英語四級的閱讀資料

　　篇1：The Source of Energy

　　A summary of the physical and chemical nature of life must begin, not on the Earth, but in the Sun; in fact, at the Sun’s very center.

　　It is here that is to be found the source of the energy that the Sun constantly pours out into space as light and heat. This energy is liberated at the center of the Sun as billions upon billions of nuclei of hydrogen atoms collide with each other and fuse together to form nuclei of helium, and in doing so, release some of the energy that is stored in the nuclei of atoms. The output of light and heat of the Sun requires that some 600 million tons of hydrogen be converted into helium in the Sun every second. This the Sun has been doing for several thousands of millions of years. The nuclear energy is released at the Sun’s center as high-energy gamma radiation, a form of electromagnetic radiation like light and radio waves, only of very much shorter wavelength. This gamma radiation is absorbed by atoms inside the Sun to be reemitted at slightly longer wavelengths. This radiation, in its turn is absorbed and reemitted. As the energy filters through the layers of the solar interior, it passes through the X-ray part of the spectrum eventually becoming light. At this stage, it has reached what we call the solar surface, and can escape into space without being absorbed further by solar atoms. A very small fraction of the Sun’s light and heat is emitted in such directions that after passing unhindered through interplanetary space, it hits the Earth.

　　能量的來源

　　概說生命的物理和化學(xué)特性必須始于太陽--確切地說，是太陽的核心，而非地球。 能量來自太陽的核心。

　　在這里，太陽不停地以光和熱的形式向空間傾瀉出能量。 數(shù)十億計(jì)的 氫原子核在太陽的核心碰撞并且聚變生成氦。 在此過程中一部分原本儲存于原子核中的能量被釋放出來。 太陽所產(chǎn)生的光和熱需要每秒將六億噸氫轉(zhuǎn)化為氦。 這樣的轉(zhuǎn)化在太陽中已經(jīng)持續(xù)幾十億年了。核能在太陽的核心被釋放為高能的伽馬射線。這是一種電磁射線， 就象光波和無線電波一樣，只是波長要短得多。這種伽瑪射線被太陽內(nèi)的??。 這新的射線再次被吸收，而后釋放。 在能量由太陽內(nèi)部一層層滲透出來的過程中，它經(jīng)過了光譜中 X 射線部分，最后變成了光。在此階段，能量到達(dá)我們所稱的太陽表層，并且離散到空間而不再被太陽原子所吸收。只有很小一部分 太陽的光和熱由此方向釋放出來，并且未被阻擋，穿越星空，來到地球。

　　篇2：Vision

　　Human vision like that of other pr mates has evolved in an arboreal environment. In the dense complex world of a tropical forest, it is more important to see well than to develop an acute sense of smell.

　　In the course of evolution members of the primate line have acquired large eyes while the snout has shrunk to give the eye an unimpeded view. Of mammals only humans and some primates enjoy color vision. The red flag is black to the bull. Horses live in a monochrome world Light visible to human eyes however occupies only a very narrow band in the whole electromagnetic spectrum. Ultraviolet rays are invisible to humans though ants and honeybees are sensitive to them. Humans have no direct perception of infrared rays unlike the rattlesnake which has receptors tuned into wavelengths longer than 0.7 micron. The world would look eerily different if human eyes were sensitive to infrared radiation. Then instead of the darkness of night, we would be able to move easily in a strange shadowless world where objects glowed with varying degrees of intensity.

　　But human eyes excel in other ways. They are in fact remarkably discerning in color gradation. The color sensitivity of normal human vision is rarely surpassed even by sophisticated technical devices.

　　視覺

　　人類的視覺，和其它靈長目動物的一樣，是在叢林環(huán)境中進(jìn)化出來的。在稠密、復(fù)雜 的熱帶叢林里，好的.視覺比靈敏的嗅覺更加重要。

　　在進(jìn)化過程中，靈長目動物的眼睛變大，同時鼻子變小以使視野不受阻礙。在哺乳類動物中，只有人和一些靈長目動物能夠分辨顏色。紅旗在公�？磥硎呛谏�的，馬則生活在一個單色的世界里。 然而，人眼可見的光在整個光譜中只占一個非常狹窄的頻段。人是看不到紫外線的，盡管螞蟻和蜜蜂可以感覺到。與 響尾蛇不同，人也不能直接感受到紅外線。響尾蛇的感覺器可以感受波長超過 0.7 微米的光線。如果人能感受到紅外線的話，這世界看上去將十分不同，而且恐怖。 到那時，將與夜的黑暗相反，我們能輕易地在一個奇異的沒有陰影的世界里走動。 任何物體都強(qiáng)弱不等 地閃著光。

　　然而，人眼在其它方面有優(yōu)越之處。事實(shí)上，人眼對顏色梯度具有非凡的分辨 能力。普通人類的視覺感受色彩的靈敏程度，甚至連精密的技術(shù)裝備都很難超越。

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