Astronomy Part 2

Question 1

Explain that the ultimate fate of the universe depends on its density.

Answer 1

• Density of universe greater than ρ0: Gravitational forces eventually halt the expansion of matter and reverse the process towards a Big Crunch. The universe is closed.
• Density of universe less than ρ0: Gravitational forces cannot halt the expansion of matter. The universe expands forever. The universe is open.
• Density of universe = ρ0: The universe will expand forever but the rate of expansion tends towards zero after infinite time. The universe is flat.