Last modified: Sat 4/26/97 2315 PDT
 Canon Terms |
Object | Classes | AggMatterBody; SolidBody; CrystallineBody; AmorphousBody; LiquidBody; GaseousBody; FluidBody; EMSpectrum |
| Instances | (none) | ||
| Event | Classes | ExhibitRelativePosition; ExhibitRelativeVelocity; ExhibitRelativeDirection; Work; ExhibitForce; ExhibitAggEnergy; ExhibitKineticEnergy; ExhibitMass; ExhibitThermalEnergy; ExhibitTemperature; ExhibitWaveMotion; ExhibitEMField; ExhibitElectricalField; ExhibitMagneticField; ExhibitEMEnergy; EmitEMRadiation; EmitLight; EmitLightColor; ExhibitVolume; ExhibitDensity; IncTempThruMeltingPoint; Melt; DecTempThruFreezingPoint; Freeze; IncTempThruBoilingPoint; Boil; DecTempThruDewpoint; Condense; | |
| Instances | (none) |
A body of aggregate matter is a Physical Agent which humans perceive or conceive to be a material object.
A body of aggregate matter can change its position with respect to the rest of the physical universe. This relative change in position is referred to as motion. The rate at which a body is changing position at any given time is the body's velocity at that time. Since relative motion involves an increase in distance from some bodies and a decrease in distance from other bodies, it is useful to express positions toward which a body is moving as that body's direction of motion: any given position in the uinverse either lies in the body's direction of motion or it does not.
Work is an event in which a body of aggregate matter is caused to change its velocity and/or direction. The cause for such a change is referred to generically as a force, the amount of work done being proportional to the strength of the force and the amount by which the velocity and/or direction of the affected body is changed. Forces arise ultimately from the interaction among the fundamental matter particles. At that scale, it is believed that all forces observed in the physical universe have only four possible causes, the so-called fundamental forces. Since forces arise from the interaction between bodies of matter, it can be said that one body can exert a (net) force on another, i.e. that a body of matter can do work.
It has been observed that (a) not all bodies of aggregate matter have the ability to do the same amount of work, (b) when one body exerts a net force on another body, the net ability of the two bodies to do work does not change (other things being equal), and (c) this conservation of the ability to do work consists in a decrease in the force-exerting body's ability to do work (proportional to the strength of the force exerted) and an equal increase in the affected body's ability to do work. The ability to do work is obviously a very important characteristic of aggregate matter and its behavior, and the property has in fact been given its own name: energy, or more precisely aggregate energy.
A body of aggregate matter in motion is said to contain kinetic energy proportional to the body's velocity. (Note that, since the motion of bodies is relative to other bodies, so too is the kinetic energy of a body -- its ability to exert a force -- relative to other bodies.) Not all bodies exhibit the same proportion of kinetic energy (ability to do work by virtue of its velocity) to their velocities, however. The unobserved characteristic of bodies which accounts for the amount of kinetic energy the body contains at a given velocity is called the body's mass. So the kinetic energy of a body is proportional to both its velocity and its mass. (Note that, since the kinetic energy of a body is relative to other bodies, so too is the mass of a body relative to other bodies.)
The study of the way bodies of aggregate matter behave is the subject matter of mechanics, part of physics. The study of the way a body exerts forces on another (relative to which it is not in motion) is the subject matter of statics, part of mechanics. The study of the way bodies in motion behave is the subject matter of dynamics, part of mechanics. The study of the way in which bodies in motion exert forces on other bodies is the subject matter of kinematics, part of mechanics.
The particles within a body of matter are (for all practical purposes) in constant motion relative to each other, so those particles also contain kinetic energy proportional to their velocity and mass. The aggregate motion of populations of particles within a body of matter gives rise to a form of aggregate energy known as heat or thermal energy. The amount of thermal energy in a body is expressed as the body's temperature. The study of heat is the subject matter of thermodynamics (or sometimes thermal physics), part of physics.
The motion of particles within a body of matter can be completely random, as in the kinetic basis of heat. When it is not, however, regularly recurring patterns often emerge over a period of time which are referred to as wave motion. The study of wave motion is the subject matter of wave mechanics, part of physics.
The aggregate motion of particles within a body of matter which carry an electrical charge (or, put differently, the aggregate motion of populations of electrical charges) gives rise to another form of aggregate energy known as electromagnetism. This phenomenon is also referred to as electricity and magnetism, which are different aspects of the same thing.
It has been observed that, like aggregate matter, aggregate populations of photons (the mediating force-carrying particles in interactions among electrically charged matter particles) also have the ability to do work, i.e. they also have energy. Not all populations of photons have the same amount of energy, however, which is explainable in terms of different amounts of energy in different individual photons. The amount of energy in a photon is expressed as its wavelength, because part of certain mathematical models sometimes used to describe the behavior of subatomic particles, including photons, look very similar to the mathematical models used to describe wave motion. Whereas electromagnetism arises as the aggregate motion of populations of electrical charges, the form of energy which arises as the aggregate behavior of populations of photons is known as electromagnetic energy (or electromagnetic radiation). Electromagnetic radiation at all possible wavelengths is classified within the open-ended continuum known as the electromagnetic spectrum.
Light is electromagnetic radiation which lies within a certain region of the electromagnetic spectrum (i.e. which is composed of photons the wavelengths of which lie within a certain interval). Light at different wavelengths within that region is perceived by humans as color. The study of light is the subject matter of optics, part of physics.
Another important property of aggregate matter is the fact that it takes up space, i.e. it has volume. Since the mass and volume of a body of matter seem to be mutually independent, it is useful to be able to express for a body of matter how much mass is occupying how much volume. This expression, the amount of mass per unit of volume, is the body's density.
Aggregate matter is said to be solid when its particles have such low levels of kinetic energy, i.e. their random motion is at such low velocities, that the relative positions of the particles do not change (although the particles may vibrate in place, as it were). Speaking of low levels of kinetic energy in a body's particles is the same as speaking of low levels of heat in the body or of the body's low temperature.
Solid matter is said to be crystalline when the constituent particles are organized in repeating, three-dimensional patterns. Solid matter that is not crystalline is said to be amorphous. The study of crystalline matter is the subject matter of crystallography.
Aggregate matter is said to be liquid when its particles have enough kinetic energy, i.e. are in random motion with sufficient velocity, for them to change their relative positions within the body of matter, but not enough kinetic energy to change their positions so much that the entire body occupies a markedly greater volume (thus greatly reducing the density of the body). The temperature at which a solid body changes to a liquid is that body's melting point, which is a constant property of every different kind of crystalline matter.
Aggregate matter is said to be gaseous if its particles have so much kinetic energy, i.e. are in random motion with such great velocity, that the body as a whole occupies a much greater volume (at a much lower density, consequently) than the same matter in solid or liquid form (with lower levels of kinetic energy, i.e. random particle motion at lower velocities). The temperature at which a liquid body changes to a gas is that body's boiling point.
Liquids and gases are often subsumed under the term fluids, i.e. non-solid matter of any density. Although the behavior of fluids arises ultimately from the same kinds of mechanical processes as that of solid matter, it is often more useful to observe and describe the behavior of fluids at the emergent level of the liquid or gaseous body rather than at the underlying level of particles in random motion. The study of the behavior of fluids at both levels is the subject matter of fluid mechanics, part of physics.
