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By Root 706 0

the big bang singularity and as described in more detail in the next chapter. The farther back a theory lays the initial point of the universe, the smaller entropy must have been then in order to have been able to grow continuously to its current value. One must postulate a very special and highly ordered initial state, whence a deterministic picture leads precisely to the state of our universe at present (a process called fine-tuning in the language of cosmologists). By itself, a postulate of this form may be acceptable; but if a special initial state is introduced, a good theory should also provide a convincing explanation for its origin. Thus the issue has changed somewhat: How can one explain the present, apparently so special state of the universe without already assuming a very special initial state?

This viewpoint, with its problematic nature, is very influential, but is often only the result of faulty analogies. What we want to explain in cosmology is, for one thing, the picture given by the universe on large scales, and also the possibility of our closer neighborhood in the solar system allowing our existence as a life-form. With this, we essentially have the kinds of observations made now and for the foreseeable future. Seen cosmologically, the present universe is of interest only as a macroscopic state given independently of its details, and whose form follows quite well from current cosmological theories.

Cosmological observations, such as the distribution of background radiation or of galaxies, determine a few parameters as collective quantities not influenced by the precise positions of single stars. For our existence, properties of the solar system, for instance the distance of Earth from the sun, are tremendously important, for other values would make Earth too cold or too hot for life as we know it. But this is only a limited number of parameters, all playing the role of collective quantities. Compatible with this macroscopic state is a multitude of microscopic states—states that, except for our solar system, differ from the macroscopic state revealed by cosmological observations only in details below the galactic scale. In cosmology, such details are of no importance, except for properties of our solar system when they are essential for the existence, for instance, of life.

For a superobserver outside the universe, the current exact configuration of galaxies and stars down to our solar system, but also of other ones in the universe, would seem highly special. He would conclude that it could only have come from a very finely tuned initial state, no matter at what time it is posited. But we are no such observer, which cannot even exist in the physical world. We are observers who must draw our conclusions, as daring as they may be, from a position within the universe. We view not only the macroscopic state of the universe in cosmology and its collective quantities, but also a part of the microscopic state in daily life on Earth by our mere existence. A sizable part of our observational data from the cosmological standpoint is, even if it can be grasped by collective quantities, partially a characterization of the microscopic state.

Thus we are not in a situation in which we would be interested only in macroscopic quantities, a situation in which entropy is an important parameter. We sit as it were on a splinter of the broken mug, and for us this splinter is at least as important as the whole thing. There are innumerable configurations of splinters, but the chances are very small that any one of them will take the particular form of the one where we happen to find ourselves. As observers in the interior of the system as the whole universe represents it, we follow selected microscopic details and suspend problems as they would arise from an increase in entropy. We see our neighborhood very precisely, a standpoint counting as microscopic for cosmological states. We see a very special configuration, but one that is simply microscopic and random. The splinter where we live just happens to be as we find it;