Things that are currently invisible

The things that science knows and sees are only a small part of what probably exists. Of course, science and technology should not take "vision" literally. Although our eyes cannot see them, science has long been able to "see" things like air and the oxygen it contains, radio waves, ultraviolet light, infrared radiation, and atoms.

We also see in a sense antimatterwhen it violently interacts with ordinary matter, and that in general is a more difficult problem, because although we saw this in the effects of interaction, in a more holistic sense, as vibrations, it was elusive for us until 2015.

However, we still, in a sense, do not "see" gravity, because we have not yet discovered a single carrier of this interaction (i.e., for example, a hypothetical particle called graviton). It is worth mentioning here that there is some analogy between the history of gravity and .

We see the action of the latter, but we do not directly observe it, we do not know what it consists of. However, there is a fundamental difference between these "invisible" phenomena. No one has ever questioned gravity. But with dark matter (1) it is different.

How g dark energywhich is said to contain even more than dark matter. Its existence was inferred as a hypothesis based on the behavior of the universe as a whole. "Seeing" it will probably be even more difficult than dark matter, if only because our common experience teaches that energy by its very nature remains something less accessible to the senses (and instruments of observation) than matter.

According to modern assumptions, both dark ones should make up 96% of its content.

So, in fact, even the universe itself is largely invisible to us, not to mention that when it comes to its limits, we only know those that are determined by human observation, and not those that would be its true extremes - if they exist at all.

Something is pulling us along with the entire galaxy

The invisibility of some things in space can be harrowing, such as the fact that 100 neighboring galaxies are continuously moving towards a mysterious point in the universe known as Great attractor. This region is about 220 million light-years away and scientists call it a gravitational anomaly. It is believed that the Great Attractor has a mass of quadrillions of suns.

Let's start with the fact that it is expanding. This has been happening since the Big Bang, and the current speed of this process is estimated at 2,2 million kilometers per hour. This means that our galaxy and its neighboring Andromeda galaxy must also be moving at that speed, right? Not really.

In the 70s we created detailed maps of outer space. Microwave background (CMB) Universe and we noticed that one side of the Milky Way is warmer than the other. The difference was less than a hundredth of a degree Celsius, but it was enough for us to understand that we were moving at a speed of 600 km per second towards the constellation Centaurus.

A few years later, we discovered that not only we, but everyone within a hundred million light-years of us, were moving in the same direction. There is only one thing that can resist expansion over such vast distances, and that is gravity.

Andromeda, for example, must move away from us, but in 4 billion years we will have to ... collide with her. Sufficient mass can resist expansion. At first, scientists thought that this speed was due to our location on the outskirts of the so-called Local Supercluster.

Why is it so hard for us to see this mysterious Great Attractor? Unfortunately, this is our own galaxy, which blocks our view. Through the belt of the Milky Way, we cannot see about 20% of the universe. It just so happens that he goes exactly where the Great Attractor is. It is theoretically possible to penetrate this veil with X-ray and infrared observations, but this does not give a clear picture.

Despite these difficulties, it was found that in one region of the Great Attractor, at a distance of 150 million light years, there is a galactic Cluster Norma. Behind it is an even more massive supercluster, 650 million light-years away, containing a mass of 10. galaxy, one of the largest objects in the universe known to us.

So, scientists suggest that the Great Attractor gravity center many superclusters of galaxies, including ours - about 100 objects in total, such as the Milky Way. There are also theories that it is a huge collection of dark energy or a high density area with a huge gravitational pull.

Some researchers believe that this is just a foretaste of the final ... end of the universe. The Great Depression will mean the universe will thicken in a few trillion years, when the expansion slows down and begins to reverse. Over time, this would lead to a supermassive that would eat everything, including itself.

However, as scientists note, the expansion of the Universe will eventually defeat the power of the Great Attractor. Our speed towards it is only one-fifth the speed at which everything is expanding. The vast local structure of Laniakea (2) of which we are a part will one day have to dissipate, as will many other cosmic entities.

The fifth force of nature

Something that we cannot see, but which has been seriously suspected of late, is the so-called fifth impact.

The discovery of what is being reported in the media involves speculation about a hypothetical new particle with an intriguing name. X17can help explain the mystery of dark matter and dark energy.

Four interactions are known: gravity, electromagnetism, strong and weak atomic interactions. The impact of the four known forces on matter, from the micro-realm of atoms to the colossal scale of galaxies, is well documented and in most cases understandable. However, when you consider that roughly 96% of the mass of our universe is made up of obscure, inexplicable things called dark matter and dark energy, it's no surprise that scientists have long suspected that these four interactions don't represent everything in the cosmos. continues.

An attempt to describe a new force, the author of which is a team led by Attila Krasnagorskaya (3), the physics at the Institute for Nuclear Research (ATOMKI) of the Hungarian Academy of Sciences, which we heard about last fall, was not the first indication of the existence of mysterious interactions.

The same scientists first wrote about the “fifth force” in 2016, after conducting an experiment to turn protons into isotopes, which are variants of chemical elements. The researchers watched as protons turned an isotope known as lithium-7 into an unstable type of atom called beryllium-8.

3. Prof. Attila Krasnohorkai (right)

When beryllium-8 decayed, pairs of electrons and positrons were formed, which repelled each other, causing the particles to fly out at an angle. The team expected to see a correlation between the light energy emitted during the decay process and the angles at which the particles fly apart. Instead, electrons and positrons were deflected 140 degrees almost seven times more often than their models predicted, an unexpected result.

“All our knowledge about the visible world can be described using the so-called Standard Model of particle physics,” writes Krasnagorkay. “However, it does not provide for any particles heavier than an electron and lighter than a muon, which is 207 times heavier than an electron. If we find a new particle in the above mass window, this would indicate some new interaction not included in the Standard Model.”

The mysterious object is named X17 because of its estimated mass of 17 megaelectronvolts (MeV), about 34 times that of an electron. The researchers watched the decay of tritium into helium-4 and once again observed a strange diagonal discharge, indicating a particle with a mass of about 17 MeV.

"The photon mediates the electromagnetic force, the gluon mediates the strong force, and the W and Z bosons mediate the weak force," Krasnahorkai explained.

“Our particle X17 must mediate a new interaction, the fifth. The new result reduces the likelihood that the first experiment was just a coincidence, or that the results caused a system error."

Dark matter underfoot

From the great Universe, from the vague realm of riddles and mysteries of great physics, let us return to Earth. We are faced with a rather surprising problem here... with seeing and accurately depicting everything that is inside (4).

A few years ago we wrote in MT about the mystery of the earth's corethat a paradox is connected with its creation and it is not known exactly what its nature and structure are. We have methods such as testing with seismic waves, also managed to develop a model of the internal structure of the Earth, for which there is scientific agreement.

but compared to distant stars and galaxies, for example, our understanding of what lies beneath our feet is weak. Space objects, even very distant ones, we simply see. The same cannot be said about the core, the layers of the mantle, or even the deeper layers of the earth's crust..

Only the most direct research is available. Mountain valleys expose rocks up to several kilometers deep. The deepest exploration wells extend to a depth of just over 12 km.

Information about rocks and minerals that build deeper ones is provided by xenoliths, i.e. fragments of rocks torn out and carried away from the bowels of the Earth as a result of volcanic processes. On their basis, petrologists can determine the composition of minerals to a depth of several hundred kilometers.

The radius of the Earth is 6371 km, which is not an easy path for all our "infiltrators". Due to the enormous pressure and temperature reaching about 5 degrees Celsius, it is difficult to expect that the deepest interior will become accessible for direct observation in the foreseeable future.

So how do we know what we know about the structure of the Earth's interior? Such information is provided by seismic waves generated by earthquakes, i.e. elastic waves propagating in an elastic medium.

They got their name from the fact that they are generated by blows. Two types of elastic (seismic) waves can propagate in an elastic (mountainous) medium: faster - longitudinal and slower - transverse. The former are oscillations of the medium occurring along the direction of wave propagation, while in transverse oscillations of the medium they occur perpendicular to the direction of wave propagation.

Longitudinal waves are recorded first (lat. primae), and transverse waves are recorded second (lat. secundae), hence their traditional marking in seismology - longitudinal waves p and transverse s. P-waves are about 1,73 times faster than s.

The information provided by seismic waves makes it possible to build a model of the Earth's interior based on elastic properties. We can define other physical properties based on gravitational field (density, pressure), observation magnetotelluric currents generated in the Earth's mantle (distribution of electrical conductivity) or decomposition of the Earth's heat flow.

The petrological composition can be determined on the basis of comparison with laboratory studies of the properties of minerals and rocks under conditions of high pressures and temperatures.

The earth radiates heat, and it is not known where it comes from. Recently, a new theory has emerged related to the most elusive elementary particles. It is believed that important clues to the mystery of the heat radiated from within our planet may be provided by nature. neutrino - particles of extremely small mass - emitted by radioactive processes occurring in the bowels of the Earth.

The main known sources of radioactivity are unstable thorium and potassium, as we know from rock samples up to 200 km below the earth's surface. What lies deeper is already unknown.

We know it geoneutrino those emitted during the decay of uranium have more energy than those emitted during the decay of potassium. Thus, by measuring the energy of geoneutrinos, we can find out what radioactive material they come from.

Unfortunately, geoneutrinos are very difficult to detect. Therefore, their first observation in 2003 required a huge underground detector filled with approx. tons of liquid. These detectors measure neutrinos by detecting collisions with atoms in a liquid.

Since then, geoneutrinos have only been observed in one experiment using this technology (5). Both measurements show that About half of the heat of the Earth from radioactivity (20 terawatts) can be explained by the decay of uranium and thorium. The source of the remaining 50%... it is not yet known what.

5. Model map of the intensity of geoneutrino emissions on Earth - forecasts

In July 2017, construction began on the building, also known as DUNEscheduled for completion around 2024. The facility will be located almost 1,5 km underground in the former Homestack, South Dakota.

Scientists plan to use DUNE to answer the most important questions in modern physics by carefully studying neutrinos, one of the least understood fundamental particles.

In August 2017, an international team of scientists published an article in the journal Physical Review D proposing a rather innovative use of DUNE as a scanner to study the interior of the Earth. To seismic waves and boreholes, a new method of studying the interior of the planet would be added, which, perhaps, would show us a completely new picture of it. However, this is just an idea for now.

From cosmic dark matter, we got to the insides of our planet, no less dark for us. and the impenetrability of these things is disconcerting, but not as much as the anxiety that we do not see all the objects that are relatively close to the Earth, especially those that are in the path of collision with it.

However, this is a slightly different topic, which we recently discussed in detail in MT. Our desire to develop methods of observation is fully justified in all contexts.