Bob asked:

What is life?

Answer by Helier Robinson

The best answer I know of is due to the physicist Erwin Schroedinger, who said that life i.e. very high negative entropy in dynamic equilibrium. Entropy is a concept in physics usually popularised as disorder, so that negative entropy is order. So very high negative entropy is very high order. Dynamic equilibrium is moving equilibrium, as opposed to static equilibrium: a spinning top is in dynamic equilibrium, a brick wall is in static equilibrium. Entropy, as a concept, occurs in the second Law of Thermodynamics, which says that in any closed system entropy may increase to the maximum possible, but will not decrease. Living systems lose negative entropy all the time, according to this law, but replace it by feeding: either on sunlight or on other life. This steady loss and replacement is their dynamic equilibrium. Death is the failure of this equilibrium.