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Perception Through Models

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.