Chapters Eight and Nine - The Origin of the Fate of the Universe & The Arrow of Time

The universe was first described be the "Big Bang model". This stated that as the universe expands, the radiation and temperature drop by half. By using this theory, scientists can say that at the beginning of time, the universe was thought to have zero size, and thus infinite heat. But as the universe expanded, the temperature of the radiation decreased. Within only a few hours of the big bang, helium production would have ceased, along with other elements. And after that, for the next ~ million years, the universe would have continued expanding without much of anything happening. Eventually, all that is left in the universe would condense and collapse.

Chapter nine describes the idea of time. Hawking explains that at one point, all believed that time was a concrete idea that flowed evenly for everyone. This theory remained popular until quantum theory proved it wrong. Research about the speed of light led to the belief that time flows differently for every body. The second law of thermodynamics proves that as time moves forward, chaos increases. The example Hawking uses is a cup sitting on a table. The cup, in perfect condition, is at a high level of order. If the cup were to fall to the ground and shatter, the cup would be a very low level of order. The cup can not be completely repaired to the order level it was prior to the fall and return to the same position on the table because time can not flow backwards.