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Re: [Phys-l] Physics Grammar



John, yes I totally agree, however, I think scale and perception are different.
I had forgotten that sound like light has two sets of measures perceived intensity or flux and absolute. Thanks.

bc remembers there are some SI units that are very un-human scaled, e.g.. Y in pascals.

John Clement wrote:

All units are actually defined in terms of a human scale, or perception.
The decibel is defined in terms of the human hearing threshold and accuracy
of volume perception. While they have been decoupled from a particular
king's foot, the SI base units are still defined as to be on a human scale.
And this is actually reasonable, because it makes them more easily
understandable. The dB scale should be defined in terms of human perception
because it is generally used for things involving human hearing.

John M. Clement
Houston, TX


I quite agree most physical quantities should not be defined in terms of
human perception, e.g. force, entropy, length (tho here at one time it
was measured by a certain king's digits), etc. However, there is at
least one quantity that is measured (defined) by human perception. And,
wow, it's LIGHT; how ironic. Yes, the lumen is defined by the standard
eye's perception of flux, and it's an SI unit.




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