Light Sphere, is that the new name to replace light bulb?

[FrodoOne]

One obviously could 'manage' with just those..

For most people, kilometres are really only relevant to very large distances (like roads and other travel etc.). However, for a high proportion of 'everyday' purposes (both 'domestically'and in most trades/professions, millimetres are a little on the small side and metres a bit on the large size, so I'd be inclined to suggest that the most 'generally convenient' are, in fact, centimetres (which are in a similar ballpark to inches).

Kind Regards, John

"centimetres (which are in a similar ballpark to inches)."
AND
THAT is the problem wirh Centimetres - they are PSEUDO Inches !

See https://en.wikipedia.org/wiki/Metrication_in_Australia
"Building and Construction"

"The building industry was the first major industry grouping in Australia to complete its change to metric. This was achieved within two years by January 1976 for all new buildings other than those for which design had commenced well before metrication began. The resulting savings for builders and their sub-contractors has been estimated at 10% of gross turnover.

In this, the industry was grateful to Standards Australia for the early production of the Standard AS 1155-1974 "Metric Units for Use in the Construction Industry", which specified the use of millimetres as the small unit for the metrication upgrade. In the adoption of the millimetre as the "small" unit of length for metrication (instead of the centimetre) the Metric Conversion Board leaned heavily on experience in the United Kingdom and within the International Organisation for Standardisation, where this decision had already been taken.

This was formally stated as follows:
"The metric units for linear measurement in building and construction will be the metre (m) and the millimetre (mm), with the kilometre (km) being used where required. This will apply to all sectors of the industry, and the centimetre (cm) shall not be used. … the centimetre should not be used in any calculation and it should never be written down"
See also

https://themetricmaven.com/wp-content/uploads/2012/03/centimetresORmillimetres.pdf

 

[ebee]

A lad a year above me at School became foreman of a large timber merchants locally.
His 3 x 2 was still called 3 x 2 although it was 75 x 50 now so just a bit smaller but whatever system they used in a conversation he always told folk it was a "Metric 13" . LOL. In other words it was about 4 metres long therefore approx 13 feet in length.

Like Frodo I`d go with mm an M but shy away from cm because then I need to convert using if using cm. Daft innit?

 

[JohnW2]

"centimetres (which are in a similar ballpark to inches)."
AND
THAT is the problem wirh Centimetres - they are PSEUDO Inches !

Maybe - but, as I wrote, they are probably the most 'obvious'/useful for a high proportion of 'everyday tasks' (both domestic and 'professional'). Distances less than 10mm are relatively rarely needed for such purposes, so the use of mm (which is the appropriate SI unit) is arguably #less convenient' than cm.

This was formally stated as follows:
"The metric units for linear measurement in building and construction will be the metre (m) and the millimetre (mm), with the kilometre (km) being used where required. This will apply to all sectors of the industry, and the centimetre (cm) shall not be used. … the centimetre should not be used in any calculation and it should never be written down"

That is a statement of formal definition of SI (MKS) measurements,but it does not alter what I have written above.

 

[JohnW2]

Like Frodo I`d go with mm an M but shy away from cm because then I need to convert using if using cm. Daft innit?

As I've said, Frodo and you are being 'correct' - even if I personally feel that cm are often 'more convenient'!

 

[ericmark]

I remember saying to 'A' level teachers, the cm is not an ISO unit, and should not be used, the answer was agreed, but until the people setting the exam stop using them, we need to continue using them.

 

[JohnW2]

I remember saying to 'A' level teachers, the cm is not an ISO unit, and should not be used, the answer was agreed, but until the people setting the exam stop using them, we need to continue using them.

As I've said, when I did my O-Levels,the metric system we were using was the 'CGS' one, so cm was then correct - but that then changed to 'MKS' ('SI') during my A-Level course.

 

[ericmark]

As I've said, when I did my O-Levels,the metric system we were using was the 'CGS' one, so cm was then correct - but that then changed to 'MKS' ('SI') during my A-Level course.

I returned to collage, after getting my degree, to improve my maths, with the idea of returning to University, never did return, but did my 'A' level around 2010, and they were using cm, so when were you doing 'O' levels? I thought 'O' levels stopped in 1988?

I seem to remember I was the last year to take an FCE (Flintshire certificate of education) as it was replaced by the CSE of which I was the first year to take them. I went on to take 'O' levels, which seemed harder than 'A' levels today. I was born 1951, so have seen the change, not all for the better, when I took my RAE it took 6 months start to finish getting licence. Now you're forced to do it in stages. Same with motorbike licence.

 

[JohnW2]

I returned to collage, after getting my degree, to improve my maths, with the idea of returning to University, never did return, but did my 'A' level around 2010, and they were using cm, ...

That rather surprises me. However, I think there may be some misunderstanding here. Although the primary, defined, unit of distance in the SI system is the metre, and although mm is 'preferred' to cm, I don't think there is anything 'wrong'/'incorrect' in using any unit which is derived from (i.e. related by some power of 10) the metre.

so when were you doing 'O' levels? I thought 'O' levels stopped in 1988?

I did most of my O-Levels in 1964, long before 1988 However, more to the point, I did most of my A-Levels in 1966 - by which timme, as I said, we were using the 'MKS' system. However,just as the case today, I don't think that there was then anything 'wrong' or 'incorrect'about the use of cm (metres x 10^-2), even though mm were 'preferred' ... a bit like BS1362 fuses, I suppose

 

[FrodoOne]

Maybe - but, as I wrote, they are probably the most 'obvious'/useful for a high proportion of 'everyday tasks' (both domestic and 'professional'). Distances less than 10mm are relatively rarely needed for such purposes, so the use of mm (which is the appropriate SI unit) is arguably #less convenient' than cm.

Distances in multiple millimetres are used all the time in Australian building construction, carpentry, plumbing etc.

Have you read watched/read the references which I gave in Posts #36 and #46 ?

 

[ebee]

As I've said, Frodo and you are being 'correct' - even if I personally feel that cm are often 'more convenient'!

Actually John, I don`t see it as being merely "correct" in any shape or form, I see it as being practical from my personal experiences alone, I have found people around me in my area locality to be a bit puzzled by cm, some of them, not everyone though, some are more conversant with cm than other measurements such as mm and the metre. May partly be an age thing.

Maybe my own experiences have left me biased, they probably have, to be fair.
I suppose a lot depends upon what everybody else works in on the majority of the time.
Many of us (older folks) think as a Km as being about 5/8 of a mile for instance or a metre as about a yard and a tenth or about a yard and three inches or two kilos being about twice plus 10% in a pound.
In fact I never got the hang of pecks, bushels and groats, before my time and amazingly drinking men and women talk of beer as "I`ll just have a gill" meaning half a pint whereas moany of them know that a gill is two pints, how daft is that but some have a tendency to do what most others around them does.
Yes a strange world. LOL.

 

[ericmark]

You make a good point, we still do not order a beer in litres or ½ litres, and to do so would likely mean people would drink more.

 

[JohnW2]

Distances in multiple millimetres are used all the time in Australian building construction, carpentry, plumbing etc.

Same here. However, it's also pretty common, particularly for consumer/retail products, for dimensions to be specified in cm.

 

[fixitflav]

Same here. However, it's also pretty common, particularly for consumer/retail products, for dimensions to be specified in cm.

Yes, but it's not preferred. As I understand it, the recommendation is to use multiples of 1000 - lengths in km, m, mm, nm, pressure in Pa, kPa, MPa except where there's a convention for a different unit e.g. bar (= 10^5 Pa) for pressure. Though of course it's not hard to convert if cm are used.

 

[JohnW2]

Actually John, I don`t see it as being merely "correct" in any shape or form,

Agreed - nor do I. As I wrote ...

...... Although the primary, defined, unit of distance in the SI system is the metre, and although mm is 'preferred' to cm, I don't think there is anything 'wrong'/'incorrect' in using any unit which is derived from (i.e. related by some power of 10) the metre.

.. so I shouldn't have used the word "correct", since it's a matter of "preferred". As I said, there's nothing wrong or incorrect in manufacturing or using 5A or 10A BS1362 fuses, even though only 3A and 13A ones are 'preferred'.

I see it as being practical from my personal experiences alone,

Indeed, and I suppose the same with me. Early teachings/experiences tend to 'stick', so maybe my subsequent life has been influenced by the fact that the first few years of my 'metric education' were in terms of CGS units.

However, I still think that in terms of 'convenience', it is better to avoid units which are smaller than 'ideal' for a particular purpose. For example, we could, if we so wished, express all prices in pence, rather than pounds, but I would suggest that, say, £123.45 is more 'convenient' (more readily 'perceived/understood) than would be 12,345 pence.

However, in all contexts, it really comes down to what is in common use and 'what one 'is used to'.

In passing, I would observe that many/most of my measuring tapes and rulers etc. are marked in cm. In this case, some of the 'convenience' may be that things would get more 'crowded' (hence not quite as easy to read) if one had the extra digit required to mark in mm ...

Kind Regards, John

 

[FrodoOne]

In passing, I would observe that many/most of my measuring tapes and rulers etc. are marked in cm. In this case, some of the 'convenience' may be that things would get more 'crowded' (hence not quite as easy to read) if one had the extra digit required to mark in mm ...

Not so.
(Also, "Dual-Scale Instruments are Evil" - see Naughtin's 1st Law in https://themetricmaven.com/naughtins-laws/ )
Such measuring devices are quite "inappropriate" - to say the least.

"All Millimetre" measuring devices are not "more crowded"

"All Millimetre" tape measures (and Rules) are available, even if mainly in Australia !
See
https://en.wikipedia.org/wiki/Tape_...)_Measuring_Tape_(Start_and_End_Sections).jpg
and
https://commons.wikimedia.org/wiki/File:Mm-cm-Tapes.jpg
where the confusing "Outsider" is the lower one !

There is even the excellent "American Made"
" FastCap ProCarpenter True32 Metric Reverse Measuring Tape"
https://www.amazon.com/Fastcap-PMMR-TRUE32-True32-Reverse-measuring/dp/B000GFHABG

See also https://themetricmaven.com/metamorphosis-and-millimeters/ )