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Re: SI and nothing else



A system of units without a single basic unit is beyond my comprehension.
Last week I told students that a statement "force is 5" means nothing
unless a unit is specified. Was I wrong?
Ludwik Kowalski

No, you were right. Having a unit is not the same as having a dimension.
Even dimensionless quantities like angles and information have distinctive
units which need to be specified. A degree is not a radian which is not a
cycle. A bit is not a byte which is not a Mbyte.

P.S.

Your photon is defined in terms of the black hole which is then defined
in terms of the same photon. What am I missing?

Nothing. The system of Planck units is uniquely determined because there is
only one photon energy/black hole mass that has the property that the hole's
Schwarzschild radius equals the photon's wavelength. This is because the
photon's wavelength is *inversely* proportional to its energy, and the photon
energy is directly proportional to the hole's mass which is *directly*
proportional to the hole's Schwarzschild radius. One length goes up while
the other goes down and they coincide at a unique value.

David Bowman
dbowman@gtc.georgetown.ky.us