Fine-tuning (physics)

In, fine-tuning is the fact that quantum field theory and general relativity theory involve fundamental constants that have experimentally-determined values that seem to be remarkably favorable to the origin and evolution of life and conscious beings. The fine-tuning in theoretical physics refers to the problem of explaining the particular experimental values. These experimental values somehow occur with a mysterious adjustment for life, somewhat as the strings of a violin are adjusted for music.

Quotes

 * There seems to be a vast landscape of possible universes. ... We live in one in which life is possible, but if the universe were only slightly different, beings like us could not exist. What are we to make of this fine-tuning? Is it evident that the universe, after all, was designed by a benevolent creator? Or does science offer a different explanation?
 * Stephen Hawking and Leonard Mlodinow,


 * The old cosmological constant problem is to understand why the is so small; the new problem is to understand why it is comparable to the present mass density. ...  does not help with either; anthropic considerations offer a possibility of solving both. In theories with a  that takes random initial values, the anthropic principle may apply to the cosmological constant, but probably to nothing else.
 * Steven Weinberg,


 * Once one starts to admit anthropic interpretations of fine-tuning problems like the cosmological constant, it is clear that such a proposal might be made for other fine-tuning problems, such as the problem of the Higgs boson mass. Certainly, we would not be here if the Higgs boson mass, and hence also the and  and  and  masses, were greatly bigger. If they were near the, for example, any collection of more than a few elementary particles would collapse into a Black Hole. More generally, if the elementary particle masses were scaled up by a factor N, the number of elementary particles in a star or planet would scale down like N–3, and for very modest N the stars would stop shining.
 * Edward Witten, (quote from p. 478) preprint