What happened before the Big Bang and what will happen after our Universe perishes? Why does dark matter matter, and what role do flat walls play in the structure of everything that exists? Ukrainian astrophysicist Maxim Chyzh, who works in the observatories of the Lviv and Bologna universities and is engaged in cosmology, talks about this.

Tell about yourself please. How did you get into astrophysics? How do you work in the Bologna and Lviv observatories?

I have been interested in physics since childhood. My father is a physicist and engineer. First, I studied at the Lviv Physics and Mathematics Lyceum, and after that I entered the Kyiv National University. T. Shevchenko to the Faculty of Physics and graduated in 2012. Then he studied for another year at the master’s course at the Paris University “Université Paris-Sud” also known as “Paris-11”.

What was the specialization?

Physics. Multispecialization: nuclear physics, particle physics, astrophysics and cosmology. The master’s work, which was in Kyiv, is devoted to more theoretical physics, particle physics. In Paris, I switched to astrophysics.

How did you get into this educational institution?

Every year, the French government provides several dozen scholarships for various professions, directions for students from Ukraine. It is not so difficult to pass the competition, because they are not in a hurry to leave for France.

And how would you rate the level of French students compared to ours?

He is tall. I may say immodestly, but I still studied among the best of our students and, having transferred to the French master’s program, I did not feel special. It was one of the strongest master groups in this area of ​​France and I was at their level.

What did you do after finishing your studies in France?

Since 2013, he has been a postgraduate student at Lviv University. There is a department of astrophysics, there is an observatory. In graduate school, I was formally at the department, but I worked at the observatory. The director of the observatory, Professor Bogdan Novosiadly, was the supervisor and supervisor. Four years later I defended my dissertation.

What is it about?

– It concerns cosmology and in particular dark energy – a hypothetical component of our Universe, which leads to its accelerated expansion. I studied it more in the theoretical aspect, but in physics there is always a reference to observations and experiments.

How did you get to the University of Bologna?

After graduating from graduate school, I continued to work at the university at the Lviv Observatory, but not 100%. Then I started doing programming and all sorts of related things around it, engineering tasks. In particular, those related to computer vision, machine learning and all sorts of things where knowledge of mathematics, and not just programming, can be useful. In recent years, I have devoted all my time to this work.

But the war began. Much has changed in principle. Our European colleagues have awakened their conscience and decided to help in any way they can. They offered many opportunities for scientists to travel to Europe and America for different levels: students, graduate students, and scientists. Many scholarships, both temporary and long-term, were opened. I think many took advantage of this, mostly the female part, because at some point it became more difficult for men to leave.

And what were the conditions? What did they offer?

For example, special scholarships for Ukrainian students, graduate students were opened in many top institutions, European and American universities.

Don’t know the scholarship amount?

As for postgraduate scholarships, these are the ones for which you can live entirely and work as in a regular job and not worry about money. This helps to fully fit into the Western world. Student houses are usually a little smaller, but they provide hostels and various support, starting with relocation assistance.

Are you currently working at the University of Bologna?

Among the support options, some universities and institutes offered remote work for Ukrainian scientists due to the fact that much has collapsed here and funding for science has largely stopped. So, in order to preserve the opportunity to work as scientists in Ukraine and help them survive, the Europeans opened positions for remote work. And I took advantage of it. I was approached by a scientist from the University of Bologna, Franco Vazza. He said that his university performed a bureaucratic miracle: it found a remote work opportunity for a Ukrainian scientist. There were one or two positions. He wrote to me because this position was not for long and it was necessary to find someone quickly. I filled out all the documents and since mid-June I have been an employee of the university, the Faculty of Physics and Mathematics.

There are different scientific groups here and the opportunity to work with people from any country from which they are invited, especially from the EU. Everything is organized in such a way that a scientist who has won a grant to finance his project is quite free to use these funds and can hire graduate students, scientists as long as this project continues, as long as money is allocated for it. That’s how they took me.

What are you doing at this university now? How is the working day?

The working day is completely free. There are no restrictions. We keep in touch (phone up and write off) daily or every few days. There are weekly seminars in scientific groups. The group led by Franco includes about 20 people: his graduate students and visiting scientists. Most of them are present in Bologna, but not all. They meet weekly for a seminar where everyone shares their current achievements. And I work with him. We use skype, slack or mail.

What do you do?

After defending my dissertation, I continue to study cosmology, but I have broadened my horizons a bit. Whereas I used to deal only with dark energy, now I’m investigating data related to the large-scale distribution of the universe as a whole. Everyone knows that there is a solar system, there is a galaxy consisting of hundreds of billions of stars. Such as the Sun and smaller, and more. And galaxies form even larger structures, clusters of galaxies, form various so-called filaments (threads), two-dimensional structures, walls – the largest cosmic structures observed in the Universe. In addition, there are still other components that make up the universe. For example, galaxies themselves are at the center of a dark matter halo.

Where?

In addition to known matter, there is also dark matter. Dark matter is matter that gravitates, just like the particles we are made of. But it is transparent to light, therefore invisible, and does not emit light itself. And not only light, it does not have any interaction with other matter at all. It is visible only by gravity, after it affects the luminous matter. Scientists no longer doubt its presence somewhere since the 70s of the last century. However, it remains little studied due to this feature of it, that it does not interact with anything.

Perhaps you have seen the news that there is a sleeping dark hole?

Black holes are a separate class of objects, also a rather interesting part of the universe, which make up a small percentage in the overall balance. But first I will finish the story of what I do. The science of large-scale distribution, matter in the universe, and history in the universe over such large spans of time is called cosmology. Its task is to explain everything that we observe on such large scales: the structure of the distribution of matter, its behavior, the expansion of the Universe, which was discovered 20 years ago and is accelerated.

What are you doing now: astrophysics or cosmology? Or do you combine activities?

The term “astrophysics” usually encompasses everything. Astrophysics and astronomy are synonyms, sometimes astronomy means observation, and astrophysics is understood as the astrophysics of stars: the physics of stars, the structure of stars, their evolution. If you try to classify in general what astronomy and astrophysics do consistently, then it is easier to do this by distance from the Earth. There is the physics of near space, the astrodynamics of satellites, there is the physics of the solar system, there is planetology, the physics of the stars themselves, their evolution, birth, death. And then there are larger structures. There is an interstellar medium in which many events and processes also take place; there is a galaxy – dwarf galaxies, satellite galaxies, giant galaxies, for example, like our Milky Way galaxy, the Andromeda galaxy. This is what galactic physics does.

And cosmology is when you look at even larger structures that form from the galaxies themselves. I have papers on cosmology and large scale distribution, but there is also one paper on solar physics. There are several papers devoted to black holes, in particular their interaction with dark energy and other compact objects such as neutron stars and white dwarfs.

What significant discoveries have been made in the last 20-30 years in cosmology that would affect our understanding of the universe?

The biggest discovery occurred at the end of the 20th century – the discovery of the accelerated expansion of the Universe. Scientists have discovered that the universe is expanding at an accelerated rate through the so-called standard candles. These are events that have a standard luminosity – that is, objects always emit approximately the same amount of light, and knowing exactly how much light was emitted, you can determine the exact distance to them.

That is, if you know the total amount of light, you know its redshift, which is due to the fact that these sources are moving away from you. You can also determine, say, the history of this expansion – how it has changed over time. And most importantly, we determined that now it is accelerating. This, in fact, was the discovery of dark energy, after which they started talking about it. Because it is a hypothetical form of energy leading to such an accelerated expansion. Although there are alternative explanations for why such an expansion occurs.

And what are the alternatives, in short?

They even have several classes. There is an explanation due to a modification of the theory of gravity – Einstein’s general theory of relativity. These modifications can be thought in such a way that, on a huge scale, gravity is replaced by anti-gravity.

What does it mean?

Each physical theory has its own scope of application. And Einstein’s general theory of relativity is confirmed quite accurately in all observations so far, but there is still a certain limit of accuracy, as far as we are sure of it. Well, there are ways that can change the equation, add some terms, for example, a lambda term. This is the same application in Einstein’s equation that Einstein himself introduced when the accelerated expansion of the Universe was not yet known, this was still at the beginning of the 20th century. He introduced it for reasons of aesthetics.

What is a lambda?

It’s just a variable in an equation.

Is it conditionally unknown X? Some unknown factor that can change anything?

Exactly. But the difference with dark energy is that this factor is attributed to the properties of space-time, and not to the properties of some new component of matter. That is, the space itself has such a property that it swells like dough with yeast.

That is, the universe is a space that inflates with time?

Yes. Now scientists cannot distinguish which of these hypotheses is correct. Both “dark energy” and the lambda term are used when talking about this extension. Well, there are other theories.

And if you look at science not only from a theoretical side, but also from a practical one? How does cosmology affect our everyday life?

Astronomy generally began as a practical science, because it helped in navigation, seafaring, in determining the exact dates. Astronomy began as a practical discipline and has gone through many stages. Therefore, of course, now there are areas necessary in the study of near space. In general, the further the object of study is from us, the less practical benefit we can derive.

Cosmology is the furthest frontier. Except that we learn the history of our universe and, accordingly, also its future. This future is measured in billions of years. This is even longer than the predicted time for the life of our Sun, which will also die out sometime. These are such scales that human civilization does not operate with yet. Perhaps we will someday reach a stage of development when humanity will be interested in the fate of galaxies, as well as the fate of the entire universe.

That is, cosmology develops such knowledge that will be needed in 200-300 years?

Or in 2000 years. Quasars are such objects that are interesting for cosmology as well. They were discovered as quasi-stellar objects. These are the nuclei of distant galaxies, in which there are black holes inside. They absorb a lot of gas and radiate very strongly and brightly. We perceive these bright objects as quasars. There are millions of them.

That is, there are millions of dead galaxies?

– They’re not dead. We see them in the past because light travels at a finite speed. It is interesting that in modern times the galaxies are not so bright, there is no such strong radiation in those galaxies that are close to us, closer to the present. Quasars are the oldest objects in galaxies. What is their essence, use? They are sources of very bright light, radio emission, sometimes light, which are easy to use for navigation because they are practically stationary on the celestial sphere. That is, they are so far away that even if they have their own movement, it is imperceptible from the Earth. They are like attached to the celestial sphere. And, accordingly, some spacecraft created by man rely on them as fixed reference points, according to which they are calibrated and determine the position, orientation. Cosmology is also interested in quasars, their nature, their distribution, because they also tell a lot about the evolution of the universe, in particular, the evolution of galaxies.

Do they also help with navigation?

Yes. They still helped, even if we did not study their nature.

About the James Webb telescope: what are the challenges for it? Why is it needed?

It was launched as a new generation telescope, after the Hubble telescope. It is the most powerful space observatory today. In terms of the quality of the optics and the sensitivity of the technology, Hubble is even stronger, which was aimed at a different wavelength range, wavelength. That is, Hubble observed visible light, also with members of the infrared range. His main goal was to study the universe in visible light, that is, in those wavelengths that we see – this is how he took photographs.

The James Webb telescope is tuned more to the infrared. The range of these waves from space to the Earth almost does not break through, because it is absorbed by the Earth’s atmosphere. Therefore, in order to see the universe in these waves, in fact, you need to go into space. The James Webb telescope was not only launched into orbit, but it was also sent to the Lagrange point, as far from the Earth as possible so that the thermal signature of our planet does not interfere with it.

Explain about infrared.

In this light, many interesting things can be observed. You can see what was done in the universe a very long time ago, because all the light emitted in the universe long ago, far from today, is redshifted by this expansion itself. The farther the light source, the more ancient it is and, accordingly, the stronger its light is shifted to the infrared region. If some galaxy shone in visible light, but did so billions of years ago, then it can come to us as infrared. Then James Webb will see this shift.

In addition, in the infrared range, many objects can be observed in our galaxy, and not somewhere far away. For example, dim stars, red and brown dwarfs. Or the same exoplanets that do not themselves shine, but reflect the light of their luminaries. Or basically they are observed through the transit method, that is, they pass through the disk of the star and leave an imprint in the infrared spectrum. Knowing such an absorption spectrum of a planet, or rather its atmosphere, one can say a lot about this planet.

For example?

For example, whether water, methane or other chemical compounds are included. Is life possible there?

To summarize, is James Webb needed to search for the possibility of life on other planets?

Yes, this is one of his main tasks. That is, the search for such elements that we will consider either the result of life, for example, methane, or, conversely, are necessary for existence (water, organic compounds).

What are the theories of the origin of the universe other than the explosion?

The big bang theory was finally formed somewhere in the middle of the 20th century. There was one observation that made this theory a winner. It was an observation of the microwave background of the universe. Microwave background irradiation, as it is also called. It was simply predicted by Georgy Gumov, our countryman from Odessa. He predicted it in the 1950s and discovered it in the 1960s.

The Big Bang Theory is a code name. It would be more correct to call the theory of a hot cramped universe in the past. This theory is that in the past the universe was much closer, hotter. It is precisely because it is expanding that it is now so cold and empty. The presence of this radiation meant that the universe was once so thick and hot that even hydrogen could not be stored in it. That is, there was such a dense plasma that hydrogen was divided into protons and electrons. And at that moment, when the universe cooled down enough for electrons to join protons and form hydrogen, the first chemical element, it was this transitional moment that gave rise to this light, which we now call the microwave background. Moreover, when this light was born, it was high-energy.

What does it mean?

These were wavelengths that were far into the ultraviolet range or even in the gamma range – beyond our sight. But due to the expansion of the universe, the wavelength of this light became, on the contrary, very long and it turned into infrared. That is, it has moved to the part where we do not see it, because the waves are very long. Although at birth they were too short. The big bang theory suggested that such radiation must be present. Therefore, when scientists in America found it, by the way, by chance, because they expected it at other wavelengths. Then it became clear that indeed the universe was hot and crowded so much that it was once a plasma. She then recombined – electrons and protons, which were free, combined and became hydrogen.

What happened before the big bang and what happened after?

If we go deeper, then in fact there was no explosion, there was an expansion from some initial state in which the matter was very dense and very hot. As for the question of what happened before the explosion, this is the question of where this matter came from, how it was formed, and why it was formed in this state – in general, there is no answer to this question. For several reasons. Firstly, it is almost impossible to find any signals from there. This microwave radiation is one of the most distant things we can see.

There are a few more markers from epochs before this recombination. Once upon a time, thermonuclear reactions took place in the universe, when it was so crowded that heavier nuclei were formed from protons. And this remnant can be traced in observations, which once again confirms the theory of the big bang – or hot cramped universe in the past. In particular, almost all the helium that exists in the universe was born in such primary nuclear fusion. After all, the universe now consists of about ¾ of hydrogen and a small amount of heavier elements that are already born in stars. But these elements have just begun to emerge. There are no markers, observations from something that happened before this primary synthesis. Accordingly, it is impossible to look even further into the past of the Universe by observation. There is a hypothesis that we can still find a relic nitrine background, as well as primary gravitational waves. Although it is very difficult, no one knows how to find them.

And what do primary gravitational waves mean?

These are the waves that were formed during the creation of the universe. The huge density of matter gave rise to the same huge perturbations of the very fabric of space-time, which also spread, expanded along with the Universe. They are still present in the Universe today, only now they are much less noticeable, because they lost their energy with the expansion of the Universe.

The big bang theory does not give an answer to where the universe came from. There are other theories. In particular, the theory of cosmic inflation, which pushes the concept of where everything came from even further back in time. She explains that all particles, all matter that we know, came from some primary field. This is more of a hypothesis than a theory. Well, there are also exotic theories that the big bang was preceded by another universe that shrunk and then ours was born. There is a theory that our universe was born from emptiness, from vacuum. In terms of energy balance, this is possible. Because the born energy is compensated by negative gravitational energy. Any energy creates gravity.

What about the future of the universe?

If cosmology solves its main problem and finds out what the Universe consists of and in what proportions it contains light, dark matter and dark energy, then this will allow us to learn not only about what it was like in the past, but also predict what it will be like in the past. future after billions of years of such expansion. There are several scenarios. The most likely to date is an infinite expansion over an infinite amount of time. That is, accelerated expansion and it will remain so. In general, the universe is expanding and will continue to expand, and everything will end with the fact that the galaxies will become isolated from each other, but will be held together by a bunch, each on its own. Now we can observe billions of galaxies, but in ten billion years they will run beyond the observation horizon due to the expansion of the universe. This is the main scenario.

There is also the big gap theory. Such an expansion will grow so rapidly that it will tear apart not only extragalactic structures, but also the galaxies themselves, and then the solar systems, and then the stars and planets. This is possible in the presence of phantom dark energy – a certain type of this mysterious substance. This will happen in the final time, but still this time is very long. There is also a third alternative big crunch scenario. In it, expansion is replaced by collapse at some point. Which of these scenarios is realized depends on the filling of the universe, on the properties of dark energy and the universe.

Tell me about the multiworld that’s popular in movie comics right now. Is it possible?
Theories of the multiverse come from the microcosm with an interpretation of quantum mechanics. In cosmology, the multiverse exists in a slightly different sense, because at the birth of the universe, many universes with different physical laws could have been born. But this is a theory that is unlikely to find any confirmation, because the laws of physics of our universe do not allow getting to another universe.

Tell me about dark matter. How is dark energy different from dark matter?

The concept of dark matter is simpler than dark energy. Imagine that you are holding a ball on a string. If you want, you can spin this ball and it will rotate. At the same time, it is clear that when the thread is suddenly cut, the ball will fly anywhere, it will not hold on to anything. Because there is centrifugal acceleration and there is a tension force that compensates for it. We need a force that would keep this ball in the center.

In fact, the universe is many such balls that rotate around a common center of gravity with their centers of gravity. In particular, this is our galaxy. This is a lot of stars that are spinning around the center and this thread holding them is gravity. But there’s a problem. It lies in the fact that scientists looked at the speed at which these stars revolve around the center of galaxies and noticed that these speeds are too high for both the gravity created by the stars themselves and the galaxy itself. This means that there is something holding them stronger than visible matter gravitates. From there, the problem of dark matter arose. It was necessary to come up with some invisible substance, but with all that, it creates this gravitational force enough that the stars can spin as fast as they are spinning now, as seen from the observations. This became clear somewhere in the 70s of the last century.

And before that, scientists noticed the same effect on the scale of clusters of galaxies: they revolve around some common centers of gravity, but too quickly for the mass that holds them together. That is, there should be more gravitating mass than luminous matter – luminous matter. It must be something so heavy that it creates such gravity that all these bodies adhere to common centers of gravity. And, accordingly, they called it dark matter and found out that by mass it should be three to four times more than visible matter.

Scientists have little doubt that this matter exists and that it affects the dynamics of the universe. And they do not give up hope of finding it not only on the scale of the galaxy, but also here on Earth – it is possible that particles of this dark matter can get into particle detectors. Therefore, scientists dig deep underground so that nothing interferes, no other particles, no other radiation, and set up various particle detectors there, and they are carefully watched to see if something appears that can be interpreted as dark matter particles. But so far, none of these experiments has confirmed that such particles exist. Dark energy is something much more mysterious.

How can cosmology have a practical impact on space exploration?
I will mention this practical aspect of cosmology again. This science is connected in a certain way with particle physics, because the past of the cosmos depends heavily on what matter is made of, how it interacts at very high energies. As cosmology has shown, there are hidden components in our universe that do not emit light and that can be seen with the help of cosmology on a large scale. They probably have some manifestations (demonstrations) at the level of elementary particles. I have already said that scientists are trying to find them, but so far without success.

Well, as far as fundamental science is concerned on a scale larger than what humanity is currently operating on, people are now mastering only the Earth’s orbit. There are missions to the Moon, Mars. But we must understand that going beyond the limits of our solar system will not happen soon. This requires technologies such as nuclear space propulsion. Now only some concepts of such installations are being created. Predicting when we will colonize our galaxy is a thankless task.

If one does succeed in designing such engines, how will cosmology help? Civilization and other life depend on cosmology because objective laws place limits on how far and how fast you can spread your civilization and your life. In general, this will tell our limits, what we will have time to do before the universe plunges into darkness, cold, or, conversely, rises.

Let’s talk about flat walls. What does it mean “the universe is a collection of flat walls”?

This is what I do. Apparently, we are talking about a large-scale distribution of matter. And here such a thing is that this is matter in the form of galaxies, clusters, it is distributed in an interesting way, that voids dominate in it. If you conditionally describe, then something akin to Swiss cheese, in which there are many holes. Only in the universe there are other ratios of matter and voids. The fact is that they are concentrated unevenly. These can be walls surrounding voids, as well as one-dimensional structures – filaments.

A filament is, in other words, a thread. Scientists have a term for such a distribution. They talk about the cosmic web. And, accordingly, these giant two-dimensional structures are called “walls”. If we look at them from the side, we can reproduce the 3D structure from their velocity field and from their coordinates. It will look like a crumpled sheet, where there is an increased density on the surface, and there are voids between the walls.

So the universe is a web?

Yes. Yes, this is lace, reminiscent of a web. But there are both 1D and 2D structures. Scientists are interested in why this happened, what laws led to such a distribution, what is the dynamics of these structures? Sooner or later they will still grab into some more point objects. Or no.

What do we still not understand?

We know the laws according to which bodies are attracted to each other and we can assume some initial distribution in which there were no these walls and these filaments. And now we know that such laws of attraction and interaction lead to just such a distribution. All this can be assumed and explained using the laws of gravity and the interaction of matter that we know. And all this is calculated. But there are many details that are yet to be clarified. For example, how long will these filaments (threads), what density, how much density will be greater on this wall than the density of galaxies in the void.

Many talk about a supermodel, that is, a combination of relativity, cosmology, quantum mechanics, in order to better understand the universe.

You are talking about the theory of everything, or the theory of the grand unification (forces of nature). This is a theory in which absolutely all interactions must be combined. It has not yet been invented, but it is the holy grail for all physicists. The search continues.