Elizabeth Jones

Physics 311

4/7/08

Book Review #3

The Fabric of the Cosmos

Brian Greene’s, The Fabric of the Cosmos is a drastic change from the previous novels read in this class. Greene uses this book to inform people of what is going on in theoretical physics and bring them up to date on many of the most enticing and debated advances, regardless of the amount of physics the reader knows. The M-theory (superstring theory) is his main focus. In order to make all the concepts and mathematics easier to understand he uses creative analogies, metaphors, illusions, and stories that make the situations interesting to picture. They really get the point across and make physics (what I normally think of as complex and confusing) seem slightly more simple. In anticipation that his book will have readers at all levels, Greene even provides brief summaries of more difficult sections for those who decided to skip or skim these parts, and a glossary at the back of the book so the reader can quickly reference terms they are not familiar with.

Greene attempts to answer and explain questions physicists have been struggling with for many years. Such questions as: Is space an entity? Why does time have a direction? Can we travel back in time? Could the universe exist without space and time? It is human nature to believe that reality is revealed to us by our experiences, but human experiences are often a misleading guide to the true nature of reality. Greene feels strongly about this issue of reality and so, “The central concern of this book is to explain some of the most prominent and pivotal of these revisions to our picture of reality, with an intense focus on those that affect our species long-term project to understand space and time” (pp. 5-6). The book often brings up famous historical physicists, Galileo Galilei, Sir Isaac Newton and Albert Einstein for example, and the discoveries and questions that have framed the thought of space and time for centuries.

Is space a human abstraction, and spacetime an Einsteinian abstraction? Or are these both physical entities? Greene discusses the inconsistencies and disagreements in the theories of Newton and March. Newton’s argument is that “even completely empty space still has space” vs. March’s argument that “In an otherwise empty universe, standing perfectly motionless and spinning uniformly are indistinguishable” (p. 35). This quite possibly could have caught Einstein’s attention and helped him along on his discoveries of the special theory of relativity and the general theory relativity. Einstein came to the conclusion that Newton was wrong in his thoughts on absolute space and absolute time. Newton believed that motion through time and motion through space were in no way connected to one another, but Einstein realized that they are linked. In his special theory of relativity Einstein discovered that “…the combined speed of any object’s motion through space and its motion through time is always precisely equal to the speed of light” (p. 49). Newton, March, and Einstein’s work (along with countless others) all plays a significant role helping to come up with answers to many long pondered physics questions.

I found the whole section based on time most interesting. From some of the oldest science fiction movies, all the way to current day shows, time travel and “time machines” have been a popular theme and dreamt about topic. Whether or not time travel is possible, and if so how we could potentially change the repeated future are some of the biggest inquiries of science still today. It is believed by many physicists that spacetime is a whole. This idea was developed by Einstein and means that the distinction between past, present and future is only an illusion. So, does time flow? There are no laws of physics that prove that time flows and in fact there are parts of the special theory of relativity that provide evidence that it does not flow. Greene gives examples of how time does flow and in a direction at that. One particular example is a glass of spilled milk. The milk can spill out of the glass but once its out it cannot recollect itself and put itself back into the glass. Therefore time flows forward. I believe that this is the natural assumption for most people, of course time flows, that’s what makes it time! I don’t think that Greene explained the theory that time doesn’t flow to a full extent. I still do know understand what is meant by this. Just like there is no evidence within physics laws that proves time flows, the arrow (direction) that we progress through time “…seems not to be found in the fundamental law of physics” either (p. 145). I had never given time a second thought before reading this. I guess it’s something most people just accept, like gravity. The fact is however, that gravity is much better understood than time is. There are laws of physics that prove gravity but nothing proves time. In physics, there is no distinction between the past and the future even though in our minds there obviously is.

The most difficult part of the book for me to follow was the explanation of the

string theory. This is when the more in-depth physics lost me a little bit. Because of this,

I mostly just skimmed this section trying to get a basic understanding of the theory and ignoring the talk of charges, spins and properties. What I got from it was that the only actual object in the string theory is the string. As a violin’s strings vibrate at different frequencies to produce different pitches, different vibrational patterns in the string theory correspond to different kinds of particles. Physicists know a lot about string theory, but it “…still lacks the kind of core principal we find at the heart of many other major advances”, and on top of that there are five different versions (p. 376). Einstein’s dream of a unification theory still lives on in many physicists. The goal is to find one theory that could embrace both quantum mechanics and general relativity.

Overall I really enjoyed this book because it brought up things that I have never thought about before and most likely never would have thought about on my own. I thought the analogies were helpful for the most part. There were some things that I still could not follow even with the help these provided but I think if he got a majority of the points across he did a pretty good job. I think this is a great book for people who are interested in basic level physics, but I would definitely not recommend it to everyone. I think if someone doesn’t have much interest in space they will find this book boring and unnecessary, but for someone interested in space and related subjects this is a very good source to help understand the basics.