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On 29-8-2010 1:53, Darren New wrote:
> nemesis wrote:
>> Darren New <dne### [at] san rr com> 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.
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