The leading explanation for the existence of spiral arms is
A) shock waves from cyclic supernovae explosions.
B) shock wave from the quasar-like eruption of the Galactic core.
C) passages of spiral density waves through the interstellar medium.
D) passages of massive globular clusters through the Galactic plane.
E) tidal streams of small galaxies being torn up by our monster Galaxy.
C
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A ball is thrown straight up with an initial speed of 30 m/s. What is its speed after 4.2 s?
A. 72 m/s B. 42 m/s C. 30 m/s D. 11 m/s
What is cosmic background radiation evidence for?
a. Dark matter. b. Dark energy. c. The Big Bang theory. d. The theory of relativity. e. Neutrino oscillations.
Significant Figures: What is the difference between 103.5 and 102.24 expressed to the correct number of significant figures?
A. 1.3 B. 1.26 C. 1.260 D. 1.2600
Spectral type, surface temperature, and color all describe the same basic characteristic of a star
Indicate whether the statement is true or false