Concept
Energy
Overview
Energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the capacity to do work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J).
Forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, the internal energy contained within a thermodynamic system, and rest energy associated with an object's rest mass. These are not mutually exclusive.
All living organisms constantly take in and release energy. The Earth's climate and ecosystems processes are driven primarily by radiant energy from the Sun.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
In the original texts
Passages from public-domain books where Energy is discussed.
Throughout the latter half of the nineteenth century, a great deal was made of the “conservation of energy,” or the “persistence of force,” as Herbert Spencer preferred to call it. This principle was not easy to state in a simple way, because of the different forms of energy; but the essential point was that energy is never created or destroyed, though it can be transformed from one kind into another. The principle…
Bertrand Russell, The A B C of Relativity
names the idea; a chapter is titled for it; states what it is; opens on it
Physics supposes that energy may be divided up: but every one of its possibilities must first be adjusted to reality. There can therefore be no question of dividing energy into equal parts; in every one of its states it manifests a certain quality, and qualities cannot be subdivided: hence a state of equilibrium in energy is impossible.
Friedrich Wilhelm Nietzsche, The Twilight of the Idols
names the idea; states what it is; opens on it
But this is not the case; consider electrified bodies; the electrostatic energy due to their mutual action will evidently depend upon their charge, that is to say, on their state; but it will equally depend upon their position. If these bodies are in motion, they will act one upon another electrodynamically and the electrodynamic energy will depend not only upon their state and their position, but upon their…
Henri Poincaré, The Foundations of Science
names the idea; a chapter is titled for it; opens on it
Between these two there presently arises the mesoderm in which becomes visible the rudiment of that vascular system, which has to fulfil the intermediate duty of transferring energy. Of these three general functions, that of accumulating energy is carried on from the outset: the endoderm, even while yet incompletely differentiated from the ectoderm, absorbs nutritive matters from the subjacent yelk. The transfer of…
Herbert Spencer, The Principles of Biology, Volume 1
names the idea; states what it is
If, therefore, the philosopher applies this principle to the solar system complete, he must at least soften its outlines. The law of the conservation of energy cannot here express the objective permanence of a certain quantity of a certain thing, but rather the necessity for every change that is brought about to be counterbalanced in some way by a change in an opposite direction. That is to say, even if it governs…
Henri Bergson, Creative Evolution
names the idea; states what it is; opens on it
Philosophers who discussed Energy
Related ideas
- Émilie du Châtelet
- Force
- Gottfried Wilhelm Leibniz
- Second law of thermodynamics
- Classical physics
- Light
- Physical property
- Life
- Mass
- Classical mechanics
- Heat
- Matter
- Atomic nucleus
- Atmosphere
- Metabolism
- Momentum
- Quantum
- Niels Bohr
- Particle physics
- Photon
- Quark
- Quantum mechanics
- Special relativity
- Field (physics)
Opposing perspectives
Place in the tradition
Part of Materialism.