Which is the warmest layer of the atmosphere?

Warmest layer of the atmosphere?

• This is a question on my science test. Would it be the troposphere or the thermosphere?

• Answer:

  It depends on what is meant by the "warmest" layer. The thermosphere normally has the highest "temperature" of the atmospheric layers, but not the highest amount of "heat". Those two terms are not interchangeable. Temperature is defined as simply the amount of energy contained in a given amount of material, be it solid, liquid or gas. Heat is both the amount of energy contained in a material PLUS how well it can be transferred to another object. See the difference? So while the thermosphere has a higher temperature (sometimes in excess of 1500 degrees C!), that part of the atmosphere is very very thin, thus there is not much heat. For example, if you stand in air that is 40 degrees F, you can keep fairly warm by moving around or with just a jacket. But if you jump into water that is 40 degrees F, it will feel much colder, and you will find it a lot harder to keep warm. Both have the same temperature, but the water is a much more effective transferrer of heat since it is denser than air. So it's a bit of a trick question. The word "warmest" would have to be defined. If it's heat, than the answer is the troposphere.