Consider this image that appears to show four identical galaxies arranged as a cross. What are we really seeing?
A) four galaxies that are nearly identical because they were born at about the same time
B) four images of a single background galaxy, created by the gravitational lens of a massive foreground galaxy or cluster
C) a large galaxy with four central masses that glow brightly
D) a picture taken with a poorly made telescope, so that a single large object appears as four fuzzy dots.
B) four images of a single background galaxy, created by the gravitational lens of a massive foreground galaxy or cluster
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The block that displaces the greatest volume of water when submerged is a
A) 1-kg block of aluminum. B) 1-kg block of iron. C) 1-kg block of lead. D) all the same
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a. 5.6 × 10^21 b. 7.5 × 10^21 c. 9.4 × 10^21 d. 1.1 × 10^21 e. 3.8 × 10^21