Layers of the Atmosphere

While there is no sharp boundary where the atmosphere ends, it gradually thins out until it merges with space at approximately 10,000 km. However, most scientific and school textbooks define the outer limit of the detectable atmosphere (the exosphere) as extending to about 1,000 km above the Earth's surface.

Nitrogen is the most abundant gas in Earth's atmosphere, making up approximately 78% of dry air. Oxygen is the second most abundant at about 21%, while carbon dioxide and water vapor exist in much smaller amounts.

The thermosphere is the layer of the atmosphere directly above the mesosphere. The mesosphere ends and the thermosphere begins at an altitude of approximately 80 km (50 miles).

The ozone layer, located in the stratosphere, absorbs the majority of the Sun's harmful ultraviolet (UV) radiation. This protection is crucial for preventing skin cancer and other ecological damage on Earth.

Almost all weather, including cloud formation, occurs in the troposphere. This is because the troposphere contains about 99% of the atmosphere's water vapor.

The troposphere is the densest layer of the atmosphere, containing approximately 75% of the total mass of the atmosphere's gases. This high density is due to gravity pulling the air molecules closest to Earth's surface.

The stratosphere begins at the top of the troposphere, which is at an altitude of approximately 12 km (ranging from about 8 km at the poles to 18 km at the equator). The boundary between these two layers is called the tropopause.

Supersonic planes and Concorde-style aircraft often fly in the lower stratosphere. The air in this layer is extremely dry and thin, which reduces drag and allows for smoother, faster flights above the turbulent weather of the troposphere.

The exosphere is the outermost layer of Earth's atmosphere, where the air is extremely thin. Many artificial satellites orbit Earth within this layer because there is very little atmospheric drag.

The Northern Lights (aurora borealis) occur in the thermosphere. This layer contains highly charged particles that interact with solar wind, creating beautiful displays of light.

Weather balloons are launched into the troposphere but typically rise high into the stratosphere to collect atmospheric data. They can reach altitudes of up to 30 to 40 km before bursting.

The ozone layer is located in the stratosphere, roughly 15 to 35 km above Earth's surface. It contains high concentrations of ozone (O3) which absorb harmful ultraviolet radiation.

Shooting stars, or meteors, burn up in the mesosphere as they enter Earth's atmosphere. The friction with the gas molecules in this layer creates enough heat to vaporize the meteors, making them visible.

Humans and almost all other living organisms live in the troposphere, which is the lowest layer of Earth's atmosphere. This layer contains the air we breathe and is where all weather occurs.