Где находится ЦЕНТР Вселенной?

The universe appears to be a smoothly running mechanism that is always in motion.
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Moons orbit their planets, planets orbit their stars, and stars in their turn, orbit the centre of their galaxy.
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This coordinated motion is predefined by the fundamental laws of nature.
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But is there a special point among all this motion?
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Does the universe have a centre?
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Before we get started, we have to decide what it is we are looking for.
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What could be called the centre of the universe?
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The central point of the Solar System is the common centre of the masses of all the objects it is comprised of,
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which in essence is almost at the centre of the Sun.
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There is a similar central point for the Milky Way and for the Virgo Supercluster that our galaxy is part of.
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Can we carry on in the same manner and eventually pinpoint the pivot of the entire universe?
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If we look at the large-scale structure of the universe, we will notice the following:
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stars form galaxies of three basic types – spiral, elliptical and irregular.
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It is quite easy to find the central point in the first two, whereas it is considerably harder to do so in those of the latter type.
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Moving on, galaxies group together to form clusters and superclusters.
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These, in their turn, form galactic filaments.
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These filaments, distributed all over the universe,
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are interspersed with mysterious areas of almost total emptiness – voids.
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Voids are areas so enormous that they would easily accommodate thousands of galaxies.
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The large-scale structure of the universe is made up of these two global components.
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Now, seen on the scale of hundreds of megaparsecs the universe turns out to be quite homogeneous.
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Its makeup resembles a sponge.
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It goes without saying that there are massive matter flows and points of matter attraction like the dark flow
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and the Great Attractor, but their influence is not global enough to make them suitable candidates for the centre of the universe.
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To date no object has been discovered in the visible universe that would qualify to be the common centre of gravity.
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In fact, if it did exist out there, its influence would be too pervasive not to be noticed.
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It is actually according to the fundamental cosmological principle that the universe is homogeneous and isotropic.
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This means that the universe would look the same irrespective of either the whereabouts of the observer
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or the direction we choose to look in.
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The cosmological principle was formulated based on copious observations of remote areas of the universe
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and is applicable on the scale of hundreds of millions of light years.
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If the potential observer on the Earth inquiringly gazed at the universe all round,
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it would appear to be a sphere with a radius measuring 46 bln light years, its centre being in the Solar System.
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This is the actual distance to the remotest visible object,
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although it took its light approximately 13.8 bln years to reach our Earth.
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The sphere is known as the observable universe, or Metagalaxy.
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However, it would be erroneous to consider our location the centre of the universe.
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This is pretty much like claiming you’re in the middle of the planet when in reality you are simply at the centre of a circle
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drawn by the horizon on the planet’s surface all around you.
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The Metagalaxy has equal chances of being either a small part of the universe or constituting it in its entirety.
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It is quite impossible at this point to find this out for certain.
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Let’s assume there is no pivot we can pinpoint in the universe today.
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Perhaps we should try a different tack, then?
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According to contemporary scientific views,
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the universe was born approximately 13.8 bln years ago as a result of the event generally referred to as the Big Bang.
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Before that time and space as we know them were virtually non-existent.
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It appears logical to suppose, therefore, that if there was a bang, it had to have a centre.
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In other words, the starting point of all.
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Let’s sneak a peak at the past.
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The consequences of the early stages of the universe’s evolution still widely manifest themselves.
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The ones that stand out are the cosmological expansion of space and the cosmic microwave background radiation,
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or the CMB radiation.
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Would observing these phenomena bear fruit?
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Would it be possible to locate the central point and did it exist at all?
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The cosmological expansion of the universe is an isotropic and homogeneous expansion of space from point to point.
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It may seem that it would be enough to just measure the velocity and direction of this expansion and then rewind time,
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as it were, thus tracing the motion back to its origins at the centre.
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But this isn’t quite as simple as that.
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Straightforward calculations would show the centre of the universe’s expansion to be in really close proximity
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to the Solar System.
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On more precise observation it will turn out that the supposed centre of the Big Bang lands right on top of the observer.
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However, the tricky part is that even if we were to travel to any other point in space,
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like a few light years away, it is this point that would appear to be the centre from which space objects recede.
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Strangely, the result will be the same in any point in the Universe…
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Imagine a balloon filled with air, with a few dots marked on it.
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They are motionless relative to each other, but if we pump more air into the balloon, the distances between the dots will grow.
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At the same time obviously none of them may be considered the centre of the balloon’s expansion.
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The dots recede from each other at a steady pace, and the rate of this process depends on the distances between them.
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The notion of the event horizon is inferred from the concept of the expansion of the universe.
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Since the rate at which objects recede depends on the distances between them,
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at a certain point the observable object is bound to move away from us at a rate exceeding the speed of light.
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According to the special theory of relativity this implies that any interaction with that object will be impossible.
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Objects beyond the event horizon are as well as gone for the observer.
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We will never find out what will happen to them next.
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In this respect the universe is a sphere with the consciously assigned centre at the point of observation,
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and its limit is marked by the event horizon.
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Different values for its radius may be produced in different models of the universe,
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but it definitely measures over 14 bln light years.
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However, any other point in the universe will have its own event horizon,
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that is why it would not be fair to favour the position of the observer and see it as the centre of the universe.
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It is hardly necessary to point out that the number of suchlike ‘centres’ would be infinite.
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So it looks like there is no way we can find the centre of the universe with the help of its cosmological expansion.
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How about relic radiation, then?
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Relic radiation, or the CMB radiation, is high-frequency background radiation
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that permeates the universe in all directions.
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Its temperature, which is approximately 2.7 K, slowly drops on account of the universe’s expansion.
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The CMB radiation is an important source of information as it originated in the early stages of the universe’s evolution
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as a result of massive recombination of protons.
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Relic radiation used to be considered homogeneous and isotropic for a long time.
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This means that a detector at any point in the universe
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and aimed in any direction should show the same density of the radiation.
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However, in recent years quite a few areas were found not to conform to this rule.
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It is the case with voids, for example.
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The CMB temperatures in these dark areas are minuscule portions of a Kelvin lower
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than the CMB temperature in the rest of space.
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There are other areas in the universe where the cosmic microwave background is anything but isotropic.
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For instance, photons may be swallowed up by a cloud of hot gas or may end up in a powerful gravitational field.
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Besides, as the Sun along with all of its planets goes round the centre of the Milky Way,
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this motion causes the CMB spectre to shift depending on the direction of measurement.
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To put it simply, the Earth moves away from the CMB radiation flow aimed at its back, as it were,
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while meeting the CMB radiation flow aimed at its front.
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This produces the Doppler effect that causes the observed radiation to shift to the red or the blue band respectively.
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Still, all cases of manifested anisotropy of the CMB are secondary.
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They are the consequences of the interaction between the CMB radiation and heavy objects – or, alternatively, voids.
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According to contemporary science, there may well have been primary deviations
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that occurred in the earliest stages of the universe’s expansion.
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If they were to be discovered, they would make a great source of valuable information about events
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taking place in the first seconds after the birth of space and time as we more or less know them.
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Unfortunately, primary anisotropy of the CMB radiation hasn’t been discovered experimentally yet.
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To sum up, on balance no point in space should be considered its centre.
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The expansion of the universe occurs simultaneously across its entire infinity,
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and no special area can be realistically and accurately singled out.
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On the ultimate global level there isn’t a single mass centre that could play the role of the pivot,
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with all other space rotating on it.
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However, this mysterious place may well exist, but too far away from us…
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The dimensions of the universe still haven’t been gauged with a satisfying degree of accuracy
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since even the latest cutting-edge measuring equipment produced by the human civilization isn’t able to reach
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beyond the event horizon.
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The part of space that can be observed by us may well be a minuscule droplet
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in comparison with the rich ocean of the universe.
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And it is hardly feasible that we will ever be able to appreciate it in its entirety…

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