Helmut Satz - Before time began: the Big Bang and the emerging universe

BEFORE TIME BEGAN

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Helmut Satz 2017

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Kosmische Daemmerung with C. H. Beck Verlag, Munich 2016.

First Edition published in 2017

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Quid faciebat deus, antequam faceret caelum et terram?

What did God do before he made heaven and earth?

A UGUSTINUS ( AD 354430)

C ONFESSIONES 11/12

Preface

Ever since humans began to think about the world in which they lived, they have asked themselves how this world came to be, why it is as it is, how it was before, how it will be in the future, and what role we will continue to play in it. All human civilizations try to give answers to these questions. Wherever we look, we see happenings which have a beginning and an end, just as our lives do. Did our universe have a beginning, and will it have an end? When we stand at night beneath the immense starlit sky, it seems natural to ask how all that was formed, how large it is, and what will become of it. We are such a tiny part of something so great, but still we can ask such questions, and perhaps it is that which makes us special.

The search for answers to these questions has led to religions, to epics, to a wealth of philosophies, and eventually, of course, to natural science. In science, cosmology has developed as the relevant branch of research, and what we want to say here is largely based on studies in its framework. Nevertheless, even if different answers to the basic questions have in the course of time seemed to contradict each other, it appears that these differences were rather superficial, and that the essentials are more in accord than initially thought. And we find today that cosmology is entering regions which for many physicists are no longer science, since they are no longer experimentally explorable. Nevertheless, they remain challenges to human thinking.

In this book I want to describe the essential steps in the formation and evolution of our universe, as they have proceeded according to the presently prevalent ideas in cosmology and physics. We will see that much is indeed in accord with previous, less scientific views. Already more than two thousand years ago, much of what today is considered as the latest scientific result was proposed simply as the outcome of logical thinking. What has been added from the time of Galilei on is certainly the insistence that all conclusions must be confirmed by experiment. It is only that which turns metaphysics into physics. Nevertheless, we note that in recent times more and more interesting ideas have been pursued, from a multiverse and parallel universes to wormholes through space and time, even though in our present world these concepts are not accessible to experiment. The world of the imaginable remains much larger than that of the testable, and so in the future, even in natural science, concepts and ideas may well survive without presently having a chance to be verified experimentally.

The basic questions we want to address here fall into three areas:

How and out of what was our universe formed, our world in time and space? What was before, and what will happen afterwards?

What are the basic building blocks of matter in our present world, and what forces determine their binding?

How could a uniform, structureless, primeval world lead to the present multitude of forms and structures?

The answers we have today to these questions are, as already indicated, still of a somewhat speculative nature, and they are certainly not accepted by all. But I believe that they are interesting enough to pursue them further. That is the aim of this book.

Less than thirty years ago, the first of these questions was still ruled out as politically incorrect. The beginning was the Big Bang, and before made no sense; there was no before. Today, many cosmologists and physicists picture the birth of our universe as a rapidly expanding bubble in a hot primordial world, one bubble among many others. We are witnessing today a second Copernican revolution: neither our solar system nor our galaxy nor our universe are the end of all things. Beyond our world there are innumerable others, similar or not similar to ours, worlds we can never reach but which should nevertheless exist. These views make the Big Bang a physical process and not a singular occurrenceit is not a unique event; there were and there will continue to be others like it, and it can also lead to an end.

The question about the building blocks of our present world and of its predecessors in earlier stages of development can today be answered in a more extensive way than ever before, thanks to progress in particle physics. The dream of a final theory, a theory in which electromagnetic, strong, and weak nuclear forces are unified into a single interaction, is still not fulfilled, but has become more conceivable. Such a theory of grand unification must describe a primordial world of great symmetry, in which all constituents are treated equally. The cooling of the universe then leads to the breaking of symmetries and thus to the different interactions. The role of gravity in such a picture still remains enigmatic, however.

The development of the complexity of our world has also led to different and perhaps even contradictory ideas. The crucial point here is the famous second law of thermodynamics, insisting on a development toward increasing entropy, and thus giving a direction to time. Does that mean that our universe should become more and more disordered and thus head toward an end without form and structure? Here two ways out have been noted. First, the increasing expansion of the universe can in the long run prevent thermal equilibrium from ever being reached. Second, the role of gravitation as the dominant force implies that in a cooling gas an equidistribution of matter is not the stable form of the medium. As long as gravity rules, a world of galaxies and radiation in empty space is thermodynamically preferable to a uniform gas of particles.

So, for all three questions, much has happened in the past 30 years, and our thinking has been thoroughly modified. Two basic approaches of physicsreduction (What are the smallest possible building blocks of matter?) and extension (Earth, planets, solar system, galaxy, supergalaxy, universe)seem to have reached their limits, through quarks and the multiverse, respectively. On the other hand, the new concept of emergence has appeared on the scene. We distinguish today fundamental observables and forces (charges, atomic binding) from emergent observables and forces (temperature, pressure) that arise from the collective effort of many constituents. It seems meaningful to present these new views of the world to a general, nonspecialist readership, and that is what I want to do here. In doing so, I want to concentrate more on the novel concepts, notions, and ideas that have come up, and less on details about who did what, when, and why. It could well be that the new conceptual developments will eventually have profound consequences in other areas of human thoughtit would not be the first time for physics. In any case, I want to show to all those interested that we are today witnessing the emergence of new ideas in natural scienceideas that so far have had a much greater impact on our thinking than they have on our technology. Whether they will ever result in advances of practical use to mankindthat remains to be seen. But they have already fundamentally changed our view of the world in which we live.