Re: [Phys-l] Mass and Energy

[John Denker <jsd@av8n.com>]

Fayngold, Moses wrote:

>   No matter what you choose, if potential energy is a form of energy, 
> it will always be in the same units as energy. If you choose Gees 
> (it sounds good to me) then both - potential energy and total energy -
> will be in Gees. No matter how hard you try you will not find a system
> of units in which energy will be in Gees but potential energy will be in
> Boos.

Oh really?  Who are you to tell me what I can and cannot choose
as my units of measure?

Suppose there is a gauge that indicates altitude in feet, from
which I infer the gravitational potential energy per unit mass.
Also suppose there is a gauge that indicates speed in knots,
from which I infer the kinetic energy per unit mass.  In this
case, the conversion factor from kinetic to potential, in my
chosen units, is:

      9 feet per knot, per hundred knots

It is not unity.

Are you trying to tell me that no such gauges exist?

>  In contrast, we know at least one system of units in which mass, 
> while being nothing more than a "form of energy", is in units other than energy.

Again:  Who are you to tell me what I can and cannot choose as my
units of measure?  Maybe you want to measure energy and mass in
different units;  maybe I want to measure them in the same units
upon occasion.


> Does not it tell you anything?

It tells me that opinions are different from laws of physics.
It tells me that Proof by Bold Assertion isn't very convincing,
especially when I know lots of counterexamples.