On 29-8-2010 1:53, Darren New wrote:
> nemesis wrote:
>> Darren New <dne### [at] sanrrcom> wrote:
>>> I'm not saying metric isn't easier. I'm pointing out that imperial 
>>> stuff,
>>> since it's based on people, is very poor at measuring things that aren't
>>> approximately relevant to people, like the weight of planets or the 
>>> size of
>>> atoms.
>>
>> It's not just that: imperial isn't precise.  I asked before and it was 
>> ignored,
> 
> Well, *now* it is precise. Obviously it wasn't precise when it was 
> formulated.  I think the foot, however, was the size of some specific 
> king's foot. And the metric measurements have changed definitions over 
> the years as well.

Such changes occur for good reasons. E.g. in the triple 
time/velocity/length you can define any two and the third can then be 
measured. Originally the speed of light was the quantity to measure. 
Nowadays that is a constant, otherwise the theoretical physicists would 
be very upset.
If you define the length then you can measure how long one second is. Or 
you define a meter and then you can measure how much time a photon takes 
to traverse that distance. Which one you choose simply depends on what 
you can measure most accurately. If your error in a meter is, say, one 
in 10^12 and in a second it is one in 10^10, it is unwise to take the 
second as definition, because the maximal achievable precision of a 
length measurement will then drop to one in 10^10.

I hope all imperial units are now defined as fractions of the metric 
ones or we will need two committees to decide when to change the places 
of meters and seconds. However, if you look at the wiki page about 
imperial units some conversions are exact, whereas others are given to 
be exact to 4 or 5 decimal places. Much larger than the scientific 
uncertainty in the values, so that supports nemesis' claim, although 
perhaps not in the way he/she meant.

Post a reply to this message