Halley's Comet last passed Earth in 1986. It will be due back in: ...

[jilianpiloj]

Halley's Comet last passed Earth in 1986. It will be due back in:
 
  A) 2012.
  B) 2048.
  C) 2061.
  D) 2086.
  E) the twenty-third century.

Question 2

What factors would determine that we live in a matter-dominated universe?
 
  What will be an ideal response?

[Amiracle]

Answer to Question 1

C

Answer to Question 2

The density of matter can be approximately determined through observation; it's about 10-27 kg/m3. The microwave background (which is more abundant than starlight) can be converted into an equivalent amount of matter using E = mc2. The result is a density of 10-31 kg/m3. Since this is much lower than the matter density, we conclude we live in a matter dominated universe.

[jilianpiloj]

TY

[Amiracle]

You're welcome