1. It is easy to convert between different metric units for the same kind of quantity. Everything is related by various factors of ten: just move the decimal place!
3. ... all scientists (... use ...) the metric system .... The metre and its various other units related by factors of ten (femtometre, nanometre, centimetre, kilometre) .... The kilogram and its related units of mass is used to measure everything ...
While #1 is certainly true and is a very important advantage of metric, it is NOT THE ONLY simplification that the metric system provides. The other simplification is one appreciated more by scientists, but is significantly more important.
That other advantage is the one usually identified as coherence. It does not involve the relationship between units for the SAME type quantity (several different length units, or several different mass units). Instead it involves units of DIFFERENT types of quantity (such as power, force and speed, or force, mass and acceleration).
These relationships are even easier than the ones between same types of units (which are 10 or 100 or 1000 times one another). These relationships are ones in which one thing always equals just ONE time of another.
===================== Example showing the advantage of metric are:
Energy: 1 joule = 1 newton-meter Force: 1 newton = 1 kilogram-metre per second squared Power: 1 watt = 1 joule per second Pressure: 1 pascal = 1 newton per square metre Electric Current: 1 ampere = 1 coulomb per second Electric Potential: 1 volt = 1 joule per coulomb
======================= Corresponding examples showing the DISadvantage of NON-metric are: (all pounds are pounds-force unless specified otherwise)
Energy: 1 BTU = 777.9 foot-pounds
1 calorie = 3.088 foot-pounds
1 horsepower-hour = 1 980 000 foot-pounds
Force: 1 (pound force) = 32.17 (pounds mass)-feet per second squared
Power: 1 HP = 550 foot-pounds per second
1 BTU per hour = 0.2161 foot-pounds per second
Pressure: 1 atmosphere = 14.70 pounds per square inch
1 centimetre of Mercury = 0.1934 pounds per square inch
Electric Current: (there are no non-metric units)
Electric potential: (there are no non-metric units)========================
The advantage is clear and substantial. And they are as important as (or more so than) the decimal relations between units of the same kind.
Regards, Bill Hooper Fernandina Beach, Florida, USA ======================== SIMPLIFICATION begins with SI ========================
