Everything about Physical Quantity totally explained
A
physical quantity is a physical
property that can be quantified. This means it can be measured and/or calculated. The value of a physical quantity
Q is expressed as the
product of a
numerical value , or the 21 components of the
elastic compliance tensor (inverse of the stiffness tensor), or the proper elements (six eigenvalues and 15 angles) of any of the two tensors, etc. Again, we're selecting coordinates over a 21-dimensional quality space. On this space, each point represents a particular elastic medium.
It is always possible to define the distance between two points of any quality space, and this distance is —inside a given theoretical context— uniquely defined. For instance, two periodic phenomena can be characterized by their periods,
and
, or by their frequencies,
and
. The only definition of distance that respects some clearly defined invariances is
log
log
.
These notions have implications in physics. As soon as we accept that behind the usual physical quantities there are quality spaces, that usual quantities are only special
coordinates over these quality spaces, and that there's a metric in each space, the following question arises: Can we do physics intrinsically, for example, can we develop physics using directly the notion of physical quality, and of metric, and without using particular coordinates (for example, without any particular choice of physical quantities)? In fact, physics can (and must?) be developed independently of any particular choice of coordinates over the quality spaces, for example, independently of any particular choice of physical quantities to represent the measurable physical qualities. This point of view has recently been developed (Tarantola, 2006
(External Link
) ).
Books
Cook, Alan H. The observational foundations of physics, Cambridge, 1994. ISBN 0-521-45597-9.
Fourier, Joseph. Théorie analytique de la chaleur, Firmin Didot, Paris, 1822. (In this book, Fourier introduces the concept of physical dimensions for the physical quantities.)
Tarantola, Albert. Elements for physics - Quantities, qualities and intrinsic theories, Springer, 2006. ISBN 3-540-25302-5. (External Link)Further Information
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