The proposition that the presence of human life is connected with the properties of the Universe. There are various forms of the anthropic principle. The least controversial is the weak anthropic principle, according to which human life occupies a special place in the Universe because it can evolve only where and when the conditions are suitable for it. A more speculative version, the strong anthropic principle, asserts that the laws of physics must have those properties that allow life to evolve. In recent years, the weak anthropic principle has been used to explain many properties of the Universe, such as the values of the fundamental constants and the number of dimensions of space, on the grounds that if they did not have these values human life would never have evolved. However, the validity of arguments of this kind is very uncertain unless, as some speculative theories suggest, there are actually many universes, each having different values for the fundamental constants and possibly different numbers of dimensions (see Multiverse). If that is true, some of these universes would contain no life at all, some would contain very different life from ours, and our Universe would obviously contain our kind of life.
Subjects: Astronomy and Astrophysics.