The universe is a huge space filled with nebulae, star clusters, individual stars, planets with their satellites, various comets, asteroids and, ultimately, a vacuum, as well as dark matter. It is so huge that the completeness of the answer to the question of how large it is, unfortunately, is limited by our current level of technology development. However, understanding the size of the universe involves understanding several key factors. One of these factors, for example, is an understanding of how the cosmos behaves, as well as an 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 outside the visible Universe is still a mystery to us and is the subject of endless debate and debate among astrophysicists of all stripes. Today we will try to explain in simple words what science has arrived at by the present moment in terms of understanding the dimensions of the Universe, and we will try to answer one of the most burning and complex questions about its nature. But first, let's look at the basic principles of how scientists determine distance in space.
Shine
The simplest method for determining distance in space is by using light. However, if we take into account the way in which light travels in space, then it should be understood that those objects that we see from Earth in space will not necessarily look the same. 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.
The speed of light is 300,000 kilometers per second, but for space, for such a gigantic space, the concept of a second is not an ideal value to measure. In astronomy, it is customary to use the term light year to determine distance. One light year is roughly 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 how long it will take for the light of an object to reach us.
The simplest example of time and distance differences is the light of the Sun. The average distance from us to the Sun is about 150,000,000 kilometers. Let's say you have the right telescope and eye protection for observing the Sun. The bottom line is that everything that you will see through a telescope actually happened to the Sun 8 minutes ago (this is how much light it takes to get to the Earth). Light of Proxima Centauri? 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!
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Light and its properties have played a key role in our understanding of how huge the universe is. At the moment, our capabilities allow us to look into 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 further away an object is, the distance to which we want to measure, the more difficult it is to do it. 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 outside 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? Let's explain with a simple example. First close one eye 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 - approximately within a radius of 100 light years. But when this method also becomes ineffective, scientists resort to others.
The next method for determining the distance is called the "main sequence method". It is based on our knowledge of how stars of a certain size change over time. Scientists first 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 this data. Again, this method is very limited and only works for stars that belong to our galaxy, or those within a radius of 100,000 light years.
Astronomers rely on the Cepheid measurement method to look further. It is based on the discovery of the American astronomer Henrietta Swan Leavitt, who discovered the relationship between the period of the brightness change and the luminosity of a star. Thanks to this methods, many astronomers were 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 come close to the question of the size of the universe. Therefore, we turn to the ultimate measurement tool based on the principle of redshift (or redshift). The essence of redshift is similar to the principle of the Doppler effect. Think of a railway crossing. Ever notice how the sound of a train whistle changes with distance, getting stronger as you approach and getting quieter as you move away?
Light works in much the same way. Look at the spectrogram above, see black lines? They indicate the limits of absorption of color by chemical elements in and around the light source. The more the lines are shifted to the red part of the spectrum, the further the object is from us. Scientists also use these spectrograms to determine how fast an object is moving away from us.
So we smoothly and got to our answer. Most of the redshifted light comes from galaxies that are about 13.8 billion years old.
Age is not the main thing
If after reading you have come to the conclusion that the radius of the universe we observe is only 13.8 billion light years, then you have left out one important detail. The fact is that during these 13.8 billion years after the Big Bang, the universe continued to expand. In other words, this means that the real size of our Universe is much larger than indicated in our original measurements.
Therefore, in order to find out the real size of the Universe, it is necessary to take into account another indicator, namely, how quickly the Universe has expanded since the Big Bang. Physicists say that they were finally able to derive the necessary numbers and are confident that the radius of the visible universe at the moment is 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, they are able to make out in the depths of space. These calculations do not answer the question of the true size of the universe. In addition, scientists wonder about some discrepancy, according to which the more distant galaxies in our universe are too well formed to be considered that they appeared immediately after the Big Bang. It took much longer for this level of development.
Perhaps we just do not see everything?
The inexplicable fact mentioned above opens up a whole series 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 concluded that the size of the entire universe could be 250 times the size of the observed one.
We are indeed able to measure distances to objects within the observable universe, but what lies beyond this boundary, we do not know. Of course, no one says that scientists are not trying to figure it out, but, as mentioned above, our capabilities are limited by our level of technological progress. In addition, one should also not immediately discard the assumption that scientists may never know the real size of the entire universe, given all the factors that are in the way of solving this issue.
NIKOLAY KHIZHNYAK