You don't say who the addressee is for that letter, Bill, although I assume it was someone at Apple Computer.
Bill Potts SI Navigator (http://metric1.org) -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Hooper Sent: Saturday, July 21, 2007 17:28 To: U.S. Metric Association Cc: USMA Subject: [USMA:39122] Metric Time Your proposal for metric time (as seen in your Apple Widget for a metric clock) is incompatible with the International System of Units (SI), which is the modern METRIC SYSTEM in use by 95% of the world's population. It is incompatible because SI is based on a small number of fundamental units, one of which is the second of time. ABSOLUTELY ALL other measurements are related to these few basic measures, so that modifying or discarding any one of them is tantamount to destroying the entire system of measurements for the whole world. It is the interconnection between all units that makes the SI metric system powerful, not just the fact that units are related by simple numbers like 10 and 100. You cannot tamper with one unit without considering how it affects all others. (If you choose to leave all others the same and use the "metric clock" ONLY for time of day, then you are promoting two unrelated systems to learn and to use, instead of just one. Also, since your "metric time" would be incompatible with all other metric units, I think it would be ridiculous to call your time "metric" at all. Your time units are not metrically compatible with the SI second. The "day" is the length of the day and it's length is determined primarily by the rotation of the Earth on it's axis. The SI second is defined as a size that makes the day equal to 86400 seconds long (86400 s) on average. That leads to the following for your other time measures (with some values in minutes or hours in order to relate them to the old time units): 1 day = 86400 s (24 hours, of course) 1 deciday = 8640 s (2.4 hours) 1 centi day = 864 s (14.4 minutes) 1 milliday = 86.4 s (1.44 minutes) 1 moment = 8.64 s None of these is related to the second by a simple factor and therefore they are all incompatible with virtually ALL other measurements. To give you just some samples of what I'm talking about: The watt is used to measure power, which is how fast energy flows. It is equal to the flow of one joule of energy PER SECOND. Thus, using "moments" for the time unit in your system would cause the watt to be equal to 8.84 joules per moment. EVERYTHING that is measured in watts (and kilowatts and megawatts and milliwatts) would have to be changed. The ampere is used to measure the rate of flow of electric charge. It is equal to one coulomb of charge PER SECOND. Substitute your "moment" or any other of your units for the second and EVERYTHING that is now measured in amperes (or milliamperes or kiloamperes) would need to be changed. Pascals are units of pressure and pressure is merely a force applied to a surface divided by the area of the surface. Force is measured in newtons and newtons are related to SECONDS, so that substituting any of you units for seconds would change how all forces and all pressures are measured. I think the above shows that it would be monumentally difficult to eliminate the second of time in favor of any one of your units. As a result, we would then have to have all of your time units AND ALSO the second (and the millisecond, the kilosecond, etc.) Far from simplifying things, your system makes them more complex. To make a small improvement in measuring time of day, your system would make a monumental mess of virtually ALL other measurements for 95% of the people of the world. Sorry, but that doesn't seem to me to be a good trade off. I hope you will abandon your effort to promote your ill conceived metric time and metric clock. Sincerely, (Dr.) william Hooper Certified Advanced Metrication Specialist Professor of Physics (retired) The University of Virginia's College at Wise
