millimeters, centimeters and inches

[JimmyH155]

I am very impressed that most of you people in this forum use either inches or millimeters.
Will somebody please tell those august contributers to AS & S that me, the reader - having been brought up in the good old days of the Imperial system - have only just got used to mm. I am an Engineer and we consider the use of cm to be the domain of the rag trade and misinformed educationalists who teach cm in schools. I had to do a mental calculation this morning when reading in the magazine.." should be visible in a 7.5cm"
Centimeters are housewives units, not technical units.

[Dennis]

I hear you brother, I hear you....

Cheers

Dennis

[Miaplacidus (Brian)]

Well, I like the metric system. Curious how history is written into the units we use. But how schizoid is it to have eyepiece diameters measured in inches but their focal lengths measured in millimetres, to be told the aperture of a particular telescope is so many inches but it's focal length is this many millimetres, or that a particular mount weighing so many kilograms can carry up to X number of pounds?

[xelasnave]

Well I have figured that a shilling is worth 10 cents and a quid is worth $2-00 so the ruler thing is not that bad . I have noticed many in "trades" use mm only and to me that sounds like Italian money ..seems a lot but not really.
alex

[slice of heaven]

The metric revolution created the saying "measure twice, cut once".
A metre is supposed to represent a 10millionth of the distance from the pole to the equator, a metre falls short by .2mm of this. They should have "measured it twice, cut once"
The current definition of a metre is the distance light travels in 1/299,792,458 of a second in a vacuum. So much for replacing fractions with decimals
Now the length of a metre is totally dependant on the duration of time

[[1ponders] (Paul)]

Now the length of a metre is totally dependant on the duration of time

Which we know is not constant, but dependant the effect of mass on space (eg black hole) or the speed at which you are travelling, which is measured in meters per sec, which are dependant on the.......

[astroron (Ron)]

It was all that confusion that caused the loss of a mars space craft a few years ago

It's really simple, well maybe not for an engineer, a centimeter is 10 millimeters, do I need to go on? Oh, OK, for the engineers, there are 100 centimeters to the meter and 1000 of them to the kilometer, you see it all works in multiples of 10, just like a dozen except logical. Hopefully I have educated about 57/64th's of the viewers here, but that's another story.

[ballaratdragons (Ken)]

I can't help it but I like to work in Imperial! That's what I was brought up on and I still use it.

I can't even grasp weight in metric. All I know is I weigh around 12 stone, but kilograms has me lost.

It took us ages as kids to learn to convert to Celcius from Farenheit, and Pounds shillings and pence to $ and cents. It was a confusing time in history as a young'en, to have to change over after just spending all your school years learning one way, then have to throw it all out!

But I am prepared to give or take an inch

[Gargoyle_Steve (Steve)]

I began to learn imperial measurements in school, but around grade 3 we started learning the S.I. system (metric measurements) so I grew up on both. That was over 30 years ago now - which dedfinitely shows something about the average age of people on this site perhaps as I should literally be the youngest specific age that was taught the imperial system.

I quote my height as 5'8", but my weight as being >100 kg's.
(Mind your own business!!!! lol .. let's just say I am TRUE metric man - a few years ago my weight exceeded 100kg's at the same time my waist exceeded 100cm's).

I put 34-36 psi of air in my tyres, which run on 16" wheels, but my other set of wheels for my 4x4 are 15" diameter running 235/70 (ie 235 mm width) tyres. My petrol tank holds 132 litres of fuel, and 65 litres of LPG in the gas tank, but I work out my economy in miles per gallon if I want a figure that means something to me as to how well or badly it is running.

I read the celsius figures on my thermometer, but I still quote atmospheric pressure as 14 psi (at sea level - my old chem teacher would be horrified that I didn't quote it as 101.3 kPa instead) and I know that a 20 knot wind will make the rigging on a 15 foot hobie-cat "hum".

I simply use or quote whichever figures work well for me, the ones that I can best understand or appreciate in the privacy of my own mind, but if you want a system of measurements that makes some kind of sense then the metric measurements win hands down, and I can work exclusively in them just fine if I need to.

[CoombellKid]

Ever tried driving from Canada to the US, had me going along
the highway at 60kms to Seattle from White Rock once, until
my Canadian friend enlightened me

regards,CS

Rob

[Starkler (Geoff)]

Imperial measurements need to be done away with for good.
Everything in the S.I. system ties together in a way that makes sense and is easy to calculate.

eg. 1 litre of water weighs 1kg
1 litre of water has a volume of 1/1000 of a cubic metre or 10cm x 10cm.

1 joule is the energy expended exerting a force of 1 newton over 1 metre.
1 joule = 1 watt second

The downside of this is talking about fuel consumption. Who asks about the Kilometreage of their car?

[slice of heaven]

Looks good on paper Geoff, that's the way it was created.
I use both systems easily, and can convert from one to the other fairly well. Imperial measurements are easier to break down to smaller units than metric without having to resort to fractions. Metric can generally be multiplied easier.
Metric doesn't cover all bases of measurement very well though. Imperial does.
1 nautical mile is the distance of 1 minute of arc along a meridian (average) = 1.85??kms.
60 nautical miles is 1 deg of arc = ?????? kms. Too hard
5400 n/miles is 90 deg of arc = 10000kms + the bit they forgot to measure

[Jonathan]

I'm a Toolmaker by trade and do work for the local and US markets which means I have to know both systems of measurement to a high degree of accuracy. So for me either system is no problem to use.
This same metric/imperial discussion came up at work tonight. The conclusion was that the imperial system is awkward and outdated and should be banned from use worldwide! I could go on for ever about why I dislike the imperial system, but I won't
The biggest flaw in the metric system is the use of the centimetre. It's only used in measuring TV's (plasma tv's seem to be measured in inches though) and when making clothes, but it's taught in schools as being a standard unit of measurement. It's much easier to work in microns, mm, m, km.

[OneOfOne (Trevor)]

Originally Posted by ballaratdragons

It took us ages as kids to learn to convert to Celcius from Farenheit, and Pounds shillings and pence to $ and cents.

I can remember when the currency was changed too (I can still remember the words to the song "in come the dollars...."), my parents owned a Milk Bar. I can still remember customers coming in and saying "why couldn't they just wait until all the old people had died!"

I always find it amusing that the Americans fought for their independence from the British, only to one of the last remaining countries that continues to use the "British" measurement system, even the poms use metric.

[JimmyH155]

My original query was why do the "experts" in the AS & S talk about centimers? Thanks Johnathon for those words. Yes I couldn't care a tinker's cuss about whether to use Imperial or metric - just don't refer to telescope sizes as "cm". As I said at the beginning - housewives units.

[Kieken]

I'm having less and less problems with switching between this imperial and the metric system. IOt's just a matter of keeping your head clear when using both systems at once.

1 pound is 0.45kg and 1kg is 2.2 pounds
1 stone is 14 pounds so somewhere near 6.36kg
1 mile is 1.6km so 1 km is 0.625 miles
1 yard is 0.90m or 90cm (roughly)
14 foot is somewhere near 30cm
1 inch is 2.54 cm.

[mickoking]

I am very much a metric man

As for centimetres I must agree it is a stupid unit, I never use it myself. I did notice it was used in AS&T, telescope specifications to my knowledge are never done in CM's. The imperial units Feet and Stone are also absolutely meaningless to me.

Viva Metric

[ballaratdragons (Ken)]

I forgot to mention in my post above, I am not Pro or Con either way. I just prefer Imperial coz that's what was drummed into me for my whole school life.

and I do agree, cm is dumb!

[Kieken]

Yup, i prefer metre(s) to .