Fall 2000 ASTR 1120-001 Quiz 4

Choose the single best answer and enter it on your scantron form. Be sure to fill in your name and student number.

1. A fundamental postulate of special relativity is:
   (a)�there exists an absolute time, the same for all observers; (b)�objects in a gravitational field fall at the same rate; (c)�light is both a particle and a wave; (d)�light diminishes as the inverse square of distance; (e)�the speed of light is the same for all observers.

2. Which of the following is not a consequence of Einstein's theory of special relativity:
   (a)�the uncertainty principle; (b)�E�=�m�c²; (c)�the speed of light is an absolute speed limit; (d)�time dilation; (e)�Lorentz contraction?

3. A friend in a racecar passes you at almost the speed of light. Relative to you, the light from the racecar's headlamps:
   (a)�moves hardly at all; (b)�moves at almost the speed of light; (c)�moves at the speed of light; (d)�moves almost twice the speed of light; (e)�moves almost four times the speed of light.

4. You are not normally aware of special relativistic effects because:
   (a)�you cannot see light; (b)�you are not near a black hole; (c)�you move at much less than the speed of light; (d)�of quantum mechanical effects; (e)�special relativity involves advanced mathematics.

5. If you traveled through the Galaxy at near the speed of light, the Galaxy would appear:
   (a)�normal, but moving by fast; (b)�relativistically beamed ahead of you; (c)�relativistically beamed behind you; (d)�concentrated in a thin ring perpendicular to the direction you are moving; (e)�invisible.

6. The superluminal (faster-than-light) motion observed in some cosmic jets indicates that:
   (a) special relativity is wrong; (b) the jet is moving faster than the speed of light; (c) the jet is moving towards us at almost the speed of light; (d) the jet is moving away from us at almost the speed of light; (e) the jet is falling into a black hole.

7. You watch a friend fall through the horizon of a 30 solar mass black hole. Which of the following is false? The friend appears:
   (a)�extremely redshifted at the horizon; (b)�to freeze to a halt at the horizon; (c)�to fall all the way to the central singularity; (d)�stretched by tidal forces; (e)�dead.

8. At the instant you pass through the horizon of a 10⁸ solar mass black hole, you observe that:
   (a) time has come to a halt (your watch has stopped); (b) all the future of the Universe passes before your eyes; (c) the Universe appears concentrated into an ever-diminishing patch of sky, which closes off entirely at the instant you pass inside, leaving you in blackness; (d) you are roasted by the Hawking radiation; (e) nothing special happened at the horizon.

9. The x-ray binary Cyg�X-1 contains an optically-observed massive blue main sequence primary in orbit with a compact companion. Astronomers believe that the compact companion is a black hole because:
   (a) it is ripping the primary to pieces; (b) its mass exceeds the maximum mass of a neutron star; (c) the Hubble Space Telescope reveals a black object at the center of the accretion disk; (d) the primary appears highly distorted; (e) the x-rays are so energetic.

10. Which of the following statements about wormholes is false:
    (a) wormholes connecting different Universes exist as mathematical solutions of general relativity; (b) the collapse of a star to a black hole produces a wormhole; (c) if a wormhole formed, it would be unstable and would fly apart rapidly; (d) a traveler could not pass through a wormhole; (e) to stabilize a wormhole would require negative mass at its throat.