This diagram shows the structure of the Sun's interior. Two major regions inside the Sun, the convective zone and the radiative zone, are named for the way heat travels through them.
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Thermal Physics

Thermal physics is a field of science that deals with heat and temperature. When we study topics like global warming, the Earth's solid and liquid cores, and the way in which energy flows from the center of the Sun to its surface, we need to understand thermal physics.

Temperature is a familiar idea that is a big part of thermal physics. Three scales for measuring temperature are in common use: Fahrenheit, Celsius (or Centigrade), and Kelvin. The temperature of a gas is really a measure of the average speed with which molecules or atoms are hurtling about. We infer the temperatures of stars from their colors; hot stars are blue while cooler ones are red.

In our everyday speech, heat and temperature mean the same thing. In the language of thermal physics, the two terms have different meanings. Heat is the amount of thermal energy stored in an object. Heat can flow from one object to another, transferring energy in the process. The flow of heat can melt ice or warm the surfaces of planets near a star. The Laws of Thermodynamics describe the fundamental physics of heat and its flows.

Heat flows from hot places to cold ones, and often drives the motions of other materials. Convection and conduction are two common ways by which heat can flow. Electromagnetic radiation, especially at infrared wavelengths, can convey heat across a vacuum. We study heat flows to understand the circulation of ocean currents, the outflow of energy from the Sun, and the workings of rocket motors.

Last modified May 28, 2010 by Randy Russell.

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