托福閱讀真題再現(xiàn)：

版本1:

文章先講太陽系里的東西都有相同的起源。先是說所有的東西是在一起的，然后說地球由于地表的水、火山活動和一個什么過程使得地球連較古老的石頭都沒有了。所以只能測定月球的隕石的成分了，結(jié)論是月球的表面和隕石的時間都是46億年。因為月球表面沒有地球的這些活動，所以可以測定。

后面又說宇宙的星系都在不斷地拉開距離，通過星系的紅移可以確定距離還有速度，發(fā)現(xiàn)宇宙一直在膨脹。發(fā)現(xiàn)宇宙在137億年前是一個點。然后就有了宇宙大爆炸。

版本2： 講地球和宇宙年齡的測量。先說太陽系大部分物質(zhì)是同一時間形成的，然后說地球年齡難是因為誰腐蝕。接著引入一種物質(zhì)，可以通過同位素測年齡。結(jié)果是和月球上的較古老的石頭近似。然后說宇宙在膨脹，大爆炸。通過紅移測年齡。

版本3： 天文類， 某種地球上的物質(zhì)和月球上較古老的物質(zhì)證明他。都始于自4.6million年前，于是證明太陽系的年齡是4.6 Million years. 另外還有種通過判斷各星球一種wavelength的大小推斷出他們在多少年前都是從個spot發(fā)展出來，于是判斷了big bang的時間。

托福閱讀相關(guān)詞匯：

origin 起源

meteorite 隕石

galaxy 星系

expansion 膨脹

red shift 紅移

wavelength 波長

解析：

天文主題文章的詞匯專業(yè)性較強，需要提前對相關(guān)專題的TPO文章的生詞熟悉，盡量減少生詞恐懼帶來的內(nèi)耗。另外，出現(xiàn)天文理論的文章，結(jié)構(gòu)通常都會比較清晰，但要著重識別對理論內(nèi)容的態(tài)度傾向。

托福閱讀相關(guān)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.Accelerating universe

The accelerating universe is the observation that the universe appears to be expanding at an increasing rate. In formal terms, this means that the cosmic scale factor has a positive second derivative,[1] so that the velocity at which a distant galaxy is receding from us should be continuously increasing with time. In 1998, observations of type Ia supernovae also suggested that the expansion of the universe has been accelerating since around redshift of z~0.5. The 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics were both awarded to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess, who in 1998 as leaders of the Supernova Cosmology Project (Perlmutter) and the High-Z Supernova Search Team (Schmidt and Riess) discovered the accelerating expansion of the Universe through observations of distant ("High-Z") supernovae.

observations.[edit]

The simplest evidence for accelerating expansion comes from the brightness/redshift relation for distant Type-Ia supernovae; these are very bright exploding white dwarfs, whose intrinsic luminosity can be determined from the shape of the light-curve. Repeated imaging of selected areas of sky is used to discover the supernovae, and then followup observations give their peak brightness and redshift. The peak brightness is then converted into a quantity known as luminosity distance (see distance measures in cosmology for details).

For supernovae at redshift less than around 0.1, or light travel time less than 10 percent of the age of the universe, this gives a nearly linear redshift/distance relation due to Hubble's law. At larger distances, since the expansion rate of the universe has generally changed over time, the distance/redshift relation deviates from linearity, and this deviation depends on how the expansion rate has changed over time. The full calculation requires integration of the Friedmann equation, but the sign of the deviation can be given as follows: the redshift directly gives the cosmic scale factor at the time the supernova exploded, for example a supernova with a measured redshift implies the Universe was of its present size when the supernova exploded. In an accelerating universe, the universe was expanding more slowly in the past than today, which means it took a longer time to expand from 2/3 to 1.0 times its present size compared to a non-accelerating universe. This results in a larger light-travel time, larger distance and fainter supernovae, which corresponds to the actual observations: when compared to nearby supernovae, supernovae at substantial redshifts 0.2 - 1.0 are observed to be fainter (more distant) than is allowed in any homogeneous non-accelerating model.

Corroboration[edit]

After the initial discovery in 1998, these observations were corroborated by several independent sources: the cosmic microwave background radiation and large scale structure, apparent size of baryon acoustic oscillations, age of the universe, as well as improved measurements of supernovae, X-ray properties of galaxy clusters and Observational H(z) Data.

Explanatory models[edit]

Models attempting to explain accelerating expansion include some form of dark energy, dark fluid or phantom energy. The most important property of dark energy is that it has negative pressure which is distributed relatively homogeneously in space. The simplest explanation for dark energy is that it is a cosmological constant or vacuum energy; this leads to the Lambda-CDM model, which has generally been known as the Standard Model of Cosmology from 2003 through the present, since it is the simplest model in good agreement with a variety of recent observations. Alternatively, some authors (e.g. Benoit-Lévy & Chardin, Hajdukovic, Villata) have argued that the universe expansion acceleration could be due to a repulsive gravitational interaction of antimatter.

Theories for the consequences to the universe[edit]

As the Universe expands, the density of radiation and ordinary and dark matter declines more quickly than the density of dark energy (see equation of state) and, eventually, dark energy dominates. Specifically, when the scale of the universe doubles, the density of matter is reduced by a factor of 8, but the density of dark energy is nearly unchanged (it is exactly constant if the dark energy is a cosmological constant).

Current observations indicate that the dark energy density is already greater than the mass-energy density of radiation and matter (including dark matter). In models where dark energy is a cosmological constant, the universe will expand exponentially with time from now on, coming closer and closer to a de Sitter spacetime. In this scenario the time it takes for the linear size scale of the universe to expand to double its size is approximately 11.4 billion years. Eventually all galaxies beyond our own local supercluster will redshift so far that it will become hard to detect them, and the distant universe will turn dark.

In other models, the density of dark energy changes with time. In quintessence models it decreases, but more slowly than the energy density in ordinary matter and radiation. In phantom energy models it increases with time, leading to a big rip.