At what altitude does the thermosphere begin?

The thermosphere begins at an altitude of approximately 50 miles (or about 80 kilometers) above the Earth's surface. This layer of the atmosphere is characterized by a significant increase in temperature with altitude due to the absorption of high-energy solar radiation by a small number of gas particles. In the thermosphere, temperatures can soar to thousands of degrees Celsius, but this doesn't necessarily mean it would feel hot to a human because the density of particles is extremely low. This temperature increase is a result of the limited number of molecules that can absorb energy, leading to energetic collisions that raise thermal energy significantly.

Understanding the structure of the atmosphere is crucial for numerous fields, including aerospace and environmental science. The other altitudes mentioned represent different atmospheric layers: the troposphere extends up to about 8 to 15 miles, the stratosphere goes up to about 30 miles, and the mesosphere lies between the stratosphere and the thermosphere, encompassing altitudes that reach up to around 50 miles. This context helps clarify the position of the thermosphere within the entire atmospheric structure.