User:WillowW/Nature

From Wikipedia, the free encyclopedia

1 Broadest definition
2 Physical definition
3 Personifications and divinities
4 Contrasted with civilization
5 Contrasted with urban culture
6 Semiotics of Nature

[edit] Broadest definition

The broadest conception of Nature is the definition of the medieval philosopher Johannes Scotus Eriugena, who defined Nature as simply everything: everything that exists and everything that does not exist. In this definition, time is not considered; thus, it is more proper to say that Nature includes everything that exists, has existed and will exist, as well as everything that does not exist, has never existed and will never exist.

Eriugena's all-embracing definition of Nature has not been adopted by later philosophers, but it seems pertinent to understanding the peculiar behaviour of quantum physics, particularly the path-integral formulation of Feynman. According to the present understanding, Nature explores all possible realities, but allows only one to exist. Expressed mathematically, all possible realities contribute equally to the probability amplitudes for the various outcomes of an experiment; however, only one outcome is chosen to be objective reality in the process of quantum measurement, also known as the collapse of the wavefunction. In this way, even that which does not exist (all possible realities) can influence that which does exist (the objective reality); the non-existent is as much part of Nature as the existent. This broad conception of Nature is also anticipated somewhat in the Buddhist doctrines of shunyata and interdependent development of reality.

[edit] Physical definition

It is more customary to define Nature as everything that exists, has existed and will exist. In this usage, the concept of Nature is synonymous with reality, the universe and physics.

This definition of Nature was developed by early Greek philosophers, particularly Thales and Parmenides. The high point of that tradition came with Aristotle, who defines Nature as το παν (everything); in his great work On nature (Φυσικης), Aristotle divides Nature into three basic elements: matter (the stuff of which the universe is made), form (the arrangement of that matter) and change (how matter is created, destroyed or altered in its properties, and similarly, how form is altered). The laws of Nature were conceived as the rules governing the properties of matter, form and change. Later philosophers such as Lucretius, Averroes, Avicenna and Baruch Spinoza refined these divisions of Nature; for example, Averroes and Spinoza discern natura naturans (the active principles governing Nature) from natura naturata, the passive elements upon which the former act.

The present best model of Nature is the Standard model, which consists of 18 physical constants, the rules of quantum field theory, general and special relativity, and four fundamental interactions, each of which correspond to a symmetry of Nature that must be preserved. In this model, all matter is composed of 12 elementary particles, each having spin 1/2 (fermions): six types of quarks (up, down, strange, charm, top and bottom), three types of leptons (the electron, muon and tau, with three types of neutrinos. Each of these particles has an antiparticle; for example, the antiparticle of the electron is the positron. However, these antiparticles can be considered as time-reversed versions of their particle; the positron is merely an electron that is moving backwards through time.

The arrangement of material particles is described by their distances to one another in space and time. Interestingly, these spatial and temporal distances are not elements of reality in themselves, but depend on the frame of reference. Thus, the distance between two particles can be altered simply by moving at a different speed relative to them, without changing anything in the particles themselves. As understood from special relativity, the particles do not merely appear to be closer; rather, they are closer in the new reference frame. Similarly, the order of events is altered by changing reference frames. However, special relativity sets limits on how much these spatial and temporal distances can be altered; specifically, a spatial distance Δx can be converted into a temporal distance Δt as long as the space-time distance Δs is preserved

Δ s 2 = Δ x 2 - c 2 Δ t 2

where c is the speed of light. Thus, only Δs is real, only Δs is part of Nature, not the individual Δx or Δt themselves. A point in space and time is called an event and the collection of events is called spacetime.

Similarly, matter and energy can be considered as different aspects of an underlying reality. For example, the addition of any form of energy to a physical system increases its mass. The property of invariant mass is intrinsic to a system, and independent of the frame of reference; thus, it can be considered as part of Nature. The rest mass can be considered as the energy that a particle has by virtue of moving through time (i.e., existing), in the same way that kinetic energy is the energy of moving through space.

Another tenet of modern physics is that empty spacetime (the "vacuum") has properties and exists in a real sense, acting on matter and being acted upon by matter. These effects are described by Albert Einstein's theory of general relativity. The force of gravitation is an example of the influence of spacetime on matter, whereas high concentration of matter causes space-time to become curved. Moreover, empty space can spontaneously give birth to material particles through quantum fluctuations; for example, the radiation emitted by black holes is composed entirely of particles spawned from empty space.

It is generally assumed that there is only one universe, i.e., one connected spacetime continuum in which material particles move, the universe. However, it is possible that there are multiple disjoint continua that do not affect one another, and that conceivably could have different values for the basic physical constants of the Standard model. The set of all such continua is called the multiverse. Another physical conception of the multiverse is the many-worlds hypothesis of quantum mechanics. Regardless of the underlying physics, all such multiverses could be considered as part of Nature.

[edit] Personifications and divinities

Although Nature was first conceived abstractly by the Greek philosphers, it has been personified, even deified, from earliest recorded history. Personifications of Nature is often associated with personifications of creation and fertility, corresponding to the identification of Nature and life. Similarly, Nature divinities are also associated with Earth or Sun divinities, corresponding to the identification of the Earth or Sun giving life.

[edit] Female

The majority of Nature divinities are female, especially fertility goddesses, perhaps because of the long-known fact that males are not always necessary for reproduction. The earliest such goddesses include the Babylonian/Sumerian goddess Tiamat ("Mother of all life"), the Greek goddess Gaia (the Earth), the Shinto goddess Amaterasu (the Sun), and the Hindu conception of Prakrti (material reality). In modern times, the most common personifications are the Great Goddess, Mother Nature and the Earth Mother, which are associated with all existence, all life and the Earth, respectively. Nature goddesses are often characterized by a triple nature, but not all triple goddesses are Nature goddesses (e.g., the Erinyes, Norns and Moirae).

[edit] Male

In some cultures, the primeval spirit reponsible for all creation is exclusively male; examples include the ancient Egyptian god Ptah, the Orphic god Phanes and his successor Mithras, as well as the conception of Brahma/Brahman in Hinduism.

[edit] Couples and dualism

In still other cultures, reality/life/creation is believed to emanate from a couple or two interacting forces, such as the Great Goddess and the Horned God in Celtic culture, the yin and yang in Chinese philosophy, or the emanation of Vajradhara (also called Adi-Buddha or Samantabhadra) and his consort Samantabhadri in Tantric Buddhism.