Reading aloud Why the world is as it is has hitherto been considered a question for philosophers, but not for science, which only wants to describe the nature of the world and does not care why the fundamental laws of nature are so, as they are. The philosophical question is now also pressing for the cosmologist, as it has become increasingly clear that even minimal changes in the fundamental physical properties of our universe would have dramatic consequences: there would be no living beings, let alone intelligent creatures like us humans who formulate these laws of nature or discover. The physical standard model, which was co-founded by Murray Gell-Mann and describes the smallest building blocks of matter, contains, for example, 20 constants whose values ​​can not be deduced from deeper principles - a situation that is unsatisfactory for physicists.

But the exact value of these constants depends on which atoms and molecules can exist at all. And if the fundamental forces of nature were only slightly stronger or weaker, there would be no stable planetary orbits, no stars and galaxies, or the universe would have collapsed long ago. The same applies to many other physical and cosmological parameters: the smallest deviations from their actual value would result in a boring, life-threatening universe.

All this can hardly be a coincidence, because the probability for the creation of a life-friendly universe is practically zero, the physicists calculated for the insane value 1:10 high 229th But this "impossible" universe - our - there are still all natural constants in he has the necessary value. This "fine-tuning" is not trivial, but extremely amazing. Without them we would not exist. "It almost seems like the universe of intelligent life forms has been tailor-made, " explains astrophysicist Martin Rees of the University of Cambridge. Some scientists even go so far as to accept this as an indication of the existence of higher powers, and some even venture the adventurous converse conclusion that the universe is what it is because it exists.

But has the cosmic stage really been set up for the appearance of man? Do we live, as it were, in a universe made to measure? The problem is reminiscent of the situation in biology before Charles Darwin developed his theory of evolution, allowing a whole new view of life. Until then, a "teleological" mindset was widespread: the "adaptation" of sentient beings to their environment was traced back to their inherent purpose or outward plan. display

Darwin showed that new or modified properties, which are the result of accidental changes in the genetic material, are subjected to a hard selection by the environment and sometimes manifest in a reproductive advantage of their carriers. The assumption of purposes and goals in nature was thus superfluous - the interplay of mutation and selection is sufficient as an engine for evolution completely.

"Could the physical properties of the Universe not have come from a similar interaction of chance and necessity?" Asked Lee Smolin again and again. During a sailing trip, he was struck by the flash of inspiration, which he has now developed into a provocative hypothesis, which was received by his colleagues, sometimes with enthusiasm and sometimes with skeptical disbelief. If it should turn out that Smolin is right, he may without exaggeration be called a "cosmic Darwin."

Smolin's basic idea is that universes multiply like living beings. In doing so, they should change slightly and be selected in terms of their properties - that is, subject to a cosmic evolution. But how can universes be duplicated? Smolin's Answer: Using Black Holes as they are produced by the collapse of massive, burned-out stars. In the center of these black holes, density and temperature become infinite, space and time lose their meaning. This extreme state - one calls it singularity - could, according to the scientist, become the nucleus of a new universe, which in a big bang breaks off its original universe and henceforth leads one's own existence.

How this could happen, Smolin must leave open. Our physics is not developed enough to describe such processes. Only a theory capable of uniformly describing all natural forces will bring clarity here. In this respect, Smolin's starting point is speculative, but at least in principle verifiable.

However, the genius of his consideration lies somewhere else: If baby universes can really sprout out of black holes - like yeast cells from their peers - and if there is a slight, random variation of the laws of nature, then different rates of reproduction of these daughter universes result. One can speak of a cosmic Darwinism.

=== Rüdiger Vaas

© science.de

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