Imperial versus metric

[Mars90000000]

It's not a matter of which is better and which is worse. They're both equally used in different aspects. Sure, most people only see one of them in their lives. Those living in metric system see SI using more than anything else, and vice versa for imperial units. But that's not to say one is better. Once you get past that and start doing complicated math in whichever field you are, unit conversions becomes first hand. The rule is simple, answer the question in the units it was asked in. If it's imperial, you're free to convert it to metric for your own ease of calculations, but just convert back at the end.

Sure, temperature in Fahrenheit might seem like a useless scale to a lot of people who are used to Celcius and Kelvin degrees (K = C + 273.15), but Fahrenheit is useful in that a lot of calculations and formulae use Rankine degrees (Ra = F + 459.67). So it's not entirely useless. There are several units of Work (ergs, dynes, joules) that can be used depending on the situation that you're in.

The more recent papers that you find and formulae and what not, probably use the metric system since that's the most commonly used system now. However, we don't reinvent the wheel every time, so the formulae that were found 50, 60, years ago, remain as they are, and they probably use the imperial unit system.

[Azivegu]

It's not a matter of which is better and which is worse. They're both equally used in different aspects. Sure, most people only see one of them in their lives. Those living in metric system see SI using more than anything else, and vice versa for imperial units. But that's not to say one is better. Once you get past that and start doing complicated math in whichever field you are, unit conversions becomes first hand. The rule is simple, answer the question in the units it was asked in. If it's imperial, you're free to convert it to metric for your own ease of calculations, but just convert back at the end.

Sure, temperature in Fahrenheit might seem like a useless scale to a lot of people who are used to Celsius and Kelvin degrees (K = C + 273.15), but Fahrenheit is useful in that a lot of calculations and formula use Rankine degrees (Ra = F + 459.67). So it's not entirely useless. There are several units of Work (ergs, dynes, joules) that can be used depending on the situation that you're in.

The more recent papers that you find and formula and what not, probably use the metric system since that's the most commonly used system now. However, we don't reinvent the wheel every time, so the formula that were found 50, 60, years ago, remain as they are, and they probably use the imperial unit system.

Don't want to be mean, but when was the last time you had a chemistry class where they asked for an answer in the x unit scale and also gave the necessary data in the same unit scale? I usually spend a quarter of my time on test just to recalculate to another unit and double checking everything. If it was in the imperial system then I would need an entire book to remember everything. With metric you know it is a power of 10, and that is beautiful. Just like the AX paper scale, it has more real world applications than imperial.

Sure there are uses for both systems, but which one is based of of something you actually need and which one isn't (hint: even most farmers aren't going to measure in barley)

[Surefoot]

There's really not much to say in defence of the imperial system IMO. It's not used because it's better, it's used because it's perceived to be too much hassle to get rid of.

That's a correct answer, there's not much more to say about it.

Aviation is the only industry I've personally come across that actually uses imperial for real engineering, and that's because of the influence of some large US manufacturers. Do engineers working outside of aerospace in the US actually use imperial much?

Russian aerospace engineering use metric excusively. Actually russian planes have all metric instruments. European stuff is a mixed bag: older planes use imperial, space going stuff uses metric, newer planes seem to use metric (and again, not all of them).

When playing a russian plane sim it's disturbing at first if you're used to flying with regular US/EU instruments as the numbers seem very low (esp. altimeter)... bad habits die hard.

As for US engineering outside of aerospace: NASA uses metric (which has caused problems with sub contractors in the past), and as far as i know electrical engineering use metric as well. Not sure about construction - i'd have to contact one of my colleagues.

Edited January 2, 2014 by Surefoot

[Mars90000000]

www.youtube.com/watch?v=ZMByI4s-D-Y

[Extemporary]

I'm in a bit of an odd situation, because I've used metric all my life in nearly every application, except one. I'm a pilot in North America, so I have to use feet, nautical miles, inches of mercury, inch-pounds, etc. The thing is, I can be in the air and estimate the distance to something in nautical miles, but I really have no idea how far that would be in any other situation. Within aviation I understand it all fine, but I can't intuitively connect it to anything outside that particular field.

On the topic of the actual discussion, though, as one might guess I am partial to metric. It causes me physical pain when I have to calculate centre of gravity and torque using 'inch-pounds' in order to load x 'gallons' of fuel.

[jwenting]

European stuff is a mixed bag: older planes use imperial, space going stuff uses metric, newer planes seem to use metric (and again, not all of them).

metric/imperial conversions caused the Ariane V first flight to crash. They caused major production delays and cost overruns in the Airbus A380 as well (the British design department used imperial, the French and Germans used metric, when they tried to fit the British and Franco-German components together the rounding errors induced by the conversion ended up being higher than the tollerances...).

[Kryten]

metric/imperial conversions caused the Ariane V first flight to crash.

That would be pretty impressive, given no country using the imperial systems supplies Ariane parts or software.

[vetrox]

The problem with this whole metric vs imperial debate is simple human nature. You stick with what you know. If you are brought up from the age of 0 with something in a certain way then its hard to do it any other way

Im in the uk.

I was brought up to read my weight in stone and pounds. Therefore if someone said they weighed 10 stone I would know how much they weighed just from instinct and being used to that unit of measure. (i have since forced myself to use kg for weight)

My parents still cook with fluid ounces and whatever but I have always used metric measurements (ml and litres etc) so when my mum tells me that i should put a couple of ounces of something in...i am completley confused because thats not the unit of measure i was bought up with.

• The biggest problem (especially in the uk) is the mixture of imperial and metric in everyday use. I drive my car in miles yet i dont know how many yards that uses. My fuel efficiency is measured in miles per (british) gallon but I buy my fuel in litres...
  
• In the winter the weather reports give temperatures in degrees C and in the summer its degrees F. My parents measure heat in farrenheit but i use celcius.
  
• People describe a persons height by feet and inches yet I have always had my height measured in centimeters.
  
• I give my baby 7 teaspoons of formula in 210ml of water...I put a cup of [insert spice here] into my bread of which i used x amount of grams of flour
  

and so on

Until a few decades ago we still used an imperial currency system (before my time) half pennies...what a crazy concept.

Another really problematic thing with imperial measurements (and probably the reason science and engineering is done in metric) is the difference in measurements between countries. I used to think american cxars were really innefficient and used heaps of fuel until I found out that the american gallon is different to a british gallon.

I prefer the metric system (i know dont know how much 10 stone is any more but i know i weigh 72 kg) but some imperial stuff is so imprinted on my brain i cant get rid of it. I know the size of my engines bore and stroke in milimeters yet I cant get used to the concept of kilometers per hour which is what the rest of europe use -.- All my socket sets are in mm but when i see American books or videos on car mechanics and engineering they all use imperial sockets. I know my cars torque in Newton meters but everyone else says it in foot-pounds

Edited January 2, 2014 by vetrox

[WhiteWeasel]

The problem with this whole metric vs imperial debate is simple human nature. You stick with what you know. If you are brought up from the age of 0 with something in a certain way then its hard to do it any other way

Ten characters

[Kerbin Dallas Multipass]

Russian aerospace engineering use metric excusively. Actually russian planes have all metric instruments. European stuff is a mixed bag: older planes use imperial, space going stuff uses metric, newer planes seem to use metric (and again, not all of them).

Imperial is international standard in aviation. Russia, China etc changed the flight levels in their airspace to feet in 2011.

All modern planes use imperial only instrumentation. The only exceptions are barometric pressure and in some cases weight

They caused major production delays and cost overruns in the Airbus A380 as well (the British design department used imperial, the French and Germans used metric, when they tried to fit the British and Franco-German components together the rounding errors induced by the conversion ended up being higher than the tollerances...).

citation needed

To my knowledge the French and the Germans used two different versions of a design software causing all sorts of conversion errors.

[Nibb31]

metric/imperial conversions caused the Ariane V first flight to crash. They caused major production delays and cost overruns in the Airbus A380 as well (the British design department used imperial, the French and Germans used metric, when they tried to fit the British and Franco-German components together the rounding errors induced by the conversion ended up being higher than the tollerances...).

- The Ariane 5 maiden-flight failure was due to a software failure in a calculator that was reused from Ariane 4. They omitted to modify the software to take into account the different flight parameters. It's widely documented: http://esamultimedia.esa.int/docs/esa-x-1819eng.pdf

- The A380 delays were mainly due to an underestimation of the wiring work because of a mismatch between the seat configurations that Airbus thought the airlines would want and the actual seat configurations that were ordered. I couldn't find any evidence of your statement, so again "citation needed".

Edited January 2, 2014 by sal_vager
Removed personal attack

[peadar1987]

- The A380 delays were mainly due to an underestimation of the wiring work because of a mismatch between the seat configurations that Airbus thought the airlines would want and the actual seat configurations that were ordered. I couldn't find any evidence of your statement, so again "citation needed".

I heard the wiring delays were because Airbus switched to aluminium wiring from copper to save mass, not anticipating the longer lead time required to process and manufacture aluminium wire. In either case, I doubt it was due to a metric/imperial mix-up. All engineering in the UK is done in metric except for legacy projects like maintenance of last-generation nuclear plants.

[Camacha]

I understand that the Apollo computers were internally using metric units. To help the astronauts, who were used to imperial units as pilots, the numbers were converted to display as those.

It somewhat amuses me, as computers already display in the decimal system to make human readability easier - as opposed to their native binary systems.

It's not a matter of which is better and which is worse.

Please be aware that this discussion was started to discuss the real world implications of the different systems, not what system is better or worse Analysis of advantanges and disadvantages, personal experiences and interesting anecdotes are more than welcome though!

[Surefoot]

metric/imperial conversions caused the Ariane V first flight to crash. They caused major production delays and cost overruns in the Airbus A380 as well (the British design department used imperial, the French and Germans used metric, when they tried to fit the British and Franco-German components together the rounding errors induced by the conversion ended up being higher than the tollerances...).

I know, right, a colleague of mine was there during the launch (he was working on Ariane systems). When he came back and told us the story (at the time we only knew the launch was borked, but not why) we had a good laugh.

That would be pretty impressive, given no country using the imperial systems supplies Ariane parts or software.

True, that was actually due to a british engineer who programmed the ascent module (*) using imperial, while that module was fed with metric units. That made the rocket get too much AoA and veer off course brutally, at which point control room decided to auto destruct the launcher.

(*) pretty much like Mechjeb's function of the same name, this module makes sure the rocket stays on a proper trajectory.

Imperial is international standard in aviation. Russia, China etc changed the flight levels in their airspace to feet in 2011.

Interesting. All the russian aircrafts i have seen were using exclusively metric, that includes helicopters and SU-27 derivatives (which is disturbing if you come from a western aerospace culture). 2011 is quite recent though, not sure there is still any hardware using imperial.. And that makes no sense intuitively, the international standard for measurements is metric (and imperial is used absolutely nowhere in Russia and China). Very weird decision. Do you have any source ?

Edited January 3, 2014 by Surefoot

[Tank Buddy]

I live in the US and would prefer to use the metric system for professional activities. (Science, engineering, etc.) On the other hand, I like to use Imperial units "casually". I am more comfortable with them and they feel logical to me, but the metric system is more logical in every manner.

I like Fahrenheit because there are more whole numbers for the temperatures that occur on Earth and where I live.

As for dates, I feel January 1st, 2014 flows better than The first of January, 2014.

[Surefoot]

I like Fahrenheit because there are more whole numbers for the temperatures that occur on Earth and where I live.

Like 0 for water freezing and 100 for boiling ? O wait (snark snark) (sorry)

I see what you mean but when you do serious scientific work, these imperial units stop making any sense.

(re about Ariane official documentation: they protect their staff by obsucating the error as a "conversion error" not specifying the real cause, that would be politically incorrect and counter productive to fingerpoint a british national on such an international program).

Edited January 3, 2014 by Surefoot

[dharak1]

I don't think that people actually read out the dates based on order. My grandfather asked me to red him something out of the insurance booklet thing he had and i was so used to the American system I told him May first 2014 because it said 5/1/14 But it was actually January fifth. I write it like the booklet but because no one else does I read it the American way. I say it interchangeably like first of January or January first when and I'm asked my birthday I always say 27th of June.

[ZedNova]

Wouldn't it make more sense to read dates off in order like from a calender? ( Year, month day. )

[Surefoot]

That's how we do it in ISO format (ISO 8601). But that's mostly for computer programming, for human language it's much more natural starting from the day, mostly for natural language reasons.

Like when reading an address, you start with the street, then zip and town, then state then country.

[vetrox]

Ahhh ye olde date layout discussion.

Its a regional thing. There isnt really a right or wrong its jsut whatever you were brought up with. Its not hard to convert U.S date format to UK. Its similar with time. UK people say "half past one" (ok we normally shorten it to "half one" which seems really wierd) or a "quarter to two". But U.S peeps say one thirty or one fourty five

Its like those crazy french people. They dont say "Green car" they say "Car green" MADNESS!!!

[koshelenkovv]

I don't think that people actually read out the dates based on order. My grandfather asked me to red him something out of the insurance booklet thing he had and i was so used to the American system I told him May first 2014 because it said 5/1/14 But it was actually January fifth. I write it like the booklet but because no one else does I read it the American way. I say it interchangeably like first of January or January first when and I'm asked my birthday I always say 27th of June.

Here in Russia we use dotted '05.01.14' or dashed '2014-01-05' notation. So, If I see somewhere '5/1/14' I know that it's American month-first date.

[Charzy]

I've never understood American dating. Why would you have the month before the day and then the year?

Having it in order (day, month, year) seems so much more intuitive.

[ZedNova]

I've never understood American dating. Why would you have the month before the day and then the year?

Having it in order (day, month, year) seems so much more intuitive.

I always thought it's because we usually try to find the month on the calender before the day.

If i said i have a dentist appointment on the 23rd of of may, then i'd turn the calender to may, then find the day.

[peadar1987]

To be honest, the system that makes the most sense is YYYY/MM/DD, as this means that a list of dates will be sorted into the correct order without any special date-specific jiggery-pokery. I believe the US military use this format, at least in certain applications

[SargeRho]

The system that makes the most sense is DD/MM/YYYY, since days change the most often, then months, then years.