The shrinking universe will push us into a black hole. But noticing the end of the world won't be easy

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The shrinking universe will push us into a black hole. But noticing the end of the world won't be easy
The shrinking universe will push us into a black hole. But noticing the end of the world won't be easy

New work by Russian researchers indicates that the Universe has not always been expanding - and will contract again in the foreseeable future. Moreover, it is doubtful that humans will be able to survive the cycle of its compression. But the good news is that the universe itself is no longer in danger of heat death. We understand the details.


Eternal death awaits the universe?

There are two main problems in modern physics and cosmology: 85% of the mass is unknown what (dark matter) and the bulk of the energy is also unknown what (dark energy). However, it follows from observations that it is the first "unknown what" serves as the "glue" that holds together the matter of galaxies, and the second - dark energy - pushes the Universe in all directions.

The first fact is easy to come to terms with: without it we would have nowhere to live. Without galaxies, the density of gas would be low, stars and planets simply would not have arisen. The second looks much more unpleasant: if there is dark energy, the Universe will expand forever, which means it will experience heat death. The stars will go out, and new ones will not form, because the old ones will take gas. Everything will cool down to temperatures incompatible with complex life, and the density of matter as space-time expands will become truly insignificant. The frightening picture, based on today's data, will last forever: in the expanded Universe, due to the low concentration of matter, no reverse contraction is possible. Dark energy will continue to expand it forever, but there will be no one to watch.

It looks like you'll have to suffer a lot at first

No matter how unpleasant the picture may seem, from the point of view of physicists, for a long time it looked the simplest and most logical. But it is not for nothing that we have called dark matter and energy problems for physicists as well: in recent years it has begun to seem that they are simply unsolvable.

Let's start with dark matter: attempts to write it off as some unknown particles (WIMP) in recent years have clearly failed. At the same time, there is no generally accepted alternative to them either. This situation is so deplorable that some physicists, out of despair, already propose to adjust the laws of gravitation to the observations so that this dark matter is excluded.

Dark energy was no better. It was considered a kind of cosmological constant, "pushing" space in all directions with the same force at any point. But observations by the Planck Space Telescope show the opposite. It turns out that the rate of expansion of the Universe along the inhomogeneities of the relict radiation measured by it is only 67.66 ± 0.42 kilometers per second per megaparsec of space (a megaparsec is equal to 3.26 million light years). But according to the data of the Hubble Space Telescope, which observed the distance of objects close to the Earth, the Universe is expanding at a completely different speed - 74, 03 ± 1, 42 kilometers per second per megaparsec.


Naked Science has already written that the situation with dark matter is far from hopeless. In recent years, the LIGO gravitational observatory has revealed an unexpectedly large number of mergers of black holes of stellar masses - this is the name for black holes with a mass of up to a hundred solar masses. These mergers can only happen at the frequency observed by LIGO if there are simply a huge number of such black holes, much more than expected before the launch of LIGO.

Stellar mass black holes originate from stars. This means, like stars, should not be evenly distributed in the Universe, but concentrated in clusters.Dark matter, as it is clear from its dispersal of the edges of galactic disks, is located in a dark halo around galaxies. From all this, scientists have previously concluded that the black holes that make up dark matter can be collected in dark globular clusters.

But two critical questions remain. Where did these black holes come from in such numbers? And what is going on with dark energy - why is its influence near our Galaxy stronger than in billions of light years from it?

Source of Black Holes: Phoenix Universe

The recent article by N. N. Gorkavy and S. A. Tyulbashev in the Astrophysical Bulletin is a serious new step in answering these questions. Its authors rightly point out that not all stars can turn into black holes, but only one of thousands (mostly massive). Meanwhile, the estimated number of stars in the universe is only 100 sextillions (one hundred billion trillion). One thousandth of these is only 100 quintillion (one hundred billion billion).


And this is a thousand times less than necessary for black holes of the masses that LIGO detects to be responsible for dark matter. Obviously, some unexpected source of such black holes is needed. Researchers propose the idea of ​​a phoenix universe for the role of such a source. According to it, the existing Universe has gone through many cycles of contraction and expansion - and our cycle is not the first or even the hundredth. He is just one of many that came before him and will come after. In the first phase of each cycle, our Universe is expanding, as it is happening now. In the second phase, it gradually begins to shrink.

As they contract, the distances between black holes are constantly decreasing. In the final phase of the contraction cycle, the diameter of the universe becomes not one hundred billion light years, as it is now, but only ten light years. With such a compression, the concentration and energy of the relic radiation photons raises the temperature of the Universe from three kelvin to ten billion. At a similar temperature, all the atoms of heavy elements produced in all the stars of the Universe decay: they are simply destroyed by the gamma photons of the relict radiation.


However, black holes, unlike atoms of heavy elements, are practically indestructible: particles can fall into a black hole, but not escape. Therefore, in the Universe at the moment of its extreme compression up to ten light years, only they and a part of neutron stars remain from large objects.

This is where the fun begins. In a relatively small space of a dozen light years, billions of trillions of black holes turn out to be close neighbors. Due to the small distance, the frequency of their mergers increases sharply. But each such merger, as we know from the LIGO data, is accompanied by the transformation of ~ 5% of the mass of merging holes into gravitational waves. As Einstein noted, gravitational waves by themselves have no mass. As a result, a significant part of the mass in such a contracting universe begins to turn into gravitational waves. If all black holes merge with each other, their number will be halved, and the total mass of the Universe will be reduced by at least 5%. The remaining black holes can merge with each other and further - and then the mass of the Universe will decrease by 5% in each cycle. As a result, it can decrease by orders of magnitude.

However, it should be remembered: the compression of the Universe is due to the gravitation of the objects existing in it. If their mass at the time of mass mergers of black holes decreases significantly, the gravitating mass of the Universe will sooner or later become too small for the contraction to continue. A distant analogy: if we take the solar system and begin to sharply reduce the mass of the sun, then sooner or later it will become so small that the planets of our system will simply fly apart in different directions. This analogy is distant because there is no centrifugal force in the Universe. Instead, another term of force works, the calculations for which can be seen here (and visually - in the picture below).


This is exactly what happens in the model of the Phoenix Universe described by Gorkav and Tyulbashev.Having reached compression up to about ten light years, it "burns" the nuclei of heavy atoms in gamma photons. Along the way, the merging of black holes transforms most of the mass of "dark matter" into gravitational waves - and when this transformation reaches a critical threshold, the compression of the Universe stops and it begins to expand sharply. This moment in the model is interpreted as the "Big Bang" - the beginning of the next cycle of development of the same Phoenix Universe.

At first, there are no heavy elements in it. After some time from the Big Bang, the temperature - due to the expansion of space-time - drops so much that light atoms of baryonic matter, such as hydrogen or helium, appear. The supermassive black holes left over from the last cycle become centers of attraction for light gases. So, gradually around these giant BHs, galaxies will appear. The authors of the new work call such holes "seed", because they are the "seed" for the formation of galaxies.

It should be noted that the idea of ​​the formation of galaxies around a central massive black hole was expressed much earlier: this was indicated by observations of such objects in the early Universe. However, until the new work of Gorkavy and Tyulbashev, the mechanism for the formation of such unusually early supermassive black holes remained unclear.

But how can our expanding universe become contracting?

As we noted above, the "Big Bang" occurs due to the transformation of a part of dark matter (in the form of black holes) into gravitational waves that have no mass. However, this is not the end of the role of gravitational waves in the Universe. When colliding with black holes, they are absorbed by them. Because of this, the mass of black holes - the dark matter of our Universe - is gradually increasing. When it becomes large enough, the expansion of space-time is inhibited, and then turns into its opposite - contraction.


In other words, the evolution of the Phoenix Universe is somewhat similar to the work of a colossal pendulum. When the pendulum moves up, its kinetic energy turns into potential energy. And the speed of upward movement gradually decreases - and then gives way to downward movement.

The Universe, as it expands, converts the energy of gravitational waves into mass - until the mass becomes so much that expansion gives way to contraction. At the end of the contraction cycle, the mass of merging black holes partially turns into gravitational waves, which is why the contraction cycle is replaced by a sharp, explosive expansion (Big Bang).

This is all very interesting, but how can we check it?

Scientific theory must be testable. The idea of ​​superstrings at one time had a lot of fans among physicists, but their number fell sharply when it became clear that no predictions could be made from it. Then to check whether they are correct or not - and to confirm or refute the theory.

The authors of the new article believe that a significant part of the observations that can confirm their theory have already been carried out. By means of calculations, they show that their model produces about the same number of black holes of stellar masses (that is, lighter than a hundred Suns), which could explain their frequent mergers, recorded by LIGO. Yes, such holes often merge, but still their number grows from cycle to cycle, and therefore can be much more than if the Universe were "disposable". Yes, it is impossible to get one hundred sextillion BHs from one hundred sextillion stars, but if the main part of the BH is from the past cycles of the Phoenix Universe, then their number is quite understandable.

The number of supermassive black holes (more massive than a million Suns) left over from past cycles in their model is also close to the observed one. Today it is believed that there are about the same number of supermassive black holes as there are large galaxies in the Universe - about one hundred billion. Again, within the framework of the previously existing cosmology, it is impossible to explain where billions of very large BHs came from already in the early Universe - but in the Gorkavy-Tyulbashev model it is possible.


But this, of course, is not enough. It is possible to fit the model to the already observed results without even noticing the fit (unconsciously). What is needed is predictions - something that science still does not know, but what follows from the model and can be verified by astronomers in new observations.

The authors of the new work consider such a prediction the thesis about the presence of dark globular clusters of black holes of stellar mass in the halo of galaxies. They conclude: "Studying the motion of stars [outside our Galaxy] from astrometric catalogs (and Gaia data) will help find dark globular clusters in the disk of the Galaxy."

The logic here is clear: passing between the Earth and the star of another galaxy, dark globular clusters, although rare, will create a gravitational lens that will be easy to distinguish from other parts of the sky.

In a comment for Naked Science, Nikolai Gorkavy noted:

“Calculations predict that a powerful burst of gravitational radiation will occur when the universe is compressed to several light years and the massive merger of black holes. At the moment of birth, such waves have a frequency of one hundred hertz, but by now they have stretched ten billion times - up to nanohertz frequencies. While the new article was in the editorial office, the NANOGrav consortium on pulsar emission variations discovered a stochastic background of nanohertz gravitational waves. This discovery may become as direct evidence of a cyclic model of the Universe, as once relic electromagnetic radiation became convincing confirmation of the model of a hot Universe and the Big Bang."

Neutron stars: another legacy of the past universe?

Another unusual prediction of the Gorkavy-Tyulbashev model is relic neutron stars. The authors note that the gravitational bond energy per nucleon (particle of the atomic nucleus) for a neutron star will be in the region of 100 megaelectronvolts. Actually, there is nothing surprising here: the density of the substance of a neutron star is such that a matchbox filled with it would weigh three billion tons, and therefore the force of gravity is 200 billion times greater than that of the Earth.

Therefore, even when gamma-quanta of the relict radiation of the contracting Universe are heated up to one hundred billion degrees, such neutron stars will not be completely destroyed. But part of their mass can still be lost during the shelling with gamma quanta. These relic neutron stars can "grow thin" from the original mass to 0, 1-0, 2 solar. Due to the decrease in mass, the compression of the substance of the neutron star will also decrease: in diameter it will be several times larger than the usual one.

This is a rather interesting prediction that, at first glance, cannot be verified. Indeed, neutron stars from the previous cycles of the Phoenix Universe will cool down and will long ago cease to have the rapid rotation and radiation that would allow the detection of a part of ordinary neutron stars. And yet there is a way to find them. Such neutron stars can sometimes merge with each other, as during the event GW170817, registered by LIGO in 2017.

The gravitational waves generated by it traveled 130 million light years before reaching our planet. By analyzing the difference in the arrival of gravitational waves in different parts of the Earth, it is possible to find out the parameters of merging neutron stars. If they are noticeably less than the norm, there will be serious grounds to suspect that it is not neutron stars from our era that are merging, but rather relic objects that survived the Big Bang.

By the way, one of the neutron stars in the GW170817 event most likely had a mass between 0.86 and 1.36 solar masses. This is noticeably less than that of the vast majority of neutron stars, and it is below the Chandrasekhar limit, the mass threshold beyond which a compact object can become a neutron star. It is very difficult for a neutron star to lose mass - as we mentioned, its gravity is hundreds of billions of times stronger than Earth's.If the object, which requires 1.38 solar masses (Chandrasekhar limit), has for some reason become noticeably less mass, it is a reason to think about whether LIGO registered a relic neutron star in 2017.

There is also a slightly different scenario for the detection of relic neutron stars - in their mergers with black holes. In January 2020 alone, LIGO recorded two such events at once. In this case, we were talking about large neutron stars, but if the fusion product is less massive, this is again a reason to think about whether we are talking about the death of a relic from the past Universe.


In addition, the authors believe that relic neutron stars can be found among the so-called "strange" pulsars. Among them - and simply "slow" pulsars with a long period of radio signals reaching the terrestrial observer. There are also "rotating radio transients". These are something like pulsars with large and often unequal (all the time different) periods between signals. Today, about a hundred of these exotic objects are known and they were still very poorly understood. The authors of the new work believe that large periods and incorrectness of their signals are expected for relic neutron stars that have already lost almost all of their original rotation energy (it is this energy that feeds the radiation of pulsars).

It is still difficult to understand how this is so. Logically, however, relic neutron stars from past universes would often be in galactic halos - as would dark matter (relic black holes). Almost half of the known neutron pulsar stars are slowly rotating, with a period of at least 0.5 seconds. At the same time, they really gravitate not to the disks of galaxies, but rather to the galactic halo, and even the speed of their movement - no higher than 60 kilometers per second. The other half of the pulsars are located mainly in the disks of galaxies and have a much shorter rotation period - less than 0.2 seconds. And the speed of their movement is much higher - about 150 kilometers per second.

The "slow" neutron stars from the galactic halo are indeed somewhat similar to the hypothetical relic neutron stars of Gorkavy and Tyulbashev. A neutron star forms at the site of a supernova explosion, which is rarely perfectly symmetrical. Therefore, it is logical to expect high velocities of motion from a nonrelict neutron star. A relic neutron star has passed through rather dense media during its life, and it is logical that it gradually lost its speed - it had at least tens of billions of years for this.

Another prediction of the new work: relic neutron stars with a mass of 0, 1-0, 2 solar can enter binary systems from an ordinary star and a relic neutron star. Such systems will look like a standard star that has an almost invisible companion, with a mass of 0.1-0.2 solar. "Mass detection of such systems will statistically testify" in favor of their existence, the authors note. This is especially important because most of the relic neutron stars can hardly be detected as pulsars: the oldest of them simply will not have the required rotational energy. They will simply lose it in hundreds of billions of years of their "life".

Will the end of the world fall into a gigantic black hole?

The key feature of the model: it shows the presence of a huge black hole somewhere in the universe. Much more massive than any supermassive black hole already discovered. It must be so huge that it will eventually swallow up the entire Universe, including, of course, the Earth and each of us.

It must be understood that we are not talking about some kind of catastrophe, the end of the world in the eschatological sense of the word. Falling into a black hole threatens spaghettification and death only if the hole is small - stellar masses. Already falling into a supermassive black hole does not threaten you with spaghettification.After all, it is so large that the difference in the effect of tidal forces on your head and legs will be insignificant - and it will not “turn into spaghetti” a person falling into it.


Most likely, getting into such an object for most of us will be not only painless, but also imperceptible. Only astronomers will notice that at first - for billions of years in a row - the redshift in distant galaxies will gradually disappear. This will mean the approach of the Main Black Hole boundary. Then it suddenly changes to blue - the Universe is from expanding to contracting. Actually, this will be the main sign that a black hole has swallowed us.

Unfortunately, this does not mean that earthly civilization will survive as a result of this process. Yes, the compression of the universe will most likely take billions of years. Until the expansion stops, according to Gorkavy's estimates, it is 10-20 billion years. Reverse compression could take another 20-39 billion.

But the end will come anyway. At first, the night sky will become so hot that life on the surfaces of all planets will die. Then hot - one hundred billion degrees! - the whole rapidly shrinking Universe will become in general.

Man is not a neutron star. In the end, the gamma quanta of the relict radiation will destroy all ordinary atoms, and we will not be able to survive the compression cycle of the phoenix-universe. Perhaps there is some way out of this situation, but so far nothing is known about it.

On the other hand, these events are unlikely to be caught by our readers. So our distant descendants will have to worry about them. This is if they live to such distant times, which, of course, is also not a fact. However, to paraphrase a famous character, the New Year also always sneaks up unexpectedly. And until the very last moment, it seems that there is still plenty of time before it.

What follows from all this?

The content of the new article seriously resembles an attempt at a revolution in cosmology. Perhaps this is the first theory of our era, offering a logical and coherent explanation of what dark matter and dark energy are. The first turns out to be relic black holes, the second, in fact, does not exist. A similar "pushing" effect was produced by the influence of the Main Black Hole.


The new concept also makes it possible to understand why the expansion rate of the Universe far from us (observations of Planck for relict radiation of great antiquity) is less than near (observations of Hubble for stars in the vicinity of the Galaxy). Indeed, if the expansion of the Universe gave it a loss of mass in the past, then in the distant past the expansion rate should clearly have been different from that observed today. The equality of these speeds is required only by the concept of dark energy. But in the new cosmological model there is no dark energy, which is why such a requirement is also removed.

“A number of observational works indicate the anisotropy [inhomogeneity of properties depending on the direction] of the Universe and its closedness. These phenomena do not fit into the inflationary theory of a one-time universe, but are fully consistent with the new model of a cyclic universe."

Nikolay Gorkavy

Additional strengths of the concept: It explains the main mystery of galaxy formation. Scientists have noted for several years that galaxies could not have arisen without supermassive black holes at their centers. And these holes there are observed by astronomers already in the first hundreds of millions of years of the existence of the Universe - and their mass reaches billions of solar. The new model offers a completely natural solution to the question "where did these black holes come from?"

It is the same as for dark matter from black holes of stellar masses: we were supplied with them by the early universes that existed in our place before the Big Bang. By the way, it follows from this that in the very first Universe there was no noticeable number of galaxies: there was no "seed" in the form of huge black holes, which by their gravitation collect gas into galaxies.

From the pros of a new job it is worth moving on to its cons.

The work of Gorkavy and Tyulbashev is unlikely to cause - and this we put it very mildly - quick and widespread acceptance of its theses by the bulk of scientists. For that, it is too different from the standard cosmological model of the "disposable universe". The idea of ​​hundreds of cycles of expansion and contraction of the Universe itself is not too new - even Georgy Gamov, who predicted relic radiation, considered the universe to be just that.

But the mechanisms proposed by Gorkav and Tyulbashev are extremely unusual and unusual for the ear: the compression of the Universe due to the accumulation of mass by black holes; its expansion is due to the dumping of mass by the same black holes emitting gravitational waves. This is undoubtedly a new step in cosmology. So new that the bulk of physicists did not think about such things in principle. It comes to the point that the opponents of this idea are not even aware of Einstein's textbook opinion that gravitational waves have no mass. Such scientists seriously argue that the loss of the total mass of the Universe is therefore impossible: they say, the mass of black holes will simply turn into masses of gravitational waves and nothing will change.

There is one more problem: the Gorkavy-Tyulbashev theory, in fact, can close such areas of science as the search for WIMPs, dark energy and the theory of quantum gravity. The history of science has not known examples when supporters of scientific ideas displaced from the mainstream would voluntarily admit their obsolescence and change their views on their own. It is doubtful that this time we will see any other reaction.


And finally, the last problem with the new job: its relatively compressed size. Modern science relies on the format of journal publications, which are of necessity very short. Due to the brevity, only a small result can be stated in a way that is understandable to other scientists. Indeed, large results cannot be easily explained in four to five pages of a standard article.

We have already noted more than once that specialization in modern science has reached such proportions that even experimental physicists often look at the work of theoreticians with amazement, but without understanding. In such conditions, it is required to explain - and not once - literally every thesis of the new theory.

Yes, the work of Gorkavy and Tyulbashev is several times larger than the standard sizes. But it is unlikely that it will be enough for other physicists to fully understand this concept in its entirety. A book is needed here - a scientific monograph - and one that is written popular enough so that even those physicists who are not gravitationalists can understand why gravitational waves have no mass, how the Universe could exist for hundreds of cycles in a row, and why there are alternative explanations for dark matter and dark energy at the moment really look pretty weak.

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