Chapter 16 Quiz
1.
What do we mean by dark matter and dark energy?
Dark matter” is the name given to the
unseen mass whose gravity governs the observed motions of stars and gas clouds.
“Dark energy” is the name given to whatever might be causing the expansion of
the universe to accelerate
2.
What is the evidence for dark matter in
galaxies?
Rotation curves of galaxies are flat,
indicating that most of their matter lies outside their visible regions.
3.
What is the evidence for dark matter in clusters
of galaxies?
Masses measured from galaxy motions,
temperature of hot gas, and gravitational lensing all indicate that the vast
majority of matter in clusters is dark
4.
Does dark matter really exist?
Either dark matter exists or our
understanding of our gravity must be revised
5.
What might dark matter be made of?
There does not seem to be enough normal
(baryonic) matter to account for all the dark matter, so most astronomers
suspect that dark matter is made of (non-baryonic) particles that have not yet
been discovered
6.
What is the role of dark matter in galaxy
formation?
The gravity of dark matter seems to be what
drew gas together into protogalactic clouds, initiating the process of galaxy
formation
7.
What are the largest structures in the universe?
Galaxies appear to be distributed in
gigantic chains and sheets that surround great voids
8.
Will the universe continue expanding forever?
Current measurements indicate that there is
not enough dark matter to prevent the universe from expanding forever
9.
Is the expansion of the universe accelerating?
An accelerating universe is the best
explanation for the distances we measure when using white dwarf supernovae as
standard candles
10. Who
discovered this acceleration?
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