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Years before the advent of plate tectonics―the widely accepted theory, developed in the mid-1960's, the holdsthat the major features of Earth's surface are created by the horizontal motions of Earth's outer shell, or lithosphere― a similar theory was rejected by the geological community. In 1912, Alfred Wegener proposed, in a widely debated theory that came to be called continental drift, that Earth's continents were mobile. To most geologists today, Wegener's The origin of Continents and Oceans appears an impressive and prescient document, containing several of the [hl:5]essential presumptions[/hl:5] underlying plate tectonics theory: the horizontal mobility of pieces of Earth's crust; the essential difference between oceanic and continental crust; and a causal connection between horizontal displacements and the formation of mountain chains. Yet despite the [hl:2]considerable overlap[/hl:2] between Wegener's concepts and the later widely embraced plate tectonics theory, and despite the fact that continental drift theory presented a possible solution to the problem of the origin of mountains at a time when existing explanations were seriously in doubt, in its day Wegener's theory was rejected by the vast majority of geologists.Most geologists and many historians today believe that Wegener's theory was rejected because of its lack of an adequate mechanical basis. Stephen Jay Gould, for example, argues that continental drift theory was rejected because it did not explain how continents could move through an apparently solid oceanic floor. However, as [hl:1]Anthony Hallam[/hl:1] has pointed out, many scientific phenomena, such as the ice ages, have been accepted before they could be fully explained. The most likely cause for the rejection of continental drift―a cause that has been largely ignored because we consider Wegener's theory to have been validated by the theory of plate tectonics―is the nature of the evidence that was put forward to support it. Most of Wegener's evidence consisted of homologies—similarities of patterns and forms based on direct observations of rocks in the field, supported by the use of hammers, hand lenses, and field notebooks. In contrast, the data supporting plate tectonics were impressively geophysical—instrumental determinations of the physical properties of Earth garnered through the use of seismographs, magnetometers, and computers.
(This passage was excerpted from material published in 1996.)When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a localdeficit of mass. This deficit shows up as a gravity anomaly: the removal of the material that has been ejected to make the hole results in an area of slightly lower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impact basins on the surface of Earth's Moon would show such negative gravity anomalies, since they are, essentially, large holes in the lunar surface. Yet data collected in 1994 by the Clementine spacecraft show that many of these lunar basins have no anomalously low gravity and some even have anomalously high gravity. [hl:1]Scientists[/hl:1] speculate that early in lunar history, when large impactors struck the Moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the Moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no low gravity anomaly in the resulting basin. Later, however, as the Moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such [hl:3]gravitational compensation[/hl:3] probably would not occur: the outer layer of the Moon is too cold and stiff.
Linda Kerber argued in the mid-1980's that after the American Revolution (1775-1783), an ideology of "republican motherhood" resulted in a surge of educational opportunities for women in the United States. Kerber maintained that the leaders of the new nation wanted women to be educated in order to raise politically virtuous sons. A virtuous citizenry was considered essential to the success of the country's republican form of government; virtue was to be instilled not only by churches and schools, but by families, where the mother's role was crucial. Thus, according to Kerber, motherhood became pivotal to the fate of the republic, providing justification for an unprecedented attention to female education.Introduction of the republican motherhood thesis dramatically changed historiography. Prior to Kerber's work, educational historians barely mentioned women and girls; Thomas Woody's 1929 work is the notable exception. Examining newspaper advertisements for academies, Woody found that educational opportunities increased for both girls and boys around 1750. Pointing to "An Essay on Woman" (1753) as reflecting a shift in view, Woody also claimed that practical education for females had many advocates before the Revolution. Woody's evidence challenges the notion that the Revolution changed attitudes regarding female education, although it may have accelerated earlier trends. Historians' reliance on Kerber's "republican motherhood" thesis may have obscured the presence of these trends, making it difficult to determine to what extent the Revolution really changed women's lives.
People's television-viewing habits could be monitored by having television sets, when on, send out low-level electromagnetic waves that are reflected back to the sets. The reflected waves could then be analyzed to determine how many persons are within the viewing area of the sets. Critics fear adverse health effects of such a monitoring system, but a proponent responds, "The average dose of radiation is less than one chest x-ray. As they watch, viewers won't feel a thing."Which of the following issues would it be most important to resolve in evaluating the dispute concerning the health effects of the proposed system?
PREP07 Test 1 For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6 ?
PREP2012 Contemporary cognitive scientists maintain that emotions, which are biological functions, evolved in the nervous system to help animals survive in hostile environments and procreate, and feelings are products of the conscious mind, reflecting the interpretation of emotions.
As the cost of wireless service has steadily dropped over the last year and as mobile phones have become increasingly common, many people are finding that they can avoid toll charges on their home phones, using their mobile phones for making long-distance calls at night or on weekends, at a time which many wireless companies provide unlimited airtime for a small monthly fee.
OG12 OG15 Warning that computers in the United States are not secure, the NationalAcademy of Sciences has urged the nation to revamp computer security procedures, institute new emergency response teams, creating a special nongovernment organization to take charge of computer security planning.
PREP07 Test 1 If n and m are positive integers, what is the remainder when $$3^{(4n+2+m)}$$ is divided by 10?(1)n=2(2)m=1
PREP07 Test 1 How many of the 42 people in a group are employed students？(1)29 of the 42 people are employed(2)24 of the 42 people are students
OG15 OG16 OG17 OG18 OG19 OG20 OG2022 Bengal-born writer, philosopher, and educator Rabindranath Tagore had the greatest admiration for Mohandas K. Gandhi the person and also as a politician, but Tagore had been skeptical of Gandhi's form of nationalism and his conservative opinions about India's cultural traditions.
PREP07 Test 1 A furniture dealer purchased a desk for $150 and then set the selling price equal to the purchase price plus a markup that was 40 percent of the selling price. if the dealder sold the desk at the selling price, what was the amount of dealer's gross profit from the purchase and the sale of the desk?
PREP07 Test 2 PREP08 Test 1 The primary purpose of the passage is to
The growth of the railroads led to the abolition of local times, which was determined by when the sun reached the observer's meridian and differing from city to city,and to the establishment of regional times.
In ancient Mesopotamia, prior to 2900 B.C., wheat was cultivated in considerable quantities, but After 2900B.C., production of that grain began to decline as the production of barly increased sharply.Some historians who study ancient Mesopotamia content that the decline in wheat production was due to excessive irrigation, lack of drainage, and the consequent accumulation of salt residues in the soil.Which one of the following, if true, most help to support the historian's contention concerning the reasons for the decline in wheat production in ancient Mesopotamia?
One pervasive theory explains the introduction of breakfast cereals in the early 1900s as a result of the growing number of automobiles, which led to a decline in horse ownership and a subsequent grain glut; by persuading people to eat what had previously been horse feed, market equilibrium was restored.
In the xy-plane, does the point (a, b) lie above the line y = x ?(1) a = 2(2) b = a + 2
Eco efficiency (measures to minimize environmental impact through the reduction or elimination of waste from production processes) has become a goal for companies worldwide, with many realizing significant cost savings from such innovations. Peter Senge and Goran Carstedt see this development as laudable but suggest that simply adopting eco efficiency innovations could actually worsen environmental stresses in the future. Such innovations reduce production waste but do not alter the number of products manufactured nor the waste generated from their use and discard; indeed, most companies invest in eco efficiency improvements in order to increase profits and growth. Moreover, there is no guarantee that increased economic growth from eco efficiency will come in similarly eco efficient ways, since in today's global markets, greater profits may be turned into investment capital that could easily be reinvested in old-style eco-inefficient industries. Even a vastly more eco efficient industrial system could, were it to grow much larger, generate more total waste and destroy more habitat and species than would a smaller, less eco efficient economy. Senge and Carstedt argue that to preserve the global environment and sustain economic growth, businesses must develop a new systemic approach that reduces total material use and total accumulated waste. Focusing exclusively on eco efficiency, which offers a compelling business case according to established thinking, may distract companies from pursuing radically different products and business models.
A recent study has provided clues to predator-prey dynamics in the late Pleistocene era. Researchers compared the number of tooth fractures in present-day carnivores with tooth fractures in carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Brea tar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher than those in the present-day species.In considering possible explanations for this finding, the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples. They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits. They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores—in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species.Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.
Archaeology as a profession faces two major problems. First, it is the poorest of the poor. Only paltry sums are available for excavating and even less is available for publishing the results and preserving the sites once excavated. Yet archaeologists deal with priceless objects every day. Second, there is the problem of illegal excavation, resulting in museum-quality pieces being sold to the highest bidder.I would like to make an outrageous suggestion that would at one stroke provide funds for archaeology and reduce the amount of illegal digging. I would propose that scientific archaeological expeditions and governmental authorities sell excavated artifacts on the open market. Such sales would provide substantial funds for the excavation and preservation of archaeological sites and the publication of results. At the same time, they would break the illegal excavator's grip on the market, thereby decreasing the inducement to engage in illegal activities.You might object that professionals excavate to acquire knowledge, not money. Moreover, ancient artifacts are part of our global cultural heritage, which should be available for all to appreciate, not sold to the highest bidder. I agree. Sell nothing that has unique artistic merit or scientific value. But, you might reply, everything that comes out of the ground has scientific value. Here we part company. Theoretically, you may be correct in claiming that every artifact has potential scientific value. Practically, you are wrong.I refer to the thousands of pottery vessels and ancient lamps that are essentially duplicates of one another. [hl:4]In one small excavation in Cyprus[/hl:4], archaeologists recently uncovered 2,000 virtually indistinguishable small jugs in a single courtyard. Even precious royal seal impressions known as l'melekh handles have been found in abundance —more than 4,000 examples so far.The basements of museums are simply not large enough to store the artifacts that are likely to be discovered in the future. There is not enough money even to catalog the finds; as a result, they cannot be found again and become as inaccessible as if they had never been discovered. Indeed, with the help of a computer, sold artifacts could be more accessible than are the pieces stored in bulging museum basements. Prior to sale, each could be photographed and the list of the purchasers could be maintained on the computer. A purchaser could even be required to agree to return the piece if it should become needed for scientific purposes.It would be unrealistic to suggest that illegal digging would stop if artifacts were sold on the open market. But the demand for the clandestine product would be substantially reduced. Who would want an unmarked pot when another was available whose provenance was known, and that was dated stratigraphically by the professional archaeologist who excavated it?