Multiple Choice Questions

What is Einstein's cosmological constant?
  • a repulsive force that counteracts gravity and was introduced to allow for a static universe
  • a graph showing how orbital velocity depends on distance from the center for a spiral galaxy
  • White-dwarf supernovae are slightly dimmer than expected for a coasting universe.
  • All matter decays to a low-density sea of photons and subatomic particles.
T/F:Approximately 90 percent of the mass of the Milky Way is located in the halo of the galaxy in the form of dark matter.
  • True
  • False
Why can't the dark matter in galaxies be made of neutrinos?
  • It is a name given to whatever is causing the expansion of the universe to accelerate with time.
  • matter that we have identified from its gravitational effects but that we cannot see in any wavelength of light
  • Galaxies appear to be distributed in chains and sheets that surround great voids.
  • Neutrinos travel at extremely high speeds and can escape a galaxy's gravitational pull.
What is the evidence for an accelerating universe?
  • the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe.
  • Galaxies appear to be distributed in chains and sheets that surround great voids.
  • White-dwarf supernovae are slightly dimmer than expected for a coasting universe.
  • velocities of distant objects that are not caused by the expansion of the universe
What is the primary form of evidence that has led astronomers to conclude that the expansion of the universe is accelerating?
  • the expansion of the universe
  • observations of white dwarf supernovae
  • It consists of atoms or ions with nuclei made from protons and neutrons.
  • We construct its rotation curve by measuring Doppler shifts from gas clouds at different distances from the galaxy's center.
Imagine that it turns out that dark matter (not dark energy) is made up of an unstable form of matter that decays into photons or other forms of energy about 50 billion years from now. Based on current understanding, how would that affect the universe at that time?
  • there are different Doppler shifts among the individual stars in the galaxy.
  • The galaxies in clusters would begin to fly apart.
  • observations of white dwarf supernovae
  • the agent causing the universal expansion to accelerate
The text states that luminous matter in the Milky Way seems to be much like the tip of an iceberg. This refers to the idea that
  • Most dark matter probably consists of weakly interacting particles of a type that we have not yet identified.
  • Dark matter is the dominant form of mass in both clusters and in individual galaxies.
  • dark matter represents much more mass and extends much further from the galactic center than the visible stars of the Milky Way.
  • Yes, they tell us that dark matter is spread throughout the galaxy, with most located at large distances from the galactic center.
When we see that a spectral line of a galaxy is broadened, that is, spanning a range of wavelengths, we conclude that
  • Most dark matter probably consists of weakly interacting particles of a type that we have not yet identified.
  • measuring the temperatures of stars in the halos of the galaxies
  • They respond to the weak force but not to the electromagnetic force, which means they cannot emit light.
  • there are different Doppler shifts among the individual stars in the galaxy.
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Multiple Choice Questions
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