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The upshot of all this is that you can't trust any
units to carry lasting significance; all is vanity.
Each and every choice of units represents essentially
*a model of what is significant*. What is vitally
relevant to one observer may be trivial and ridiculous
to another. Lest this seem a depressing appraisal,
consider that the same is true of all our means of
perception, even including the physical sensing apparatus
of our own bodies: our eyes are sensitive to an incredibly
tiny fraction of the spectrum of electromagnetic radiation;
what we miss is inconceivably vast compared to what we
detect. And yet we see a lot, especially under the light
of Sol, which at the Earth's surface happens to peak in
just the region of our eyes' sensitivity. Our eyes are
simply a model of what is important locally, and well
adapted for the job.
The only understanding you can develop that is
independent of units has to do with how dimensions can
be combined, juxtaposed, *etc.* - their *relationships*
with each other. The notion of a velocity as a ratio of distance
to time is a concept which will endure all vagaries
of fashion in measurment. This is the sort of concept
that we try to pick out of the confusion. This is the
sort of understanding for which the physicist searches.

** Next:** Number Systems
** Up:** Units and Dimensions
** Previous:** Choice of Units

Jess H. Brewer -
Last modified: Wed Dec 16 11:30:25 PST 2015