Evolution of the Universe

The evolution of the universe also confronts us with many open questions. We know that tiny fractions of a second after the Big Bang all matter existed as a primordial soup consisting of quarks, gluons, photons and leptons. As the universe expanded and cooled down, a new phase of matter came into being, composed of protons, neutrons and electrons - the building blocks of our present world.


What we already know...

The composition of matter - the hierarchy of consecutive levels from the microscopic to the macroscopic scale - is closely linked to the sequence of the evolutionary eras that our universe has passed through. The universe was born in the Big Bang, and expanded explosively while gradually cooling down from an initial state of extreme energy densities and temperatures. A sequence of metamorphoses brought it to its current state, and will continue to alter our universe in the future. At the very beginning of the universe, elementary particles were formed from pure radiation fields. Out of a primordial soup consisting of quarks, gluons, photons, and leptons the building blocks of atomic nuclei - neutrons and protons - came into being just fractions of a second after the Big Bang. Within the first three minutes the lightest atomic nuclei were formed. Neutral atoms came into existence only 300,000 years later. They accumulated into huge gas clouds, from which the first stars were born after about one billion years. Atomic nuclei fused inside the stars to form the chemical elements up to iron. The heaviest elements were generated in violent stellar explosions. These processes still go on today - 13,7 billion years after the big bang - and will continue into the distant future.

The cosmic evolution is directly determined by the laws of physics and by the fundamental symmetries of nature. Our quest for understanding the origin and the development of the universe, and therefore our own existence, is one of the basic motivations for scientific research.


...and what we would like to know

Although we know the approximate sequence of events in the cosmic drama, there are still many unanswered fundamental questions concerning the details.


About a millionth of a second after the Big Bang, all matter existed as an unimaginably hot, dense primordial soup consisting of quarks, gluons and other elementary particles. Like electrons in a plasma, quarks were able to move about quasi-freely in this quark-gluon plasma. Scientists believe that similar forms of matter might exist in the interior of neutron stars.
Is it possible to use nuclear reactions to recreate and study the transition from nuclear matter to quark-gluon matter?

It wasn't until a billion years after the big bang that the first complex atomic nuclei and thus the chemical elements were formed at the cores of stars and in stellar explosions. Prior to this, there existed only hydrogen and the lighter elements, up to lithium.
How do heavier nuclei and elements come into being? What is the significance of unstable nuclei in this process?

The moderate temperature and pressure conditions on earth were favorable for the birth of life. The great majority of matter in the universe is subject to extremely high pressures and temperatures - in the earth's core, for example, or even more dramatically, in the center of larger planets and of the sun.
What is the state of matter under extreme temperatures and pressures?

Astronomical research has demonstrated that the universe now contains only matter, and that no antimatter exists. Scientists' qualitative explanation for this is that physical laws violate certain fundamental symmetries. However, cases of this symmetry violation found in experiments are not sufficient to quantitatively understand how matter survived in the universe.
Can we discover new information in nature regarding symmetry violations?

We know from the movement of the galaxies that there must be approximately 20 times more mass in the universe than we can directly observe. It has been suggested that this so-called dark matter possibly includes new types of particles bound by the strong interaction, the existence of which we have not yet been able to prove in experiments.
Will it be possible to discover more about these new forms of matter under improved experimental conditions?


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