Plate tectonics states that
A) the continents move through Earth's crust like an icebreaker through ice.
B) earthquakes occur because tectonic plates break like a dropped dinner plate.
C) tectonic plates have not moved since Pangaea broke up.
D) tectonic plates are in slow, but constant motion.
Answer: D
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Atmospheric molecules do not fly off into outer space due to
A) their chaotic speeds. B) their relatively low densities. C) Earth gravitation. D) cohesive forces.
Which of the following is a principal advantage of CCDs over photographic film?
A) CCDs allow long exposures (e.g., minutes or hours), and film does not. B) CCDs can record the colors of astronomical objects accurately, while film cannot. C) CCDs capture a much higher percentage of the incoming photons than does film. D) Images recorded with CCDs never require any image processing, while images recorded by film often do. E) CCDs can be attached to modern telescopes more easily than cameras.
How do disk stars orbit the center of the galaxy?
A) They all orbit in roughly the same plane and in the same direction. B) They have orbits randomly inclined and in different directions relative to the galactic center. C) They follow spiral paths along the spiral arms. D) They follow orbits that move up and down through the disk, typically taking them about 50,000 light-years above and below the disk on each orbit.
The energy of a photon
a. is proportional to the wavelength of the light. b. is inversely proportional to the wavelength of the light. c. depends only on the speed of the light. d. depends only on the mass of the photon. e. depends on both the mass and speed of the photon.