We explain what a magnitude is and the characteristics of scalar, vector and tensor magnitudes.
What is a magnitude?
By the term magnitude, in general, we must understand simply the measure of something. An object, a living being, a force of nature, all have measurable and quantifiable dimensions and features, which can be expressed through mathematical language, that is, magnitudes.
The word magnitude comes from the Latin magnitudo, translatable as “greatness”, since in principle this term applies to the dimensions of physical bodies, that is, concrete objects, each one inscribed in a measurement system or system of measurements.
Length, height, depth, for example, are dimensions that can be expressed in units of measurement such as the meter, the kilometer or the centimeter. On the other hand, values such as the goodness or cruelty of a person cannot be objectively measured, and therefore do not constitute magnitudes.
Thus, the magnitudes they are the subject of study of physics. Each system of units and measurements available proposes its own standard based on which to carry out its measurements: the International System (SI), for example, proposes, as we said before, the meter as the unit of measurement of length. Now, the magnitudes can be of three types, depending on their nature:
- Scalar magnitudes, when they can be measured and expressed totally through a number, without it being necessary to explain any other meaning, such as direction. Its values can be independent of the observer, dependent on the position of the object, or the movement of the observer. Examples of these are: length, temperature, mass, volume, time, electrical charge, etc.
- Vector quantities, for which a specific number is not enough to be measured, since they have an orientation or a sense that must be expressed through a vector: a line segment with direction. Such is the case of speed, force, acceleration, light intensity or the electric field, for example.
- Tensor magnitudes, those that respond to representations through changing models, depending on the state of movement or the orientation of the observer.
As we have seen, every magnitude is necessarily expressed as a set of mathematical units framed in a logical system. Some of them are conventional, arbitrary units, such as the meter, the kilogram or the second, while others are necessarily understood from combinations of conventional units, such as the Newton (kg. M / s2) or July (kg. m2/ s2).
However, the term magnitude can also be used in a figurative way, to refer to the gravity or importance of something, as occurs in phrases such as “The magnitude of the events cannot be underestimated” or “the magnitude of my love is immeasurable”, meaning in those cases that it is something very large, that is, of proportions -figuratively- difficult to measure big.