ASTRO 142 Chapter Notes - Chapter 16: Grand Unified Theory, Particle Horizon, Event Horizon
Document Summary
Horizon is any surface that demarcates events that can be seen from those that cannot be seen. Event horizon is a light-like surface that divides space-time into two regions; that which can be observed, and that which cannot: the schwarzschild radius of a nonrotating black hole is an event horizon. Particle horizon is a surface beyond which we cannot see because the light from father objects has not had time to reach us over the age of the universe. This would require extreme fine tuning if the universe is not exactly flat. Why is structure the same everywhere even though different parts of the universe were not causally connected early in the big bang model. Relic problem is the problem in standard cosmology in which various theories of particle physics would invariably produce massive particles that are not observed: occurs because grand unified theories predict massive particles that are not observed.
