What is the function of the atmosphere?

I'm not qualified to answer if you're looking for a religious response, but if you're looking for an answer that focuses on the purposes that the properties of the atmosphere serve, then using the word "function" implies that it exists for a purpose, which is similar to asking what the function of a rock is—it has many properties that allow it to support life and to cause weather.

The atmosphere is the envelope of gases that surrounds the Earth and stays there because of Earth's gravity. It is separated into layers, or spheres, each of which has specific characteristics; the two most significant to humans are the troposphere and stratosphere.

The troposphere is the layer of the atmosphere that is closest to Earth and rises to a height of 28000 feet to 70000 feet, depending on the location and temperature of the Earth. This layer is extremely important to humans because it surrounds us, supplying oxygen, and is responsible for most of the weather, which is also the primary driver of the water cycle.

The next layer is the stratosphere (the layer that lies between the troposphere and the stratosphere is known as the Tropopause). The stratosphere is significant because, in addition to a few extreme weather events (such as hurricanes and massive thunderstorms that reach this height), it is home to a significant concentration of ozone, which blocks UV light, which can be extremely harmful to animal cells.

The Van Allen belts, which are magnetic bands that encircle the Earth and are separate from the atmosphere, block high energy particles like cosmic rays and solar wind, so it is erroneous to believe that the atmosphere shields humans from them.

The atmosphere serves several functions, including:

1. Providing oxygen for respiration
2. Absorbing and distributing solar radiation
3. Regulating temperature through the greenhouse effect
4. Protecting Earth's surface from harmful solar radiation
5. Facilitating the water cycle
6. Transporting and distributing heat and moisture around the globe.

The function of the atmosphere is to provide a protective layer around the Earth, regulating temperature, protecting life from harmful solar radiation, and facilitating weather and climate patterns through the circulation of air and moisture.