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A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire co_meta_ry orbit. Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles’ individual orbits are perturbed by planetary gravitational fields. A recent computer-modeling experiment tested this hypothesis by tracking the influence of planetary gravitation over a projected 5,000-year period on the positions of a group of hypothetical dust particles. In the model, the particles were randomly distributed throughout a computer simulation of the orbit of an actual meteor stream, the Geminid. The researcher found, as expected, that the computer-model stream broadened with time. Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream. Surprisingly, the computer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.
Whenever the Earth passes through a meteor stream, a meteor shower occurs. Moving at a little over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over a day to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled “pipe” and one as it exited. There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next.
Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 show just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.
The primary focus of the passage is on which of the following?
Comparing two scientific theories and contrasting the predictions that each would make concerning a natural phenomenon
Describing a new theoretical model and noting that it explains the nature of observations made of a particular natural phenomenon
Evaluating the results of a particular scientific experiment and suggesting further areas for research
Explaining how two different natural phenomena are related and demonstrating a way to measure them
Analyzing recent data derived from observations of an actual phenomenon and constructing a model to explain the data
Traditional social science models of class groups in the United States are _base_d on economic status and assume that women's economic status derives from association with men, typically fathers or husbands, and that women therefore have more compelling common interest with men of their own economic class than with women outside it. Some feminist social scientists, by contrast, have argued that the basic division in American society is instead _base_d on gender, and that the total female population, regardless of economic status, constitutes a distinct class. Social historian Mary Ryan, for example, has argued that in early-nineteenth-century America the identical legal status of working-class and middle-class free women outweighed the differences between women of these two classes: married women, regardless of their family's wealth, did essentially the same unpaid domestic work, and none could own property or vote.
Recently, though, other feminist analysts have questioned this model, examining ways in which the condition of working-class women differs from that of middle-class women as well as from that of working-class men. Ann Oakley notes, for example, that the gap between women of different economic classes widened in the late nineteenth century: most working-class women, who performed wage labor outside the home, were excluded from the emerging middle-class ideal of femininity centered around domesticity and volunteerism
Which of the following statements best characterizes the relationship between traditional social science models of class and Ryan's model, as described in the passage?
Ryan's model differs from the traditional models by making gender, rather than economic status, the determinant of women's class status.
The traditional social science models of class differ from Ryan's in their assumption that women are financially dependent on men.
Both Ryan's model of class and the traditional social science models assume that women work, either within the home or for pay.
The traditional social science models of class differ from Ryan's in that they focus on a different period of American history than Ryan's model does.
Both Ryan's model of class and the traditional models consider multiple factors, including wealth, marital status, and enfranchisement, in determining women's status.
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