying the properties real world we are at any rate confronted with what may be called physical or practical infinity. For example, we encounter quantities so large (or so small) that, from a certain point of view, they are no different from infinity. These quantities lie beyond the quantitative limit beyond which any further changes in them no longer have any noticeable effect on the essence of the process under consideration.
Thus, infinity indisputably exists objectively. Moreover, both in physics and in mathematics, we encounter the concept of infinity at almost every step. This is not an accident. Both of these sciences, especially physics, despite the seeming abstractness of many provisions, in the final analysis, always start from reality. This means that nature, the Universe actually has some properties that are reflected in the concept of infinity.
The totality of these properties can be called the real infinity of the Universe.
Just about the complex. Why is the Universe infinite and where to look for aliens?
We are starting a new column “Simply about the complex”, within which we will ask specialists in different areas the simplest, sometimes even childishly naive questions about everything in the world. And our interlocutors will endure our importunity, intelligibly and naturally talking about complex things. Today we are talking with Belarusian photographer and astronomer Viktor Malyshchits, well known to our readers for a series of articles on space.
Let's start with the most important. Where did the aliens go and why, despite all our efforts, have we still not found them (and they - us)?
In an attempt to detect intelligent life forms, humanity uses radio signals. But we do not know what kind of communication they use. Maybe the aliens do not know about radio waves or have long abandoned them?
There are other questions as well. In what format should the signal be sent? What areas of space? How to increase the likelihood that the signal is understandable? Many signaling events are PR promotions. For example, in 1974, a radio signal was sent from the Arecibo observatory towards the globular star cluster M13. Someone said, they say, there are 100 thousand stars, at least ten will have aliens! They just keep silent that this cluster is 24 thousand light years away. And do not forget that the probable answer needs the same amount.
Part of Arecibo's message
It is better to try to look for some signals yourself than to send them. However, neither one nor the other has yet yielded any results.
- Space is boundless, the Universe is infinite. How did scientists come to this conclusion?
We assume that our world has a certain structure: there are galaxies, clusters of galaxies, superclusters of galaxies, etc. But on a scale of several hundred million light-years, our world is homogeneous, and, as far as we can see, nothing changes there. There is no indication that the structure of the universe is trying to cluster closer to any center or edge. Based on these observations, it is concluded that, probably, everything is the same in the future.
The trouble is that no matter what telescopes we build, we cannot see the whole world. The maximum that we can see is those objects that are at a distance of 13.7 billion light years from us (the age at which our Universe is estimated). Light has already reached us from them. But after all, something could happen further, it’s just that the light signal did not have time to reach from there.
Thus, there is a border beyond which we cannot break through. But what is behind it, we can only guess, extrapolating the knowledge that we have.
Why did people stop flying to the moon? After all, today for this much more possibilities than 50 years ago. Maybe conspiracy theories don't lie?
I don't believe in any conspiracy theories. The answer to the question is quite simple: sending a man to the moon is a very, very expensive project. In the 1960s, there was a different geopolitical situation, the US and the USSR actively participated in the space race. It was necessary to catch up and overtake the rival, people wanted this, they were ready to give up material wealth in order to be the first.
Today the society has become more well-fed. Of course, we can now resume flights to the Moon, we can even fly to Mars. The only question is - how much will it cost taxpayers? We want to have Good work, comfortable rest, brand new iPhone and everything else. Are people ready to give it up?
In addition, today's technology has reached such a level that a person is not needed, it is much cheaper to do without him. A person is a heavy piece of meat, in which only the head and hands work normally, and everything else is an extra load, which, in addition to everything else, needs a bunch of life support systems. A small lunar rover with a bunch of sensors would weigh a lot less, it wouldn't need oxygen or water, and it would be a lot cheaper to launch it to the moon than it would be to launch a human.
What color are planets and nebulae really? In the photographs, they are so beautiful and colorful, but when we look at the night sky or into space through a telescope, we do not see this colorful beauty.
The concept of color is very arbitrary. For a man it's not so much absolute value how much is relative. How does the human eye work? It constantly adjusts the white balance. Here we are sitting in the office and we see yellow light bulbs, while the sheet of paper under them looks white, and now everything outside the window is somehow blue. Let's go outside during the day, and everything will seem white there. This is because our eyes are constantly adjusting so that the background light is grayish. Therefore, it is very difficult to talk about color during the day, a lot depends on the background lighting. But at night, when there is no background lighting, our eyes set the white balance to a specific value.
Remember that the eye's photoreceptors include cones and rods? It is the latter that are responsible for night vision, and they do not recognize colors in low light. Therefore, in a telescope, we see the nebula as a kind of diffuse, colorless haze. But for the camera there is no difference, low light or strong light, it always captures the color.
Do you know what is the most popular color among nebulae? Pink! Nebulae are mostly made up of hydrogen, which glows red, slightly blue and purple when exposed to nearby stars, resulting in a pink color.
So the cosmos is colored, we just don't see these colors. We can only distinguish the colors of the brightest stars and planets. Everyone, for example, sees that Mars is not green, but orange, Jupiter is yellowish, and Venus is white. When processing images, they try to fit them to these colors. Although there are no strict rules. Often through telescopes or spacecraft the planet is photographed in slightly different ranges, and not in standard RGB. Therefore, the colors in the pictures may not always be natural.
Telescope "Hubble"
The Rosette Nebula in the Hubble Palette
In general, with space frames there are two options. According to the first, the objects are trying to show as realistic as possible, they are shot in RGB, the nebulae are pinkish, the stars are of a normal color. As a second example, one can cite such a technique as the “Hubble palette” (the name arose due to the fact that photographs from this particular telescope were first processed in this way). Elements such as oxygen, hydrogen, sulfur and some others glow only in certain ranges of the spectrum. There are special filters that can show, for example, only hydrogen or only sulfur. You put a filter - only the structure of hydrogen in the nebula is fixed, you put another one - you see only oxygen. For an astronomer, this is important, because you can trace the distribution of different chemical elements. But how to show all this to people? Then, purely conditionally, they decide to color hydrogen in green, sulfur in red, and oxygen in blue. It turns out a beautiful and at the same time informative picture, which, however, has little in common with the original.
Why large asteroids discovered so late? After all, often they learn about them only when they are already as close as possible to the Earth.
Let's see how asteroids are generally detected. The same part of the starry sky is photographed several times. If some "asterisk" moves, then it is an asteroid or something like that. Next, you need to check the bases, calculate the orbit and see if the object will collide with the planet.
The problem is that an asteroid dangerous for the Earth is just a boulder with a diameter of a couple of tens of meters. It is very difficult to see a 20-30-meter block in space. Plus, they're almost black.
I would say that, on the contrary, we should be proud that people learned to detect asteroids so early. Previously, even the most terrible of them were discovered only after they flew by.
- Isn't there a lot of space debris in orbit? How dangerous is he?
Many! And the biggest problem is that we can't do anything with it yet. You can only try not to throw anything into space or throw it out so that it burns up in the atmosphere. In low orbits, where most of the satellites, including broken ones, are located, the earth's atmosphere is slightly present and gradually slows down the movement of debris. It eventually falls to Earth and burns up in the atmosphere.
What to do with more high orbits? If the amount of debris reaches a critical value, then an avalanche-like formation of debris will begin. Imagine that some particle collides with a satellite at an incredible speed - it will also scatter into hundreds of blanks that will collide with other particles, etc. As a result, the planet will be surrounded by a cocoon of debris, and space will become unsuitable for research. Fortunately, we are still far from this critical value.
- Where do people get hysteria about the planet Nibiru? Have you, as an experienced astronomer, seen it?
People love to believe in conspiracy theories. This is our psychology, we want to believe in the unreal. No one has really seen this planet, astronomers do not take it seriously.
Why didn't they come up with artificial gravity? She's in all science fiction films!
Physics has not yet been discovered! Theoretically, of course, it is possible to build a huge ring in space that spins at a certain speed. Then, due to the centrifugal force, gravity can be obtained. But all this is more fantasy than reality. So far, it is easier to teach people to work in zero gravity.
In ancient times, very little was known to man, regarding the knowledge of today, and man strove for new knowledge. Of course, people were also interested in where they live and what is outside their home. After some time, people have devices for observing the night sky. Then a person understands that the world is much larger than he once imagined it and reduced it only to the scale of the planet. After a long study of the cosmos, new knowledge opens up to a person, which leads to an even greater study of the unknown. The person asks the question “Is there end of space? Or is space infinite?
End of space. theories
The very question of infinity outer space, of course, the question is very interesting and torments all astronomers and not only astronomers. Many years ago, when the Universe began to be intensively studied, many philosophers tried to answer themselves and the world about the infinity of the cosmos. But then it all boiled down only to logical reasoning, and there was no evidence confirming that the end of the cosmos exists, as well as denying it. Also at that time, people believed and believed that the Earth is the center of the Universe, that all cosmic stars and bodies revolve around the Earth.
Now scientists also cannot give an exhaustive answer to this question, because everything comes down to hypotheses and there is no scientific proof of one or another opinion about the end of space. Even with modern scientific achievements and technologies, a person cannot answer this question. All this because of the well-known speed of light. The speed of light is the main assistant in the study of space, thanks to which a person can look into the sky and receive information. The speed of light is a unique quantity, which is an indefinable barrier. The distances in space are so huge that they do not fit in a person's head and light needs whole years, or even millions of years, to overcome such distances. Therefore, the farther a person looks into space, the farther he looks into the past, because the light from there travels for so long that we see what it was or a cosmic body millions of years ago.
The end of space, the boundaries of the visible
The end of space, of course, exists in the vision of man. There is such a boundary in space beyond which we cannot see anything, because the light from those very distant places has not yet reached our planet. Scientists do not see anything there and, probably, this will not change very soon. The question arises: “Is this border the end of the cosmos?”. It is difficult to answer this question, because nothing is visible, but this does not mean that there is nothing there. Perhaps a parallel universe begins there, or maybe a continuation of the cosmos, which we do not yet see, and there is no end to the cosmos. There is another version that
Did you know that the universe we observe has pretty definite boundaries? We are accustomed to associate the Universe with something infinite and incomprehensible. but modern science to the question of the "infinity" of the Universe offers a completely different answer to such an "obvious" question.
According to modern concepts, the size of the observable universe is approximately 45.7 billion light years (or 14.6 gigaparsecs). But what do these numbers mean?
The first question that comes to mind ordinary person How can the universe not be infinite at all? It would seem that it is indisputable that the receptacle of everything that exists around us should not have boundaries. If these boundaries exist, what do they even represent?
Suppose some astronaut flew to the borders of the universe. What will he see before him? Solid wall? Fire barrier? And what is behind it - emptiness? Another universe? But can emptiness or another Universe mean that we are on the border of the universe? It doesn't mean that there is "nothing". Emptiness and another Universe is also “something”. But the Universe is that which contains absolutely everything “something”.
We arrive at an absolute contradiction. It turns out that the border of the Universe should hide from us something that should not be. Or the boundary of the Universe should fence off “everything” from “something”, but this “something” should also be a part of “everything”. In general, complete absurdity. Then how can scientists claim the ultimate size, mass, and even age of our universe? These values, although unimaginably large, are still finite. Does science argue with the obvious? To deal with this, let's first look at how people came to the modern understanding of the universe.
Expanding the boundaries
From time immemorial, man has been interested in what the world around them is like. You can not give examples of the three whales and other attempts of the ancients to explain the universe. As a rule, in the end it all came down to the fact that the basis of all things is the earthly firmament. Even in the times of antiquity and the Middle Ages, when astronomers had extensive knowledge of the laws of motion of the planets along the "fixed" celestial sphere The earth remained the center of the universe.
Naturally, even in Ancient Greece there were those who believed that the earth revolves around the sun. There were those who talked about the many worlds and the infinity of the universe. But constructive justifications for these theories arose only at the turn of the scientific revolution.
In the 16th century, the Polish astronomer Nicolaus Copernicus made the first major breakthrough in the knowledge of the universe. He firmly proved that the Earth is only one of the planets revolving around the Sun. Such a system greatly simplified the explanation of such a complex and intricate motion of the planets in the celestial sphere. In the case of a stationary Earth, astronomers had to come up with all sorts of ingenious theories to explain this behavior of the planets. On the other hand, if the Earth is assumed to be mobile, then the explanation for such intricate movements comes naturally. Thus, a new paradigm called "heliocentrism" was strengthened in astronomy.
Many Suns
However, even after that, astronomers continued to limit the universe to the "sphere of fixed stars." Until the 19th century, they were unable to estimate the distance to the luminaries. For several centuries, astronomers have unsuccessfully tried to detect deviations in the position of stars relative to the Earth's orbital motion (annual parallaxes). The tools of those times did not allow for such accurate measurements.
Finally, in 1837, the Russian-German astronomer Vasily Struve measured the parallax. This marked a new step in understanding the scale of the cosmos. Now scientists could safely say that the stars are distant likenesses of the Sun. And our luminary is no longer the center of everything, but an equal “resident” of an endless star cluster.
Astronomers have come even closer to understanding the scale of the universe, because the distances to the stars turned out to be truly monstrous. Even the size of the orbits of the planets seemed insignificant compared to this something. Next, it was necessary to understand how the stars are concentrated in.
Many Milky Ways
As early as 1755, the famous philosopher Immanuel Kant anticipated the foundations of the modern understanding of the large-scale structure of the universe. He hypothesized that the Milky Way is a huge rotating star cluster. In turn, many observable nebulae are also more distant "milky ways" - galaxies. Despite this, until the 20th century, astronomers adhered to the fact that all nebulae are sources of star formation and are part of the Milky Way.
The situation changed when astronomers learned to measure the distances between galaxies using. The absolute luminosity of stars of this type is strictly dependent on the period of their variability. Comparing their absolute luminosity with the visible one, it is possible to determine the distance to them with high accuracy. This method was developed in the early 20th century by Einar Hertzschrung and Harlow Shelpie. Thanks to him, the Soviet astronomer Ernst Epik in 1922 determined the distance to Andromeda, which turned out to be an order of magnitude greater than the size of the Milky Way.
Edwin Hubble continued Epic's undertaking. By measuring the brightness of Cepheids in other galaxies, he measured their distance and compared it with the redshift in their spectra. So in 1929 he developed his famous law. His work definitively disproved the entrenched view that the Milky Way is the edge of the universe. Now he was one of the many galaxies that once considered him integral part. Kant's hypothesis was confirmed almost two centuries after its development.
Subsequently, the connection between the distance of the galaxy from the observer and the speed of its removal from the observer, discovered by Hubble, made it possible to compile a complete picture of the large-scale structure of the Universe. It turned out that the galaxies were only a tiny part of it. They connected into clusters, clusters into superclusters. In turn, superclusters fold into the largest known structures in the universe - filaments and walls. These structures, adjacent to huge supervoids () and constitute a large-scale structure of the currently known universe.
Apparent infinity
From the foregoing, it follows that in just a few centuries, science has gradually fluttered from geocentrism to a modern understanding of the universe. However, this does not answer why we limit the universe today. After all, until now it was only about the scale of the cosmos, and not about its very nature.
The first who decided to justify the infinity of the universe was Isaac Newton. Revealing the law gravity, he believed that if space were finite, all her bodies would sooner or later merge into a single whole. Before him, if someone expressed the idea of the infinity of the Universe, it was only in a philosophical key. Without any scientific justification. An example of this is Giordano Bruno. By the way, like Kant, he was ahead of science by many centuries. He was the first to declare that the stars are distant suns, and planets also revolve around them.
It would seem that the very fact of infinity is quite reasonable and obvious, but the turning points in science of the 20th century shook this “truth”.
Stationary Universe
The first significant step towards the development of a modern model of the universe was made by Albert Einstein. The famous physicist introduced his model of the stationary Universe in 1917. This model was based on the general theory of relativity, developed by him a year earlier. According to his model, the universe is infinite in time and finite in space. But after all, as noted earlier, according to Newton, a universe with a finite size must collapse. To do this, Einstein introduced the cosmological constant, which compensated for the gravitational attraction of distant objects.
No matter how paradoxical it may sound, Einstein did not limit the very finiteness of the Universe. In his opinion, the Universe is a closed shell of a hypersphere. An analogy is the surface of an ordinary three-dimensional sphere, for example, a globe or the Earth. No matter how much the traveler travels the Earth, he will never reach its edge. However, this does not mean that the Earth is infinite. The traveler will simply return to the place where he started his journey.
On the surface of the hypersphere
In the same way, a space wanderer, overcoming the Einstein Universe on a starship, can return back to Earth. Only this time the wanderer will move not on the two-dimensional surface of the sphere, but on the three-dimensional surface of the hypersphere. This means that the universe has a finite volume, and hence finite number stars and mass. However, the universe does not have any boundaries or any center.
Einstein came to such conclusions by linking space, time and gravity in his famous theory. Before him, these concepts were considered separate, which is why the space of the Universe was purely Euclidean. Einstein proved that gravity itself is a curvature of space-time. This radically changed the early ideas about the nature of the universe, based on classical Newtonian mechanics and Euclidean geometry.
Expanding Universe
Even the discoverer of the "new universe" himself was not a stranger to delusions. Einstein, although he limited the universe in space, he continued to consider it static. According to his model, the universe was and remains eternal, and its size always remains the same. In 1922, the Soviet physicist Alexander Fridman significantly expanded this model. According to his calculations, the universe is not static at all. It can expand or contract over time. It is noteworthy that Friedman came to such a model based on the same theory of relativity. He managed to apply this theory more correctly, bypassing the cosmological constant.
Albert Einstein did not immediately accept such a "correction". To the aid of this new model came the previously mentioned discovery of Hubble. The recession of galaxies indisputably proved the fact of the expansion of the Universe. So Einstein had to admit his mistake. Now the Universe had a certain age, which strictly depends on the Hubble constant, which characterizes the rate of its expansion.
Further development of cosmology
As scientists tried to solve this problem, many other important components of the Universe were discovered and various models of it were developed. So in 1948, Georgy Gamow introduced the “hot universe” hypothesis, which would later turn into the big bang theory. The discovery in 1965 confirmed his suspicions. Now astronomers could observe the light that came from the moment when the universe became transparent.
Dark matter, predicted in 1932 by Fritz Zwicky, was confirmed in 1975. Dark matter actually explains the very existence of galaxies, galaxy clusters and the very structure of the Universe as a whole. So scientists learned that most of the mass of the universe is completely invisible.
Finally, in 1998, during the study of the distance to, it was discovered that the Universe is expanding with acceleration. This next turning point in science gave rise to modern understanding of the nature of the universe. Introduced by Einstein and refuted by Friedmann, the cosmological coefficient again found its place in the model of the Universe. The presence of a cosmological coefficient (cosmological constant) explains its accelerated expansion. To explain the presence of the cosmological constant, the concept was introduced - a hypothetical field containing most of the mass of the Universe.
The current idea of the size of the observable universe
The current model of the Universe is also called the ΛCDM model. The letter "Λ" means the presence of the cosmological constant, which explains the accelerated expansion of the universe. "CDM" means that the universe is filled with cold dark matter. Recent studies suggest that the Hubble constant is about 71 (km/s)/Mpc, which corresponds to the age of the Universe at 13.75 billion years. Knowing the age of the Universe, we can estimate the size of its observable region.
According to the theory of relativity, information about any object cannot reach the observer at a speed greater than the speed of light (299792458 m/s). It turns out that the observer sees not just an object, but its past. The farther the object is from it, the more distant past it looks. For example, looking at the Moon, we see the way it was a little more than a second ago, the Sun - more than eight minutes ago, the nearest stars - years, galaxies - millions of years ago, etc. In Einstein's stationary model, the Universe has no age limit, which means that its observable region is also not limited by anything. The observer, armed with more and more advanced astronomical instruments, will observe more and more distant and ancient objects.
We have another picture with modern model Universe. According to it, the Universe has an age, and hence the limit of observation. That is, since the birth of the Universe, no photon would have had time to travel a distance greater than 13.75 billion light years. It turns out that we can say that the observable Universe is limited from the observer by a spherical region with a radius of 13.75 billion light years. However, this is not quite true. Do not forget about the expansion of the space of the Universe. Until the photon reaches the observer, the object that emitted it will already be 45.7 billion light years away from us. years. This size is the particle horizon, and it is the boundary of the observable Universe.
Over the horizon
So, the size of the observable universe is divided into two types. The apparent size, also called the Hubble radius (13.75 billion light years). And the real size, called the particle horizon (45.7 billion light years). It is important that both of these horizons do not at all characterize the real size of the Universe. First, they depend on the position of the observer in space. Second, they change over time. In the case of the ΛCDM model, the particle horizon expands at a rate greater than the Hubble horizon. The question of whether this trend will change in the future, modern science does not give an answer. But if we assume that the Universe continues to expand with acceleration, then all those objects that we see now will sooner or later disappear from our “field of vision”.
So far, the most distant light observed by astronomers is the CMB. Looking into it, scientists see the Universe as it was 380,000 years after the Big Bang. At that moment, the Universe cooled down so much that it was able to emit free photons, which are captured today with the help of radio telescopes. At that time, there were no stars or galaxies in the Universe, but only a continuous cloud of hydrogen, helium and a negligible amount of other elements. From the inhomogeneities observed in this cloud, galactic clusters will subsequently form. It turns out that it is precisely those objects that will form from the inhomogeneities of the cosmic microwave background radiation that are located closest to the particle horizon.
True Borders
Whether the universe has true, unobservable boundaries is still the subject of pseudoscientific speculation. One way or another, everyone converges on the infinity of the Universe, but they interpret this infinity in completely different ways. Some consider the Universe to be multidimensional, where our "local" three-dimensional Universe is just one of its layers. Others say that the Universe is fractal, which means that our local Universe may be a particle of another. Do not forget about the various models of the Multiverse with its closed, open, parallel universes, wormholes. And many, many more different versions, the number of which is limited only by human imagination.
But if we turn on cold realism or simply move away from all these hypotheses, then we can assume that our Universe is an endless homogeneous container of all stars and galaxies. Moreover, at any very distant point, whether it be in billions of gigaparsecs from us, all the conditions will be exactly the same. At this point, the particle horizon and the Hubble sphere will be exactly the same with the same relict radiation at their edge. Around will be the same stars and galaxies. Interestingly, this does not contradict the expansion of the universe. After all, it is not just the Universe that is expanding, but its very space. The fact that at the moment of the big bang the Universe arose from one point only indicates that the infinitely small (practically zero) sizes that were then have now turned into unimaginably large ones. In the future, we will use this hypothesis in order to clearly understand the scale of the observable Universe.
Visual representation
Various sources provide all sorts of visual models that allow people to realize the scale of the universe. However, it is not enough for us to realize how vast the cosmos is. It is important to understand how such concepts as the Hubble horizon and the particle horizon actually manifest. To do this, let's imagine our model step by step.
Let's forget that modern science does not know about the "foreign" region of the Universe. Discarding the versions about the multiverses, the fractal Universe and its other "varieties", let's imagine that it is simply infinite. As noted earlier, this does not contradict the expansion of its space. Of course, we take into account the fact that its Hubble sphere and the sphere of particles are respectively 13.75 and 45.7 billion light years.
The scale of the universe
Press the START button and discover a new, unknown world!
To begin with, let's try to realize how large the Universal scales are. If you have traveled around our planet, you can well imagine how big the Earth is for us. Now imagine our planet as a grain of buckwheat, which moves in orbit around the watermelon-Sun, the size of half a football field. In this case, the orbit of Neptune will correspond to the size of a small city, the area - to the Moon, the area of the boundary of the influence of the Sun - to Mars. It turns out that our solar system is just as more earth how much more Mars is buckwheat! But this is only the beginning.
Now imagine that this buckwheat will be our system, the size of which is approximately equal to one parsec. Then the Milky Way will be the size of two football stadiums. However, this will not be enough for us. We will have to reduce the Milky Way to a centimeter size. It will somehow resemble coffee foam wrapped in a whirlpool in the middle of coffee-black intergalactic space. Twenty centimeters from it, there is the same spiral "baby" - the Andromeda Nebula. Around them will be a swarm of small galaxies in our Local Cluster. The apparent size of our universe will be 9.2 kilometers. We have come to understand the universal dimensions.
Inside the universal bubble
However, it is not enough for us to understand the scale itself. It is important to realize the Universe in dynamics. Imagine ourselves as giants, for whom the Milky Way has a centimeter diameter. As noted just now, we will find ourselves inside a ball with a radius of 4.57 and a diameter of 9.24 kilometers. Imagine that we are able to soar inside this ball, travel, overcoming whole megaparsecs in a second. What will we see if our universe is infinite?
Of course, before us will appear countless all kinds of galaxies. Elliptical, spiral, irregular. Some areas will be teeming with them, others will be empty. main feature will be that visually they will all be motionless, while we will be motionless. But as soon as we take a step, the galaxies themselves will begin to move. For example, if we are able to see in centimeter Milky Way microscopic solar system, we can observe its development. Having moved away from our galaxy by 600 meters, we will see the protostar Sun and the protoplanetary disk at the time of formation. Approaching it, we will see how the Earth appears, life is born and man appears. In the same way, we will see how galaxies change and move as we move away from or approach them.
Therefore, than in more distant galaxies we will peer, the more ancient they will be for us. So the most distant galaxies will be located further than 1300 meters from us, and at the turn of 1380 meters we will already see relic radiation. True, this distance will be imaginary for us. However, as we get closer to the CMB, we will see an interesting picture. Naturally, we will observe how galaxies will form and develop from the initial cloud of hydrogen. When we reach one of these formed galaxies, we will understand that we have overcome not 1.375 kilometers at all, but all 4.57.
Downscaling
As a result, we will increase in size even more. Now we can place entire voids and walls in the fist. So we will find ourselves in a rather small bubble from which it is impossible to get out. Not only will the distance to objects on the edge of the bubble increase as they approach, but the edge itself will move indefinitely. This is the whole point of the size of the observable universe.
No matter how big the Universe is, for the observer it will always remain a limited bubble. The observer will always be at the center of this bubble, in fact he is its center. Trying to get to some object on the edge of the bubble, the observer will shift its center. As you approach the object, this object will move further and further away from the edge of the bubble and at the same time change. For example, from a shapeless hydrogen cloud, it will turn into a full-fledged galaxy or further a galactic cluster. In addition, the path to this object will increase as you approach it, as the surrounding space itself will change. When we get to this object, we will only move it from the edge of the bubble to its center. At the edge of the Universe, the relic radiation will also flicker.
If we assume that the Universe will continue to expand at an accelerated rate, then being in the center of the bubble and winding time for billions, trillions and even higher orders of years ahead, we will notice an even more interesting picture. Although our bubble will also increase in size, its mutating components will move away from us even faster, leaving the edge of this bubble, until every particle of the Universe wanders apart in its lonely bubble without the ability to interact with other particles.
So, modern science does not have information about what the real dimensions of the universe are and whether it has boundaries. But we know for sure that the observable Universe has a visible and true boundary, called the Hubble radius (13.75 billion light years) and the particle radius (45.7 billion light years), respectively. These boundaries are completely dependent on the position of the observer in space and expand with time. If the Hubble radius expands strictly at the speed of light, then the expansion of the particle horizon is accelerated. The question of whether its particle horizon acceleration will continue further and change to contraction remains open.
