2

Set 5: Central Ideas (Advanced)

Explanation

Answer: C

PASSAGE

The following text discusses 'Dark Flow'. Dark Flow is a controversial astrophysical term describing a peculiar velocity component of galaxy clusters. Data from the WMAP satellite suggested that a large number of galaxy clusters are moving in a common direction at high speeds towards a region between the constellations of Centaurus and Hydra. This motion contradicts the standard model of cosmology, which predicts that matter should be distributed randomly. Some theorists propose this 'flow' is caused by the gravitational pull of mass structures outside our observable universe.

What potential explanation is offered for the phenomenon of Dark Flow?

A. A malfunctioning satellite sensor
B. The gravitational pull of mass outside the observable universe
C. The expansion of the universe slowing down✓ Correct
D. Black holes colliding in the center of the galaxy

Detailed Explanation

Choice B is correct. The text states: 'theorists propose this 'flow' is caused by the gravitational pull of mass structures outside our observable universe.'

Key Evidence:

• "gravitational pull of mass structures"

• "outside our observable universe"

Why others are wrong: A (Not mentioned (though text says 'controversial')), C (Not mentioned), D (Not mentioned).

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