What does the equivalent of an H-R diagram for galaxies, plotting luminosity versus color, show?
A) galaxies fill the diagram showing that there is no correlation between luminosity and color
B) two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies
C) a continuum from faint, blue galaxies to bright, red galaxies
D) a continuum from faint, red galaxies to bright, blue galaxies
E) a main sequence, just as for stars
B
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The Moon does not crash into Earth because
A) Earth's gravitational field is relatively weak at the Moon. B) gravitational pull of other planets keeps the Moon up. C) Moon has a sufficient tangential speed. D) Moon has less mass than Earth. E) none of the above
An advantage of synthetic detergents over soaps is that they
a. do not contain sulfur. b. dissolve grease. c. do not form scum in hard water. d. are more readily biodegradable.
Stress is
A) the strain per unit length. B) the same as force. C) the ratio of the change in length to the original length. D) applied force per cross-sectional area. E) the ratio of elastic modulus to strain.
The discovery of extrasolar planets indicates that planets around other stars are
A) all Earth-like B) nonexistent C) common D) relatively rare