It is known that Universe formed as a result of the so-called explosion. But this does not mean that we know everything about her. Let's start with the fact that the explosion was not such that it all started with a dense substance with a high temperature and then cooled down. Moreover, it is still not clear whether The central part of the universe.
It is logical to assume that if it is expanding, then from somewhere, it means it exists. Let's look at how the Trinity test took place. After 16 milliseconds have passed from the start of the explosion, the upper part of the fireball is at an altitude of 200 m. That is, the explosion occurs at a certain point and spreads out.
In this case, the fastest moving material gets out faster. And the energy density further from the epicenter of the explosion decreases faster. As time passes composition of the universe changes, galaxies and stars are formed. Then they merge with large galaxies. That is, we think that the further we look, the younger there is Universe, which is incorrect.
How things really are
In fact, at any distance Universe looks equivalent. And at a great distance there are many more objects than at a shorter distance. At the same time, scientists suggest that if Universe formed as a result of an explosion, its center should be the Milky Way. But isn't it too generous of her that we are in the very center of her? If the beginning of the universe was precisely the explosion, we would move away from its center.
Thus, it is logical to assume that the Universe began not from a dense and hot state, and not from an explosion, but from expansion - and this is a slightly different concept. And it does not at all speak in favor of the fact that the countdown started from 1 point. It could be an entire area.
Moreover, big Bang could occur in several parts at once. It is difficult for a person to perceive this state of affairs, but it has reasonable grounds.
Take light, for example, it is already clear that thanks to it we see very distant parts of galaxies as they were in the past. What we see is a special cosmic background, it can be seen absolutely from any part of the Universe.
Wherein the center of the universe there may not be. And where it came from may be infinity. And if there is a center, it may be located where we cannot even imagine. People don't have enough information to know for sure that they are right. We simply see everything from our human point of view.
“In fact, what they draw on a ball they draw on a plane and, accordingly, in space the analogy should be different.”
When the ball is _very_ large, it is very difficult to distinguish it from the plane. Previously, people were, for example, sure that the Earth was flat.
"The geometric center exists [...] don't know where to look[...]"
And you tell them. If they knew what size fingers it would help.Answer
Here's what Steven Weinberg, Nobel laureate in physics, writes:
“In the beginning there was an explosion. Not the kind of explosion that is familiar to us on Earth and which starts from a certain center and then spreads, capturing more and more space, but an explosion that occurred simultaneously everywhere, filling from the very beginning “all space,” and each a particle of matter rushes away from any other particle. In this context, "all space" can mean either all the space of the infinite Universe, or all the space of the finite Universe, which is closed on itself, like the surface of a sphere."So there is an answer: there was no center, especially a geometric one, since there was no space as such. Sort of like a clickless BigBang.
And in general, these verbal descriptions using analogies are given for non-specialists and they do not pretend to be accurate, much less critically resistant. Therefore, in order to fully understand the essence, you need to look at the formulas describing the process, having previously raised the level of knowledge of the matan to the appropriate one.
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Oh! What beautiful craftiness! "Science-weary" people managed to mislead humanity with this fairy tale about a balloon. In fact, what they draw on a ball they draw on a plane and, accordingly, in space the analogy should be different. The geometric center exists - the region of space where the Lord "snapped his fingers." Why is this not advertised - that is the question! I see two answers - either they simply don’t know where to look, or it’s forbidden...
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The analogy with an inflated balloon is not correct and leads people into an even greater stupor.
I stick to the following analogy.
Let's say we live in the most common for us, Euclidean, three-dimensional space. And nothing unusual happens in it, except for one thing. All rulers, and in general all instruments for measuring distance, decrease by a certain distance per year, for example, by one millimeter per meter in length, and we do not have a way to stop this process. We simply notice that the distances between objects increase relative to the measuring instruments. That is, if you draw a point anywhere, then set aside a distance equal to 5 meter rulers from it, and put another point. Then in ten years the distance between the points will be 5 meter rulers and approximately 50 millimeters. Since the rulers have become smaller, we need more rulers to measure the distance. And wherever you place such points, the same thing happens everywhere, the distance between them increases. That is, we have found that the universe is expanding. But, excuse me, where is the center of this expansion? But he’s not there! It is not needed to present this analogy. The center is the observer, who sees all objects moving away from him. And all observers will think that they are the center of expansion, but the center is a point, and a point cannot be the size of the entire universe - this cannot be. Thus, it turns out that the center of expansion of the universe is everywhere, and this is a fundamental property of the universe - “It is expanding.”
In fact, the rulers do not shrink, but the space expands, i.e. the distances between objects increase. In the real Universe, the rate of decrease is much slower. But if the ruler were one megaparsec in size, then the speed of its decrease relative to space would be equal to 74 km/s. Well, the meter ruler from our analogy will decrease by a millimeter not in one year, but in 14 million years. Edwin Hubble discovered this; he determined that everything that is at a distance of one megaparsec from an observer moves away from him at a speed of 74.2 ± 3.6 km/s, and this value is called the “Hubble Constant”. That is, if in our time we take two points in space, the distance between which is one meter, then after 14 million years, they (the points) will move away from each other by one millimeter, and the distance between them will be 1001 millimeters.
But let's try to imagine what happened 14 million years ago, it turns out that the distance between these points was 999 millimeters. Well, 28 million years ago - 998 millimeters. If we continue counting, we will find that 14 billion years ago (a thousand times 14 million years) the distance between our points was zero millimeters. It does not matter which points in our time we take, at a distance of one meter, or one megaparsec, the distance between any points 14 billion years ago was equal to zero. That is, in the history of the Universe there is one significant date when all distances were equal to zero, and the matter seemed to be compressed into a point.
It turns out that 14 billion years ago, something happened, and after that all the points began to move away from each other, space began to expand. Since in everyday life we see all sorts of explosions, fireworks for example, scientists called what happened 14 billion years ago not just an explosion, but the Big Bang, the Universe began to expand. But, as we already understood, this has nothing to do with the explosion.
P.S. One millimeter increase per meter in length over approximately 14 million years is simply a reduction of the Hubble constant to ordinary concepts. When calculating, I simplified and rounded a little. Currently, the age of the universe is estimated to be 13.75 ± 0.11 billion years, so my rough estimate of 14 billion years is not that rough.
Thank you for your attention. I will be glad to listen to your questions.
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The question is simple and may not be very smart: does the expansion of space affect the distances between “close” objects: planets in star systems, for example, or stars within a galaxy?
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In the modern era, this model only works on a large scale, approximately the scale of superclusters of galaxies and larger. On smaller scales, matter is clumped together under the influence of gravitational attraction, and these clumps do not expand individually, although they continue to retreat from each other.
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Yes, I see, thank you. Those. can we assume that any “structure” within which gravitational forces act is not subject to expansion due to the expansion of space and all changes occur only due to gravitational forces? Why exactly does this happen? Is it gravity that causes such objects to remain “stable” in expanding space?
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This is a bit ambiguous. The expansion of space has been discovered at unimaginably huge distances, but at short distances these effects are indefinable. Those. It’s impossible (maybe it’s possible, but we haven’t figured out how) to set up an experiment to detect the expansion of space inside the laboratory. Therefore, scientists go the opposite way and come up with mathematical models of how the universe expands. And after that, they look to see whether the model fits the experimental data or not. But as soon as someone runs an experiment that does not fit into the existing model, the current model is modified in such a way that it fits the experiment. This is the same as when we were children, we adjusted the solution to some mathematical problem to the correct answer. But unlike school, where the correct answer was always one and 100% accurate. In real life, it’s not like this for scientists, today it’s the same, but with 95% accuracy, tomorrow it’s a little different, but more accurate. The funny thing is that scientists, when fitting a model to an experiment, do the same as children at school; when the answer does not agree, they begin to come up with all sorts of interesting constructions, with the help of which the solution more or less begins to describe the experiment. So, for example, they “invented” black matter, black energy. But, if a careless student adjusts the task to the answer out of laziness. Scientists do this in order to at least somehow explain what is happening. This is actually not bad, all the “inventions” of scientists are usually later discovered experimentally. Examples: planet Neptune, Pluto, electron, neutrino, spin in elementary particles.
It was a prelude, now the answers to the question.
1) That is can we assume that any “structure” within which gravitational forces act is not subject to expansion due to the ACTION OF GRAVITATIONAL FORCES?
As far as I understand the current model, yes.
2) Does gravity influence this?
Apparently yes.3) Why exactly does this happen?
This is a fundamental question. And there is no answer to it. But we can say that this happens this way, because the consequences of the model that scientists have come up with speak about this.PS. I apologize for the multi-books, but fundamental questions are probably answered this way :-). I hope that it became a little clear to you.
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Yes, everything is clear, thank you very much for such a detailed explanation. As you understand, there is no one in particular to ask such “childish” questions. You do not need to “justify” science in its “adjusted” strategy for understanding the World; it seems to me that this is the only possible way to understand reality - to build models based on observations and refine or change them as new observations become available. :)
As for my question, it was caused by the fact that when trying to imagine an expanding space, an intuitively erroneous idea arises that since the space itself expands, then everything in it expands. But since this is not the case, and material objects in the form of “inseparable pieces of matter” or even significantly larger structures do not expand (or there is no way to record such an expansion), then this precisely gives rise to these questions... it turns out that space, expanding, “crawls out from under” the objects in it... or am I making some fundamental mistakes in my reasoning due to insufficient education in this area :)
Thanks again for the clarification :))
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Sorry if this is offtopic. But regarding fundamental errors, well, I don’t know what to call it. An example is that scientists have been searching for the Higgs boson for several decades. They built the Tevatron - not enough, they decided to build a large hadron collider and specialize it in searching for the Higgs boson. But after 2 years of work, we haven’t found anything yet. The funny thing is that the so-called Standard Model is a theoretical construct in particle physics that describes the electromagnetic, weak and strong interactions of all elementary particles, but does not include gravity. So, almost all experiments at the level of elementary particles agree with it. But it (SM) implies the existence of the Higgs boson, which they just can’t find. Either they are searching poorly, or the model is incorrect, that’s the dilemma.
But absence is also a result, and now a non-Higgs model of the world is being developed in parallel.It's about mistakes. They also teach us something.
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Well, yes, a good and well-known explanation. But in a couple of places it is no better (or even worse) than the ball example:
- there is also a “but it’s just the other way around” (it’s not the ruler that’s shrinking, actually)
- no approaches to why there was a BOOM, but now it’s smooth
- no clues as to why not only “everything was at zero distance”, but also there were no protons there - and then BAM appeared.
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If we take the big bang theory as a basis, then this whole ball was once precise, and if the movement within the boundaries of the “ball”-space was the same in all directions, then the geometric center of the universe is the point from which the expansion began. And this center is calculated simply.
We need data on the redshifts of galaxies from two points in space. And the further these points are removed from each other, the more accurately the center will be calculated.
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Here on the site there is an article by A. Levin, “Almighty Inflation,” which explains why the Big Bang event is unobservable. There is an observability horizon for the Universe, which does not allow us to observe the entire Universe, and therefore the space-time parameters of the event called the Big Bang are unknown.
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The answer to such a not at all childish question puzzled me.
Let's say there are three galaxies A, B and C, lying on the same straight line and at the same time flying away from each other. Doesn't it follow from this that a pair of these galaxies are moving in the same direction, albeit at different speeds?
There must be a point on this line from which the galaxies began to move?
Or does Euclidean geometry not work here?
Sorry if the question turned out to be completely stupid.
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If you look for a center on the surface of a ball, then it is not there, but if you draw several perpendiculars to this surface, they will intersect at the center of the ball. He is. Our universe is four-dimensional and if you look for a center in three dimensions, there is none. Let's draw perpendiculars in the fourth dimension and get the center of our universe at a distance of 13.7 billion years ago. The fourth dimension is time. We are beings who in the fourth dimension move only in one direction (We are three-dimensional beings). Therefore, we can observe the expansion of the universe. And the mind helps us look back and far ahead. And the center of the Universe is located at a distance of 13.7 billion years ago.
KOP.
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The proposed analogy with a ball does not work.
The surface of the ball is 2-dimensional, and in order to have no center, it must be curved in the 3rd dimension.
Our world is 3-dimensional, and in order to have no center, it must be curved in the 4th dimension. And according to the latest data, it is flat, with high accuracy.
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Cas: Where is the center of the universe?
"Elementary Watson!"
The point is not to determine the center, but that while in the Universe it is impossible to indicate in which part of it you are. This is the basis of the General Theory of Relativity, tested and proven many times. The Finite or Infinite Universe looks the same from the inside. If we imagine the Universe as finite, then the closer “to the edge”, the earlier in time from its beginning. Space-Time is a single physical entity. You cannot move in Space without moving in Time.
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In the center of the ball there is a point relative to which it expands (each point of the ball, when inflated, has an equal velocity relative to this point). This means that such a point exists in the Universe, isn’t it?
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Let’s not forget that the Big Bang is just one of the theories that does not yet contradict non-observations. I wouldn’t be at all surprised if in 300 years science abandons this theory. Therefore, it is not entirely correct to write “In fact, the expansion of the Universe should not have a center...” Especially for children.
It would be more correct to say that “as modern science believes, the expansion of the Universe should not have a center...”. I think this is important to encourage curiosity, and to avoid children learning modern science as a series of dogmas.
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Too much is unknown.... How much dark energy and matter is there and what is it anyway? ... Using the example of an inflating ball of the “universe”: maybe inside this ball there is another... “dark” center of the universe, which is also inflated, but is in a different metric and is present next to every galaxy, and we notice it by the discrepancy between gravity ...god knows, maybe through this dark center you can get to any point in the universe..
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Mr. Wiebe, you are defaming yourself when you imagine our Universe as a two-dimensional surface of a rubber ball! And you take and place the same galaxies and stars and other black and white holes inside this ball, and then, continuing to inflate the ball and us, tell us that the ball has no center! And this is how it is with you everywhere: complete deception and complete metaphysics! Don’t you understand that this way you will definitely destroy the physical sciences and that it is high time to take the tracks off the feet of our frisky horse named Science-Physics and let her go free - into the vastness of the universe! You are not its creator; it is not for you to control it and the minds of thinking people!
I will try to give my explanation to the best of my modest capabilities. First of all, it should be noted that before the Big Bang (BB), the space whose center we are looking for did not exist, since this space arose precisely thanks to the BB. This means that there was no place in space in which BV occurred, and which could be considered the center.
In addition, during the explosion, space expanded (and continues to do so) so that the distribution density of energy and matter throughout space remained, on average, the same. In other words, there was no scattering of explosion products, characteristic of a conventional explosion. In a normal explosion, the trajectory of the fragments shows where the center is, but in the case of a BV, the space exploded along with the “contents”, and there was no scattering of fragments.
You might argue that in this case, too, you can find the center if you imagine the Universe as a ball. In this case, the center will be a point equidistant from the boundaries of the ball. But here there is a “surprise”: although the Universe is finite (the amount of matter, energy and volume of space are not infinite quantities), it is also limitless. That is, there are simply no boundaries from which one could measure the distance. In a sense, the center can be considered any point in the Universe. Any of us can call ourselves, for example, the center of the Universe and will be right. “How is this possible?!” another reader will exclaim. And here's the thing.
Let's again imagine the Universe as a "ball", and ourselves inside this ball. Let's say we fly in a straight line in search of the edge of the Universe. Having flown up to the place where the edge should be, we will not see anything special - everything will be the same as everywhere else: stars, galaxies, etc. It just turns out that having flown out of the “ball” we immediately flew into it from the opposite side. Continuing the straight line movement, we will return to the same place from where we started moving. And it doesn't depend on the direction.
An interesting consequence can be drawn from this. Imagine that we have such vision that is capable of piercing the abyss at any distance with a “thin needle”. And here we stand, looking at the sky, and suddenly we notice that wherever we look, we see... ourselves! Yes, yes, when we glance in any direction, we find ourselves looking at the back of our heads. And this “other person” is not a copy, not another copy, but we are the only copy.
I hope I didn't overload it too much? Popular enough?
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“Loaded” not much except for this: “Before BV, space did not exist” and “it arose thanks to BV.”
In my humble opinion (not necessarily correct), all the problems of physics that raise “childish” questions that it cannot adequately answer are related to the fact that physics has been driven into a mathematical dead end, when when explaining “childish” questions, it is not the essence of phenomena that is revealed, but make reference to the formulas and their constituent members. But the essence of these members is absolutely not defined. For example, reveal the essence of the fundamental concept ENERGY.
Its forms are known: matter and radiation, the types of its manifestation are known: quantum fields of various natures (material, interaction fields, etc.), there is a fundamental law of conservation of energy (contrary to the BV theory). But what this substance called Energy is is not revealed. And it cannot be said that this is an empty term, since mass and the entire material world are clots of energy (E = mc2, hence m is a special form of energy).
With a high degree of probability it can be assumed that Energy is the basis of the Universe. In the absence of external impulses, Energy is neutral and has a uniform density. External impulses cause its disturbances in the form of waves of various types (electromagnetic, gravitational, etc.) and the formation of different-scale “clumps” with mass (electrons, neutrons, protons, quarks and other material particles) and, ultimately, the material structure of our Universe . In these arguments, the nature and origin of the impulses that remove Energy from a state of rest and equilibrium are unclear. It can be assumed that they arose repeatedly and in different parts of space.
Now about space and the problem of its infinity. Man imagines himself to be the “navel of the Universe,” although in terms of his parameters he in no way corresponds to its size, but he is trying to study it with his own metric. Hence the misunderstanding of its infinity. With the improvement of research methods and tools, humanity will push further and further the “boundaries” of the Universe, becoming convinced of its infinity.
Thanks to everyone who read this post to the end, and to those who understood something from it.
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According to Einstein's fairly well-tested theory, no matter where we are in the Universe, it looks the same. Each point differs only in how much time has passed since the beginning of the expansion. Therefore, the center is the “oldest” place, but it is impossible to determine it.
But, remembering the principle: “never say “never”,” I thought, if not the center, then the direction to the “center of expansion”, it will be possible to indicate when comparing maps of the anisotropy of the electromagnetic, neutrino and gravitational cosmic microwave background radiation. If the latter two are ever measured.
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The center of the Universe is possible, but it is difficult to identify. Imagine, our entire Universe is billions of times larger than the part we see. And this part, expanding along with the entire Universe, flies away from its center at superluminal speed.
How can you notice this? If the energy density of the universal medium - ether/vacuum - is almost the same both inside our part of the Universe and beyond its borders (beyond the Hubble sphere). This will not cause any noticeable anisotropy in the temperature of the cosmic microwave background radiation. The presence of a center and an edge of our Universe can only be assumed within the framework of the version of the multiplicity of expanding universes. And this assumption must be tested indirectly - by identifying the consequences of such a variant of the multiverse in past or future experiments.
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Our Universe began with the Big Bang, but this does not mean that we pictured it correctly. Most of us think of it as a real explosion: where everything starts out hot and dense, and then cools and cools as individual fragments fly further and further. But this is not true at all. Therefore, the question arises: does the Universe have a center? Is cosmic background radiation really the same distance from us no matter where we look? After all, if the Universe is expanding, this expansion must have started somewhere?
Let's think for a moment about the physics of an explosion and what our universe would be like if it started with one.
The first stages of the explosion during the Trinity nuclear test, 16 milliseconds after the explosion. The top of the fireball is at an altitude of 200 meters. July 16, 1945
The explosion starts at a point and quickly expands outward. The fastest moving material comes out the fastest and therefore spreads the fastest. The further you are from the center of the explosion, the less material will catch up with you. The energy density decreases as time passes, but further away from the explosion it falls faster because the energetic material in the surrounding area is thinner. No matter where you are, you will always be able - unless you are destroyed - to reconstruct the center of the explosion.
The large-scale structure of the Universe changes over time as tiny defects grow to form the first stars and galaxies and then merge to form the large, modern galaxies we see today. The further you look, the younger the Universe.
But this is not the Universe we see. The Universe looks the same at large and small distances: the same densities, the same energies, the same galaxies, etc. Distant objects that move away from us at high speeds do not match in age with objects that are located closer to us and move with lower speeds; they seem younger. And at a great distance there are not fewer objects, but more. And if we look at how everything in the Universe moves, we see that even though we see tens of billions of light years away, we have reconstructed the center right where we are.
The Laniakea Supercluster, where the position of the Milky Way is marked in red, represents only one billionth the volume of the observable Universe. If the Universe began with a bang, the Milky Way would be exactly at the center.
Does this mean that we, out of all the trillions of galaxies in the Universe, were at the center of the Big Bang? And that the original "explosion" was configured in just such a way - with irregular, heterogeneous energy densities, "reference points" and a mysterious 2.7 K glow - to place us at its center? How generous it would be for the Universe to set itself up so that we end up at this incredibly unrealistic starting point.
During an explosion in space, the outer material will be removed the fastest, which means that it will be the material that exhibits other properties fastest as it moves away from the center, as it will lose energy and density faster.
But general relativity tells us that this is not an explosion, but an expansion. The universe began in a hot, dense state, and it was its fabric that expanded. There is a misconception that it had to start from one point, but no. The whole region had such properties - filled with matter, energy, etc. - and then simply universal gravity came into play.
These properties were the same everywhere - density, temperature, number of galaxies, etc. But if we could see this, we would find evidence of an evolving Universe. Since the Big Bang happened all at once and everywhere a certain time ago in some region of space, and this region is all we can see if we look from our point of view, we see a region of space that is not very different from our own position in the past. It's hard to understand, but try.
Looking back across large cosmic distances is like looking back in time. It's been 13.8 billion years since the Big Bang where we are now, but the Big Bang also happened in other places. Light traveling through time from those galaxies means we are seeing distant regions as they were in the past.
Galaxies whose light took a billion years to reach us are visible to us as they were a billion years ago; galaxies that appear to us ten billion years later look the same as they were exactly that time ago. 13.8 billion years ago, the Universe was full of radiation, not matter, and when neutral atoms first formed, this radiation did not go away, cooled and redshifted due to the expansion of the Universe. What we see as the cosmic microwave background is not only the afterglow of the Big Bang, but it is visible from anywhere in the Universe.
The universe does not necessarily have a center. What we call the "region" of space in which the Big Bang occurred may be infinity. If there is a center, it could be literally anywhere, and we wouldn't know about it because we don't observe enough of the Universe to get complete information. We would need to see an edge, a fundamental anisotropy (where different directions look different) in the temperatures and numbers of galaxies, and our Universe on the largest scales appears the same everywhere and in all directions.
There is no place from which the Universe began to expand, there is a time when the Universe began to expand. This is exactly what the Big Bang was: a state into which the entire observable Universe passed at a certain moment. This is why looking in all directions means looking back in time. That is why the Universe is homogeneous in all directions. This is why our history of cosmic evolution can be traced as far as our observatories can see.
It is possible that the Universe has a finite shape and size, but if so, then this information is not available to us. The part of the Universe we observe is finite, and this information is not contained in it. If you think of the Universe as a balloon, a loaf of bread, or anything else by analogy, don't forget that we can only access a tiny part of the actual Universe. All we see is a small part of it. And whether it is finite or infinite, it never ceases to expand and decompress.
The universe is not expanding in any way; it just becomes less dense.
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The universe looks roughly the same in all directions, but distant galaxies appear younger and less evolved than those closer
We know that our Universe began with the Big Bang, but this does not mean that we all imagine it correctly. Most people imagine it as an explosion: when everything started from a hot and dense state, and then expanded to the sides and cooled, while various fragments moved away from each other. But no matter how attractive this picture may be, it is wrong. Our reader has a related question?
It’s interesting how it turns out that the universe has no center and the relict radiation is distant in any direction at an equal distance from us. It seems to me that if the universe is expanding, then you can always find the place where it began to expand.
Let's first think about the physics of explosion, and what our Universe would be like if it started with an explosion.
The first stages of the explosion during the Trinity nuclear test, 16 milliseconds after detonation. The top of the explosion reached 200 m.
The explosion begins at a certain point and quickly expands in all directions. The fastest moving debris moves outward faster than the rest. The further you are from the center of the explosion, the less material will reach you. The energy density decreases everywhere over time, but further from the center of the explosion it decreases faster, since the material is more dispersed at the outskirts of the explosion. It doesn't matter where you are - if the explosion didn't destroy you, you can always reconstruct the center of the explosion.
The large-scale structure of the Universe changes over time, with small imperfections growing to form the first stars and galaxies, then merging together to form the large, modern galaxies we see today. Looking further into the distance, we see a younger Universe, just like our local region was in the past.
But this is not the kind of Universe we observe. It looks the same at long and short distances: the same density, the same energy, the same number of galaxies. Distant objects moving away from us at greater speed do not appear similar in age to those closer to us and moving more slowly; they look younger. At long distances there are no fewer objects, there are more of them. And if we look at the pattern of motion in the Universe, we will see that despite the fact that we can look tens of billions of light years away, the center invariably turns out to be close to us.
The Laniakea Supercluster, where the location of the Milky Way is shown in red, represents only one billionth the volume of the observable Universe. If the Universe began in an explosion, then the Milky Way should have been near the center
Does this mean that we, out of the trillions of galaxies in the Universe, accidentally ended up at the center of the Big Bang? And that the initial explosion was set up in exactly this way, and irregular, inhomogeneous densities, energies, and a mysterious glow with a temperature of 2.7 K were taken into account? How petty the universe would be if it was set up in such an unrealistic way from the beginning.
An explosion in space would cause the outer layers of material to move outward faster than the others, meaning they would become less dense, lose energy faster than others, and exhibit different properties the further away from the center they move. Also, the explosion would need to expand somewhere, and not stretch space itself. Our Universe does not correspond to this description.
Instead, General Relativity predicts not an explosion, but an expansion. A universe that began in a hot, dense state and whose very fabric is expanding. There is a misconception that this process began from one point - this is not so! There was a region of space with such properties, filled with matter, energy, etc., and then the Universe began its evolution under the influence of the laws of gravity.
It has similar properties everywhere, including density, temperature, number of galaxies, etc. If we look outside, we will find evidence of an evolving universe. Since the Big Bang happened everywhere at the same time a finite time ago in an entire section of space, and we can only observe that section, then when we look from our vantage point, we see a section of space that is not very different from our location in the past.
Looking into cosmic distances means looking into the past. We live 13.8 billion years after the Big Bang, but the Big Bang happened in all other observable places. The time it takes for light to travel to other galaxies means that we see these distant regions as they were in the past.
Galaxies whose light took a billion years to reach us look as they did a billion ice years ago! 13.8 billion years ago, the universe was dominated by radiation rather than matter, and when neutral atoms first formed in the universe, this radiation remained and then cooled and redshifted due to the expansion of the universe. What we observe as cosmic microwave background radiation is not only the residual glow from the Big Bang, but this radiation can be seen from anywhere in the Universe.
Only a few hundred microkelvins—a few parts in 100,000—separate the hottest regions from the coldest in the CMB pattern.
The universe does not necessarily have a center; what we call the "patch" of space in which the Big Bang occurred may be of infinite size. If there is a center, it could literally be anywhere and we wouldn't know about it; The part of the Universe we observe is not enough to know this. We would need to see an edge, a fundamental anisotropy (where different directions are different from each other) in temperatures and number of galaxies, and our Universe, on the largest scales, actually looks the same everywhere and in all directions.
Artist's impression of the observable universe
There is no place where the Universe began to expand due to the Big Bang; There is a time from which the Universe began to expand. This is exactly what the Big Bang is - a condition that affects the entire observable Universe at a certain moment. Therefore, looking at long distances in all directions means looking into the past. Therefore, all directions have approximately the same properties. And so our history of cosmic evolution can be traced back as far as our observations can reach.
Galaxies similar to the Milky Way and their past
It is possible that the Universe has a finite size and shape, but if so, this information is not available to us. The part of the Universe accessible to us for observation is finite, and that information is not contained within this part. If you imagine the Universe in the form of a ball, a loaf, or any other analogy you like, remember that you only have access to a tiny part of the real Universe. What we're seeing is the lower limit of what's out there. It can be finite, it can be infinite, we are only sure that it is expanding, its density is decreasing, and the further we look, the deeper into the past we can look. As astrophysicist Cathy Mack said:
The universe is expanding as your consciousness expands. It’s not expanding somewhere; you just become less stupid [ dense (English) – “dense”, as well as “dull” / approx. translation]
The word “Universe” has been known to everyone since early childhood. This is what we remember when we raise our heads and, holding our breath, look into the endless sky filled with the lights of stars. We ask ourselves: “How infinite is our Universe? Does it have specific spatial boundaries, and finally, is it possible to find the place where the center of the Universe is located?
What is the Universe
This term is usually understood to mean the entire variety of stars, which can be seen not only with the naked eye, but also with the help of a telescope. It includes many galaxies. Since we cannot yet see the Universe completely, its boundaries are inaccessible to our eyes. It may well turn out that it is completely infinite. It is also impossible to determine its shape for sure. Most often it is presented in the shape of a disk, but it may well turn out to be spherical or oval. And no less controversy arises around the question of where the center of the Universe is.
Where is the center of the universe located?
There are various theories to explain this concept. Thus, one can recall Einstein: according to it, the center of the Universe can be considered any point relative to which measurements are made. Over the years of human existence, the view on this problem has undergone serious changes. It was once believed that the Earth was the center of the Universe and the entire universe. According to the ancients, it should have been flat in shape and supported by four elephants, which, in turn, stood on a turtle. Later, the heliocentric model was adopted, according to which the center of the Universe was located on the Sun. And only when scientists realized that the Sun is just one of the celestial stars, and not the largest, ideas about the center of the Universe came to the form that we have today.
The so-called “Big Bang Theory” was proposed to the entire astronomical community by Fred Hoyle, a famous physicist, as an explanation for the origin of the Universe. Today it is perhaps the most popular in a variety of circles. According to this theory, the space that our Universe now occupies arose as a result of a very rapid, explosion-like expansion from a negligibly small initial volume. On the one hand, according to all human ideas, such a model should have not only well-defined boundaries, but also a center, which is located in the place from which the expansion actually began. But there are matters that are simply impossible for people living in the limited to imagine. Likewise, the point that is the astronomical center of space may be located in another dimension inaccessible to us.
Hubble Telescope Research
Recently, there were reports in the media that the Hubble orbital telescope took a series of photographs of the core of our Universe. And a certain city was discovered in the center of the Universe, from which galaxies fan out. It is not yet possible to explore it in detail, since it is located too far away.
Wherever the point of the astronomical center of our Universe is, we will not yet be able to not only reach it, but even just see it.
