Is it true that a black hole is growing in the Earth and the Americans have confirmed this with a recent observation? Rave? And on the Internet they write that it is growing … But if the curious inhabitants of the Web read the primary sources, they would know what could force physicists to consider such an exotic scenario.
Truly I tell you: on May 4, 1925, the Earth will hit the celestial axis! (M. A. Bulgakov, "Heart of a Dog").
Test transformations
"Physicists have confirmed the growth of a black hole inside the Earth." This is how the anonymous journalist A. N. on the website of the ANHA agency, created in Belgium by a group of Kurdish journalists, titled his article dated July 25, 2018. How the black hole inside our planet affects the Kurdish liberation movement is unclear, but the search engine gives this message as the main source, which served as the starting point for the work of journalists of other online publications specializing in delivering super interesting news to the public. The essence of the Kurdish message was that the journal Physical Review Letters published a fresh article on the work of the ANITA probe. It flies over Antarctica and detects neutrino fluxes. So, from the data of the probe it follows that a black hole is growing in the Earth. However, adds a Kurdish journalist,some scientists consider this an indication of a thermonuclear reaction taking place inside the Earth, which explains global warming.
ANITA prepares for flight. Photo: Brian Hill of the University of Hawaii-Manoa.
Russian journalists, having creatively reworked the text, add that, according to some experts, this is not a black hole playing pranks, but a race of diggers that sends neutrinos to the surface of the Earth. In general, opinions differed, but research continues (the latter is true: the probe continues to observe).
The most interesting thing here is that the article was not published at all, only accepted in print, and it was impossible to find its full text on the journal's website at that time - only an abstract, where there is not a word about black holes or thermonuclear reactions, and among 63 co-authors there is not one with a Kurdish surname. However, as is customary today, the preliminary text of the article is available on the arXiv.com website, and it has been there since March 14, 2018. From this text, we were able to extract the details of an interesting study, for which we can express gratitude to the online journalists who drew attention to this not the most, at first glance, impressive work.
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Smoke over ice
The essence of the work is as follows. NASA's ANITA probe (from ANtarctic Impulsive Transient Array) was first launched around Antarctica a long time ago - on December 15, 2006 near McMurdo Station. Since then, approximately every two years, it has been flying about a month in a balloon in the upper atmosphere at an altitude of 35–37 km above sea level or 33–35 km above the ice surface, gradually shifting towards the pole. The objective of the experiment is to detect the appearance of ultrahigh-energy neutrinos of cosmic origin. Having collected the data, the researchers analyze it for a couple of years, change something in the detector and launch the probe into flight again. The fourth experiment took place at the end of 2016, so, apparently, in the near future we will learn new results. So far, the analysis boils down to those eventsthat were recorded on the first three flights.
Where do the neutrinos of ultrahigh, exaelectron-volt (EeV) energies come from - and this is millions of times more teraelectron-volts (TeV), which are achieved on the most powerful device created by human hands, the Large Hadron Collider - will be discussed below, but first we will talk about methods of detecting such neutrinos.
In 1962, GA Askar'yan, the future Lenin Prize laureate, and then a researcher at the Physical Institute of the USSR Academy of Sciences PN Lebedev (FIAN), put forward an interesting idea. If a particle moves through a solid medium at a speed greater than the speed of light in this medium, it generates a compact, several cubic centimeters in size, a cloud of charged particles - electrons and positrons. This cloud should not leave any traces during its movement due to the equality of the total charges of electrons and positrons. However, Askar'yan suggested that when moving in a dense medium, the equality of the number of these particles is violated very quickly - there are 20% more electrons, that is, an electric current arises, which generates coherent (as in a laser) radiation with certain characteristics. Catching this radiation,you can fix the presence of such a cloud.
Scheme of neutrino detection by the Askaryan effect. Figure: Predrag Miocinovic.
Until the end of the 1980s, Askaryan's idea did not attract much attention, but as astrophysics developed, researchers faced the task of fixing ultrahigh-energy neutrinos. As is known from physics, the higher the energy, the lower the particle flux. Accordingly, the fewer particles, the larger the detector should be, especially considering that neutrinos are extremely reluctant to interact with matter. For example, a cubic meter of ice is quite suitable for capturing TeV neutrinos: such an IceCube detector was built in Antarctica. However, already for fixing neutrinos with an energy of a thousand times more (PeV), thousands of cubic meters of ice are needed, and for the next discharge of energies, EeV, millions are needed.
It is impossible to build such a detector, so you have to use some natural objects, for example, the Antarctic ice sheet or the Moon. The first one turned out to be the most convenient. Firstly, launching a probe over Antarctica is much easier than equipping an interplanetary expedition. Secondly, cold ice, being a dielectric, perfectly transmits radio emission, namely, radio emission should arise when the Askar'yan effect is realized in the case of ultrahigh-energy neutrinos.
In the late 1990s and early 2000s, experiments were carried out that confirmed the Askaryan effect in dielectrics such as salt, lunar regolith and ice. For example, to test the latter's suitability as a detector, in 2006, researchers piled five and a half tons of pure ice and sent a beam of electrons and protons from an accelerator at it. An ANITA probe hung over the ice at a height of eight meters, which recorded the corresponding radiation. So its efficiency was proved.
Events
And so the research began. The probe flew over Antarctica, observing about one and a half million cubic kilometers of ice in one flyby. Alas, not a single signal from a high-energy neutrino hitting the Antarctic ice was recorded. However, some interesting events were noticed. First of all, these were traces of super-energetic particles of cosmic rays with energy in EeV entering the atmosphere. There were about one and a half to two dozen such events for the first and third overflights (during the second overflight, ANITA canceled the task of fixing cosmic ray traces). When an energetic particle of rays enters the atmosphere, it, colliding with any molecule, generates a shower of secondary particles. These, in turn, form radio emission, and it, reflected from the ice, enters the probe's detectors. That the downpour is fallingand the radiation is reflected and flies upwards - important: this affects the polarization of the signal. Antennas ANITA are perfectly able to fix this polarization and thus distinguish a signal of cosmic origin from an anthropogenic signal. In general, signals from cosmic rays were expected.
But among the signals recorded, there were several strange ones. During the first flight, two signals were found that came from behind the horizon line, in which the reflection did not change polarization. In all other respects, the signal corresponded to those received from cosmic rays. These two signals were identified as coming from a cosmic ray propagating horizontally.
But there were two more abnormal signals. The first, obtained during the first flight, was initially rejected, since it did not fit into the theory at all. But when a similar signal was recorded during the third flight, they had to be subjected to additional analysis. Both signals came far beyond the horizon line: the angular coordinate corresponded to −27-30 °. In fact, the signal came from underground, and it propagated upward, that is, it was not reflected. It turned out that these signals were generated by exaelectron-volt (with an energy of 0.5 EeV) showers of particles that arose in the ice or not high above it and flew upward towards space.
What is this, the desired event from a high-energy neutrino? No, the shape of the signal did not correspond in the least to the theory of the Askarian effect. And it was here that all sorts of fantasies began, in particular those that caused a sensation in July 2018.
Tau hypothesis
The main problem is that there are no sources of sufficient power on Earth to create a particle with energy in exelectron-volts. Therefore, one has to turn to sources of cosmic origin. However, if the shower was generated by a cosmic particle that hit the Earth from the opposite side of the ANITA probe, it means that it passed from 5 to 7 thousand kilometers of solid. No ion of cosmic rays is capable of this, only neutrinos. Therefore, it was suggested that the shower gave a tau lepton, generated by the collision of a tau neutrino with matter. In this case, the neutrino itself possessed exaelectron-volt energy. This tau lepton, being highly unstable, but moving at a speed close to the speed of light, could survive until the intersection of the ice surface with the atmosphere, or even fly out of the ice to a height of several kilometers,where and decay, giving rise to the desired shower of daughter particles.
This beautiful hypothesis has one weak point. Neutrinos of such energies during their travel through the Earth should have interacted with matter one and a half times and disappeared, giving rise to a tau lepton. That, decaying, in turn, could give rise to the next tau-neutrino, but with much less energy. It turns out that with such a mechanism, a much higher-energy neutrino should be present at the input than is possible, based on the existing picture of the universe: otherwise, the tau lepton of the required energy cannot be obtained at the output. This means that it is necessary to revise the model of the interaction of neutrinos with matter in order to ensure its unhindered travel through the multi-thousand-kilometer thickness, or to look for other sources of ultrahigh-energy neutrinos.
In an attempt to find at least some explanation, the researchers looked to see if there was a catastrophe in the right sector of space that could give neutrinos of sufficiently high energy. In the second case, indeed, it was possible to find a supernova SN2014dz, which could be responsible for the event, but the probability of this turned out to be statistically insignificant. In addition, its neutrino luminosity turned out to be much higher than it follows from the data on the luminosity in the visible range, and these neutrinos should have been noticed by other neutrino detectors. And for the first event, no possible candidates were found at all. Physicists stopped at this, hoping to get more information on the next ANITA flights, and to find something related to both anomalous events in the databases with the observation results of other detectors.
Cosmic neutrinos
Ultra-high-energy neutrinos are one of the hottest topics in astrophysics. Here is how Predrag Miocinovic, a member of the ANITA collaboration, spoke about them poetically at a conference in Stanford in 2004: “They represent the third leg that is necessary to support the entire modern astrophysical theory, and together with optical observations and the study of cosmic rays will give a clearer idea of the inner structure of the most energetic machines in the universe."
The problem is this. In the 1960s, when Askar'yan was inventing the mechanism of the effect named after him, two other groups of theoretical physicists invented limits on the energy of cosmic rays. They were Kenneth Greisen from Cornell University and G. T. Zatsepin and A. V. Kuzmin from FIAN. Their articles were published in 1966, that is, just after random measurements by Arno Penzias and Robert Wilson recorded the presence of relict radiation with temperature, for which they received the Nobel Prize in Physics 1978. A calculation based on their data showed that protons with energies of 10–100 EeV will collide with relict photons and lose energy, giving rise to daughter particles. The path length turned out to be large - about 50 Mpc, but still it is much less than the size of the visible Universe. Therefore, the energy of cosmic rays cannot exceed this limit (now it is called the GZK limit, by the names of the discoverers). Indeed, reliable data indicating that higher energy cosmic rays exist has not yet been obtained.
A little later, in 1969, V. A. Berezinsky (who did not live to see the well-deserved Nobel Prize for neutrino oscillations, see Chemistry and Life, No. 11, 2016) and G. T. Zatsepin showed that such collisions give birth to neutrinos with an energy a couple of orders of magnitude lower than that of the original particles of cosmic rays. Such neutrinos with energy in EeV or a little less are now called BZ neutrinos, and so they interact so weakly with the microwave background that they can fly from the depths of the Cosmos to the Earth. If it was possible to fix them, the theory would receive reliable confirmation.
But, as you can see, so far things are not going well with him, but some incomprehensible data that do not follow from any theory emerge. And as soon as the cosmic origin of both discovered particles is in question, the temptation arises to say: what if this is something else? what if their source lies inside the earth? Since the energy of the particles is extremely high, shouldn't they be generated by the most terrible creation of the Universe - a black hole?
Estimated particle spectrum during the evaporation of a microscopic black hole formed at the Large Hadron Collider.
In principle, the conversation that ultrahigh-energy neutrinos can turn into a microscopic black hole when colliding with ice has been going on for a long time, even at the stage of preparation for the ANITA experiment. As Predrag Miocinovic notes in the already mentioned speech, referring to two articles in 2002, such a hole should instantly evaporate according to the Hawking mechanism and give rise to particle showers, which can be recorded thanks to the same Askarian effect. This will lead to a false increase in the number of events that ANITA registers. Since no neutrino events have been noticed for twelve years of work, apparently this hypothesis is not very consistent.
Could a microscopic black hole of cosmic origin pierce the Earth and, flying out from the other side, cause an upward high-energy shower of particles, similar to that produced by the decay of a tau lepton? The question is not easy, and the answer depends on how such a black hole behaves.
Within the existing consensus, a microscopic black hole from a particle with energies above TeV can form, provided that our space has hidden dimensions. During evaporation, it forms many elementary particles, but their spectrum is unknown, and different theories give very different estimates, especially since not only the parameters of hidden measurements are unknown, but their very presence is questionable. It is not difficult to distinguish between the products of evaporation of a black hole and decay of a lepton in special detectors of an elementary particle accelerator. But whether ANITA, which catches only radio emissions, can do this is not very clear.
The main thing is that there are scenarios according to which, once a microscopic black hole appears, it turns out to be long-lived. It evaporates only when it turns out to be larger than the size of the hidden dimensions, and until that moment it is either stable or absorbs matter and grows. In this scenario, flying through the Earth (which takes several tens of milliseconds) and actively absorbing matter, since its density is high, the hole, having reached a critical size, will go into a metastable state: how much matter has been absorbed, so much has evaporated in the form of showers of particles. These showers will cause upward propagating radiation, including radio emission from the depths of the Earth. Having flown out of the solid, the hole will lose the ability to grow due to the low density of the surrounding matter, will close within the limits of hidden dimensions and disappear without a trace in space.
It is possible that such hypothetical considerations, based on unverified and highly speculative models, allowed some enthusiasts to attract a black hole inside the Earth to explain the anomalies recorded by the ANITA probe.
Sergey Komarov