ACT Reading Practice Natural Science

Which of the following statements best expresses the main idea of the passage?

• Bailin began studying the Sagittarius Dwarf when he was a graduate student in astronomy.

• The gravitational tidal forces of the Milky Way are destroying the Sagittarius Dwarf

• Most astronomers have come to an agreement that evidence about how galaxies have formed is, at best, circumstantial.

• Evidence suggests that the warp in the Milky Way's disk results from the Milky Way's interaction with a small satellite galaxy.

It can reasonably by inferred that the problem the author mentions in line 33 refers to:

• a particular aspect of Bailin's theory for which there is little evidence.

• a mathematical computation that led Bailin to focus on the Sagittarius Dwarf.

• the question of which physical processes caused the warp in the Milky Way.

• the potential impact of wobbly gyrations on the Milky Way's rotation.

It can reasonably be inferred from the passage that the small satellite galaxy referred to in lines 35-36 is:

• the Small Magellanic Cloud

• the Sagittarius Dwarf

• a known but yet unnamed galaxy

• a hypothetical galaxy that is believed to exist but has yet been found.

Based on the passage, which of the following statements best describes Bailin's study as it relates to the field of astronomy?

• It led astronomers to the discovery of a warp in the Milky Way's disk

• In convinced more astronomers to focus their attention on the center of the Milky Way

• It revealed problems with the basic assumptions held by most astronomers.

• It provided evidence for an idea that scientists had long considered a possibility by had not yet proved.

According to the passage, Bailin discovered that the angular momentum of the warped portion of the Milky Way and the angular momentum of the Sagittarius Dwarf are:

• identical in quantity but different in direction

• identical in direction but different in quantity

• identical in both quantity and direction

• different in both quantity and direction

According to the passage, the central bulge of the Milky Way is comprised of:

• 80% of the galaxy's stars

• older stars and a black hole

• a galactic plane and several dwarf planets

• a loose agglomeration of unidentified matter.

The author refers to the swirling pattern of a hurricane primarily in order to:

• help explain the shortcomings of the plum-and-pizza metaphor

• argue that the unpredictability of the rotation of spiral galaxies requires a new metaphor

• emphasize the particular aspects of the Milky Way that make it unique

• describe how the movement of the Milky Way creates gravitational tides.

The passage directly compares the Milky Way's disk as it is affected by its warp to:

• a pasta maker churning out spaghetti

• pizza dough being spun in the air by a chef.

• a thin-crust pizza balanced on top of a plum.

• two figure skaters coming together for a combination spin

According to the passage, which of the following statements best describes the movement of the Sagittarius Dwarf with respect to the Milky Way?

• It appears to be in a roughly polar orbit around the Milky Way

• It appears to orbit the Milky Way at an angle of roughly 45 degrees

• It follows the movement of the stars in the Milky Way's disk, though at a slightly faster rate

• It once followed the movement of the stars in the Milky Way's disk, but now seems to move more erratically along its own path.

The passage describes angular momentum as the amount of a system's:

• vertical deviation within an orbital path

• movement in a straight line through space

• gravitational pull

• spin or rotation