[time-nuts] 15 ns vs. 15 nS

John Day johnday at wordsnimages.com
Tue May 22 10:05:20 EDT 2007

```At 09:15 AM 5/22/2007, you wrote:
>Happy memories...
>
>I remember being switched half way through my "A" Level Physics course from
>cgs to MKS in 1968.
>
>Legal here in UK to show weights & measures in shops in both metric and
>imperial systems. Fuel at petrol (gas) stations sold in litres, and distance
>on roads still shown in miles (!!). Never did understand how the US gallon
>was smaller than the Imperial one though...

I used to know the answer. When the American colonies were founded
their were a number of 'specialised' gallons in use in Britain -
depending what was being measured. The 3.785l gallon is an old wine
gallon from somewhere in Britain.

What I could never understand was how come the US quart has 32 fluid
ounces when the imperial has always (to the best of my knowledge) had
40. Maybe some early form of attempted rationalisation?

The other quaintness is US length measurement, each of the four
customary units, inch, foot, yard and mile has two slightly different
definitions - one for 'normal' use based on the International Units
agreement of 1959, and the other known as US survey measure. Prior to
1959 US standard measure was the same as survey measure! So in 1959
the US standard mile got just a little bit smaller.

John

>Rob
>
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of John Day
>Sent: 22 May 2007 14:03
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] 15 ns vs. 15 nS
>
>At 08:26 AM 5/22/2007, you wrote:
> >I was basing my observation on the three fundamental units - M, K, & S,
> >as taught in the 60's. Just goes to show how things have changed...
>
>You mean the old MKSA system? I was taught that in high school too, after we
>abandoned the cgs system. But I was in Australia at the time. Metric
>conversion started there in 1970 (I was in college by then), SI was
>introduced to primary schools in 1972 and to high schools in 1973. For all
>practical purposes, conversion to SI was complete by 1976.
>
>So having started out with the centimetre, gramme, second system, moving to
>the so-called 'rationalised' metre, kilogramme, second, Ampere system the
>move to SI at university seemed trivial. The really difficult thing has been
>to move to a partially metricated country in my 50's. Trying to delve back
>into the recesses of my teenage years to once again work in pounds at the
>food store has not been fun! Here in Canada it seems that we are legally
>required to show prices in the store in both, or at least it is customary to
>do so, but ask for something in metric quantity in many smaller stores and
>it suddenly seems I have grown an extra head or two overnight. At least my
>butcher now has a scale that will work in metric units!
>
>John
>
>PS: Don't get me started on trying to deal with US Customary measure when
>living there in the 70's! Little did I realise that a gallon was not really
>a gallon after all.
>
>J
>
>
> >Rob
> >
> >-----Original Message-----
> >From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> >Behalf Of John Day
> >Sent: 22 May 2007 12:43
> >To: Discussion of precise time and frequency measurement
> >Subject: Re: [time-nuts] 15 ns vs. 15 nS
> >
> >At 04:05 AM 5/22/2007, Rob Kimberley wrote:
> > >As Seconds are a fundamental unit of the SI system, shouldn't the "S"
> > >be upper case?
> >
> >Of seven SI 'base units' only two - K for thermodynamic temperature and A
> >for electrical current are capitalised. On the basis of your suggestion we
> >would need to campaign for a change in 5 units, not just one.
> >
> >John
> >
> >
> > >Over to you fellow "nuts".
> > >
> > >Rob Kimberley
> > >
> > >-----Original Message-----
> > >From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > >Behalf Of James Maynard
> > >Sent: 22 May 2007 08:26
> > >To: Discussion of precise time and frequency measurement
> > >Subject: [time-nuts] 15 ns vs. 15 nS
> > >
> > >Didier Juges wrote:
> > > > Sorry, it's not 15nS rms, it's 15nS at 1 sigma.
> > > >
> > > > Didier KO4BB
> > > >
> > > >
> > >A long s we are being pedantic:
> > >15 ns = 15 nanoseconds, but 15 nS = 15 nanosiemens.
> > >
> > >I am sure in the time-nuts list, we are concerned with nanoseconds, not
> > >nanosiemens!
> > >
> > >
> > >
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> > >
> > >
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> >
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