Mastering Astronomy Chapter: 17 – Flashcards
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Notice that an observer located at the Local Raisin sees raisins 1, 2 and 3 all move away from her during the animation. But what would an observer located at Raisin 2 see? An observer located at Raisin 2 would find that __________.
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Raisin 1 and Raisin 3 both move away from her
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The table in the animation shows you the speeds of raisins 1, 2, and 3 as measured from the Local Raisin. Suppose instead you measured speeds as seen from Raisin 2. An observer at Raisin 2 would measure __________.
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Local Raisin speed = 4.0 cm/hr; Raisin 1 speed = 2.0 cm/hr; Raisin 3 speed = 2.0 cm/hr
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The following statements describe ways in which the analogy might apply to the real universe. Which statements are correct?
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~An observer at any raisin sees more distant raisins moving away faster, just as an observer in any galaxy sees more distant galaxies moving away faster. ~The raisins stay roughly the same size as the cake expands, just as galaxies stay roughly the same size as the universe expands. ~The average distance increases with time both between raisins in the cake and between galaxies in the universe.
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Deep surveys of the universe indicate that the largest structures in space are no larger than about 50 Mpc in size.
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True
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If the universe had an edge, that fact would violate the assumption of isotropy in the cosmological principle.
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False
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Hubble's law implies that the universe will expand forever.
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False
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The cosmological redshift is a direct measure of cosmic expansion.
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True
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The cosmic microwave background is the highly redshifted radiation of the early Big Bang.
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True
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Olbers's paradox is resolved by
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the finite age of the universe.
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The galactic distances used to measure the acceleration of the universe are determined by observations of
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exploding white dwarfs.
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The age of the universe is estimated to be
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greater than the age of the Milky Way Galaxy.
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Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as:
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the Cosmological Principle.
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The concept that the direction of observation does not matter overall is
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isotropy.
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The concept that on the grandest of scales, the universe is similar in appearance everywhere is
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homogeneity
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What does the Hubble law imply about the history of the universe?
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The universe had a beginning and has expanded since, giving it a finite age.
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In which of the following models will the universe stop expanding?
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Closed Universe
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The presently accepted value of the Hubble constant gives an age of
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14 billion years.
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What is the meaning of a "closed" universe?
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The universe will someday stop expanding and begin collapsing inward.
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If the density of the universe is greater than critical, then
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the universe is closed, gravity wins, and will shrink to the Big Crunch.
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The expansion rate of the Universe is
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increasing
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In the critical density universe now proposed, the ratio of dark energy to matter is about
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3 to 1
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What temperature has the Big Bang cooled to by now?
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Just over 2.7K
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The discovery of the cosmic microwave background was important because
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it was was experimental verification of a prediction from the Big Bang theory.
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Concerning dark energy, we do know
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its density remains constant over time, so it is not important in the early Universe.
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What key event happened during the decoupling epoch?
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expansion cooled the universe enough that protons could capture electrons in orbit.
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The cosmological redshift is a direct measure of the expansion of the universe, thus independent of direction.
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True
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The cosmological redshift is actually not a velocity at all, but a measure of the expansion of space-time.
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True
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The Big Bang was an expansion of matter into empty space.
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False
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The universe has been expanding at the same rate since its formation.
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False
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The cosmic microwave background is the total of all the radio emissions from all the galaxies and quasars in the universe.
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False
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Because almost all galaxies show redshifted spectra, we know that
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the universe is expanding.
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The darkness of the night sky in an infinite universe is addressed in
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Olbers's paradox.
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The redshift of the galaxies is correctly interpreted as
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space itself is expanding with time, so the photons are stretched while they travel through space.
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The latest studies from ________ led to the discovery of "dark energy."
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Type I supernovae at very large red shifts
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The Big Bang formed
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hydrogen and helium, but nothing else.
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Before the decoupling,
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the Universe was opaque to radiation.
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The 3 K background radiation represents
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the time of decoupling.
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In the Grand Unified Theory, the superforce was
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a union of the gravitational, strong and weak nuclear, and electromagnetic forces.
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The satellite that found the ripples in the cosmic background that led to galaxies is
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COBE
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In 1992, COBE observations revealed
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there are small ripples in the microwave background, the seeds of galaxies.
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The tiny ripples in the background radiation COBE found are due to
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a gravitational redshift caused by growing dark clumps.
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An infinite universe is a basic assumption of the cosmological principle.
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False
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The cosmological principle is the ultimate extension of the Copernican principle to the entire universe, in that there is no center at all.
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True
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Olbers's paradox seeks the explanation for why the night sky is dark.
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True
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Olber's Paradox is solved in part by the fact that the universe is not infinitely large nor infinitely old.
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True
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In the Big Bang model, two possible fates exist: expansion forever, or cosmic collapse.
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True
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Gravity alone is sufficient to halt the expansion of the universe.
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False
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The latest observations of distant Type I supernovae suggest the universe is slowing down more than we had expected.
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False
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Like dark matter, the newly-found dark energy will also retard the expansion of the universe.
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False
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The 3 K background radiation is just the redshifted gamma wavelength radiation of the decoupling.
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True
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Decoupling refers to the separation of matter and antimatter during inflation.
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False
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Primordial nucleosynthesis implies the Big Bang makes all elements up to iron.
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False
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Deuterium abundance suggests that normal matter makes up only 3-4% of the critical density.
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True
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The COBE data allow us to test the isotropy of the universe.
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True
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COBE found the cosmic microwave background to be absolutely uniform everywhere.
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False
