One day I'll finish this book: Brian Greene's, The Fabric of the Cosmos. My first seven summaries were:
b. Spinning Space Buckets
c. Relativity and the Absolute
d. Particles Separated at Birth
e. Does time flow?
f. Does time have an arrow?
g. Quantum crazy
1. This chapter was about symmetry in the universe, and I found it much more enjoyable than the last two (maybe because I understood it better). Greene suggests that perhaps the most significant finding of modern science is that "Symmetry underlies the laws of the universe" (219).
You can move from here to there (translational symmetry). You can rotate (rotational symmetry). You can transport across the galaxy. The same laws work everywhere. You can move at a constant velocity and Einstein says the laws will work the same. You can accelerate, and Einstein's general relativity says the laws work the same. "Symmetries are the foundation from which laws spring" (225).
2. Time of course is not currently symmetrical. "The existence of time thus relies on the absence of a particular symmetry" (226).
But the cosmos is fantastically uniform on a large scale. Cosmic background radiation is amazingly uniform everywhere. This bespeaks 1) to the young universe being homogeneous and 2) to the development of the cosmos being nearly identical everywhere. It also suggests that time has generally elapsed the same everywhere in the universe as well.
The universe is expanding. Interestingly, the more distant the galaxy, the faster it is receding--and in every direction. The general consensus is that space itself is swelling. Space is getting bigger. Every point in the universe is moving away from every other point like pennies taped to a balloon you are blowing up. There is no center.
3. So if there were clocks taped to a universal balloon, they are all ticking the same, even though the expansion of space is causing them to move rapidly away from each other. They are not moving through space but space is "moving" between them. So some parts of the universe may seem to be moving faster than the speed of light, but it is rather a consequence of the space expanding between things.
The chapter also looks at the shape of space. It isn't really known, but an infinitely flat space is possible, perhaps even the leading contender according to Greene. Other possibilities are a spherical shape, a saddle shape, and a Pac Man flat screen where you leave one side and come back on the other.