Atmosphere

Top of Atmosphere

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Solar system escape velocity vs surface temperature

Atmosphere refers to the layer of gases surrounding a planet or other celestial body that is held in place by the body's gravity. Earth's atmosphere is composed of a mixture of nitrogen (78%), oxygen (21%), argon (0.93%), carbon dioxide (0.04%), and trace amounts of other gases. It plays a crucial role in supporting life by providing oxygen for breathing, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night.

Composition

The Earth's atmosphere is divided into five main layers, from lowest to highest:

• Troposphere: The lowest layer of the atmosphere, where weather occurs and where the majority of the atmospheric water vapor exists. It extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles).
• Stratosphere: Located above the troposphere and extending up to about 50 kilometers (31 miles) above the Earth's surface. This layer contains the ozone layer, which absorbs and scatters the solar ultraviolet radiation.
• Mesosphere: Extends from the top of the stratosphere to about 85 kilometers (53 miles) above the Earth. It is where most meteors burn up upon entering the Earth's atmosphere.
• Thermosphere: Ranges from about 85 kilometers (53 miles) to 600 kilometers (372 miles) above the Earth. The auroras occur in this layer.
• Exosphere: The outermost layer of Earth's atmosphere, extending from the top of the thermosphere to about 10,000 kilometers (6,200 miles) into space.

Functions

The atmosphere has several key functions:

• Breathing: Provides oxygen for humans and animals, and carbon dioxide for plants during photosynthesis.
• Climate control: Acts as a medium for transporting moisture, distributing heat around the globe, and playing a significant role in the water cycle.
• Protection: Shields the Earth from harmful solar radiation and reduces the impact of meteoroids through ablation.

Atmospheric Pressure

Atmospheric pressure is the force per unit area exerted against a surface by the weight of the air above that surface in the atmosphere of Earth. It decreases with increasing altitude.

Climate and Weather

The atmosphere is integral to the Earth's climate and weather patterns. It absorbs energy from the sun, recycles water and other chemicals, and works with the Earth's magnetic fields to guide the planet's climate system.

Human Impact

Human activities, such as the burning of fossil fuels and deforestation, have significant impacts on the atmosphere. These activities increase the concentrations of greenhouse gases, leading to global warming and climate change.

Exploration and Study

The study of Earth's atmosphere and its processes is called meteorology. Scientists use various tools, including weather balloons, satellites, and radar, to study the atmosphere's dynamics and its effects on the Earth's environment.