|
|
|
Main Menu
|
|
Sections
Meta
Talkback
Downloads
Information
|
|
|
|
|
![[parent]](https://images.physicslibrary.org/images/uparrow.png) Viewing Message
|
|
|
| ``Re: types for PP''
by pbruin on 2005-08-20 14:41:34 |
|
| Perhaps it would be nice to have three separate types for physical quantities, units and (fundamental) constants. That way, if you were to create different kinds of indexes for the encyclopedia (alphabetical, by classification, by type, etc.), it would be an efficient way to keep all the units together, all the quantities together and all the constants together.
I think a constant is not a quantity; a quantity is (at least according to Wikipedia's definition) either a property of physical systems that can be measured, or the outcome of such a measurement, expressed in the right units. A constant does have a unit, but it is not a unit itself.
There is no 1-to-1 correspondence between quantities and units: quantities may have multiple possible units (e.g. seconds, years) or be dimensionless, and units could be applicable to different quantities, although in that case they often have different names, like the joule and the newton metre.
Having different categories seems somewhat clearer to me than having one category encompassing quantities, units and fundamental constants (I'm not sure if a type called `Measurement', `Standards', or `Physical quantities and units' would be entirely appropriate for physical constants, by the way). Also, the classification does not have a designation for the description of constants (only for measuring them), and 06.20.Fn also seems to be about measurement of standards for units like the metre (since it is in the `Metrology' category) instead of general descriptions of them.
In short, I'd suggest the types Quantity, Unit and Constant (or maybe Fundamental constant, since other constants like spring constants are actually quantities; on the other hand, e.g. Wien's constant is not a quantity but also not really fundamental, and furthermore it is difficult to clarify exactly which constants are fundamental). If you're going for one category, maybe `Quantities and units' would be the best choice (although being a plural that doesn't quite fit with the rest of the types).
|
| | [ reply | up | top ] | |
|
|
|
|
|
|
|
