The Fabric of The Cosmos - Post 1

      From the beginning of the book, Brian Greene discusses cosmological principles, and how they fit in with theories of the twentieth century.  One example in particular is the big bang, string theory, and the big crunch.  Once string theory was developed, a principle was discovered about the matter concentration of the universe.  The theory, in its most basic sense, explains how the universe has been expanding since the big bang, and will continue to expand due to the low concentration of matter in the space time fabric.  The lower the concentration of matter is in the system, the less gravitational pull it exerts, keeping the system steady.  Because our universe is expanding, the concentration of matter in space decreases, which in turn decreases the total gravitational pull on the system, causing the universe to expand faster.  This fact was discovered decades ago, and it has been the belief of some scientists that the universe will exist in an ever expanding state until the matter in it becomes so incredibly sparse, that it is impossible to distinguish any forms.  This is know as the big freeze. However, with the discovery of string theory, it is discovered that although the matter in the universe remains unchanging, different Planck string vibration frequencies could off-put gravitational pull constants, thus reversing the expansion of the universe.  Once the universe began its contraction, it would increase in speed until the matter became so dense, it ceased to exist in the matter form.  This is known as the big crunch.  This principle has been explored by recent cosmologists, and is favored by many.