I don't understand. The relationship between calorie and joule isn't a feature of SI. It's a conversion between two different systems.
Are you saying that you do not think that joules, ergs, calories, and Calories are not all part of the metric system?
My point is that the metric system includes two different base systems (mks and cgs). As a result it has a dual set of units for almost everything. Why anyone would think that is a good idea is beyond me. Why is the mks system based upon the kilogram instead of the gram? Why is the cgs system based upon the centimeter instead of the meter? Why is the metric system not based upon the meter, gram, second, (and coulomb)?
Can you tell me the conversion factor between a joule and an erg? (Before we started this thread, I thought it was 1000 but I see that it is 1000000. Then some genius decided to add the calorie as another unit of energy. Then another genius decided to call the kilocalorie a Calorie. That is just plain silly.
The dual nature of the metric system creates all sorts of hidden power of ten conversion factors. Then another genius decided that the unit of volume is the liter instead of the cubic meter. Another hidden conversion factor of 1000. Why?
There are many examples of where the hidden powers of 10 factors in metric can cause problems. An example: Back in July, I was having a discussion about the size of a drop of ink from an ink jet printer. The finer drops are about 1 picoliter. That is 10^-12 liters. The cube root of 10^-12 is 10^-4 so I said that is a volume of a cube which is 100 um on a side. About an hour later, I realized that answer is too large by factor of 10. (Did you remember that hidden conversion factor?)
Frankly for a system that was 'designed to be rational', the metric system is not very well designed. (Yes. The 'English' system has many faults also.)
Dan
While you make some interesting points, if you are going to whine about the calorie being part of the metric system, please find an official statement by anybody to the effect that it actually _is_ part of the metric system.
Interesting.
Gee, one of the first things that every class that I have ever seen on the metric system mentions is the calorie and that it is the amount of heat required to raise one gram of water one degree centigrade (when I took classes it was centigrade and not celsius).
Microsoft in it's Encarta Encyclopedia says that the calorie is metric.
The part in my earlier post about the metric system having two slightly different versions is still relevant and a great source of confusion and errors. Why is the unit of volume a litre and not a cubic meter?
Dan
A final note: Wikipedia also says that the metric system was not originally French.
"The metric system, including the metre, was first fully described by Englishman John Wilkins in 1668 in a treatise presented to the Royal Society, some 120 years before the French adopted the system."
The first thing that comes to mind is that a cubic metre is 1000 litres ; )
Yes, an example of a 'hidden' power of ten conversion factor i.e. 1000. Why chose a cubic decimeter as a unit of volume? For the mks system it should be a cubic meter. For the cgs system it should be the cubic cm. For those people the really really like the size of litres, they could use either milli-m^3 or kilo-cm^3. (One of the things that I like about the metric system is the various prefixes (pico, micro, milli, kilo, mega, giga, etc.) fo handling scaling issues.)
Once again I really dislike that there are two separate but similar systems. That maximizes the chances of mixing units from the two systems or a conversion error. The silliness about the base mass unit for the mks being a kilo-something and the base length unit for cgs being centi-something just emphasizes the confusion.
Dan
"J. Clarke" snipped-for-privacy@cox.net wrote in news: snipped-for-privacy@news7.newsguy.com:
It's a trivially small measure of heat. That amount of heat necessary to raise the temperature of 1 ml or 1 gram of water by 1 degree centigrade. Fudge with starting temperature and standard pressure to get a bit more accurate.
When talking calories, I believe, the prefix kilo is often discarded, hence the notion that the above 1 gram should be replaced by 1 kilogram. However, the 1 gram, 1 degree thing is the "official" definition.
For the same reason that the Imperial system uses the quart or the gallon for most everyday volume measurements, instead of the cubic yard: because it's a convenient size.
Things that are measured in cubic yards in the Imperial system *are* measured in cubic meters in the metric system.
It depends on who's doing the talking. To a physicist or chemist, "calorie" refers to heating 1 gram of water, as stated above. What a nutritionist calls a "calorie" (e.g. what you see on the label of a can of beans) refers to heating 1 kg of water, and the scientist calls it a kilocalorie.
Yes, we all know what a calorie _is_. Are you next going to define the British Thermal Unit in an effort to show that _it_ is part of the metric system?
The fact that something is defined in metric units doesn't make it part of the system.
Consider the definition of calorie that you gave above. Substitute "mineral oil" or "mercury" or "grits" or "cat hair" for "water" and you get a different unit, which you can give a name. Does that make each of those units part of the metric system?
Is that a standard cubit or the lower forearm cubit?
Because most adults can drink a litre of beer but would struggle with a cubic metre?
speak for yourself :)
I hereby challange you to drink one cubic metre of beer in 24hrs and put the results up on utube!
I will sit and enjoy my one litre over the same period.
(only kidding - honest)
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