Re: [uom-ontology-std] What is mass?

[ravi sharma <drravisharma@xxxxxxxxx>]

Joe

 

The three are not necessarily equivalent when examined in quantum and astrophysical context.

Your response certainly needs further thought but for now I would say that Item 1, physical theory of mass is hopefully currently preferred to be kept out of scope of units and transformations area.  As the following factors would illustrate and take us to divergence from U&M practical ontology point of view.

 

Mass - m can change depending on how fast objects are moving (rest mass of photon is zero), but so far we have found inertial and gravitational mass to be equivalent (Dicke, now more accurate observations). The closer examination of mass-energy equivalence (and possible changes) might challenge our understanding - due to factors and knowledge of dark matter and dark energy, missing mass, grey holes, better / tonsorial corrections to general relativity and by examination of gravitational lenses in astrophysical observations.

Hence we keep 1 limited to practical and possibly solar system applicable limit. Still how do we handle quantum effects on similar quantities and laser wavelengths etc.,  that would come into units(?).

 

 

Martin

 

We heard Dr. David Leal yesterday in ontolog event on UCUM, and what I understood that he was presenting a view that practitioners would like such as radiologist wanting to know enough about radiation units, at the same time related bio parameters such as height, body mass etc as a set of related quantities for a given set of community or practices such as medicines.

Does that view contradict SI/VIM?

 

Thanks.

Ravi

On Fri, Sep 25, 2009 at 4:45 PM, Joe Collins <joseph.collins@xxxxxxxxxxxx> wrote:

I agree we need "kind".

Just because two quantities have the same units doesn't make them
indistinguishable. You cannot look to the units alone.

I believe that angle and count are distinguishable by their ostensive
definitions: they are not measured by the same procedure.

The "kind" concept as a defined abstraction may seem a little arbitrary, but it
usually follows from the ostensive definitions. If not, it should follow from
known laws of physics whether two things are of the same kind.
Things of the same kind can be meaningfully compared (>, <, =, etc.), which
usually means they show up in the same law of physics or a set of
measurements/experiments shows the kinds cannot (yet) be distinguished.
(We can never know if they can never be distinguished).

Sometimes things are not considered to be the same kinds of quantity and are
later determined to be of the same kind. Mass shows up in these three apparently
distinct laws: F=m*a, |Fg|=G*m1*m1/(|r*r|), E=m*c*c. From the classical view
these describe three unrelated classes of phenomena. Is it the same kind of mass
in each case? Physical theory says "yes".

jbc

Martin S. Weber wrote:
> Joe Collins wrote:
>  > (...)
>> My question is, "Do we need more than this?".
>>
> My answer on that one is (which I believe to be consistent with SI/VIM):
> "Add more until you can tell the difference between energy and torque."
> (or, equivalently "the diff. between an angle and a count")
>
> ...which brings us back to "kind of quantity", something of which I thought
> would've been accepted for quite some time already. I'm confused ...
>
> Regards,
>
> -Martin
>
> _________________________________________________________________
> Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
> Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
> Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
> Shared Files: http://ontolog.cim3.net/file/work/UoM/
> Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard

--
_______________________________
Joseph B. Collins, Ph.D.
Code 5583, Adv. Info. Tech.
Naval Research Laboratory
Washington, DC 20375
(202) 404-7041
(202) 767-1122 (fax)
B34, R221C
_______________________________

_________________________________________________________________

Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
Shared Files: http://ontolog.cim3.net/file/work/UoM/
Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard

-- 
Thanks.
Ravi
(Dr. Ravi Sharma)
313 204 1740 Mobile
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/  
Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx 
Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/  
Shared Files: http://ontolog.cim3.net/file/work/UoM/  
Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard    (01)