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Astronomy is the science of celestial bodies (from the ancient Greek words aston - star and nomos - law). It studies visible and actual movements and the laws that determine these movements, shape, size, mass and surface relief, the nature and physical state of celestial bodies, interaction and their evolution.
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Exploring the Universe The number of stars in the galaxy is in the trillions. The most numerous stars are dwarfs with masses about 10 times less than the Sun. In addition to single stars and their satellites (planets), the Galaxy includes double and multiple stars, as well as groups of stars bound by gravity and moving in space as a single whole, called star clusters. Some of them can be found in the sky through a telescope, and sometimes even with the naked eye. Such clusters do not have a regular shape; more than a thousand of them are currently known. Star clusters are divided into open and globular. Unlike open star clusters, which consist primarily of main sequence stars, globular clusters contain red and yellow giants and supergiants. Sky surveys carried out by X-ray telescopes mounted on special artificial Earth satellites led to the discovery of X-ray emissions from many globular clusters.
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Structure of the Galaxy The overwhelming majority of stars and diffuse matter in the Galaxy occupies a lens-shaped volume. The Sun is located at a distance of about 10,000 Pc from the center of the Galaxy, hidden from us by clouds of interstellar dust. At the center of the Galaxy there is a nucleus, which has recently been carefully studied in the infrared, radio and X-ray wavelengths. Opaque clouds of dust obscure the core from us, preventing visual and conventional photographic observations of this most interesting object in the Galaxy. If we could look at the galactic disk from above, we would find huge spiral arms, mostly containing the hottest and brightest stars, as well as massive clouds of gas. The disk with spiral branches forms the basis of the flat subsystem of the Galaxy. And objects that concentrate towards the Galactic core and only partially penetrate into the disk belong to the spherical subsystem. This is a simplified form of the structure of the Galaxy.
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Types of galaxies 1 Spiral. This is 30% of galaxies. They come in two types. Normal and crossed. 2 Elliptical. Most galaxies are believed to have the shape of an oblate sphere. Among them there are spherical and almost flat. The largest known elliptical galaxy is M87 in the constellation Virgo. 3 Not correct. Many galaxies have a ragged shape without a clearly defined outline. These include Our Local Group's Magellanic Cloud.
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The Sun The Sun is the center of our planetary system, its main element, without which there would be neither the Earth nor life on it. People have been observing the star since ancient times. Since then, our knowledge of the luminary has expanded significantly, enriched with numerous information about the movement, internal structure and nature of this cosmic object. Moreover, the study of the Sun makes a huge contribution to the understanding of the structure of the Universe as a whole, especially those of its elements that are similar in essence and principles of “work”.
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The Sun The Sun is an object that has existed, by human standards, for a very long time. Its formation began approximately 5 billion years ago. At that time, in place of the solar system there was a vast molecular cloud. Under the influence of gravitational forces, vortices began to appear in it, similar to earthly tornadoes. In the center of one of them, the substance (mostly hydrogen) began to become denser, and 4.5 billion years ago a young star appeared here, which after a long period of time received the name Sun. Planets gradually began to form around it - our corner of the Universe began to take on the appearance familiar to modern humans. -
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The yellow dwarf Sun is not a unique object. It is classified as a yellow dwarf, a relatively small main sequence star. The “service life” allotted to such bodies is approximately 10 billion years. By space standards, this is quite a bit. Now our luminary, one might say, is in the prime of his life: not yet old, no longer young - there is still half his life ahead.
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Light Year A light year is the distance that light travels in one year. The International Astronomical Union has given its explanation of the light year - this is the distance that light travels in a vacuum, without the participation of gravity, in a Julian year. The Julian year is equal to 365 days. It is this decoding that is used in scientific literature. If we take professional literature, then the distance is calculated in parsecs or kilo- and megaparsecs. Until 1984, a light year was the distance that light travels in one tropical year. The new definition differs from the old one by only 0.002%. There is no particular difference between the definitions. There are specific numbers that determine the distance of light hours, minutes, days, etc. A light year is equal to 9,460,800,000,000 km, a month is 788,333 million km, a week is 197,083 million km, a day is 26,277 million km, an hour is 1,094 million km, a minute is about 18 million km., second - about 300 thousand km.
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Galaxy Constellation Virgo Virgo can be best seen in early spring, namely in March - April, when it moves to the southern part of the horizon. Due to the fact that the constellation has an impressive size, the Sun is in it for more than a month - from September 16 to October 30. On ancient star atlases, Virgo was represented as a girl with an ear of wheat in her right hand. However, not everyone is able to discern just such an image in a chaotic scattering of stars. However, finding the Virgo constellation in the sky is not that difficult. It contains a star of the first magnitude, thanks to the bright light of which Virgo can be easily found among other constellations.
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Andromeda Nebula The closest large galaxy to the Milky Way. Contains approximately 1 trillion stars, which is 2.5-5 times larger than the Milky Way. It is located in the constellation Andromeda and is distant from Earth at a distance of 2.52 million light years. years. The plane of the galaxy is inclined to the line of sight at an angle of 15°, its apparent size is 3.2 × 1.0°, its apparent magnitude is +3.4m.
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Milky Way The Milky Way is a spiral galaxy. Moreover, it has a bridge in the form of a huge star system, interconnected by gravitational forces. The Milky Way is believed to have existed for over thirteen billion years. This is the period during which about 400 billion constellations and stars, over a thousand huge gas nebulae, clusters and clouds were formed in this Galaxy. The shape of the Milky Way is clearly visible on the map of the Universe. Upon examination, it becomes clear that this cluster of stars is a disk whose diameter is 100 thousand light years (one such light year is ten trillion kilometers). The thickness of the star cluster is 15 thousand, and the depth is about 8 thousand light years. How much does the Milky Way weigh? It is not possible to calculate this (determining its mass is a very difficult task). Difficulties arise in determining the mass of dark matter, which does not interact with electromagnetic radiation. This is why astronomers cannot definitively answer this question. But there are rough calculations according to which the weight of the Galaxy ranges from 500 to 3000 billion solar masses
Incredible facts
Have you ever wondered how big the Universe is?
8. However, this is nothing compared to the Sun.
Photo of the Earth from space
9. And this view of our planet from the moon.
10. This is us from the surface of Mars.
11. And this view of the Earth behind the rings of Saturn.
12. And this is the famous photograph" Pale blue dot", where the Earth is photographed from Neptune, from a distance of almost 6 billion kilometers.
13. Here is the size Earth compared to the Sun, which doesn’t even fit completely into the photo.
Biggest star
14. And this Sun from the surface of Mars.
15. As the famous astronomer Carl Sagan once said, in space more stars than grains of sand on all the beaches of the Earth.
16. There are many stars that are much larger than our Sun. Just look how tiny the Sun is.
Photo of the Milky Way galaxy
18. But nothing can compare to the size of the galaxy. If you reduce The sun to the size of a leukocyte(white blood cell), and shrink the Milky Way Galaxy using the same scale, the Milky Way would be the size of the United States.
19. This is because the Milky Way is simply huge. That's where the solar system is inside it.
20. But we see only very much a small part of our galaxy.
21. But even our galaxy is tiny compared to others. Here Milky Way compared to galaxy IC 1011, which is located 350 million light years from Earth.
22. Think about it, in this photograph taken by the Hubble telescope, thousands of galaxies, each containing millions of stars, each with their own planets.
23. Here is one of galaxy UDF 423, located 10 billion light years away. When you look at this photograph, you are looking billions of years into the past. Some of these galaxies formed several hundred million years after the Big Bang.
24. But remember that this photo is very, a very small part of the universe. It's just an insignificant part of the night sky.
25. We can quite confidently assume that somewhere there is black holes. Here's the size of the black hole compared to Earth's orbit.
> Scale of the Universe
Use online interactive scale of the universe: real dimensions of the Universe, comparison of space objects, planets, stars, clusters, galaxies.
We all think of dimensions in general terms, such as another reality, or our perception of the environment around us. However, this is only part of what measurements actually are. And above all, the existing understanding measurements of the scale of the Universe– this is the best described in physics.
Physicists suggest that measurements are simply different facets of perception of the scale of the Universe. For example, the first four dimensions include length, width, height and time. However, according to quantum physics, there are other dimensions that describe the nature of the universe and perhaps all universes. Many scientists believe that there are currently about 10 dimensions.
Interactive scale of the universe
Measuring the scale of the Universe
The first dimension, as mentioned, is length. A good example of a one-dimensional object is a straight line. This line only has a length dimension. The second dimension is width. This dimension includes length; a good example of a two-dimensional object would be an impossibly thin plane. Things in two dimensions can only be viewed in cross section.
The third dimension involves height, and this is the dimension we are most familiar with. Combined with length and width, it is the most clearly visible part of the universe in dimensional terms. The best physical form to describe this dimension is a cube. The third dimension exists when length, width and height intersect.
Now things get a little more complicated because the remaining 7 dimensions are associated with intangible concepts that we cannot directly observe but know exist. The fourth dimension is time. It is the difference between past, present and future. Thus, the best description of the fourth dimension would be chronology.
Other dimensions deal with probabilities. The fifth and sixth dimensions are associated with the future. According to quantum physics, there can be any number of possible futures, but there is only one outcome, and the reason for this is choice. The fifth and sixth dimensions are associated with the bifurcation (change, branching) of each of these probabilities. Basically, if you could control the fifth and sixth dimensions, you could go back in time or visit different futures.
Dimensions 7 to 10 are related to the Universe and its scale. They are based on the fact that there are several universes, and each has its own sequence of dimensions of reality and possible outcomes. The tenth and final dimension is actually one of all possible outcomes of all universes.
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Being close to a black hole is not the safest option for any space object. After all, these mysterious formations are so...
If you get out of the solar system, you will find yourself among stellar neighbors living their own lives. But which star is closest? ...
Which are on it. For the most part, we are all chained to the place where we live and work. The size of our world is amazing, but it is absolutely nothing compared to the Universe. As the saying goes - "born too late to explore the world, and too early to explore space". It's even insulting. However, let's get started - just be careful not to get dizzy.
1. This is Earth.
This is the same planet that is currently the only home for humanity. The place where life magically appeared (or maybe not so magically) and in the course of evolution you and I appeared.
2. Our place in the solar system.
The closest large space objects that surround us, of course, are our neighbors in the solar system. Everyone remembers their names from childhood, and during lessons about the world around them they make models. It so happened that even among them we are not the biggest...
3. The distance between our Earth and the Moon.
It doesn't seem that far, right? And if we also take into account modern speeds, then it’s “nothing at all.”
4. In fact, it’s quite far away.
If you try, then very accurately and comfortably - between the planet and the satellite you can easily place the rest of the planets of the solar system.
5. However, let's continue talking about planets.
Before you is North America, as if it were placed on Jupiter. Yes, this small green speck is North America. Can you imagine how huge our Earth would be if we moved it to the scale of Jupiter? People would probably still be discovering new lands)
6. This is Earth compared to Jupiter.
Well, more precisely six Earths - for clarity.
7. Rings of Saturn, sir.
The rings of Saturn would have such a gorgeous appearance, provided they revolved around the Earth. Look at Polynesia - a bit like the Opera icon, right?
8. Let's compare the Earth with the Sun?
It doesn't look that big in the sky...
9. This is the view of the Earth when looking at it from the Moon.
Beautiful, right? So lonely against the backdrop of empty space. Or not empty? Let's continue...
10. And so from Mars
I bet you wouldn't even be able to tell if it was Earth.
11. This is a shot of Earth just beyond the rings of Saturn
12. But beyond Neptune.
A total of 4.5 billion kilometers. How long would it take to search?
13. So, let's go back to the star called the Sun.
A breathtaking sight, isn't it?
14. Here is the Sun from the surface of Mars.
15. And here is its comparison with the Scale of the star VY Canis Majoris.
How do you like it? More than impressive. Can you imagine the energy concentrated there?
16. But this is all bullshit if we compare our native star with the size of the Milky Way galaxy.
To make it more clear, imagine that we have compressed our Sun to the size of a white blood cell. In this case, the size of the Milky Way is quite comparable to the size of Russia, for example. This is the Milky Way.
17. In general, stars are huge
Everything that is placed in this yellow circle is everything that you can see at night from Earth. The rest is inaccessible to the naked eye.
18. But there are other galaxies.
Here is the Milky Way compared to the galaxy IC 1011, which is located 350 million light years from Earth.
Let's go over it again?
So, this Earth is our home.
Let's zoom out to the size of the solar system...
Let's zoom out a little more...
And now to the size of the Milky Way...
Let's continue to reduce...
And further…
Almost ready, don't worry...
Ready! Finish!
This is all that humanity can now observe using modern technology. It’s not even an ant... Judge for yourself, just don’t go crazy...
Such scales are hard to even comprehend. But someone confidently declares that we are alone in the Universe, although they themselves are not really sure whether the Americans were on the Moon or not.
Hang in there guys... hang in there.
Did you know that the Universe we observe has fairly definite boundaries? We are used to associating the Universe with something infinite and incomprehensible. However, modern science, when asked about 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 the mind of an ordinary person is how can the Universe not be infinite? It would seem that it is indisputable that the container of all that exists around us should have no boundaries. If these boundaries exist, what exactly are they?
Let's say some astronaut reaches the boundaries of the Universe. What will he see in front of him? A 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? After all, this does not mean that there is “nothing” there. Emptiness and another Universe are also “something”. But the Universe is something that contains absolutely everything “something”.
We arrive at an absolute contradiction. It turns out that the boundary of the Universe must hide from us something that should not exist. Or the boundary of the Universe should fence off “everything” from “something”, but this “something” should also be part of “everything”. In general, complete absurdity. Then how can scientists declare the limiting size, mass and even age of our Universe? These values, although unimaginably large, are still finite. Does science argue with the obvious? To understand this, let's first trace how people came to our modern understanding of the Universe.
Expanding the boundaries
Since time immemorial, people have been interested in what the world around them is like. There is no need to give examples of the three pillars 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 earth's surface. Even in the times of antiquity and the Middle Ages, when astronomers had extensive knowledge of the laws of planetary movement 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 spoke 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, Polish astronomer Nicolaus Copernicus made the first major breakthrough in 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 movement of planets in the celestial sphere. In the case of a stationary Earth, astronomers had to come up with all sorts of clever theories to explain this behavior of the planets. On the other hand, if the Earth is accepted as moving, then an explanation for such intricate movements comes naturally. Thus, a new paradigm called “heliocentrism” took hold in astronomy.
Many Suns
However, even after this, 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 stars. For several centuries, astronomers have tried to no avail to detect deviations in the position of stars relative to the Earth’s orbital movement (annual parallaxes). The instruments of those times did not allow such precise measurements.
Finally, in 1837, the Russian-German astronomer Vasily Struve measured parallax. This marked a new step in understanding the scale of space. Now scientists could safely say that the stars are distant similarities to 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 planets’ orbits seemed insignificant in comparison. Next it was necessary to understand how the stars are concentrated in .
Many Milky Ways
The famous philosopher Immanuel Kant anticipated the foundations of the modern understanding of the large-scale structure of the Universe back in 1755. He hypothesized that the Milky Way is a huge rotating star cluster. In turn, many of the observed nebulae are also more distant “milky ways” - galaxies. Despite this, until the 20th century, astronomers believed that all nebulae are sources of star formation and are part of the Milky Way.
The situation changed when astronomers learned to measure distances between galaxies using . The absolute luminosity of stars of this type strictly depends on the period of their variability. By 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 Scelpi. Thanks to him, the Soviet astronomer Ernst Epic in 1922 determined the distance to Andromeda, which turned out to be an order of magnitude larger than the size of the Milky Way.
Edwin Hubble continued Epic's initiative. 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 established view that the Milky Way is the edge of the Universe. Now it was one of many galaxies that had once been considered part of it. Kant's hypothesis was confirmed almost two centuries after its development.
Subsequently, the connection discovered by Hubble between the distance of a galaxy from an observer relative to the speed of its removal from him, made it possible to draw a complete picture of the large-scale structure of the Universe. It turned out that the galaxies were only an insignificant part of it. They connected into clusters, clusters into superclusters. In turn, superclusters form the largest known structures in the Universe—threads and walls. These structures, adjacent to huge supervoids (), constitute the large-scale structure of the currently known Universe.
Apparent infinity
It follows from the above 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 we were talking only about the scale of space, and not about its very nature.
The first who decided to justify the infinity of the Universe was Isaac Newton. Having discovered the law of universal gravitation, he believed that if space were finite, all its bodies would sooner or later merge into a single whole. Before him, if anyone expressed the idea of the infinity of the Universe, it was exclusively in a philosophical vein. Without any scientific basis. An example of this is Giordano Bruno. By the way, like Kant, he was many centuries ahead of science. He was the first to declare that stars are distant suns, and planets also revolve around them.
It would seem that the very fact of infinity is quite justified and obvious, but the turning points of science of the 20th century shook this “truth”.
Stationary Universe
The first significant step towards developing a modern model of the Universe was taken by Albert Einstein. The famous physicist introduced his model of a stationary Universe in 1917. This model was based on the general theory of relativity, which he had developed a year earlier. According to his model, the Universe is infinite in time and finite in space. But, as noted earlier, according to Newton, a Universe with a finite size must collapse. To do this, Einstein introduced a cosmological constant, which compensated for the gravitational attraction of distant objects.
No matter how paradoxical it may sound, Einstein did not limit the very finitude 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 a traveler travels across 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 from which he began his journey.
On the surface of the hypersphere
In the same way, a space wanderer, traversing Einstein’s Universe on a starship, can return back to Earth. Only this time the wanderer will move not along the two-dimensional surface of a sphere, but along the three-dimensional surface of a hypersphere. This means that the Universe has a finite volume, and therefore a finite number of stars and mass. However, the Universe has neither boundaries nor any center.
Einstein came to these conclusions by connecting 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 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. Although Einstein 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, Soviet physicist Alexander Friedman 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 this “amendment.” This new model came to the aid of the previously mentioned Hubble discovery. 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 question, many other important components of the Universe were discovered and various models of it were developed. So in 1948, George 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 Universal structure itself as a whole. This is how scientists learned that most of the mass of the Universe is completely invisible.
Finally, in 1998, during a study of the distance to, it was discovered that the Universe is expanding at an accelerating rate. This latest turning point in science gave birth to our modern understanding of the nature of the universe. The cosmological coefficient, introduced by Einstein and refuted by Friedman, 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 a cosmological constant, the concept of a hypothetical field containing most of the mass of the Universe was introduced.
Modern understanding of the size of the observable Universe
The modern model of the Universe is also called the ΛCDM model. The letter "Λ" means the presence of a cosmological constant, which explains the accelerated expansion of the Universe. "CDM" means that the Universe is filled with cold dark matter. Recent studies indicate that the Hubble constant is about 71 (km/s)/Mpc, which corresponds to the age of the Universe 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 an observer at a speed greater than the speed of light (299,792,458 m/s). It turns out that the observer sees not just an object, but its past. The farther an object is from him, the more distant the past he looks. For example, looking at the Moon, we see as 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 its observable region is also not limited by anything. The observer, armed with increasingly sophisticated astronomical instruments, will observe increasingly distant and ancient objects.
We have a different picture with the modern model of the Universe. According to it, the Universe has an age, and therefore a limit of observation. That is, since the birth of the Universe, no photon could have traveled 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 to a spherical region with a radius of 13.75 billion light years. However, this is not quite true. We should not forget about the expansion of the space of the Universe. By the time the photon reaches the observer, the object that emitted it will be already 45.7 billion light years away from us. years. This size is the horizon of particles, it is the boundary of the observable Universe.
Over the horizon
So, the size of the observable Universe is divided into two types. 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). The important thing is that both of these horizons do not at all characterize the real size of the Universe. Firstly, they depend on the position of the observer in space. Secondly, they change over time. In the case of the ΛCDM model, the particle horizon expands at a speed greater than the Hubble horizon. Modern science does not answer the question of whether this trend will change in the future. 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”.
Currently, the most distant light observed by astronomers is the cosmic microwave background radiation. Peering into it, scientists see the Universe as it was 380 thousand years after the Big Bang. At this moment, the Universe cooled down enough that it was able to emit free photons, which are detected 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 an insignificant amount of other elements. From the inhomogeneities observed in this cloud, galaxy clusters will subsequently form. It turns out that precisely those objects that will be formed from inhomogeneities in the cosmic microwave background radiation are located closest to the particle horizon.
True Boundaries
Whether the Universe has true, unobservable boundaries is still a matter of pseudoscientific speculation. One way or another, everyone agrees on the infinity of the Universe, but interprets this infinity in completely different ways. Some consider the Universe to be multidimensional, where our “local” three-dimensional Universe is only one of its layers. Others say that the Universe is fractal - which means that our local Universe may be a particle of another. We should not forget about the various models of the Multiverse with its closed, open, parallel Universes, and wormholes. And there are many, many different versions, the number of which is limited only by human imagination.
But if we turn on cold realism or simply step back from all these hypotheses, then we can assume that our Universe is an infinite homogeneous container of all stars and galaxies. Moreover, at any very distant point, be it 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. There will be the same stars and galaxies around. Interestingly, this does not contradict the expansion of the Universe. After all, it is not just the Universe that is expanding, but its space itself. The fact that at the moment of the Big Bang the Universe arose from one point only means that the infinitely small (practically zero) dimensions that were then have now turned into unimaginably large ones. In the future, we will use precisely 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 understand the scale of the Universe. However, it is not enough for us to realize how big the cosmos is. It is important to imagine how concepts such as the Hubble horizon and the particle horizon actually manifest themselves. 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 versions of 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 that its Hubble sphere and particle sphere are respectively 13.75 and 45.7 billion light years.
Scale of the Universe
Press the START button and discover a new, unknown world!
First, let's try to understand how large the Universal scale is. 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 moving in orbit around a watermelon-Sun the size of half a football field. In this case, Neptune’s orbit will correspond to the size of a small city, the area will correspond to the Moon, and the area of the boundary of the influence of the Sun will correspond to Mars. It turns out that our Solar System is as much larger than the Earth as Mars is larger than buckwheat! But this is just the beginning.
Now let’s 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. The Milky Way will also have to be reduced to centimeter size. It will somewhat resemble coffee foam wrapped in a whirlpool in the middle of coffee-black intergalactic space. Twenty centimeters from it there is the same spiral “crumb” - the Andromeda Nebula. Around them there will be a swarm of small galaxies of our Local Cluster. The apparent size of our Universe will be 9.2 kilometers. We have come to an understanding of 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. Let's 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. Let’s imagine that we are able to float inside this ball, travel, covering entire megaparsecs in a second. What will we see if our Universe is infinite?
Of course, countless galaxies of all kinds will appear before us. Elliptical, spiral, irregular. Some areas will be teeming with them, others will be empty. The main feature will be that visually they will all be motionless while we are motionless. But as soon as we take a step, the galaxies themselves will begin to move. For example, if we are able to discern a microscopic Solar System in the centimeter-long Milky Way, we will be able to observe its development. Moving 600 meters away from our galaxy, we will see the protostar Sun and the protoplanetary disk at the moment of formation. Approaching it, we will see how the Earth appears, life arises and man appears. In the same way, we will see how galaxies change and move as we move away from or approach them.
Consequently, the more distant galaxies we look at, 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 relict radiation. True, this distance will be imaginary for us. However, as we get closer to the cosmic microwave background radiation, 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 covered not 1.375 kilometers at all, but all 4.57.
Zooming out
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 at the edge of the bubble increase as they get closer, but the edge itself will shift indefinitely. This is the whole point of the size of the observable Universe.
No matter how big the Universe is, for an 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 any object at the edge of the bubble, the observer will shift its center. As you approach an object, this object will move further and further 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, since the surrounding space itself will change. Having reached this object, we will only move it from the edge of the bubble to its center. At the edge of the Universe, relict radiation will still flicker.
If we assume that the Universe will continue to expand at an accelerated rate, then being in the center of the bubble and moving time forward by billions, trillions and even higher orders of years, we will notice an even more interesting picture. Although our bubble will also increase in size, its changing components will move away from us even faster, leaving the edge of this bubble, until each particle of the Universe wanders separately in its lonely bubble without the opportunity to interact with other particles.
So, modern science does not have information about the real size of the Universe and whether it has boundaries. But we know for sure that the observable Universe has a visible and true boundary, called respectively the Hubble radius (13.75 billion light years) and the particle radius (45.7 billion light years). These boundaries depend entirely on the observer's position in space and expand over 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 acceleration of the particle horizon will continue further and whether it will be replaced by compression remains open.