Author Question: Briefly describe the four possible expansion patterns (or fates) of the universe. What will be an ... (Read 69 times)

P68T · **on:** Jul 27, 2018

Briefly describe the four possible expansion patterns (or fates) of the universe.

What will be an ideal response?

Question 2

Why isn't the Sun shrinking or expanding?

A) Because the Sun is spinning so fast, the centrifugal forces keep the surface of the Sun supported against collapse.
B) because gas pressure balances gravity in the Sun
C) because the Sun is solid
D) because the Sun has lived for billions of years

enass · **Reply #1 on:** Jul 27, 2018

Answer to Question 1

1. Re-collapsing universe: the density of the universe is greater than critical. Gravity will eventually reverse the expansion, resulting in a Big Crunch.
2. Critical universe: the density of the universe is equal to the critical density. Gravity just balances the expansion which slows toward zero as time progresses.
3. Coasting universe: the density of the universe is less than the critical density. The expansion overwhelms the attractive force of gravity and the universe expands without limit.
4. Accelerating universe: a mysterious repulsive force that acts against gravity on large scale causing the universe to expand with ever-increasing speed.

Answer to Question 2

B