What is Entropy?
The '''entropy''' of an object is a measure of the amount of [[energy]] which is unavailable to do [[work (physics)|work]]. Entropy is also a measure of the number of possible arrangements the atoms in a system can have. In this sense, entropy is a measure of uncertainty or [[randomness]]. The higher the entropy of an object, the more uncertain we are about the states of the atoms making up that object because there are more states to decide from. A law of physics says that it takes work to make the entropy of an object or system smaller; without work, entropy can never become smaller – you could say that everything slowly goes to disorder (higher entropy). The word '''entropy''' came from the study of [[heat]] and [[energy]] in the period 1850 to 1900. Some very useful mathematical ideas about probability calculations emerged from the study of entropy. These ideas are now used in [[information theory]], [[statistical mechanics]], [[chemistry]] and other areas of study. '''Entropy''' is simply a quantitative measure of what the [[second law of thermodynamics]] describes: the spreading of energy until it is evenly spread. The meaning of entropy is different in different fields. It can mean: *[[Information entropy]], which is a measure of information communicated by systems that are affected by data [[noise]]. *[[Thermodynamic entropy]] is part of the science of [[heat energy]]. It is a measure of how organized or disorganized energy is in a system of atoms or molecules. [[Category:Thermodynamics]] [[Category:Basic physics ideas]]