On 7 Oct 2003 04:35:19 -0700, (Pat Norton) wrote:

Dave Ludlow wrote:
So why bother changing the name at all?

That sounds like "Why SI?".

In part, I think you are right, but not completely. It's also in part
"Why does SI do that?" It includes issues within SI like the already
mentioned degrees Celsius and not degrees centigrade, and

micrometers (or micrometres), not microns
kelvins, not degrees Kelvin
pascals, not newtons per square metre (not exactly the same as the
previous two, as the latter is still a proper characterization even
though the special name for this unit has been added)

Note that there are many different units
of pressu
pascal
bar

barye = dyne per square centimeter, the cgs unit of pressure. Bars
are so obsolete that they didn't even fit in with the old cgs systems.

atmosphere
inch of water
mm of water

more often cm of water (lung pressure, etc.)

inch of mercury

usually at 60°F in older measurements, most often at 32 °F (and
25.4000 times millimeters of mercury, which wasn't always true)

mm of mercury

aka torr

foot of water
pound per square inch
pound per square foot

kilogram per square centimeter (and another name for it, a technical
atmosphere)

ton(UK) per square foot
ton(US) per square foot

A U.S. Navy ship, the tanker USNS Henry J. Kaiser is 27,561
tons deadweight. How much is that is SI units?

Call them long tons and short tons, please.

Aviation has been using multiple units for weather (inch of mercury,
pascal, bar). More units are in legal and technical specificiations
(pound/inch², ton/inch²). Units of measurement for aviation are of
international importance and agreed via ICAO. It has compiled a
standard set of units:

"The standardized system is based on the International System of Units
(SI) and will eventually eliminate the use of different units of
measurement for the same quantity and provide for the standardized
application of all units of measurement for those quantities used in
air and ground operations."
www.icao.int/icao/en/pub/memo.htm

That standardized system includes metres per second for wind speeds,
another area with three different units used in aviation weather yet
today, right?


Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/