Cosmos on Nautilus: The Not-So-Fine Tuning of the Universe
http://cosmos.nautil.us/feature/113/the-not-so-fine-tuning-of-the-universe
There’s more than one way to build a universe suitable for life.
Before there is life, there must be structure. Our universe synthesized atomic nuclei early in its history. Those nuclei ensnared electrons to form atoms.
Those atoms agglomerated into galaxies, stars, and planets. At last, living things had places to call home. We take it for granted that the laws of physics
allow for the formation of such structures, but that needn’t have been the case.
Over the past several decades, many scientists have argued that, had the laws of physics been even slightly different, the cosmos would have been devoid of
complex structures. In parallel, cosmologists have come to realize that our universe may be only one component of the multiverse, a vast collection of universes
that makes up a much larger region of spacetime. The existence of other universes provides an appealing explanation for the apparent fine-tuning of the laws of
physics. These laws vary from universe to universe, and we live in a universe that allows for observers because we couldn’t live anywhere else.
Astrophysicists have discussed fine-tuning so much that many people take it as a given that our universe is preternaturally fit for complex structures. Even
skeptics of the multiverse accept fine-tuning; they simply think it must have some other explanation. But in fact the fine-tuning has never been rigorously
demonstrated. We do not really know what laws of physics are necessary for the development of astrophysical structures, which are in turn necessary for the
development of life. Recent work on stellar evolution, nuclear astrophysics, and structure formation suggest that the case for fine-tuning is less compelling
than previously thought. A wide variety of possible universes could support life. Our universe is not as special as it might seem.