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灰尘是人人讨厌的东西，它有碍环境?生，危害人体健康。因此，古往今来，人们总是「时时勤拂拭，勿使染尘埃。」然而你可曾想到，人类的生息离不开灰尘。假如自然界真的没有灰尘，我们将面临怎样的境地呢？
灰尘颗粒的直径一般在万分之一到百万分之一毫米之间。人眼能看到的灰尘，是灰尘中的庞然大物，细小的灰尘只有在高倍显微镜下才能看得见。灰尘的主要来源是土壤和岩石。它们经过风化作用后，分裂成细小的颗粒。这些颗粒和其它有机物颗粒一起在空中飘浮。它们在吸收太阳部分光线的同时向四周反射光线，如同无数个点光源。阳光经过灰尘的反射，强度大大削弱，因而变得柔和。假如大气中没有灰尘，强烈的阳光将使人无法睁开眼睛。
有趣的是，尘粒还有个「怪脾气」，容易反射光波较短的紫、蓝、青三色光，而「喜欢」吸收光波较长的其它色光。由於下层大气中的灰尘含量较高，我们在地面上看到的天空才是蔚蓝色的。假如大气中没有灰尘，天空将变成白茫茫的一片。
灰尘大多具有吸湿性能。空气中的水蒸气，必须依附在灰尘上，才能凝结成小水滴。这样，当空气中的水蒸气达到饱和时，分散的水汽便依附?灰尘而形成稳定的水滴，可以在空中长时间地飘浮。假如空气中没有灰尘，地面上的万物都将是湿漉漉的。更严重的是，天空不可能有云雾，也不可能形成雨、雪来调节气候，从地面上蒸发到上空的水也就不可能再回到地面上来。假如地球上的水越来越少，最后完全乾涸，生物就不能生存。此外，由於这些小水滴对阳光的折射作用，才会有晚霞朝晖、闲云迷雾、彩虹日晕等气象万千的自然景色。假如空气中没有灰尘，大自然将多 单调啊！
灰尘的作用告诉我们，任何事物都有它的两面性，即使是一些被人们看成是「废物」的东西，往往也有其不容忽视的存在价值。只有正确地认识它们，才能趋利避害，造福人类。

The dust is everyone hated things, it is the environment, endanger human body health?. Therefore, from ancient to modern times, people always" Fushi always ground, do not make to dye dust. " You may have thought, human interest is inseparable from the dust. If nature is really no dust, we will face what kind of situation?Dust particle diameter from 1/10000 to one millionth of a millimeter. The human eye can see the dust, dust in the huge monster, fine dust only under high power microscope can see. Dust is the main source of soil and rock. They pass through weathering, split into small particles. These particles and other organic matter particles with the floating in the air. They are part of the light absorption of the sun at the same time to the surrounding light reflection, as a point light source. Sunlight passes through the dust reflexes, strength is weakened greatly, so gentle. If the atmosphere without dust, strong sunlight will make people unable to open my eyes.Interestingly, dust has a " funny", likely reflecting light short purple, blue, three green light, and " love" absorption of light waves with longer other color. Due to the high content of dust in the atmosphere on the ground, we see the sky is blue. If the atmosphere without dust, the air will become a vast expanse of whiteness.Dust mostly with hygroscopic property. Water vapor in the air, must rely on dust, can condense into water droplets. In this way, when the water vapor in the air reaches saturation, water vapor and dust scattered attachment? Due to formation of stable water droplets in the air for a long time, can float. If the air contains no dust, the ground would be wet all. More serious is, the sky there can be no clouds, rain, snow or may be formed to regulate the climate, from the ground to the water evaporation over it will be impossible to return to the ground. If the earth is less and less water, finally completely dried up, organisms could not survive. In addition, because these small droplets of sunlight refraction effect, will have a sunset cloud, mist, rainbow sun Zhaohui, majestic and grand scenery. If the air contains no dust, nature will more monotonous!The role of dust tells us, everything has its two sides, even though some of it is considered" waste" thing, often also has its existence value can not be ignored. Only a correct understanding of them, in order to draw on the advantages and avoid disadvantages, the benefit of mankind.