In research observable means that which can be seen or measured in an experiment or research. In many scientific fields, the term “observable” is used in a technical sense to refer to properties that are measurable and quantifiable, such as position, momentum, spin etc.
The term “observable” is also used more generally to refer to anything that can be observed or measured. This could include abstract concepts such as pain, love or beauty which cannot be directly measured but can be observed or experienced.
In anthropology, the notion of observation as part of ethnography is critical to the discipline. Observations can be made of people’s behavior, both in naturalistic settings and in controlled experiments. Observations can also be made of artifacts and other physical evidence.
In economics, the term “observable” is used to refer to anything that can be observed or measured. This could include economic data such as prices, GDP, inflation or unemployment. It could also include non-economic data such as the number of hours worked or the amount of leisure time enjoyed.
The term “observable” is also used in philosophy to refer to anything that can be observed or experienced. This could include abstract concepts such as pain, love or beauty which cannot be directly measured but can be observed or experienced.
In physics, particularly in quantum physics, a system observable is a measurable operator, or gauge, where the property of the system state can be determined by some sequence of physical operations. For example, these operations might involve submitting the system to various electromagnetic fields and eventually reading a value off some gauge. In systems governed by classical mechanics, any experimentally observable value can be shown to be given by a real-valued function on the set of all possible system states. Physically meaningful observables must also satisfy transformation laws that relate to observations performed by different observers in different frames of reference. These transformation laws are automorphisms of the state space, that is bijective transformations that preserve some mathematical property.