Heat is defined as energy in the process of being transferred from one object to another because of the temperature difference between them. Temperature variation across space can be generated by a number of different processes. A few physical laws can describe the nature of electromagnetic radiation. One of these laws suggests that any object above the temperature of absolute zero emits radiation to its surrounding environment. Another law suggests the quantity and quality of the radiation emitted is determined by the radiating body's temperature.
Chemical energy comes in many different forms.
However, the most important form, as it relates to this course, is the chemical energy generated by life in various types of organic molecules through the process of photosynthesis. The sun is the major source of energy for biotic and abiotic systems on the Earth. The sun creates large amounts of electromagnetic radiation through atomic fusion. This solar energy travels through space decreasing in intensity with distance from the sun. Only a small percentage of this energy emitted by the sun is intercepted and received by the Earth.