The first instants after the Big Bang: Interview to Viatcheslav Mukhanov

“The efforts to understand the Universe is one of the very few things that lift human life a little above of the level of farce, and give it some of the grace of tragedy”, wrote Nobel-Prize winning physicist Steven Weinberg in “The First Three Minutes” (1977). Few scientists have given a more significative contribution to the resolution of the mystery of the origins of the Universe as Prof. Viatcheslav Mukhanov, of Ludwig Maximilian University in Munich. In 1981, when he was a Ph. D student at the Lebedev Physical institute in Moscow, he was the first astrophysicist to propose a quantum mechanical origin of the macroscopic structures of the universe. Thirty years later, his intuition has finally found an experimental confirmation in the recent measurements of the cosmic background waves where, 13,8 billions of years later, “traces of memory” of the very first instants of the rapid expanding universe described by Mukhanov’s formulas could, miraculously, still be observed. For his discovery, this year he will be appointed with the prestigious Max Plank Medal. Michele Fossi, journalist, writer and Chemist, met Prof. Viatcheslav Mukhanov to discuss about the first seconds after the Big Bang, our spot in the universe and his memories of Soviet times.

Michele – You have the reputation of being one of the major experts of the very first instants after the Big Bang, the so-called “Inflationary epoch,” which lasted between 10-33 and 10-32 seconds. What happened in that fraction of a blink of an eye?

Prof. Muchanov – At this time the universe was increasing its speed of expansion. Normally gravity is an attractive force. Therefore it acts like brakes in the car, that is, tries to decrease the speed of expansion. However under certain conditions gravity can become similar to antigravity, that is, it can serve the role of a gear in the car. For instance, at present the dark energy produces antigravity on huge scales and therefore the speed of expansion is growing. We assume that some kind of dark energy was also dominant in the very remote past right after creation of our universe. The dark energy is similar to fuel, one needs to accelerate the car to a high speed. The inflationary epoch is the time when the dark energy has accelerated the speed of the expansion of new born universe to a huge value. It was the main reason for producing initial Big Bang and in fact for creation of our universe from nothing!

Michele – Was time flowing differently in that special phase of the new born universe? Was the inflationary epoch the beginning of time?

Prof. Muchanov – No, after universe begins its accelerated inflationary expansion the time in the new born universe was flowing as usually and everything can be described by the Einstein’s theory of gravity. However, nobody knows what was before. Some theories assume that universe was created from nothing and then inflationary epoch was really at the beginning of time. However, one could also in principle imagine that the universe was cyclic, where the contraction and bounce precede the current expansion. In this case time is eternal and has no beginning.

Michele – According to the theory that you proposed already back in the 80’s, the quantum effects, which are usually important in atomic and smaller scales can also be responsible for the shaping universe in huge scales, namely, they can eventually produce the galaxies, stars and planets. How do you explain this behavior of the laws of quantum physics? What is, thirty years after, the most important contribution that the theory of quantum fluctuations gave to our understanding of the universe?

Prof. Muchanov – At the very beginning our universe was extremely small and only after expansion it became so huge as today. Therefore the scales over which the light would be travelling over millions of years at present were initially smaller than the size of atoms. This is why the quantum effects, which normally are important only in atomic and subatomic scales, could also be relevant for galactic scales, which originally were extremely small. As a result the same physics, namely, Heisenberg uncertainty relation, which is a cornerstone of the quantum theory, can be equally relevant not only for the stability of atoms but also for the origin of galaxies. According to this principle there always exist the minimal variation of the matter density from place to place which later on can grow to form the galaxies, stars and planets. However, initially these variations (fluctuations) are extremely small and should be amplified. As I found in 1981, the stage of accelerated expansion can do this job very well and as a result it produces the seeds (embryos) for the galaxies right after Big Bang. For a long time the “galaxy embryos” are frozen and only after 300 thousand years they start to develop to produce the galaxies we observe on the sky today. The theory of quantum fluctuations makes concrete robust predictions for the properties and the shape of these “galaxy embryos”. How can we check these predictions? Here in the game comes the cosmic microwave background radiation, which pervades our universe. It decoupled from the rest of the matter precisely at the time when the universe was just few hundreds thousands years old. Therefore with the help of this radiation we obtain the direct photograph of the young few hundreds thousands years old universe. The photographs taken during last 20 years became so good that they allow us to see the fine features of the “galaxy embryos” in great details. The best photograph was recently taken by the European Planck satellite. It shows the astonishing coincidence of the embryos properties with those ones, which were theoretically predicted more than thirty years ago. I think this proves the quantum origin of galaxies beyond any reasonable doubt and I do not know anybody who would seriously oppose this conclusion today. Therefore, after more than thirty years since invention of the theory we have experimentally verified that quantum physics really played a crucial role in creation of structure in our universe and we have to thank quantum fluctuations (nothing) for our existence.

Michele – Which part of the theory has been assessed with inconfutable measurements? And which are the experiments that will be carried in the next years you that you think will give a further experimental confirmation to the inflation theory you initially proposed just on the basis of mathematical formulas?

Prof. Muchanov – As I said above the quantum origin of the structure was unambiguously proved and it became an unavoidable part of any theory, which describes the early universe. We simply have no any alternative to it. I would like to stress that about 20 years ago there were many competitors to quantum fluctuations, which at present are all ruled out experimentally. Concerning the question when quantum fluctuations were really amplified, the answer is not yet as unambiguous as for quantum origin of galaxies. There exist still some people who claim that quantum fluctuations could, in principle, be amplified, for instance, on the stage of super-slow contraction in cyclic universe. Although I am personally skeptical about this possibility to rule it out completely we need further experiments. In particular, inflationary epoch also predicts the existence of the gravitational waves, ripples of the space-time, the discovery of which was last year wrongly reported by BICEP experiment. The search for these ripples will continue in the next 10-15 years and if they will be found we will be sure not only in quantum origin of the universe structure but also we will know the exact mechanism of amplification of these fluctuations.

Michele – Has the cosmic inflation theory strong opponents today and what is the major objection of those who confute your theory?

Prof. Muchanov – My theory is not confuted anymore by anybody because it refers to the quantum origin of the universe structure, which has no alternatives. Some serious opponents can, however, still question whether the quantum fluctuations were really amplified on inflation or on some other stage of evolution, by essentially the same mechanism. The main objections against inflation are of rather metaphysical nature and related with the question what is natural and what is not so natural. However, I admit that what looks natural for me can looks not so natural for some other people. Therefore in natural science the only way to decide, who is right, is to go for further experiments, which I mentioned before. This is nevertheless is somehow secondary question which I believe finally will also be answered. The most striking conclusion that we all came out of quantum fluctuations has already been firmly established by recent experiments.

Michele – The “axis mundi”, also called “cosmic axis,” “world pillar,” “center of the world” is a concept present in most religions and mythologies of the world, representing, in the most various forms, the connections between earth and sky, between lower and higher realms (e.g. the Mt Olympus for the ancient Greek or the Black Hills for the Sioux). I wonder what form a “cosmic axis” can take in the mind of an astrophysicist. Are there, out there in the space, places of passage, transit, where the universe we live in, or part of it, is channelled into something else?

Prof. Muchanov – In fact, we live in a very ordinary place in a huge universe, with ordinary sun and on ordinary planet. There is nothing special about us, about our place in this world and “no any special connections between earth and sky”. We are mediocre! This is what astrophysics, which made tremendous progress during last century, teaches us. Therefore, I think we should decouple the phantasy of the ancient Greeks from reality, which we try to learn using observations and experiments.

Michele – I like to think of the Big Bang itself as the ultimate “Axis mundi,” the transition event that transformed the “previous” universe into another one. Do you personally think that a previous universe existed before the actual one and if so, do you think we can ever find a trace of its existence?

Prof. Muchanov – According to inflationary theory our universe could be easily created from nothing (by the way in accordance with the phantasy of many ancient religious philosophers) or, as alternative, there could be the previous cycle of contraction and after bounce the universe starts to expand again. I personally prefer to think about creation of our universe from nothing. There could be many disconnected universes, which are constantly produced. However here we are entering the field of wild speculations and it is not only unclear how these speculations can be verified or ruled out, there is no even self-consistent mathematical description of the pictures above. Therefore, in distinction from quantum origin of galaxies, the speculations about creation of the universe as a whole are not yet the subject of natural science and I do not want to discuss them.

Michele – Do we know where the Bing bang explosion took place? Are we able to give an approximate location of the area of the space where it all started inflating and expanding?

Prof. Muchanov – These questions are somehow wrongly formulated. In fact, it is most likely that the space and time were created together with universe and therefore one cannot ask where and when Big Bang took place.

Michele – I see, I just have a hard time visualizing a universe where time and space do not exist. I actually never felt that what Kant was saying. That time and space are two inner categories we humans need to look at the world, is more true. I wonder if this is the hardest thing to “imagine” or if there are other discoveries or models proposed by modern physics that somehow you have a hard time visualizing.

Prof. Muchanov – I also have a hard time to visualize for instance “nothing.” On the other hand there was “nothing” before universe was created and at the moment we do not even have good mathematical description of “nothing.” Therefore it is wrong to ask where and when universe was created. The questions “where and when” by themselves already assume the existence of space and time. As Saint Augustine of Hippo (354-430) said long ago “The world and time had both one beginning. The world was made not in time, but simultaneously with time.” I think one should not even try to get unambiguous and too concrete images of many of the concepts of modern physics. For instance when I speak about quantum particle or extra dimensions I have no clear image of these concepts in my head. I do not even try to visualize five dimensional space, because in distinction from three dimensional space it is simply impossible. What, in fact, is unambiguous in physics are the concrete formulae behind of the concepts. This is why many of the popular articles (where the formulae are normally not allowed) people mix personal subjective images with reality unambiguously reflected only in formulae. Mathematics is really unavoidable if you want to understand deeply the essence of the discoveries in physics.

Michele – Today’s inflation models have evolved beyond the original assumption of a single inflation event giving birth to a single universe. In theories of so-called “eternal inflation,” the inflationary phase of the Universe’s expansion lasts forever, at least some regions of the Universe. According to this model, these regions expand exponentially rapidly, with the result that most of the volume of the Universe at any given time is inflating, even now, into other “parallel universes.” If such parallel universes were to exist, what would be the areas of passage, the “cosmic axes,” between one universe and the other? Can such universes communicate with each other, exchanging radiations or even matter, or is this forbidden by some physics law?

Prof. Muchanov – In fact, this extension of the original idea seems to have brought more problems rather than resolving the original problems. On the other hand, “eternal inflation,” which damages the predictability of the theory of quantum fluctuations is based on the extension of idea far beyond the range where it was experimentally checked. This extension is also not unavoidable and I found the model, where eternal inflation with all its problems is avoided. This does not mean that there are no other parallel universes, but all these universes in my theory are more or less the same and hence in distinction from “eternal inflation” there is no problem with predictions. I doubt that the traces of other universes in eternal inflation can be somehow convincingly checked observationally and therefore I do not think that this hypothesis in its present form is plausible.

Michele – Do you think the cosmological revolution you gave a great contribution to could have somehow some impact on the way human beings perceive their place on earth? What are for us human beings on this periferic planet the philosophical consequences of these discoveries?

Prof. Muchanov – I believe so. I think it is astonishing to find out how ordinary our universe is and how easily it could be created. Even more astonishing is that some very abstract ideas, which people were discussing for ages, we were able to formalize and verify experimentally, thus making out of cosmology, which for a long time was considered mainly as a field of natural philosophy (with a lot of bla-bla-bla) the field of natural science. Experimental evidence for the theory is so impressive that today nobody doubts that we are all originated from quantum fluctuations and although we live in a very ordinary universe on extremely ordinary planet we seems not completely stupid. Because I professionally deal mainly with the facts I prefer to leave the speculations to the reader who should draw his own philosophical conclusions from the facts we have established.

Michele – On a more biographic note: What are your memories of the academic environment during soviet times? Is there something that you miss of that environment and maybe also something that you don’t miss at all?

Prof. Muchanov – I recall that academic environment was just great. Perhaps it is mostly because I was very fortunate to interact a lot with the greatest Russian physicists for whom physics, was their main religion. I was much younger and very enthusiastic and therefore could allow myself not to care too much about everyday things with which most of the people are occupied. I could think about physics even in the numerous long lines to buy a food or some other necessary things. I recall that the surrounding surrealistic “material world” was sometimes more abstract for me than the universe which always looked more reasonable. The everyday problems were finally somehow re-solved, sometimes in a miraculous way. What I can say for sure that I am not missing at all the Kafkian’s type everyday environment of soviet times and soviet system.

Published on DUST #7, “Axis Mundi”, March 2015

issue7-3
Photo credit: Louis shot by Willy Vanderperre – styled by Olivier Rizzo. Courtesy of DUST magazine

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