Black Hole silhouetted against the Milky Way Fall 2006 ASTR 2030 Homepage

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 clicker Fall 2006 ASTR 2030 Black Holes: Clicker Questions

    Wed 2006 Aug 30 (not graded):

  1. A black hole is:
    A. A pulsar.
    B. A quasar.
    C. A collapsed star.
    D. An object whose gravity is so strong that not even light can escape.
    E. Science fiction.

  2. The event horizon of a black hole is:
    A. The point from within which light cannot escape.
    B. The surface of a black hole.
    C. The entrance to a wormhole, which will transport you to another place and time.
    D. The center of the black hole, where the spacetime curvature becomes infinite.
    E. A place where space and time as we know them come to an end.

  3. The singularity of a black hole is:
    A. The point from within which light cannot escape.
    B. The surface of a black hole.
    C. The entrance to a wormhole, which will transport you to another place and time.
    D. The center of the black hole, where the spacetime curvature becomes infinite.
    E. A place where space and time as we know them come to an end.

  4. Will the probe fall into the black hole?
    A. Yes.
    B. No.

    Fri 2006 Sep 1 (not graded):

  5. Thorne names the black hole at the center of our Galaxy:
    A. Hades.
    B. Sagittario.
    C. Scorpio.
    D. Gargantua.
    E. He does not give it a name.

  6. How long does Thorne say that our journey to the center of the Milky Way, 30,000 lightyears distant, will take, from our point of view? We accelerate at one gee (one Earth gravity) for the first half of the journey, then decelerate at one gee for the second half.
    A. Almost no time.
    B. 20 years.
    C. 30,000 years.
    D. Much longer than 30,000 years.

  7. For what kinds of black holes do astronomers see evidence?
    A. Exploding mini-black holes.
    B. Stellar-sized black holes.
    C. Supermassive black holes at the centers of galaxies.
    D. The Universe as a whole is a black hole.
    E. Astronomers do not observe black holes at all.

  8. When you fall through the horizon of a black hole:
    A. The view of the outside world disappears, and you find yourself in darkness.
    B. The view of the outside world changes only slightly, and there is no clue that you have actually fallen through the horizon.

  9. If you fall into a black hole:
    A. Time will appear to slow to a halt as you enter the event horizon.
    B. You will die, torn apart by tidal forces.
    C. You will die, incinerated by intensely hot radiation.
    D. You will die, crushed at the central singularity.
    E. You will pass through a wormhole into another part of the Universe.

    Wed 2006 Sep 6:

  10. Which of these Black Holes is a real known Black Hole:
    A. Hades (10 Msun, near Vega);
    B. Sagittario (4 x 106 Msun, at the center of our Galaxy);
    C. Gargantua (15 x 1012 Msun, far, far away in the vicinity of the quasar 3C273;
    D. Orion binary (a pair of 24 Msun BHs, in the Orion nebula in our Galaxy);
    E. An exploding mini-black hole.

  11. The tidal force is the difference in the gravitational force between two parts of an object (e.g. between your head and your toes). The tidal force of a black hole will tear you apart:
    A. at the event horizon;
    B. somewhere inside the event horizon;
    C. at the singularity;
    D. inside the event horizon if the black hole has a stellar-size mass, or outside the horizon if the black hole is supermassive;
    E. outside the event horizon if the black hole has a stellar-size mass, or inside the horizon if the black hole is supermassive.

  12. Which of the following is not one of the 4 postulates of Special Relativity?
    A. Spacetime forms a 4-dimensional continuum.
    B. Globally inertial frames exist.
    C. The speed of light is a constant, the same in any inertial frame.
    D. The Principle of Relativity: spacetime has no absolute existence.
    E. Spacetime can be curved.

    Fri 2006 Sep 8:

  13. According to Thorne, what influence did the Michelson-Morley (1887) experiment have on Einstein's thinking?
    A. Michelson and Morley's failure to detect any difference in the speed of light in different directions suggested to Einstein that the speed of light is a universal constant;
    B. Michelson and Morley's failure to detect the motion of the Earth through the aether suggested to Einstein that there is no aether, no absolute space or time;
    C. It provoked Einstein to think about Maxwell's equations of electromagnetism, which showed that light is electromagnetic waves;
    D. Very little.

  14. Which of the following is an inertial frame?
    A. A frame with respect to which unaccelerated objects move in straight lines at constant velocity.
    B. A rotating frame.
    C. An accelerating frame.
    D. A frame with some weird Dahlian labeling of coordinates of space and time.
    E. The frame in which you are sitting right now.

  15. On this spacetime diagram, how fast is Cerulean moving relative to Vermilion, in units of the speed of light?
    A. 0 .
    B. 1/2 .
    C. 1 .
    D. 2 .
    E. The information on the diagram is insufficient to answer the question.

  16. Why is the lightcone on a spacetime diagram unchanged by a Lorentz transformation?
    A. Because light is a kind of particle.
    B. Because light is a kind of wave.
    C. Because the speed of light is constant.
    D. Because Vermilion, not Cerulean, emitted the light.
    E. Because spacetime is absolute.

    Mon 2006 Sep 11:

  17. If light is a wave, what is waving?
    A. Air.
    B. Aether.
    C. Vacuum.
    D. Electromagnetic fields.
    E. The speed of light.

  18. Would the light have moved differently if Cerulean had emitted the light? Why?
    A. Yes.
    B. No.

  19. Lorentz invented Lorentz transformations in 1904, and Poincaré invented the Principle of Relativity in 1904/5, both before Einstein 1905. Why then does Einstein get the credit for Special Relativity?
    A. Because history is unfair.
    B. Because Lorentz's and Poincaré's work contained errors.
    C. Because Einstein made the connection to the Michelson-Morley 1887 experiment.
    D. Because it was Einstein who said that the speed of light is constant.
    E. Because Einstein abolished the aether.

  20. Is this line a "now" line for the twin on the return journey?
    A. Yes.
    B. No.

  21. If an object moves at LESS than the speed of light, then on a spacetime diagram its worldline must:
    A. point vertically upward;
    B. point in some direction < 45° from vertically up;
    C. point at 45° from vertically up;
    D. point in some direction > 45° from vertically up;
    E. any of the above.

    Wed 2006 Sep 13:

  22. Lorentz, Poincaré, and Larmor all independently discovered, before Einstein 1905, that Maxwell's equations of electromagnetism were more beautiful if they transformed according to Lorentz transformations rather than classical Galilean transformations. What example does Thorne give of Maxwell's equations being more beautiful?
    A. There were fewer equations.
    B. They predicted that electric fields are produced by static charges, while magnetic fields are produced by moving charges.
    C. They predicted that light is electromagnetic waves.
    D. They predicted that the speed of light is constant.
    E. Magnetic fields lines have no ends, under any circumstances.

  23. In the animation showing a Lorentz transformation between Vermilion's and Cerulean's frames, what is changing as the animation proceeds?
    A. Space and time are changing.
    B. The coordinate system labeling space and time is changing.
    C. Vermilion and/or Cerulean are moving.
    D. We are moving.

  24. When we accelerate to relativistic velocities, the view ahead appears to shrink. Why?
    A. Because we are moving away from the scene ahead.
    B. Because of special relativistic aberration.
    C. Because acceleration curves space.

  25. If you travel through a scene at near the speed of light, clocks attached to the scene ahead appear:
    A. slowed down compared to your own clock;
    B. to run the same rate as your own clock.
    C. speeded up compared to your own clock.

    Fri 2006 Sep 15:

  26. On a spacetime diagram, the path of light (as seen for example through a telescope):
    A. points vertically upward;
    B. point in some direction < 45° from vertically up;
    C. points at exactly 45° from vertically up;
    D. point in some direction > 45° from vertically up;
    E. points horizontally.

    Mon 2006 Sep 18:

  27. What "breaks the symmetry" between you and your twin, that allows the twin to be younger than you on return?
    A. There is no difference, so in fact you must both age the same.
    B. Twin moved through space, whereas you did not.
    C. Twin accelerated (at Kant), whereas you did not.
    D. Twin experienced a sudden loss of time at Kant.

  28. If Earth time is 4 years, then the traveler's time is:
    A. 4 years;
    B. less than 4 years;
    C. more than 4 years.

  29. On your way out to Alpha Cen, you appear to me, watching you through a telescope on Earth, to move at what speed?
    A. 0;
    B. ½ c;
    C. Near c;
    D. 2 c;
    E. Near infinite speed.

  30. On your way back from Alpha Cen, you appear to me, watching you through a telescope on Earth, to move at what speed?
    A. 0;
    B. ½ c;
    C. Near c;
    D. 2 c;
    E. Near infinite speed.

    Wed 2006 Sep 20:

  31. Very Long Baseline Interferometry (VLBI) observations of the quasar 3C273 show blobs emerging at 8c. This indicates that:
    A. Special Relativity is wrong.
    B. The blob is not a parcel of matter, but rather a wave of brightness passing along the jet.
    C. The jet is pointed almost towards us, and is moving at close to c.
    D. The jet is pointed away from us, and is moving at close to c.
    E. The jet is moving faster than c.

  32. Why is a second jet not observed in 3C273?
    A. There is no second jet.
    B. Aberration bends the second jet out of view.
    C. The second jet is relativistically dimmed out of view.
    D. The second jet is relativistically redshifted out of view.
    E. The second jet is behind the quasar, which obscures it.

  33. A magazine is doing an article on the appearance of a scene seen at near the speed of light. The editor assigns you to take a photograph, which the magazine's special effects people will distort specially relativistically. What would you photograph? What kind of lens would you use? How would you compose the scene in the viewfinder?

    Mon 2006 Sep 25:

  34. For this stellar-sized black hole (30 solar masses), the gravitational tidal force will tear you apart:
    A. Well outside the horizon of the black hole;
    B. At the horizon of the black hole;
    C. At the Schwarzschild radius of the black hole;
    D. At a non-zero radius inside the horizon of the black hole;
    E. At the central singularity.

  35. If the probe falls through the horizon thinking that time goes by normally, then you, watching from outside, see the probe clock:
    A. tick at the same rate as your clock;
    B. slow to a halt at the horizon;
    C. speed up to an enormous rate at the horizon.

  36. As the probe approaches the horizon, photons emitted by the probe appear to you:
    A. slowed in frequency;
    B. speeded up in frequency;
    C. neither slowed nor speeded up in frequency.

    Wed 2006 Sep 27:

  37. After inventing SR, Einstein invented GR:
    A. In 1905, only a few months later;
    B. In 1907, after two years of concentrated labor;
    C. In 1915, after ten years of intermittent work;
    D. Over a period of several decades, up to nearly the end of his life in 1955;
    E. Actually it was Hilbert who first invented GR.

  38. According to the river model of black holes, a person who falls through the horizon of a black hole appears to an outside observer to freeze and become highly redshifted at the horizon because:
    A. the black hole freezes at its horizon, and never actually collapses;
    B. the person who falls through the horizon experiences time come to a halt;
    C. the curvature of space becomes infinite at the horizon;
    D. the closer to the horizon a photon is emitted, the longer the photon takes to forge against the inrushing torrent of space to reach an outside observer;
    E. it's not true: an outside observer sees the infaller become highly speeded up and blueshifted.

  39. If nothing can escape from a Black Hole, how can its gravity escape?
    A. Gravity is a curvature of space, and does not need to escape.
    B. A person outside the BH experiences the gravity of the matter that long ago collapsed to, or fell into, the BH.
    C. Gravity travels faster than light.

  40. The tidal force from a spherical Black Hole:
    A. Accelerates you towards the black hole;
    B. Allows you to remain in a stable or unstable orbit around the black hole;
    C. Crushes you in the radial direction, and stretches you in the transverse direction;
    D. Stretches you in the radial direction, and crushes you in the transverse direction;
    E. Pushes and pulls you in randomly varying directions.

    Fri 2006 Sep 29:

  41. According to Thorne Ch 2, an astronaut in outer space can detect that spacetime is curved from:
    A. Measuring the speed of light (with ruler, mirror, and clock);
    B. The presence of a gravitational force;
    C. The presence of a tidal force;
    D. Outer space is empty, so spacetime there must be flat, not curved;
    E. The Principle of Equivalence implies that the astronaut cannot detect that spacetime is curved.

    Mon 2006 Oct 3:

  42. According to Thorne Ch 3, Einstein rejected black holes because:
    A. Light could not escape from them;
    B. They would be redshifted out of existence;
    C. The curvature around them would be so strong that space would close up around them, and they would disappear;
    D. The black hole would not be able to resist the force of gravity, and would collapse;
    E. A black hole is a star somehow frozen at its Schwarzshild radius, which is impossible.

  43. The "No Hair" Theorem says that isolated Black Holes are characterized by:
    A. Luminosity and Temperature;
    B. Mass and Chemical Composition;
    C. Mass, Electric Charge, and Spin;
    D. Radius and Circumference;
    E. The number and type of singularities.

  44. The worldline of an object that moves faster than light (a hypothetical "tachyon") would be:
    A. Timelike
    B. Lightlike
    C. Spacelike
    D. Could be any of the above

    Wed 2006 Oct 5:

  45. In GR, an embedding diagram is:
    A. A kind of spacetime diagram.
    B. A diagram that illustrates the curvature of space by embedding the space inside a fictional higher-dimensional space.
    C. A diagram that illustrates that curved space must exist physically inside a higher-dimensional space.
    D. A diagram that illustrates how objects move in curved space.
    E. A diagram that illustrates the depth of the gravitational potential.

  46. Does the Schwarzschild geometry describe the geometry of empty space around the Sun?
    A. Yes, to a good approximation.
    B. No, not at all.

  47. If a star, when it collapses to a black hole, appears to all outside observers to freeze forever at its horizon, does it ever actually collapse?
    A. Yes.
    B. No.
    C. It depends on your frame of reference.

  48. When the mass of a black hole increases, its horizon expands. Does the horizon appear to engulf stuff that previously fell through the horizon?
    A. Yes, stuff that previously fell into the black hole disappears.
    B. No, stuff that previously fell into the black hole remains frozen at the horizon, appearing to expand with the horizon.

    Fri 2006 Oct 7:

  49. You are in flat space. You swing a clock on a rope in a circle around you, so that the clock is moving at near the speed of light relative to you. According to Special Relativity, the clock will appear to you to tick:
    A. Slow;
    B. At the same rate as your own clock;
    C. Fast;
    D. None of the above.

  50. In the situation of the previous question, the object therefore appears to you (according to Special Relativity):
    A. Redshifted;
    B. Neither redshifted nor blueshifted;
    C. Blueshifted.

  51. Standing on the surface of the Earth, you hold a negative mass object in your hand. According to the Principle of Equivalence, which way does the negative mass object fall when you drop it?
    A. Down to the floor;
    B. It justs hangs there in mid-air, falling neither down nor up;
    C. Up to the ceiling;
    D. None of the above.

  52. An observer and an emitter are at at rest in a uniform gravitational field, with the emitter lower in the field than the observer. According to the Principle of Equivalence, the situation is equivalent to one in which there is no gravitational field and the observer is:
    A. Accelerating away from the emitter;
    B. Not accelerating;
    C. Accelerating towards the emitter.

  53. In the situation of the previous question, the emitter therefore appears to the observer (according to Special Relativity):
    A. Redshifted;
    B. Neither redshifted nor blueshifted;
    C. Blueshifted.

    Mon 2006 Oct 9:

  54. The Principle of Equivalence is:
    A. E = m c2.
    B. Gravitational mass = inertial mass.
    C. Go to the free-fall frame; then the laws of physics are the same as for inertial frames.
    D. Gravitating frame = accelerating frame.
    E. Gravity = curvature of spacetime.

  55. What lies the other side of the horizon of a realistic astronomical (as opposed to idealized mathematical) black hole?
    A. A parallel universe.
    B. A wormhole.
    C. A white hole.
    D. Empty space surrounding a singularity.
    E. The remnant of the star that collapsed to the black hole.

    Wed 2006 Oct 11:

  56. According to Thorne Ch 2, an astronaut in outer space can detect that spacetime is curved from:
    A. Measuring the speed of light (with ruler, mirror, and clock);
    B. The presence of a gravitational force;
    C. The presence of a tidal force;
    D. Outer space is empty, so spacetime there must be flat, not curved;
    E. The Principle of Equivalence implies that the astronaut cannot detect that spacetime is curved.

    Mon 2006 Oct 16:

  57. What does the silence mean? (Referring to the first scene in "Contact".)
    A. Sound waves cannot go through space.
    B. Radio waves cannot go through space.
    C. Radio waves from Earth have not yet reached this distance.
    D. Radio waves from Earth are too faint to reach this distance.
    E. Radio waves from Earth are too redshifted to reach this distance.

  58. Ellie Arroway's boyfriend Palmer Joss turns out to be, professionally:
    A. A scientist.
    B. A journalist.
    C. A religious person.
    D. A multi-billionaire.
    E. A superhero.

    Wed 2006 Oct 18:

  59. What is wrong scientifically with this scene? (Referring to the first scene from WD's "The Black Hole".)
    A. The astronauts should be weightless.
    B. The astronauts should not be able to talk to each other, because sound cannot travel in space.
    C. The gravity should not shake the astronauts.
    D. The descriptions of black holes by the science officer are wrong.
    E. The dialog sucks.

  60. What is the best way to stop being pulled into the black hole?
    A. Fire rockets continuously.
    B. Invent anti-gravity (the movie solution).
    C. Go into orbit, rely on centrifugal force.
    D. Reduce the mass of the ship by throwing almost everything overboard.
    E. Fall into the black hole and get frozen at its horizon.

  61. Why does the dialog suck?
    A. Because the script writer cannot write.
    B. Because the hero is a black hole, not a character.
    C. Because there is no conflict between the characters.

    Mon 2006 Oct 30:

  62. A gamma-ray burst is thought to be produced by what cosmic event?
    A. The explosive evaporation of a mini-black hole by Hawking radiation.
    B. A star quake on the surface of a neutron star.
    C. The merger of two neutron stars, or of a neutron star with a black hole.
    D. The explosion of a massive star whose core collapses to a black hole.
    E. A white hole.

  63. What kind of pressure holds up a white dwarf star against its gravity?
    A. Atomic pressrure.
    B. Nuclear pressure.
    C. Gas pressure of a hot plasma.
    D. Electron degeneracy pressure.
    E. Neutron degeneracy pressure.

  64. Suppose you put an electron in a box and cooled the box to absolute zero temperature (in other words, removed as much energy as possible from the box). Would the electron:
    A. Stop moving?
    B. Have a small but finite velocity?

    Wed 2006 Nov 1:

  65. Suppose you made the box smaller (and kept it at absolute zero temperature). Would the electron:
    A. Remain at rest?
    B. Go slower?
    C. Go faster?
    D. Stay the same velocity?
    E. You could not make the box smaller.

  66. If you add 0.02 solar masses to a 1.39 solar mass white dwarf, then its radius will:
    A. decrease slightly;
    B. increase slightly;
    C. collapse to a neutron star;
    D. collapse to a black hole;
    E. explode.

    Mon 2006 Nov 6:

  67. Andrea Ghez was one of the astronomers featured on the Nova program "Monster of the Milky Way". What has Andrea Ghez been doing?
    A. She has been observing large numbers of stellar-sized black holes in the Milky Way.
    B. She has been discovering that almost every large galaxy has a supermassive black hole at its center.
    C. She has been following the orbits of stars around the black hole at the center of the Milky Way.
    D. She has observed gigantic jets from supermassive black holes, and their effect on the surrounding galaxy.
    E. She has been observing gamma-ray bursts and afterglows.

  68. The transition between atomic pressure and electron degeneracy pressure in cold matter at very high density occurs when:
    A. The matter is cooled to absolute zero temperature;
    B. The matter is heated to the point where the electrons are ionized;
    C. The electrons are compressed to the point where their velocities exceed the atomic velocity c/137;
    D. The electrons are compressed to the point where their velocities approach the speed of light c;
    E. The electrons and protons fuse into neutrons.

  69. The masses of neutron stars observed in x-ray binary systems are all consistent with 1.4 solar masses. What is the significance of this mass?
    A. It is the maximum mass of a white dwarf.
    B. It is the maximum mass of a neutron star.
    C. It is the minimum mass of a black hole.
    D. It is the maximum mass of a black hole.
    E. It is probably just a coincidence.

  70. What aspect of the curve of enclosed mass versus radius suggests that there is a large mass of small radius - a black hole, Sagittario - at the Galactic center?
    A. The enclosed mass goes to zero at zero radius.
    B. The enclosed mass increases with radius.
    C. The enclosed mass is constant with radius.
    D. The enclosed mass decreases with radius.
    E. The enclosed mass is very large.

    Wed 2006 Nov 8:

  71. The x-rays emitted from Cygnus X-1 come from:
    A. The main sequence star.
    B. A neutron star.
    C. A black hole.
    D. An accretion disk around the compact object.
    E. A jet.

  72. How do astronomers conclude that a compact object in an x-ray binary is a black hole, as opposed to a neutron star?
    A. More than 3 solar masses in a space smaller than a white dwarf.
    B. The compact object is black.
    C. The compact object shows gravitational lensing.
    D. There is no sign of a pulsar or of pulsations.

  73. What evidence most convincingly suggests that there is a supermassive black hole at the center of many galaxies, such as our own Milky Way, or M87 (the central galaxy of the Local Supercluster of galaxies)?
    A. The black hole causes gravitational lensing.
    B. The supermassive black hole is in an x-ray binary star system.
    C. Hubble Space Telescope observations show gas swirling down a vortex.
    D. A relativistic jet is coming out of the core of the galaxy.
    E. Measurements of the velocities of stars and gas at the center of the galaxy indicate a large mass in a small space.

    Fri 2006 Nov 10:

  74. The increase in enclosed mass at larger radii is probably caused by:
    A. The change in velocity of stars further from Sagittario.
    B. Tidal forces.
    C. Redshifting.
    D. The mass contributed by many stars.
    E. The increase in radius of stars further from Sagittario.

  75. What is a Penrose diagram in general relativity?
    A. A diagram that illustrates the curvature of space by embedding the space inside a fictional higher-dimensional space.
    B. A kind of spacetime diagram, in which the time and space coordinates are chosen so that light moves at 450.
    C. A diagram that illustrates relativistic beaming.
    D. A diagram that illustrates the Principle of Equivalence.
    E. Penrose is an artist whose illustrations are widely used in general relativity.

  76. Why is the Reissner-Nordström solution for the interior of an electrically charged black hole, which assumes that the black hole is empty of matter except at the singularity, inconsistent?
    A. Because a charged black hole would quickly neutralize itself.
    B. Because it contains a wormhole and white hole to a new universe.
    C. Because it predicts that a huge density of mass-energy collects at the inner horizon.
    D. Because it contains a naked singularity.
    E. Because it is gravitationally repulsive in its core, so that infalling matter and charge would not fall to the singularity, and the black hole would not be empty.

    Mon 2006 Nov 13:

  77. According to the text, what is Thorne's view on the existence of wormholes in our Universe?
    A. They are purely science fiction, nothing to do with real general relativity.
    B. They exist as mathematical mathematical solutions in general relativity, but not in reality.
    C. They very probably do not exist in reality, but we do not know for sure.
    D. They probably do exist in reality, though astronomers have never detected one.
    E. They probably do exist, and quasars probably indicate the presence of wormholes.

  78. Does the white hole in the Reissner-Nordström geometry (for a charged black hole) have positive or negative mass?
    A. Positive.
    B. Negative.

    Wed 2006 Nov 15:

  79. If you fall into a realistic black hole, how do you die?
    A. You are fried by x-rays from a disk or jet.
    B. You are tidally torn apart.
    C. You are vaporized by a relativistic plasma deep inside the black hole.
    D. Your spacetime ceases at a singularity.
    E. You don't necessarily die: you may go through a wormhole to another place and time.

  80. The fact that pulsars were observed to pulse at several different radio frequencies ruled out the possibility that pulsars were LGM (Little Green Men). Why?
    A. Because any signal from LGM would be too faint to be detectable.
    B. Because LGM would probably not use radio waves.
    C. Because LGM would emit only at a single narrow frequency.
    D. Because LGM would emit a complicated signal, not just pulses.
    E. Because the probability of LGM existing is tiny.

  81. What will happen when the electron-degenerate iron core of a massive star builds up to 1.4 solar masses?
    A. The iron will undergo fission into lighter elements.
    B. The iron will fuse to heavier elements.
    C. The iron core will collapse to a neutron star.
    D. The iron core will collapse to a black hole.
    E. The iron core will explode as a supernova.

    Mon 2006 Nov 27:

  82. The 2 principal stars of the Libra constellation are:
    A. Jupiter and Saturn.
    B. Sirius A and B.
    C. Antares and Aldebaran.
    D. Castor and Pollux.
    E. Zuben Es Chamali and Zuben El Genubi.

  83. Which slingshot trajectory around the moon will send the rocket furthest out in the solar system?
    A.
    B.

  84. A more massive black hole produces Hawking radiation with longer wavelength. Therefore a more massive black hole produces Hawking radiation that is _____ energetic, and therefore has a _____ Hawking temperature.
    A. Less, lower.
    B. More, lower.
    C. Less, higher.
    D. More, higher.
    E. None of the above.

    Wed 2006 Nov 29:

  85. What is a pulsar?
    A. A supernova.
    B. A vibrating white dwarf.
    C. A rotating neutron star with a strong magnetic field.
    D. An accretion disk around a black hole.
    E. A radio signal from extraterrestrials.

  86. The x-rays and gamma-rays associated with astronomical black holes such as Cygnus X-1, or the supermassive black hole in M87, are produced by:
    A. Hawking radiation from the black hole.
    B. A companion star.
    C. A supernova explosion.
    D. Matter in an accretion disk spiraling on to the black hole.
    E. A relativistic jet emerging from the vortex of an accretion disk.
  87. As regards their Hawking radiation, more massive (as opposed to less massive) black holes are:
    A. Hotter and brighter.
    B. Hotter and fainter.
    C. Colder and brighter.
    D. Colder and fainter.
    E. Black holes are black, and they do not emit any kind of radiation.

    Mon 2006 Dec 4:

  88. Hubble's law v = H0 relates what?
    A. The redshift of a photon to its wavelength.
    B. The rotation velocity of galaxies to their diameter.
    C. The recession velocity of galaxies to their distance.
    D. The curvature of the Universe to its diameter.
    E. The acceleration of the Universe to the gravitational force.

  89. Why is the Hubble constant H0 interesting in cosmology?
    A. Because its reciprocal provides an estimate of the age of the Universe, t = 1/H0.
    B. Because its reciprocal, times the speed of light, provides an estimate of the distance to the current horizon of the Universe.
    C. Because it measures the geometry of the Universe.
    D. Because it determines the fate of the Universe.
    E. Because it suggests that there was a Big Bang.

  90. What is the Universe expanding into?
    A. Into a higher spatial dimensional.
    B. It's not expanding into anything; it's as if space itself were expanding.
    C. It's expanding into an unknown region beyond our current horizon.
    D. The future.
    E. A white hole.

  91. Where is the center of the Universe?
    A. You are the center of the Universe.
    B. The center of the Milky Way.
    C. The M87 galaxy, at the center of the Local Supercluster of galaxies.
    D. There appears to be no spatial center of the Universe.
    E. The center of the Universe is the Big Bang event itself, at time zero.

    Wed 2006 Dec 6:

  92. What observational evidence suggests that the Universe is accelerating?
    A. The Hubble diagram of galaxies.
    B. The Hubble diagram of distant (high redshift) supernovae.
    C. The uniformity of the Cosmic Microwave Background.
    D. The black body (or Planck, or thermal) spectrum of the Cosmic Microwave Background.
    E. The ages of the oldest stars in the Milky Way.

  93. What observational evidence suggests that the Universe was once much simpler than it is today?
    A. The Hubble diagram of galaxies.
    B. The Hubble diagram of distant (high redshift) supernovae.
    C. The uniformity of the Cosmic Microwave Background.
    D. The black body (or Planck, or thermal) spectrum of the Cosmic Microwave Background.
    E. The ages of the oldest stars in the Milky Way.

  94. If the Universe doubles in size every 10-35 seconds, then approximately how long will it take to increase in size by a factor of 1030 (= 2100 approximately)?
    A. 10-33 seconds.
    B. 10-31 seconds.
    C. 10-4 seconds.
    D. 1 million years.
    E. 10 billion years.

 Black Hole silhouetted against the Milky Way Fall 2006 ASTR 2030 Homepage

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