Online Quiz


1	Why do astronomers believe the Universe is expanding?
		A)	They see a redshift in the spectral lines of distant galaxies.
		B)	They can see the disks of galaxies getting smaller over time.
		C)	They can see distant galaxies dissolve, pulled apart by the expansion of space.
		D)	All of the above.


2	What is the cosmic horizon?
		A)	The place where the Big Bang occurred.
		B)	The average distance between galaxies.
		C)	The maximum distance that light can travel in the Universe's age.
		D)	The diameter of the Universe.


3	If the Universe is infinitely large, infinitely old, and expanding, the night sky should be bright. But in fact it is not. What do we call this?
		A)	The Einstein Anomaly.
		B)	Olbers Paradox
		C)	The Hubble Law.
		D)	The Neutrino Discrepancy.


4	What is the cosmic microwave background?
		A)	It is radio noise from Seyfert galaxies.
		B)	It is radiation from hot gas in intergalactic space.
		C)	It is radiation from the first stars formed when the Universe was young.
		D)	It is background noise from radiation created in the young Universe.


5	Why do astronomers believe the early Universe was hot and dense?
		A)	They detect intense x-ray emission from gas in galaxy clusters.
		B)	The amount of helium in stars implies that the early Universe was hot enough to fuse some hydrogen into helium.
		C)	They detect cosmic gamma-ray background radiation.
		D)	It is the only way inflation could have occurred.


6	How do astronomers estimate the approximate age of the Universe?
		A)	It is equal to the Hubble constant (H).
		B)	Age = 1/H
		C)	Age = 10/H
		D)	It is not possible to calculate the age of the Universe.


7	Where did helium come from the early Universe?
		A)	The early Universe was so hot and dense that fusion of protons (hydrogen) into helium could occur.
		B)	Helium was formed in the cores of stars formed in the early Universe.
		C)	Photons bombarded hydrogen atoms and broke them up into helium atoms.
		D)	Helium was not formed in the early Universe, because only neutrons were present.


8	The Big Bang theory can explain
		A)	The expansion of the Universe.
		B)	The cosmic background radiation.
		C)	The amount of helium in the Universe.
		D)	All of the above.


9	What is inflation all about in cosmology? This is the idea that
		A)	The force of gravity suddenly grew stronger in the distant past.
		B)	The Universe increased dramatically in size in an extremely brief period of time.
		C)	The number of galaxies we see at large distances is greater than the number we can see near us.
		D)	The diameters of distant galaxies are much greater than those of galaxies near us.


10	Which Big Bang “flaws” does the inflationary model resolve?
		A)	The energy of expansion is almost exactly equal to the collective gravitational force between galaxies.
		B)	The Universe is all ordinary matter with almost no antimatter.
		C)	The cosmic background radiation is smooth, but the distribution of matter in the Universe is lumpy.
		D)	All of the above.


11	What is critical density?
		A)	The density of the Universe.
		B)	The density of the most massive black hole in the Universe.
		C)	The density required for the Universe to be closed.
		D)	None of the above.


12	If its density is less than the critical density, then a universe is
		A)	open.
		B)	closed.
		C)	flat.
		D)	young.


13	What does it mean if we say the Universe is “open”?
		A)	It has positive curvature.
		B)	It will expand forever.
		C)	Its density is greater than the critical density.
		D)	Its total energy is negative


14	Approximately how long after the Big Bang did proto-galaxies form?
		A)	10 min.
		B)	1 million years (10⁶ years)
		C)	1 billion years (10⁹ years)
		D)	10 billion years (10¹⁰ years)


15	In a GUT (Grand Unified Theory), what is “unified”?
		A)	Matter.
		B)	The fundamental forces.
		C)	Galaxies.
		D)	Subatomic particles.

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