1
.
What are the basic observations about the universe that any theory of cosmology
must explain?
A basic observation that any cosmology theory must explain is the idea of an expanding
universe.
2
.
Describe some possible futures for the universe that scientists have come up with.
What property of the universe determines which of these possibilities is the correct one?
The current ratio for mass-energy density measured today has brought scientists to the
conclusion that the universe will continue expanding for all eternity at an accelerating
rate.
3
.
What does the term Hubble time mean in cosmology, and what is the current best
calculation for the Hubble time?
Hubble time indicates how old the universe is, which is currently about 15 billion years.
4
.
Which formed first: hydrogen nuclei or hydrogen atoms? Explain the sequence of
events that led to each.
Hydrogen atoms were unable to form at first considering how cold the universe was, so
hydrogen nuclei formed first.
7
.
Why do astronomers believe there must be dark matter that is not in the form of
atoms with protons and neutrons?
The material they have labeled as “dark matter” is an area whose gravity moves at
speeds very different from any other form of matter they have studied before and has
been thought to contain particles different than neutrons and protons.
