Universe formation models
Cosmic Background radiation
The big bang theory is proven in many way and there is a lot of proof that leads right towards the big bang. One of these that scientists have discovered is cosmic background radiation. Cosmic background radiation is a weak radiation noise picked up by a radio antenna. This was discovered in 1995. They say that this most definitely supports the big bang theory because most likely this radiation came from the "hot stages" of the universe. The hot stages of our universe was when we were a single point, and all the pressure caused high heat and radiation.
This radiation is mapped by a Wilkinson Microwave Anisotropy Probe launched by NASA in 2001. The steady-state theory can't explain the the cosmic background radiation so astronomers lead more and more toward the big bang theory as the way our universe formed. Cosmic background radiation comes from all direction in the universe.
The critical density
The critical density or our universe decides the fate of our universe. There are three possible out comes to the way our universe could end up. These are a flat universe an open universe and a closed universe.
Flat Universe: A flat universe would mean that our universe would slow to a halt and stop expanding over an infinite amount of time.
Open Universe: An open universe would mean that our universe, over an infinite amount of time, would never stop expanding.
Closed Universe: A closed universe would mean that over time our universe would slow and stop expanding, then begin to contract.
Flat Universe: A flat universe would mean that our universe would slow to a halt and stop expanding over an infinite amount of time.
Open Universe: An open universe would mean that our universe, over an infinite amount of time, would never stop expanding.
Closed Universe: A closed universe would mean that over time our universe would slow and stop expanding, then begin to contract.
Critical Density: The critical density of our universe is compared to the average density to decide what kind of universe we have. The critical density is approximately 10^-26 kg/m^3. If the average density of our universe is equivalent to this, our universe is flat. If the average density is higher than the critical density the universe is closed. And lastly if the average density is lower than the critica density, the universe is open.