The Last Chapter - A Brief History of Time

Chapter 8: The origin and fate of the universe

1. Generally accepted history of the universe

   1. Singularity with extremely hot temperature and infinite mass

   2. Big bang

   3. Hydrogen and helium gas break up into smaller clouds, the atoms collide with one another, temperature increases until it is hot enough to convert H to He, stars like our sun are formed

2. Anthropic principle

   1. Weak AP: the universe is infinite in space and time, the conditions necessary for the development will only be met in certain regions limited in space-time

   2. Strong AP: there are many universes, each with its own initial configuration and its own laws of science ( perhaps)

3. Sum over histories

   1. A particle does not have just a single history, but it follows every possible paths in space-time

   2. The probability that a particle passes through some particular point is by adding up the waves associated with every possible history that pass through the point

4. Curved space-time represents the history of the whole universe

   1. Space-time may be like space of the earth, only with 2 more dimensions

   2. No boundaries or edge

   3. The real universe starts at the big bang ( north pole), and ends at the big crunch (south pole)

   4. The imaginary space-time acts the opposite