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文章分析：

①Supernovas in the Milks Ways are the likeliest source for most of the cosmic rays reaching Earth. ②However, calculations show that supernovas cannot produce ultrahigh-energy cosmic rays (UHECRs), which have energies exceeding 1018 electron volts.?③It would seem sensible to seek the source of these in the universe’s most conspicuous energy factories: quasars and gamma-ray bursts billions of light-years away from Earth. ④But?UHECRs tend to collide with photons of the cosmic microwave background—pervasive radiation that is relic of the early universe. ⑤The odds favor a collision every 20 million light-years, each collision costing 20 percent of the cosmic ray’s energy. ⑥Consequently, no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHCERs.

①觀點v1，超新星可能是宇宙射線的來源

②轉(zhuǎn)折事實，但它能量不夠

③順承觀點v2，那就得去尋找那些億萬光年之外的能量來源

④轉(zhuǎn)折事實，但是這些射線是會和宇宙微波背景中的光子碰撞的

⑤順承事實，而且每兩百萬年碰撞一次，一次丟失20%的能量

⑥順承觀點， ×v2，因此超過一億光年就不是我們的目標了。

For the following question,consider each of the choices separately and select all that apply.

1. It can be?inferred?that the author of the passage would agree with which of the follow about the origin of UHECRs that reach Earth?

ABC

A. The origin is something other than supernovas in the?Milky Way.

B. The origin is most likely something other than very distant quasars?or gamma-ray bursts.

C. The origin is most likely no more than a little over 100 million light-years away from Earth.小于等于，不能超過一億光年太多。就不講人話體質(zhì)。

2. In the context of the author’s argument, the last sentence performs which of the following functions?

C

A. It explains a criterion that wasemployed?earlier?in the argument. 無關(guān)

B. It shows that an apparently plausible position is actually?self-contradictory. ?沒有證據(jù)

C. It is a conclusion drawn in the course of refuting a potential explanation.

D. It overturns an assumption onwhich an?opposing position?depends. 沒有證據(jù)

E. It states the main conclusionthat the author is seeking to establish. 作者并未明確表達觀點。不是作者要建立的結(jié)論，而是要反駁一種解釋。

補充同學(xué)對于B中self-contradictory的疑惑：

self-contradictory是自己給證據(jù)，但是觀點又不符合。問題是后面相反的證據(jù)是作者給的，這篇文章就是提供論證說明“尋找億萬年之外的來源”這個觀點本身不靠譜，不是在說原來觀點的達成過程有問題。

背景拓展：

Supernova 超新星，這個名詞是沃爾特·巴德和弗里茨·茲威基在1931年提出的：

A supernova is a powerful and luminous stellar explosion.

超新星是某些恒星在演化接近末期時經(jīng)歷的一種劇烈爆炸。這種爆炸都極其明亮，過程中所突發(fā)的電磁輻射經(jīng)常能夠照亮其所在的整個星系，并可能持續(xù)幾周至幾個月才會逐漸衰減。而在此期間，一顆超新星所釋放的輻射能量可以與太陽在其一生中輻射能量的總和相當。恒星通過爆炸可以將其大部分甚至幾乎所有物質(zhì)以高至十分之一光速的速度向外拋散，并向周圍的星際物質(zhì)輻射激波。這種激波會導(dǎo)致一個由膨脹的氣體和塵埃構(gòu)成的殼狀結(jié)構(gòu)形成，這被稱作超新星遺跡。超新星是星系引力波潛在的強大來源。初級宇宙射線中來自超新星的占了很大的比例。

cosmic rays 宇宙射線

宇宙射線，是來自外太空的帶電高能次原子粒子。

1912年，德國科學(xué)家韋克多·漢斯帶著電離室在乘氣球升空測定空氣電離度的實驗中，發(fā)現(xiàn)電離室內(nèi)的電流隨海拔升高而變大，從而認定電流是來自地球以外的一種穿透性極強的射線所產(chǎn)生的，于是有人為之取名為“宇宙射線”。

宇宙線大致可以分成兩類：原生和衍生宇宙線。來自太陽系外的天文物理產(chǎn)生的宇宙線是原宇宙線；這些原宇宙線會和星際物質(zhì)作用產(chǎn)生衍生（二次）宇宙線穿透地球的大氣層和表面。

主要的初級宇宙射線（來自深太空與大氣層撞擊的粒子）成分在地球上一般都是穩(wěn)定的粒子，像是質(zhì)子、原子核、或電子。但是，有非常少的比例是穩(wěn)定的反物質(zhì)粒子，像是正電子或反質(zhì)子，這剩余的小部分是研究的活躍領(lǐng)域。

大約89%的宇宙線是單純的質(zhì)子，10%是氦原子核（即α粒子），還有1%是重元素。這些原子核構(gòu)成宇宙線的99%。孤獨的電子（像是β粒子，雖然來源仍不清楚），構(gòu)成其余1%的絕大部分；γ射線和超高能中微子只占極小的一部分。

quasars and gamma-ray bursts 類星體和伽馬射線爆發(fā)

A quasar (/?kwe?zɑ?r/) (also known as a ?quasi-stellar object abbreviated QSO) is an extremely luminous active galactic nucleus (AGN), in which a supermassive black hole with mass ranging from millions to billions of times the mass of the Sun is surrounded by a gaseous accretion disk. As gas in the disk falls towards the black hole, energy is released in the form of electromagnetic radiation, which can be observed across the electromagnetic spectrum. The power radiated by quasars is enormous: the most powerful quasars have luminosities thousands of times greater than a galaxy such as the Milky Way.

In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several hours.

cosmic microwave background 宇宙微波背景

微波背景輻射是宇宙中“最古老的光”，就是大爆炸的遺跡，穿越了漫長的時間與空間后成為了微波，充盈在整個宇宙空間里。需要注意不要把“大爆炸”理解為一般意義上的爆炸，比如從一個點炸裂開來四散輻射，因為大爆炸并不是在某個空間中的一點發(fā)生的，是大爆炸創(chuàng)造了空間本身。在宇宙中，微波背景輻射是均勻的，來自各個方向都一樣，因此好比宇宙的“背景”。是來自宇宙空間背景上的各向同性的微波輻射，也稱為宇宙背景輻射。

The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from our galaxy was subtracted using the multi-frequency data.?

The cosmic microwave background (CMB, CMBR), in Big Bang cosmology, is electromagnetic radiation as a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination.?

With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. However, a sufficiently sensitive radio telescope shows a faint background noise, or glow, almost isotropic, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1964 by American radio astronomers Arno Penzias and Robert Wilson?was the culmination of work initiated in the 1940s, and earned the discoverers the 1978 Nobel Prize in Physics.?