Why does the Cepheid distance method fail us beyond about 20 Mpc?
A) The intergalactic dust reddens the Cepheid's light and apparent brightness.
B) Distant galaxies are younger than our Milky Way; too young to have Cepheids yet.
C) The periods of Cepheids grows longer as the distances increase.
D) Distant galaxies are seen in the past, and Cepheids evolve with time.
E) Even with the HST, the most luminous Cepheids are too faint to be seen beyond 20 Mpc.
E
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A. It moves toward the centerline. B. It moves away from the centerline. C. It doesn't change.
Acceleration: The captain orders his starship to accelerate from rest at a rate of "1 g" (1 g = 9.8 m/s2). How many days does it take the starship to reach 10% the speed of light? (Light travels at 3.0 × 108 m/s.)
Fill in the blank(s) with the appropriate word(s).
The ancient Greeks noted that the planets
A) kept step with the stars. B) were a reddish color. C) wandered around among the stars. D) moved in ellipses around the sun. E) Nonsense--the Greeks didn't know anything about the planets.
If the relative mass of a pingpong ball is 1/20 that of a golf ball, how many golf balls would you need to equal the mass of 200 pingpong balls?
A) 10 B) 200 C) 100 D) 20 E) 6.022 × 1023