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. Click on image for full size (239K GIF) Image courtesy NASA.

The scientific field of thermal physics is concerned with heat, temperature, and related issues. When we delve into topics such as global warming, the structure of Earth's solid and liquid cores, and the way in which energy flows from the center of the Sun to its surface, we need an understanding of thermal physics.

Temperature is a familiar concept that is a cornerstone of thermal physics. Three scales for measuring temperature are in common use: Fahrenheit, Celsius (or Centigrade), and Kelvin. The temperature of a gas is actually 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. The temperatures we encounter in the study of astronomical objects are extreme by Earthly standards, ranging from millions of degrees in the centers of stars to hundreds of degrees below zero on icy moons.

In our everyday speech, heat and temperature are nearly synonymous. In the language of thermal physics, the two terms have precise and quite different meanings. Heat is essentially the amount of thermal energy stored within an object; one must add much more heat to an ocean to raise its temperature one degree than to raise the temperature of a bucket of water the same amount. Heat can flow from one object to another, transferring energy in the process. The flow of heat can melt ice, drive convective currents in the air that produce thunderstorms, and warm the surfaces of planets near a star. The Laws of Thermodynamics describe the fundamental physics of heat and its flows.

Heat tends to flow 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 diffusion of gases, the circulation of ocean currents, the outflow of energy from the Sun, and the workings of rocket motors.

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. Click on image for full size (239K GIF) Image courtesy NASA.

The scientific field of thermal physics is concerned with heat, temperature, and related issues. When we delve into topics such as global warming, the structure of Earth's solid and liquid cores, and the way in which energy flows from the center of the Sun to its surface, we need an understanding of thermal physics.

Temperature is a familiar concept that is a cornerstone of thermal physics. Three scales for measuring temperature are in common use: Fahrenheit, Celsius (or Centigrade), and Kelvin. The temperature of a gas is actually 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. The temperatures we encounter in the study of astronomical objects are extreme by Earthly standards, ranging from millions of degrees in the centers of stars to hundreds of degrees below zero on icy moons.

In our everyday speech, heat and temperature are nearly synonymous. In the language of thermal physics, the two terms have precise and quite different meanings. Heat is essentially the amount of thermal energy stored within an object; one must add much more heat to an ocean to raise its temperature one degree than to raise the temperature of a bucket of water the same amount. Heat can flow from one object to another, transferring energy in the process. The flow of heat can melt ice, drive convective currents in the air that produce thunderstorms, and warm the surfaces of planets near a star. The Laws of Thermodynamics describe the fundamental physics of heat and its flows.

Heat tends to flow 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 diffusion of gases, the circulation of ocean currents, the outflow of energy from the Sun, and the workings of rocket motors.

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. Click on image for full size (239K GIF) Image courtesy NASA.

Physics also includes the study of heat and temperature. This study is called thermal physics. It helps us understand global warming, the way we get heat from the Sun or why water in the ocean moves.

To study thermal physics, you need to know about the temperature of things. There are three scales used to measure temperature: Fahrenheit, Celsius (or Centigrade), and Kelvin. In science, temperatures range a lot - from millions of degrees in the centers of stars to hundreds of degrees below zero on icy moons.

You also need to know how much heat an object is storing. Heat can flow from one object to another. This flow of heat can melt ice or make changes in our atmosphere that create thunderstorms.