Q&A Hero

Q: If the density of the universe is greater than critical, then A) there is more matter than energy. B) the universe is closed, gravity wins, and will shrink to the Big Crunch. C) the universe is flat, and Euclid is right. D) the universe will continue expanding forever. E) the universe will end up as nothing but black holes.

Q: In the closed universe model, the geometry of spacetime in two dimensions resembles the surface of a A) flat piece of paper. B) saddle. C) cylinder. D) sphere. E) pyramid.

Q: What is the meaning of a "closed" universe? A) The universe will expand forever. B) The universe will someday stop expanding and start to collapse. C) The universe will stop expanding in an infinite amount of time. D) The universe is in a steady-state. E) The universe will disappear into a white hole in time.

Q: The presently accepted value of the Hubble constant gives an age of A) 4.5 billion years. B) 8-9 billion years. C) 14 billion years. D) 18 billion years. E) 22 billion years.

Q: If Ωo is less than one, then A) the universe is closed, and must recycle. B) the universe will expand forever. C) no matter could have existed. D) only dark energy exists in the universe. E) there is more matter than energy in the universe.

Q: With a Hubble constant of 70 km/sec/Mpc, the critical density would beA) 1.4 g/cc.B) 4 x 10-36 g/cc.C) 9 x 10-27 kg/m3.D) 6.23 x 10-23 g/mole.E) 3 x 10-31 g/cc.

Q: In which of the following models will the universe stop expanding? A) open universe B) closed universe C) critical density universe D) steady state universe E) All have an ultimate collapse.

Q: If the accepted value of H were to double, A) the age of the universe would be twice as old as we originally believed. B) the age of the universe would be half what we believed. C) the Copernican principle would not be valid beyond our solar system. D) the ages of the oldest globular clusters would be invalid. E) the critical density would be halved.

Q: What does Hubble's law imply about the history of the universe? A) The universe must be infinitely old and huge. B) The universe had a beginning and has expanded since, giving it a finite age. C) The Milky Way lies exactly at the center of this expansion. D) The redshifts will lengthen with time due to dark energy. E) The redshifts will turn to blueshifts as universe contraction follows the expansion.

Q: The redshift of the galaxies is correctly interpreted as A) a Doppler shift due to the random motions of galaxies in space. B) an aging of light as gravity weakens with time. C) space itself is expanding with time, so the photons are stretched while they travel through space. D) placing our Galaxy near the center of the Local Group. E) the differences in temperatures and star formation in old and young galaxies.

Q: The darkness of the night sky in an infinite universe is addressed in A) General Relativity. B) Special Relativity. C) Steady State Physics. D) Olbers's paradox. E) the Cosmological principle.

Q: If Euclid is right, then Ωo is A) zero. B) 0.3. C) 1.0. D) 2.0. E) infinite.

Q: Because almost all galaxies show redshifted spectra, we know that A) our understanding of redshift is wrong. B) we must be at the center of the universe. C) the universe is expanding. D) the sky must be dark at night. E) the universe is closed.

Q: The concept that on the grandest of scales, the universe is similar in appearance everywhere is A) special relativity. B) general relativity. C) homogeneity. D) isotropy. E) universality.

Q: The concept that the direction of observation does not matter overall is A) relativity. B) homogeneity. C) universality. D) isotropy. E) geometry.

Q: Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as A) Olbers's paradox. B) Hubble's law. C) Wien's law. D) the cosmological principle. E) the Grand Unified Theory.

Q: COBE found the cosmic microwave background to be absolutely uniform everywhere.

Q: In the cosmological principle, we can easily test cosmic homogeneity with the red shift surveys, but isotropy cannot be so tested.

Q: It appears that the universe is composed of nearly three times as much dark energy as normal and dark matter combined.

Q: The COBE satellite was designed to image the microwave cosmological background radiation and thus study the earliest stages of the universe.

Q: The COBE data allow us to test the isotropy of the universe.

Q: In the GUT, electromagnetism and the strong nuclear force are the last to appear.

Q: There is a superforce that separates into the electromagnetic, weak, and strong nuclear forces below a critical temperature.

Q: Cosmic inflation continues today in the cosmological red shifts and dark energy.

Q: The horizon problem relates to the isotropy of the microwave background radiation.

Q: How can close analysis of the spectra of quasars let us map the whole universe?

Q: Describe the large-scale structure revealed by the redshift surveys.

Q: What is believed to be the large-scale structure of the universe?

Q: While we know of thousands of quasars, it is likely none of them still exist today; explain.

Q: Why do spirals seem to be more abundant on the HST deep surveys than they are in the present universe?

Q: How can some mergers activate spirals, and others destroy them?

Q: Explain the process of small irregular galaxies evolving into spirals and giant ellipticals.

Q: Why would galaxies colliding in a small cluster tend to stick together, while galaxies in a large cluster tend to pass through each other?

Q: In the Local Group, how might even the Milky Way become a victim?

Q: Why is the Chandra X-ray Observatory critical to mapping intracluster gas?

Q: What direct evidence has been obtained for the existence of dark matter in galaxy clusters?

Q: How can the image of a single quasar be doubled? What does that tell us about the quasar's distance?

Q: What are redshift surveys designed to show?

Q: Relate black holes in the early galaxies to quasars.

Q: Why did the quasar epoch end?

Q: Why would spiral galaxies be less common now than in the early universe?

Q: To what three types of modern survivors can the masses of the protogalactic blobs be compared?

Q: In what way is the formation of a galaxy from a cloud the opposite of stellar formation?

Q: What is the anticipated interaction of the Milky Way and Large Magellanic cloud?

Q: What is the expected result from the merger of a large irregular and a small irregular galaxy?

Q: How do head-tail radio galaxies reveal their motion?

Q: Why do we believe galaxy clusters are rich in dark matter?

Q: Quasar ________ lines are an indication of intervening cooler gas.

Q: An example of the universe's large-scale filamentary structure is the ________.

Q: On a large scale, we find the universe to have voids and ________ structure.

Q: The huge, dark, almost spherical regions between the superclusters of galaxies are called ________.

Q: There is no obvious evidence for large-scale structure greater than about ________.

Q: The greatest gravitational lensing is produced by the ________ that lie in the centers of massive galaxies.

Q: The greater the mass of the foreground cluster of galaxies, the ________ the warping of the images of the distant galaxies behind it.

Q: The huge sheet of galaxies that spans 70 200 Mpc is called the ________.

Q: The process where some fraction of the quasar's enormous energy output is absorbed by the surrounding galactic gas is called ________.

Q: The greatest redshifts yet observed for quasars is about ________.

Q: The quasar epoch ended when the galactic merger rate ________.

Q: Quasars may result from the very energetic merging of ________ in condensing galaxies.

Q: Computer simulations of the early universe clearly show the process of ________ of smaller galaxies into larger ones.

Q: In Hubble's Tuning Fork, mergers drive the arrow of time to the ________.

Q: If there had never been any galactic collisions, all galaxies today would probably be ________.

Q: The result of a galactic merger depends on the ________ of each galaxy.

Q: Giant elliptical galaxies may be the result of ________ in the centers of rich clusters.

Q: The absorption or accretion of smaller galaxies into larger ones is called ________.

Q: According to our HST deep surveys, ________ galaxies are less common now than in the early universe.

Q: The seeds of protogalaxies were comparable in mass to the ________.

Q: The primary factor for galactic evolution is ________.

Q: From studies of the rotations of galaxies and dynamics of clusters, we now think that about ________ of the mass of the universe is composed of dark matter.

Q: Using binary galaxies to find their masses assumes that, like double stars, their orbits obey ________ laws of Planetary Motion.

Q: ________ images of galactic clusters reveal large amounts of hot, intracluster gas.

Q: The galaxies that reveal their motion through the intergalactic medium are called ________.

Q: In size and mass, irregular galaxies tend to be ________ than spirals.

Q: Clusters appear to have ________ dark matter than their individual galaxies.

Q: Some quasars show absorption spectra with a smaller redshift than their emission spectra. This indicates that A) we still don't understand redshifts. B) they are much closer than previously thought. C) there is cooler gas between us and the quasar. D) their black holes are still contracting. E) their black holes are still expanding.

Q: Redshift surveys give us A) an idea of how turbulent the intergalactic gas is. B) a 3-D layout of galaxies in space. C) the total mass of the universe. D) a more accurate census of the Local Group. E) a better value of the speed of light.

Q: Gravitational lensing of distant, faint irregular galaxies may be the key to A) mapping dark matter. B) quasar energy production. C) understanding galactic rotation curves. D) understanding active galactic nuclei. E) determining galactic redshifts.

Q: The largest presently known redshifts of quasars are close to A) 0.96. B) 3. C) 7. D) 10. E) 65.

Q: If the merger theory is correct, the brightest active galactic nuclei should A) be in the smallest elliptical galaxies. B) contain the youngest stars. C) contain the least mass. D) contain supermassive black holes. E) form small irregular galaxies.

Q: A galaxy that was once a quasar is likely to A) have burned all its fuel by now and be dark. B) now be a dwarf irregular. C) have a black hole at its nucleus. D) still be a quasar. E) be less than 5 billion years old.