The concept of entropy is particularly abstract and by the same token difficult to present. Yet some scientists consider it intuitively; they need only refer mentally to actual states such as disorder, waste, and the loss of time or information. But how can degraded energy, or its hierarchy, or the process of degradation be truly represented?
Entropy is a state variable which measure the disorder of a system or the amount of energy available to be used. Mathematically, in thermodynamics entropy is given by S=Q/T where S is the entropy, Q is the internal energy and T is the temperature.
Entropy and Life
Creationists sometimes use ideas based on decreasing entropy and the second law of thermodynamics to bolster to their psuedoscience. They argue that the miracle of life violates the second law of thermodynamics because it represents a decrease in entropy which goes against the second law of thermodynamics. They neglect to remember that the second law of thermodynamics applies to closed systems. A system which can exchange energy with the outside world can decrease in entropy. Living organisms take in the energy they need to decrease their entropy, by eating food or photosynthesis, etc. If one wishes to apply the second law of thermodynamics, we must considered the whole universe as the system. When a biological organism absorbs energy and grows, thus increasing in complexity, work is done. Some energy is always wasted and some given off as heat, so in a wider context, the overall entropy is increased even when entropy decreases locally within an organism. If one is careful to decribe the system correctly, the Second Law is not violated even for living organisms.
Entropy and Information