In Ptolemy's theory, retrograde planetary motion is explained as
A) the backward part of the planet's loop-the-loop orbits around Earth.
B) due to the back-and-forth or "oscillatory" motion that planets make as they move along their circular orbits around Earth.
C) due to the natural wandering of the celestial sphere of background stars.
D) a result of Earth's motion: as Earth passes another planet, that planet appears to move backward as seen against the background stars.
E) Actually he didn't have an explanation for this.
A
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Comets with orbits that take them through the inner solar system shed sand- to pebble-size particles that then follow the comet around its orbit. How do these particles affect Earth?
A) They are the particles that produce meteor showers. B) They are the particles that produce the lights of auroras. C) They have been implicated in mass extinctions, including the extinction of the dinosaurs. D) On rare occasions, they can blanket our entire atmosphere with dust.
A mirror is rotated at an angle of 10° from its original position. How much is the rotation of the angle of reflection?
A) 10° B) 5° C) 15° D) 20° E) 40°
The kinetic energy of a pendulum is greatest
a. when its potential energy is greatest. b. at the top of its swing. c. at the bottom of its swing. d. when its total energy is greatest.
A faint white dwarf that temporarily increases in brightness as a consequence of nuclear explosions on its surface is termed
a. a nova. b. a Type II supernova. c. a bright nebula. d. a red giant.