You probably think that the universe is infinite? May be so. It is unlikely that we will ever know for sure. It will not be possible to cover our entire universe with a glance. Firstly, this fact follows from the concept of the "big bang", which states that the universe has its own, so to speak, birthday, and, secondly, from the postulate that the speed of light is a fundamental constant. To date, the observable part of the universe, which is 13.8 billion years old, has expanded in all directions to a distance of 46.1 billion light years. The question arises: what was the size of the universe then, 13.8 billion years ago? This question was asked to us by someone Joe Mascarella. Here is what he writes:

“I have seen different answers to the question of what was the size of our universe shortly after the period of cosmic inflation ended. One source states - 0.77 centimeters, another - the size of a soccer ball, and the third - more than the size of the observable universe. So which one is it? Or maybe some kind of intermediate?

Context

The Big Bang and the Black Hole

Die Welt 27.02.2015

How the universe created man

Nautilus 01/27/2015 By the way, the past year just gives us a reason to talk about Einstein and the essence of space-time, because last year we celebrated the centenary of the general theory of relativity. So let's talk about the universe.

When we observe distant galaxies through a telescope, we can determine some of their parameters, for example, the following:

- redshift (i.e. how much the light emitted by them has shifted with respect to inertial system reference);

— brightness of an object (i.e. measure the amount of light emitted by a distant object);

is the angular radius of the object.

These parameters are very important, because if the speed of light is known (one of the few parameters that we know), as well as the brightness and size of the observed object (these parameters are also known to us), then we can determine the distance to the object itself.

In fact, one has to be content with only approximate characteristics of the brightness of the object and its size. If an astronomer observes a supernova explosion in some distant galaxy, then the corresponding parameters of other supernovas located in the neighborhood are used to measure its brightness; we assume that the conditions under which these supernovae erupted are similar, and there is no interference between the observer and the cosmic object. Astronomers distinguish the following three types of factors that determine the observation of a star: stellar evolution (the difference between objects depending on their age and distance), the exogenous factor (if the real coordinates of the observed objects differ significantly from the hypothetical ones) and the interference factor (if, for example, the passage of light interference, such as dust) - and this is all among other, unknown factors.

By measuring the brightness (or size) of the observed object, using the "brightness / distance" ratio, you can determine the distance of the object from the observer. Moreover, by the characteristics of the redshift of an object, it is possible to determine the extent of the expansion of the universe during the time during which the light from the object reaches the Earth. Using the relationship between matter-energy and space-time, which Einstein's general theory of relativity speaks of, one can consider all possible combinations of various forms of matter and energy available on this moment in the Universe.

But that is not all!

If you know what parts the universe consists of, then using extrapolation you can determine its size, as well as find out what happened at any stage in the evolution of the universe, and what was the energy density at that time. As you know, the universe consists of the following components:

- 0.01% - radiation (photons);

- 0.1% - neutrinos (heavier than photons, but a million times lighter than electrons);

- 4.9% - ordinary matter, including planets, stars, galaxies, gas, dust, plasma and black holes;

- 27% - dark matter, i.e. its kind, which participates in gravitational interaction, but differs from all particles standard model;

— 68% — dark energy causing the expansion of the universe.

As you can see, dark energy is an important thing, it was discovered quite recently. For the first nine billion years of its history, the universe consisted mainly of matter (in the form of a combination of ordinary matter and dark matter). However, for the first few millennia, radiation (in the form of photons and neutrinos) was an even more important building material than matter!

Note that each of these constituents of the universe (i.e., radiation, matter, and dark energy) have a different effect on its expansion rate. Even if we know that the universe is 46.1 billion light-years across, we need to know the exact combination of its constituent elements at every stage of its evolution in order to calculate the size of the universe at any point in time in the past.

- when the universe was about three years old, the diameter of the Milky Way was one hundred thousand light years;

- when the universe was one year old, it was much hotter and denser than it is now; the average temperature exceeded two million degrees Kelvin;

- one second after its birth, the universe was too hot for stable nuclei to form in it; at that moment, protons and neutrons were floating in a sea of ​​hot plasma. In addition, at that time the radius of the universe (if we take the Sun as the center of the circle) was such that only seven of all currently existing star systems closest to us could fit in the described circle, the most distant of which would be Ross 154 (Ross 154 - a star in the constellation Sagittarius, a distance of 9.69 light years from the Sun - approx. per.);

- when the age of the universe was only one trillionth of a second, its radius did not exceed the distance from the Earth to the Sun; in that era, the rate of expansion of the universe was 1029 times greater than it is now.

If you wish, you can see what happened at the final stage of inflation, i.e. immediately before big bang. To describe the state of the universe at the earliest stage of its birth, one could use the singularity hypothesis, but thanks to the inflation hypothesis, the need for a singularity is completely eliminated. Instead of a singularity, we are talking about a very rapid expansion of the universe (i.e., inflation) that took place over a period of time before the hot and dense expansion that started the current universe occurred. Now let's move on to the final stage of inflation of the universe (the time interval between 10 in minus 30 - 10 in minus 35 seconds). Let's see what the size of the universe was when inflation stopped and the big bang happened.

Here we are talking about the observable part of the universe. Its true size is certainly much larger, but we don't know by how much. At the best approximation (based on the data contained in the Sloan Digital Sky Survey (SDSS) and information received from the Planck space observatory), if the universe is curved and collapses, then its observable part is so indistinguishable from the “non-curved” that the entire its radius must be at least 250 times the radius of the observed part.

In truth, the extent of the universe may even be infinite, since how it behaved in the early stages of inflation is unknown to us except for the last fractions of a second. But if we talk about what happened during inflation in the observable part of the universe at the very last moment (between 10 at minus 30 and 10 at minus 35 seconds) before the Big Bang, then here the size of the universe is known to us: it varies between 17 centimeters (by 10 in minus 35 seconds) and 168 meters (by 10 in minus 30 seconds).

What is seventeen centimeters? It's almost the diameter of a soccer ball. So, if you want to know which of the given sizes of the universe is closest to the real one, then stick to this figure. And if you assume the size is less than a centimeter? This is too little; however, if we take into account the limitations imposed by cosmic microwave radiation, it turns out that the expansion of the universe could not have ended with such high level energies, and hence the size of the universe mentioned above at the very beginning of the "Big Bang" (ie, the size not exceeding a centimeter) is excluded. If the size of the universe exceeded the current size, then in this case it makes sense to talk about the existence of an unobservable part of it (which is probably correct), but we have no way to measure this part.

So, what were the dimensions of the universe at the time of its birth? According to the most authoritative mathematical models describing the stage of inflation, it turns out that the size of the universe at the time of its creation will fluctuate somewhere between the size of a human head and a city block built up with skyscrapers. And there, you see, only some 13.8 billion years will pass - and the universe in which we live appeared.

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 ideas, 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 something that 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 movement of the Earth in orbit ( 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. It was now one of the many galaxies that had once considered it an 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. 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 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 state that the stars are distant suns and planets 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. your model stationary universe famous physicist introduced 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 - the 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 a finite number of 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 eventually 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 a different picture with the modern model of the 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 turn out to 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 says 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. The 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 the microscopic Solar System in the centimeter Milky Way, 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.

The Universe is a huge space filled with nebulae, star clusters, individual stars, planets with their satellites, various comets, asteroids and, in the end, vacuum, as well as dark matter. It is so huge that the completeness of the answer to the question of how big it is, unfortunately, is limited by our current level of technological development. Be that as it may, understanding the size of the universe involves understanding several key factors. One of these factors, for example, is the understanding of how the cosmos behaves, as well as the understanding that what we see is just the so-called "observable universe." We cannot find out the true dimensions of the Universe, because our capabilities do not allow us to see its “edge”.

Everything that is outside the visible universe is still a mystery to us and is the subject of endless disputes and discussions among astrophysicists of all stripes. Today we will try in simple terms to explain what science has come to by now in terms of understanding the size of the Universe, and we will try to answer one of the most burning and difficult questions about its nature. But first, let's look at the basic principles of how scientists determine distance in space.

The simplest method of determining distance in space is to use light. However, given the way light travels in space, it should be understood that the objects that we see from the Earth will not necessarily look the same in space. Indeed, in order for light from distant objects to reach our planet, it may take tens, hundreds, thousands, or even tens of thousands of years.

It is 300,000 kilometers per second, but for space, for such a gigantic space, the concept of a second is not an ideal value for measurement. In astronomy, it is customary to use the term light year to define distance. One light year is approximately equivalent to a distance of 9,460,730,472,580,800 meters and gives us not only an idea of ​​the distance, but can also tell us how long it will take the light of an object to reach us.

The simplest example of a difference in time and distance is the light of the Sun. The average distance from us to the Sun is about 150,000,000 kilometers. Suppose you have a suitable telescope and eye protection to allow you to observe the Sun. The bottom line is that everything you see through a telescope actually happened to the Sun 8 minutes ago (that's how long it takes light to get to Earth). The light of Proxima Centauri? It will reach us only in four years. Or take at least such a large star as Betelgeuse, which is about to become a supernova soon. Even if this event happened now, we would not know about it until the middle of the 27th century!

Light and its properties have played a key role in our understanding of how vast the universe is. At the moment, our capabilities allow us to look at about 46 billion light-years of the observable universe. How? All thanks to the distance scale used by physicists and astronomers in astronomy.

distance scale

Telescopes are just one of the tools for measuring cosmic distances and are not always able to cope with this task: the farther away is the object whose distance we want to measure, the more difficult it is to do so. Radio telescopes are great for measuring distances and making observations only within our solar system. They are indeed capable of providing very accurate data. But one has only to direct their gaze beyond the solar system, as their effectiveness is sharply reduced. In view of all these problems, astronomers decided to resort to another method of measuring distance - parallax.

What is parallax? Explain on simple example. Close one eye first and look at some object, and then close the other eye and look again at the same object. Notice a slight "change in position" of the object? This "shift" is called parallax, a technique used to determine distance in space. The method works great when it comes to stars that are relatively close to us - about 100 light years away. But when this method becomes ineffective, scientists resort to others.

The next way to determine the distance is called the "main sequence method". It is based on our knowledge of how stars of certain sizes change over time. First, scientists determine the brightness and color of a star, and then compare the indicators with nearby stars with similar characteristics, deriving an approximate distance based on these data. Again, this method is very limited and only works for stars that belong to our galaxy, or those that are within a radius of 100,000 light years.

To see further, astronomers rely on the Cepheid measurement method. It is based on the discovery of the American astronomer Henrietta Swan Leavitt, who discovered the relationship between the period of change in brightness and the luminosity of a star. Thanks to this method, many astronomers have been able to calculate the distances to stars not only inside our galaxy, but also outside it. In some cases, we are talking about distances of 10 million light years.

And yet, we have not yet approached the question of the size of the Universe one iota. Therefore, we turn to the ultimate measuring instrument based on the principle of redshift (or redshift). The essence of the redshift is similar to the principle of the Doppler effect. Remember the railroad crossing. Ever notice how the sound of a train horn changes with distance, getting louder as you get closer and quieter as you get farther away?

Light works the same way. Look at the spectrogram above, see the black lines? They indicate the limits of color absorption chemical elements located in and around the light source. The more the lines are shifted to the red part of the spectrum, the farther the object is from us. Based on such spectrograms, scientists also determine how fast an object is moving away from us.

So we smoothly and crept up to our answer. Most of the redshifted light comes from galaxies that are about 13.8 billion years old.

Age is not important

If, after reading this, you came to the conclusion that the radius of the Universe we observe is only 13.8 billion light years, then you have not taken into account one important detail. The thing is that during these 13.8 billion years after the Big Bang, the Universe continued to expand. In other words, this means that the actual size of our universe is much larger than our original measurements indicated.

Therefore, in order to find out the real size of the Universe, it is necessary to take into account one more indicator, namely, how fast the Universe has expanded since the Big Bang. Physicists say they have finally come up with the numbers they need and are confident that the radius of the visible universe is currently about 46.5 billion light-years.

True, it is also worth noting that these calculations are based only on what we ourselves can see. More precisely able to see in the depths of space. These calculations do not answer the question of the true size of the universe. In addition, scientists are puzzled by a discrepancy, according to which the more distant galaxies in our universe are too well formed to be considered as having appeared immediately after the Big Bang. This level of development took much longer.

Maybe we just don't see everything?

The inexplicable fact mentioned above opens up a number of new problems. Some scientists have tried to calculate how long it would take for these fully formed galaxies to develop. For example, Oxford scientists came to the conclusion that the size of the entire universe could be 250 times larger than the observed one.

We are indeed able to measure the distances to objects within the observable universe, but we do not know what is beyond this line. Of course, no one is saying that scientists are not trying to find out, but, as mentioned above, our possibilities are limited by our level of technological progress. In addition, we should also not immediately discard the assumption that scientists may never know the true size of the entire universe, given all the factors that stand in the way of resolving this issue.

The diameter of the Moon is 3000 km, the diameter of the Earth is 12800 km, the Sun is 1.4 million km, while the distance from the Sun to the Earth is 150 million km. Jupiter's diameter big planet our solar system- 150 thousand km. No wonder they say that Jupiter could be a star, in the video next to Jupiter is working star, its size () is even smaller than Jupiter. By the way, since we touched on Jupiter, you may not have heard, but Jupiter does not revolve around the Sun. The fact is that the mass of Jupiter is so large that the center of rotation of Jupiter and the Sun is outside the Sun, thus both the Sun and Jupiter rotate together around a common center of rotation.

According to some calculations, in our galaxy, which is called the "Milky Way" (Milky Way), there are 400 billion stars. This is far from the largest galaxy; there are more than a trillion stars in neighboring Andromeda.

As stated in the video at 4:35, in a few billion years our Milky Way will collide with Andromeda. According to some calculations, using any technology known to us, even improved in the future, we will not be able to fly to other galaxies, as they are constantly moving away from us. Only teleportation can help us. This is bad news.

The good news is that you and I were born at a good time when scientists see other galaxies and can theorize about the Big Bang and other phenomena. If we were born much later, when all the galaxies would have scattered far from each other, then most likely we would not have been able to find out how the universe arose, whether there were other galaxies, whether there was a Big Bang, etc. We would consider that our Milky Way (united by that time with Andromeda) is the only and unique in the entire cosmos. But we are lucky and we know something. Maybe.

Let's get back to the numbers. Our small Milky Way contains up to 400 billion stars, neighboring Andromeda is more than a trillion, and there are more than 100 billion such galaxies in the observable universe. Many of them contain several trillion stars. It may seem incredible that there are so many stars in space, but somehow the Americans took and directed their mighty Hubble telescope to a completely empty space in our sky. After observing him for several days, they received this photo:

In a completely empty patch of our sky, they found 10 thousand galaxies (not stars), each of which contains billions and trillions of stars. Here is this square in our sky, for scale.

And what is happening outside the observable universe, we do not know. The size of the universe that we see is about 91.5 billion light years. What's next is unknown. Perhaps our entire universe is just a bubble in the seething ocean of multiverses. In which other laws of physics may even apply, for example, the law of Archimedes does not work and the sum of the angles is not equal to 360 gr.

Enjoy. Dimensions of the universe in the video:

Each of us at least once wondered what a huge world we live in. Our planet is an insane amount of cities, villages, roads, forests, rivers. Most people never see half of it in their lifetime. It is difficult to imagine the grandiose scale of the planet, but there is an even harder task. The size of the Universe is something that, perhaps, even the most developed mind cannot imagine. Let's try to figure out what modern science thinks about this.

Basic concept

The universe is everything that surrounds us, about which we know and guess what was, is and will be. If we reduce the intensity of romanticism, then this concept defines everything in science that exists physically, taking into account the temporal aspect and the laws governing the functioning, interconnection of all elements, and so on.

Naturally, it is quite difficult to imagine the real dimensions of the Universe. In science, this issue is widely discussed and there is no consensus yet. In their assumptions, astronomers rely on existing theories of the formation of the world as we know it, as well as on the data obtained as a result of observation.

Metagalaxy

Various hypotheses define the universe as a dimensionless or unspeakably vast space, much of which we know little about. To bring clarity and the possibility of discussing the area available for study, the concept of Metagalaxy was introduced. This term refers to the part of the universe available for observation by astronomical methods. Thanks to the improvement of technology and knowledge, it is constantly increasing. The metagalaxy is a part of the so-called observable Universe - the space in which matter during the period of its existence managed to reach current situation. When it comes to understanding what the size of the Universe is, in most cases they talk about the Metagalaxy. The current level of technological development makes it possible to observe objects located at a distance of up to 15 billion light years from the Earth. Time in determining this parameter plays, apparently, no less a role than space.

Age and size

According to some models of the universe, it never appeared, but exists forever. However, the Big Bang theory that dominates today provides our world with a “starting point”. According to astronomers, the age of the universe is about 13.7 billion years. If you move back in time, you can return to the Big Bang. Regardless of whether the dimensions of the Universe are infinite, the observable part of it has boundaries, since the speed of light is finite. It includes all those locations that can have an impact on the terrestrial observer since the Big Bang. The dimensions of the observable universe are increasing due to its constant expansion. According to the latest estimates, it occupies a space of 93 billion light years.

Lots of

Let's see what the universe is. The dimensions of outer space, expressed in dry figures, are, of course, striking, but difficult to understand. For many, it will be easier to realize the scale of the world around them if they know how many systems, like the Solar, fit in it.

Our star and its surrounding planets are only a tiny part of the Milky Way. According to astronomers, the Galaxy has approximately 100 billion stars. Some of them have already discovered exoplanets. It is not only the size of the Universe that is striking - already the space occupied by its insignificant part, the Milky Way, inspires respect. It takes a hundred thousand years for light to travel through our galaxy!

local group

Extragalactic astronomy, which began to develop after the discoveries of Edwin Hubble, describes many structures similar to the Milky Way. Its closest neighbors are the Andromeda Nebula and the Large and Small Magellanic Clouds. Together with several other "satellites" they make up the local group of galaxies. It is separated from the neighboring similar formation by approximately 3 million light years. It’s even scary to imagine how much time it would take for a modern aircraft to cover such a distance!

Observed

All local groups are separated by a vast space. The metagalaxy includes several billion structures similar to the Milky Way. The size of the universe is truly amazing. It takes 2 million years for a light beam to travel from the Milky Way to the Andromeda Nebula.

The farther away from us is a piece of space, the less we know about its current state. Due to the finiteness of the speed of light, scientists can only get information about the past of such objects. For the same reasons, as already mentioned, the area of ​​the universe available for astronomical research is limited.

Other worlds

However, this is not all the amazing information that characterizes the universe. The dimensions of outer space, apparently, significantly exceed the Metagalaxy and the observable part. The theory of inflation introduces such a concept as the Multiverse. It consists of many worlds, probably formed simultaneously, not intersecting with each other and developing independently. The current level of development of technology does not give hope for the knowledge of similar neighboring Universes. One of the reasons is the same finiteness of the speed of light.

The rapid development of space science is changing our understanding of how big the universe is. The current state of astronomy, its theories and calculations of scientists are difficult to understand for the uninitiated. However, even a superficial study of the issue shows how vast the world of which we are a part, and how little we still know about it.