4.8-4.10 Cosmology

Graph showing the 3 possible fate of the universe:

Reference: Heinemann physics textbook

Definition of the 3 possible fates:

1. Open universe: open universe will continue to expand forever. Although gravity can slow down the rate of the expansion but it is not strong enough to stop the expansion completely

2. Closed Universe: this will continue to expand but will eventually collapse to its original self

3. Flat Universe: this is between the open and close universe. Gravity slows down the rate of expansion but will take an infinite time until it finally comes to rest

Define the Critical Density:

The critical density is the theoretical value of the density that creates a flat Universe.

Explanation of how the density of the universe relates to its fate in terms of the critical density

If the mass density were greater then the critical density then a closed universe would occur. 

If the critical density were greater than the mass density then an open universe would occur.