20140419阅读机经：
第一篇：
2012.12.2ML 宇宙理论
版本1:
一个big bang theory，一个ss theory。 Big bang有beginning,密度越来越小，ss无beginning无end，但有creation matter， 密度不变。
版本2：宇宙的两个理论，一个说物质会变化但总量不变，一个是会膨胀，最后说一个遥远的恒星的发现说明后一个理论更正确;
版本3：讲的是universe expanding 的两种理论，一个是density 在变小。
另一种是density 不变。因为不断new creation 补充变大的空间，然后发现了
一种q.它表明前一种理论更可信。
词汇：
expansion 膨胀
star 恒星
universe 宇宙
density 密度
creation 创造
space 空间
解析：
天文主题文章的词汇专业性较强，尽量减少生词恐惧带来的内耗。另外，出现理论对比的文章，结构比较清晰，但要着重识别对理论内容的态度倾向。比如这篇文章讲的就是在大爆炸理论盛行之前，有一种与之替换的稳定宇宙理论。但最后，还是大爆炸理论占了上风。
相关背景：
a. Big Bang
The Big Bang theory is the prevailing cosmological model for the early development of the universe. According to the theory, the Big Bang occurred approximately 13.82 billion years ago, which is thus considered the age of the universe. At this time, the universe was in an extremely hot and dense state and was expanding rapidly. After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, including protons, neutrons, and electrons. Though simple atomic nuclei formed within the first three minutes after the Big Bang, thousands of years passed before the first electrically neutral atoms formed. The majority of atoms that were produced by the Big Bang are hydrogen, along with helium and traces of lithium. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies, and the heavier elements were synthesized either within stars or during supernovae.
b. The steady state universe theory
In cosmology, the Steady State theory is a now-obsolete theory and model alternative to the Big Bang theory of the universe's origin (the standard cosmological model). In steady state views, new matter is continuously created as the universe expands, thus adhering to the perfect cosmological principle.
While the steady state model enjoyed some popularity in the first half of the 20th century, it is now rejected by the vast majority of professional cosmologists and other scientists, as the observational evidence points to a Big Bang-type cosmology and a finite age of the universe.
c. Big Bang or Steady State?
Creation of the Elements
The 1930s was more a decade of consolidation than of revolutionary advance in cosmology. And in the early 1940s, world war limited cosmological advance. But the war that temporarily absorbed scientific resources also promoted technologies that would lead to fundamental scientific advances.
Advances in nuclear physics helped transform cosmological speculations into quantitative calculations. This line of investigation, begun in the late 1940s, was at first pursued mainly by physicists, not astronomers. In the 1930s Georges Lemaître had suggested that the universe might have originated when a primeval "cosmic egg" exploded in a spectacular fireworks, creating an expanding universe. Now physicists found plausible numbers for the cosmic abundances of different elements that would be created in an initial cosmic explosion. But the theory of an initial cosmic explosion was soon challenged by a new hypothesis—that the universe might be in a steady state after all.
In 1946 the Ukrainian-born American physicist George Gamow considered how the early stage of an expanding universe would be a superhot stew of particles, and began to calculate what amounts of various chemical elements might be created under these conditions. Gamow was joined by Ralph Alpher, a graduate student at George Washington University, where Gamow taught, and by Robert Herman, an employee at the Johns Hopkins Applied Physics Laboratory, where Gamow consulted. Both Alpher and Herman were American-born sons of émigré Russian Jews.
Gamow assumed expansion and cooling of a universe from an initial state of nearly infinite density and temperature. In that state all matter would have been protons, neutrons, and electrons merging in an ocean of high energy radiation. Gamow and Alpher called this hypothetical mixture "Ylem" (from a medieval word for matter). Alpher made detailed calculations of nuclear processes in this early universe. For his calculations he used some of the first electronic digital computers—developed during the war for computing, among other things, conditions inside a nuclear bomb blast. It seemed that elements could be built up as a particle captured neutrons one by one, in a sort of "nuclear cooking."
The contribution of this theory was not to set forth a final solution but, no less important, to set forth a grand problem—what determined the cosmic abundance of the elements? Could the observed abundances be matched by calculations that applied the laws of physics to an early extremely hot dense phase of an expanding universe? Gamow did succeed in explaining the relative abundances of hydrogen and helium. Calculations roughly agreed with observations of stars—helium accounted for about a quarter of the mass of the universe and hydrogen accounted for nearly all the rest. However, attempts to make calculations for other elements failed to get a sensible answer for any element beyond helium. It seemed that piling more neutrons onto helium would hardly ever get you stable elements. Gamow joked that his theory should nevertheless be considered a success, since it did account for 99% of the matter in the universe.
Indeed his theory was not wrong but only incomplete. Astrophysicists soon realized that if the heavier elements were not formed during the hot origin of the universe, they might be formed later on, in the interiors of stars. The theory depended on a special property of carbon, which British astronomer Fred Hoyle measured and found as predicted. Cosmology had entered the laboratory.
The Steady-State Theory
Hoyle's triumph in explaining how most elements could be created in stellar interiors fell outside the theory in which elements were created at the very start. It was interpreted as favoring a rival theory. And Hoyle did favor a rival theory, which he had played a large part in inventing and developing. In this theory the universe had always looked much as it does now. There never had been a "big bang"—a phrase that Hoyle invented in 1950, intending the nickname as pejorative.
There is a charming story, not taken seriously by all historians, about how steady state theory began. The idea came in 1947, Hoyle claimed, when he and his fellow scientists Hermann Bondi and Tommy Gold went to a movie. The three knew each other from shared research on radar during World War II. Hoyle was versatile, undisciplined and intuitive; Bondi had a sharp and orderly mathematical mind; Gold's daring physical imagination opened new perspectives. The movie was a ghost story that ended the same way it started. This got the three scientists thinking about a universe that was unchanging yet dynamic. According to Hoyle, "One tends to think of unchanging situations as being necessarily static. What the ghost-story film did sharply for all three of us was to remove this wrong notion. One can have unchanging situations that are dynamic, as for instance a smoothly flowing river." But how could the universe always look the same if it was always expanding? It did not take them long to see a possible answer—matter was continuously being created. Thus new stars and galaxies could form to fill the space left behind as the old ones moved apart. (You can read Gamow's verse about this idea here.)
Drawings of an early and a later stage for two different models of an expanding universe. The left model obeys the cosmological principle, according to which the universe is homogenous and appears the same to an observer anywhere in the universe. The right model obeys the perfect cosmological principle, which adds to the cosmological principle the additional requirement that the universe be unchanged over time—new galaxies emerge continually within the expanding space.
To many philosophical minds, the steady-state universe proposed by Hoyle, Bondi and Gold had a major advantage over the big-bang expanding universe. In their universe the overall density was kept always the same by the continuous creation of matter. In the big-bang universe with its radically changing density, various physical laws might not apply the same way at all times. It would be impossible to extrapolate with confidence from the present back to the super-dense origin of the universe.
Steady-state theory also had an observational advantage over big-bang theory in 1948. The rate of expansion then observed, when calculated backward to an initial big bang, gave an age for the universe of only a few billion years—well below the known age of the solar system! That was certainly an embarrassment for the big bang theory.
For some time cosmologists had measured ideas against a "cosmological principle," which asserted that the large-scale properties of the universe are independent of the location of the observer. In other words, any theory that put we humans at some special place (like the center of the universe) could be rejected out of hand. Bondi and Gold insisted that the universe is not only homogenous in space but also in time—it looks the same at any place and at any time. They grandly called this the "perfect cosmological principle," and insisted that theory should be deduced from the axiom that we are not at any special place in either space or time.
Hoyle was less insistent that the perfect cosmological principle was a fundamental axiom. He preferred to have theory follow from a modification he proposed to Einstein's relativistic universe, adding the creation of matter. The two different steady-state theories had enough in common, however, to be considered one for most purposes.
Much of the later development of steady-state theory came in response to criticism. In Great Britain, especially, scientists gave considerable attention to elaborating the theory. Their arguments were largely of a philosophical nature, with little appeal to observation.
The cosmological debate acquired religious and political aspects. Pope Pious XII announced in 1952 that big-bang cosmology affirmed the notion of a transcendental creator and was in harmony with Christian dogma. Steady-state theory, denying any beginning or end to time, was in some minds loosely associated with atheism. Gamow even suggested steady-state theory was attached to the Communist Party line, although in fact Soviet astronomers rejected both steady-state and big-bang cosmologies as "idealistic" and unsound. Hoyle himself associated steady state theory with personal freedom and anti-communism.
Astronomers in the United States found the steady-state theory attractive, but they took a pragmatic approach. The rival claims of big-bang and steady-state theory must be settled by observational tests. One test involved the ages of galaxies. In a steady state, with continuous creation of matter, there would be a mixture of young and old galaxies throughout the universe. In a big bang, with only an initial creation, galaxies would age with time. And astronomers could look back in time by looking at more distant galaxies, for observing a galaxy a billion light-years away meant seeing it in light that had left it a billion years ago. Observations reported in 1948 purported to find that more distant galaxies were indeed older. Score one for the big bang. Bondi and Gold reviewed the data carefully, and in 1954 they showed that the reported effect was spurious. Score one for steady state. The age test might be able to distinguish between the rival theories in principle, but in practice it could not.
Another possible test involved the rate of expansion of the universe. In a big bang, the expansion rate would slow; in a steady state universe it would remain constant. Data from the Mount Wilson Observatory seemed to favor the big bang, but not certainly enough to constitute a crucial test.
Meanwhile there was a solution to the embarrassing calculation that put the age of a big-bang universe less than the age of the solar system. Walter Baade showed that estimates of the distances to galaxies had mixed together two different types of stars (as explained here). As a result, the size of the universe had been underestimated by about a factor of two. If galaxies were twice as distant as previously thought, then calculation with the observed rate of expansion gave an age of the universe twice as great as previously calculated — safely greater than the age of the solar system. That argument against the big-bang universe thus dissolved.
The most serious challenge to steady-state theory came from the new science of radio astronomy. Fundamental knowledge in the techniques of detecting faint radio astronomy signals advanced greatly during World War II, especially with research on radar and especially in England. After the war, research programs at Cambridge, at Manchester, and at Sydney, Australia, built radio telescopes to detect signals from outer space. They dominated radio astronomy for the next decade.
The program at Cambridge was led by Martin Ryle, who in 1974 would receive the Nobel Prize in physics for his overall contributions to radio astronomy. In 1951 Ryle believed that radio sources were located within our galaxy, and hence were of no cosmological interest. But over the next few years he became convinced that most of the radio sources he was detecting were extragalactic. His observations, then, could be used to test cosmological models. Ryle argued that his survey of almost 2,000 radio sources, completed in 1955, contradicted steady-state theory, because more distant/older sources seemed to be distributed differently from nearby ones. But he overstated the significance of his initial data. Only after more years of work would radio observations argue strongly against steady-state theory.#p#副标题#e#
第二篇：
版本一：水藻在海中的分布，作用以及影响水藻横纵分布的因素，主要讲一个颜色纵向分布。
版本二：Seaweeds，红algae深，绿algae浅。有个证据证明了红algae不能证明绿algae。
解析：本文主旨明确，结构清晰，围绕seaweed展开陈述。每段首句为topic sentence的可能性较高。做题时需注意记录笔记，对于结构化阅读及最后一题的解答有很大好处。
相关背景：
Seaweed, any red, green, or brown marine algae that grow on seashores. They are anchored to the sea bottom or to some solid structure by rootlike holdfasts that perform the sole function of attachment and do not extract nutrients as do the roots of higher plants.
Seaweeds often form dense growths on rocky shores or accumulations in shallow water. Many show a well-established zonation along the margins of the seas, where the depth of the water is 50 metres (about 165 feet) or less. The types of seaweed growing near the high-water mark, where plants are often exposed to air, differ from those growing at lower levels, where there is little or no exposure. Fucus, Macrocystis, Nereocystis, and Laminaria are widely distributed in colder zones and are absent from tropical waters.
Brown algae commonly found as seaweeds include kelps and Fucus. Among the kelps are the largest algae; certain species of Macrocystis and Nereocystis of the Pacific and Antarctic regions exceed 33 metres (100 feet) in length. Laminaria, another kelp, is abundant along both Pacific and Atlantic coasts. Gulfweed (Sargassum;) is common as free-floating masses in the Gulf Stream and the Sargasso Sea.
Red alga seaweeds include dulse (Rhodymenia), Gelidium, Chondrus, and laver (Porphyra). Various species of Chondrus (see Irish moss) carpet the lower half of the zone exposed at low tide along rocky coasts of the Atlantic.
Ulva species, commonly called sea lettuce, are among the relatively few green algal seaweeds.
Structure
Seaweeds' appearance somewhat resembles non-arboreal terrestrial plants.
· thallus: the algal body
· lamina or blade: a flattened structure that is somewhat leaf-like
· sorus: a spore cluster
· on Fucus, air bladder: a floatation-assisting organ on the blade
· on kelp, float: a floatation-assisting organ between the lamina and stipe
· stipe: a stem-like structure, may be absent
· holdfast: a specialized basal structure providing attachment to a surface, often a rock or another alga
· haptera: a finger-like extension of the holdfast anchoring to a benthic substrate
The stipe and blade are collectively known as the frond.
Ecology
Two specific environmental requirements dominate seaweed ecology. These are the presence of seawater (or at least brackish water) and the presence of light sufficient to drive photosynthesis. Another common requirement is a firm attachment point. As a result, seaweeds most commonly inhabit the littoral zone and within that zone more frequently on rocky shores than on sand or shingle. Seaweeds occupy a wide range of ecological niches. The highest elevation is only wetted by the tops of sea spray, the lowest is several meters deep. In some areas, littoral seaweeds can extend several miles out to sea. The limiting factor in such cases is sunlight availability. The deepest living seaweeds are some species of red algae.
A number of species such as Sargassum have adapted to a fully planktonic niche and are free-floating, depending on gas-filled sacs to maintain an acceptable depth.
Others have adapted to live in tidal rock pools. In this habitat seaweeds must withstand rapidly changing temperature andsalinity and even occasional drying.
附：本篇相关机经：Characteristics of seaweed plants
海草
第一段大概就在说这个海里面的东东和陆地植物有点不一样，但还是有叶绿素的，貌似还有其他神马的。。
第二段有图， 就讲这些东东要领队在在诸如石头啊什么的东西上面。说他们的类似于stem一类的东西可以达到35metres，(这里有题)还说因为这种植物不需要通过根部transportation，从ground里面吸收营养和水分，所以这个根部roots和一般的陆地植物根部不一样的(有题，问为什么他们不一样，有个选项是：因为他们不需要像leaves一样有运送水分和营养的功能，还有个选项说这个植物不需要ground的水分和营养)。。
第三段讲如果植物遇到storm的话，他们貌似会抓得更紧(有题：问遇到storm的时候这个哪门)。然后又讲说这个植物在某种情况下会die。
第四段说这个植物在海里的情况，说有三种颜色：green, blue, 和red。说是按深浅来的，只要在某Z的区域内，阳光都能照到，然后都可以活。
第五段讲这种植物可以给很多生物提供shelter。然后可以作为很多动物的food，还有一个功能，我也记不清了。然后下面有一道题问下列哪个不是这个植物可以为其他生物做的(有个选项貌似说是提供construction materials。我就选的这个。)
题目：
海草为什么会被 植物学家特别划分出来?因为它有叶绿素会进行光合作用;
为什么storm有可能造成海草死亡，因为它的根脱落。
海草跟陆上植物叶子或根作用有何不同?海草的叶子不储存水分(不确定)。
海草的根不吸收水份及营养。#p#副标题#e#
第三篇：
版本一：第三篇是鸟类的集群效应，他们怎么通过集群来保护自己的子嗣和其他的一些集体行为
版本二：Bird colony，提到parasite, cap鸟...
版本三：鸟把巢建在一起
有很多好处，例如某种鸟这样做的很成功：
1. 巢群建在岛上乱石中，防止哺乳动物来吃
2. 天敌来袭时集体抗争
3. 废弃的巢和在用的巢建在一起，以假乱真。还有利于后代存活，后代们一起被孵化，超过了天敌的需求，因此得以保存，还可以互相照看孩子。例如有种美洲的燕子，頟自到不同地方找食物，找不到的回来跟着找到的去，实现了信息共享。也有弊端，巢群外沿易受攻击，所以大家都往里面建巢，所以中心很拥挤，食物消耗也大，容易滋生寄生虫和疾病。
解析：动物行为主题是
相关背景：
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony. Colonial nesting birds include seabirds such as auks and albatrosses; wetland species such as herons; and a few passerines such as weaverbirds, certain blackbirds, and some swallows. A group of birds congregating for rest is called a communal roost. Evidence of colonial nesting has been found in non-neornithine birds (Enantiornithes), in sediments from the Late Cretaceous (Maastrichtian) of Romania.
Ecological functions
The habit of nesting in groups is believed to provide better survival against predators in several ways. Many colonies are situated in locations that are naturally free of predators. In other cases, the presence of many birds means there are more individuals available for defense. Also, synchronized breeding leads to such an abundance of offspring as to satiate predators.
For seabirds, colonies on islands have an obvious advantage over mainland colonies when it comes to protection from terrestrial predators. Other situations can also be found where bird colonies avoid predation. A study of Yellow-rumped Caciques in Peru found that the birds, which build enclosed, pouch-like nests in colonies of up to one hundred active nests, situate themselves near wasp nests, which provide some protection from tree-dwelling predators such as monkeys. When other birds came to rob the nests, the caciques would cooperatively defend the colony by mobbing the invader. Mobbing, clearly a group effort, is well-known behavior, not limited to colonial species; the more birds participating in the mobbing, the more effective it is at driving off the predator. Therefore, it has been theorized that the larger number of individuals available for vigilance and defense makes the colony a safer place for the individual birds nesting there. More pairs of eyes and ears are available to raise the alarm and rise to the occasion.
Another suggestion is that colonies act as information centers and birds that have not found good foraging sites are able to follow others, who have fared better, to find food. This makes sense for foragers because the food source is one that can be locally abundant. This hypothesis would explain why the Lesser Kestrel, which feeds on insects, breeds in colonies, while the related Common Kestrel, which feeds on larger prey, is not.
Colonial behavior has its costs as well. It has been noted that parasitism by haematozoa is higher in colonial birds and it has been suggested that blood parasites might have shaped adaptations such as larger organs in the immune system and life-history traits. Other costs include brood parasitism and competition for food and territory. Colony size is a factor in the ecological function of colony nesting. In a larger colony, increased competition for food can make it harder for parents to feed their chicks.
The benefits and drawbacks for birds of nesting in groups seem to be highly situational. Although scientists have hypothesized about the advantages of group nesting in terms of enabling group defensive behavior, escape from predation by being surrounded by neighbors (called the selfish herd hypothesis), as well as escaping predators through sheer numbers, in reality, each of these functions evidently depends on a number of factors. Clearly, there can be safety in numbers, but there is some doubt about whether it balances out against the tendency for conspicuous breeding colonies to attract predators, and some suggest that colonial breeding can actually make birds more vulnerable. At a Common Tern colony in Minnesota, a study of Spotted Sandpipers observed to nest near the tern colony showed that the sandpipers that nested nearest the colony seemed to gain some protection from mammalian predators, but avian predators were apparently attracted to the colony and the sandpipers nesting there were actually more vulnerable. In a study of a Least Tern colony in Connecticut, nocturnal avian predators in the form of Black-crowned Night Herons and Great Horned Owls were observed to repeatedly invade a colony, flying into the middle of the colony and meeting no resistance.
For seabirds, the location of colonies on islands, which are inaccessible to terrestrial predators, is an obvious advantage. Islands where terrestrial predators have arrived in the form of rats, cats, foxes, etc., have devastated island seabird colonies. One well-studied case of this phenomenon has been the effect on Common Murre colonies on islands in Alaska, where foxes were introduced for fur farming