GRE Verbal Reasoning practice: section 2 (harder)

Models of how stars evolve indicate that the young Sun was considerably dimmer than it is today: when Earth formed, the Sun probably gave off only about 70 percent of the energy it does now. Had Earth's atmosphere then been the same as it is today, the planet's surface would probably have stayed frozen for roughly its first two billion years. Yet the geological record holds ample evidence of liquid water early in that span, from sediments laid down in water to minerals that form only in its presence. This conflict, known as the faint young Sun paradox, has prompted a long list of proposed solutions.

The most widely favored explanations invoke a stronger greenhouse effect. Higher concentrations of carbon dioxide, perhaps supplemented by methane released by early microorganisms, could have trapped enough heat to offset the weaker sunlight. Such proposals gain plausibility from a feedback that operates over geological time: when the climate cools, the chemical weathering of silicate rocks, a process that draws carbon dioxide out of the atmosphere, slows down, so that carbon dioxide released by volcanoes accumulates and warms the planet again. The difficulty is one of quantity rather than principle. Some analyses of ancient soils have suggested carbon dioxide levels too low, on their own, to keep the oceans from freezing, which is one reason researchers have looked to methane and to other factors, such as a darker surface with less of the reflective continental area that exists today, to make up the difference. The paradox, in other words, may have no single solution, only a combination of partial ones.

On a small island, researchers found that songbirds nesting near the island's lighthouse began their dawn song, on average, about forty minutes earlier than birds of the same species nesting in the island's interior, which the lighthouse beam does not reach. The researchers concluded that artificial light from the lighthouse causes nearby birds to begin singing earlier.

Economic historians long told the story of eighteenth-century Europe's transformation from the supply side. New machines and new sources of power raised output, and rising output eventually raised living standards. The decisive changes, on this view, took place in workshops and mills, and consumption was their result rather than their cause. Households in this account are largely passive: they receive the benefits of industrialization only after the factories have been built. The idea of an "industrious revolution" — a term first coined to describe Tokugawa Japan and later adapted to northwestern Europe — reverses the emphasis. It proposes that, well before mechanization, many households chose to work longer and harder for the market, shifting effort away from home production and leisure, in order to buy goods they could not make themselves: sugar, tea, printed cottons, earthenware, clocks.

Part of the idea's appeal lies in what it explains. Real wages for many laborers in this period appear to have stagnated or even fallen, yet probate inventories — lists of possessions recorded at death — show ordinary households acquiring more and more modest consumer goods. If wage rates did not rise, the argument runs, households must have raised their incomes by supplying more labor: more days worked each year, and more family members, including women and children, earning wages. What drove them to do so, on this account, was the appeal of the new goods rather than the pressure of need. Demand, in this view, did not simply follow industrial growth; it helped call it forth.

Critics have pressed on two points. The first is evidential, and it concerns the extra labor itself. Estimates of working time before 1800 rest on scattered sources, such as court records in which witnesses mention what they were doing at a given hour, and such sources can show that people worked but rarely how much more they worked than their grandparents had. The second objection is conceptual. The thesis attributes the extra labor to households' desire for goods, but the same rise in work would be expected if households had simply grown poorer and were working harder merely to stay fed. Distinguishing ambition from necessity requires knowing not only that people worked more but why, and the motives of laboring families were seldom written down.

Defenders reply that the goods themselves are evidence of motive: households on the edge of subsistence do not buy teapots. The reply has force, but it may prove less than it seems, for small luxuries can be bought even by the very poor, precisely because they are small.