Earth's atmosphere is made up of the layers of air that surround Earth. Thanks to the oxygen found in the atmosphere, humans and other organisms can breathe. Yet oxygen is not the only element in the atmosphere. The atmosphere is actually made up of around 78% nitrogen and 21% oxygen. The remaining 1% of the atmosphere contains several other gases. These include argon, carbon dioxide, water vapor, and ozone. The atmosphere has four major layers. The closest layer to Earth's surface is the troposphere. The troposphere extends from Earth's surface to about 8 to 15 kilometers above sea level. It contains most of the air and oxygen in the atmosphere, so all life on Earth exists here. The troposphere is also where most of Earth's weather occurs. The closer to the ground, the warmer the air is. Higher up in the troposphere, the air becomes much colder. The second layer of the atmosphere is the stratosphere. The stratosphere extends to around 50 kilometers above Earth's surface. Near the top of the stratosphere is the ozone layer. The ozone absorbs ultraviolet (UV) radiation from the sun. The ozone layer helps protect life on Earth's surface from the sun's harmful UV radiation. Unfortunately, there are holes in several parts of the ozone layer. This could have a negative effect on life on Earth. The third layer of the atmosphere is the mesosphere. It reaches up to around 80 kilometers
above Earth. The mesosphere has the coldest temperatures in the atmosphere. It can be as cold as –100°C there. The fourth layer is called the thermosphere. It reaches up to around 600 kilometers above Earth. This is where outer space begins. The International Space Station orbits the planet in this layer. The temperatures here are extremely high. They get up to 1,200°C.
地球的大氣由圍繞地球的氣層所組成，其中的氧使人類和其他生物得以呼吸。然而，氧氣並非大氣中唯一的元素，大氣含78% 的氮和21% 的氧，其餘1% 是其他氣體，包括氬、二氧化碳、水蒸氣和臭氧。 大氣可分為四個主要氣層，最接近地面的是「對流層」，範圍從地表到海平面上8 至15 公里。大氣層中的空氣和氧氣多集中在對流層，地球上的所有生命也都在此生活。地球上的天氣變化也多發生在對流層，越接近地面，氣溫越高，頂端的氣溫則相當低。 大氣的第二層叫做「平流層」，大約延伸到地表上方50 公里的高度。接近平流層頂端為臭氧層，可吸收太陽發出的紫外線。臭氧層幫助阻擋有害的太陽紫外線，以保護地表上的生物。不幸的是，臭氧層有幾處破洞，可能對地球上的生物造成負面影響。 大氣的第三層稱為「中氣層」，最遠離地面約80 公里，是大氣層中溫度最低的區域，可低至-100℃。 大氣的第四層叫做「熱成層」，最遠離地面約600 公里。是外太空的起點，國際太空站於本層環繞地球運行。熱成層的溫度特別高，可高達1,200℃。 | 
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