Systems of units

[Paul Mitchell]

I have seen, on this board and elsewhere, people using the term "English Units" to refer to what I would call "Imperial Units" (or "measurements").

It appears to me that this is an American term. Is this the usual name for these units in the U.S.?

Is this because the term "Imperial" is frowned upon?

Here in England, and indeed the rest of the UK, they are always referred to as "Imperial", I'm sure the Scots and Welsh don't think of them as English.

I am (just) young enough that I was never taught anything but metric in school, so I was surprised when Mars Climate Orbiter was lost (link posted by Matsukov) in a mixup over Metric and Imperial measurements. The idea of doing modern engineering or science in anything but metric units was a bit of a surprise to me.

On a slightly frivolous note, I was watching Stargate last night, and somebody actually offered measurements in Ergs! Does anyone still use the CGS system?

[tjm220]

Some values in Imperial units are different when compared to English units in the US anyways. For example a US gallon for example is ~3.78L whereas the English is over 4L.

[Paul Mitchell]

Some values in Imperial units are different when compared to English units in the US anyways. For example a US gallon for example is ~3.78L whereas the English is over 4L.

Interesting, I would call those "U.S." and "Imperial" gallons respectively. The root cause of that difference is as follows:

• 1 gallon = 8 pints
  U.S. pint = 16 fluid ounces
  Imperial pint = 20 fluid ounces

[tjm220]

Yeah I suspect that the US and England had a bit of a falling out in their pasts. :wink:

[Paul Mitchell]

Yeah I suspect that the US and England had a bit of a falling out in their pasts. :wink:

You think so?

Oddly I've always thought that the U.S. definition of a pint was more logical, as a pound on both sides of the pond has 16 ounces.

[Andrew]

I was surprised when Mars Climate Orbiter was lost in a mixup over Metric and Imperial measurements.

Not according to Jim Oberg it wasn't.

I think he has also posted about this on this board under the name JimO.

Oddly I've always thought that the U.S. definition of a pint was more logical, as a pound on both sides of the pond has 16 ounces.

A US fluid ounce is slightly larger than an Imperial one. Did you know that?

[Ut]

On a slightly frivolous note, I was watching Stargate last night, and somebody actually offered measurements in Ergs! Does anyone still use the CGS system?

Yeah. Astrophysicists.
Oy.

[Tobin Dax]

On a slightly frivolous note, I was watching Stargate last night, and somebody actually offered measurements in Ergs! Does anyone still use the CGS system?

Yeah. Astrophysicists.
Oy.

Real Astronomers do is what I was told when I came here for Grad School. I now have to think to remember the values of constants in mks (or SI, if you prefer).

BTW, Paul Mitchell, I've heard Star Trek characters use dynes a number of times, so use of cgs isn't unique to Stargate.

[Ut]

JANSKY~@!

Sorry. I still suffer through day terrors.

[Van Rijn]

Here's some info on the different systems:

http://www.unc.edu/~rowlett/units/index.html

There were some interesting bits here on english units -

http://www.unc.edu/~rowlett/units/custom.html

and here on where things are and aren't in the U.S.

http://www.unc.edu/~rowlett/units/usmetric.html

This comment fits my experience exactly:

In the 1970's there was a major effort to increase the use of the metric system, and Congress passed the Metric Conversion Act of 1975 to speed this process along. However, American consumers generally rejected the use of metric units for highway distances, weather reports, and other common measurements, so little was accomplished except for the encouragement of faster metric conversion in various scientific and technical fields.

When I was in school they made a point of emphasizing metric units, since we were told we were going to be switching over within the decade. Didn't happen of course. I still think in feet and pounds. I have no real problem with metric units, but I tend to translate the measurements back to what I'm comfortable with. Mind you, I suspect most Americans couldn't tell you the length of a meter or equivalent weight of a kilogram.

[Paul Mitchell]

A US fluid ounce is slightly larger than an Imperial one. Did you know that?

No I did not.

By how much?

[Paul Mitchell]

BTW, Paul Mitchell, I've heard Star Trek characters use dynes a number of times, so use of cgs isn't unique to Stargate.

Now you say that, it does sound awfully familliar

[Paul Mitchell]

Mind you, I suspect most Americans couldn't tell you the length of a meter or equivalent weight of a kilogram.

Now there's a whole other minefield, over here that's a "metre" (the French spelling), and a "meter" is a measuring device.

[Andrew]

A US fluid ounce is slightly larger than an Imperial one. Did you know that?

No I did not.

By how much?

Apparently they are in the ratio 1.04.

[kylenano]

CGS - I remember at university, some years ago now, a lecturer giving the mass of a star in grammes. (We did use solar masses too.)

[Ut]

Mind you, I suspect most Americans couldn't tell you the length of a meter or equivalent weight of a kilogram.

Now there's a whole other minefield, over here that's a "metre" (the French spelling), and a "meter" is a measuring device.

That's not a minefield. That's "international convention"

Ahh, time to dig out the ol' metremeter.

[mike alexander]

For weight and volume, English units are based on powers of two, sort of, which makes as much sense as powers of ten.

I think it was Philip Morrison (where I first heard it, anyway) who pointed out that the ounce/ pound system is more 'logical' than the metric system if you are just starting out.

[Van Rijn]

Now there's a whole other minefield, over here that's a "metre" (the French spelling), and a "meter" is a measuring device.

Oh, we have meters too - my digital multimeters, for instance. Isn't alternative spelling great? When I see "metre" I think "meat re" (as in "regroup"). "Sceptic" is better - I read that as "septic" and I always want to add "tank" after it. And I just cannot abide by "aluminium." :wink:

On the other hand, I wish we used "lift" instead of "elevator." That is an evil word.

[frogesque]

Gallon, Wipikedia

In the US a gallon is 3.78541 litres: see U.S. customary units
An Imperial gallon is 4.54609 litres: see Imperial unit.

Link gives full definitions and equivalences

Both the Imperial and United States gallon are equal to 8 pints. However in the US a pint is 16 fluid ounces whereas an Imperial pint is 20 fluid ounces. Thus a U.S. gallon is 128 fl. oz and an Imperial gallon is 160 fl. oz; this means that a US fluid ounce is around 1.8047 cu. ins and an Imperial fl. oz is around 1.7339 cu. ins. The US fluid ounce is actually bigger than the imperial, although the US gallon is smaller.

[Bad jcsd]

For weight and volume, English units are based on powers of two, sort of, which makes as much sense as powers of ten.

I think it was Philip Morrison (where I first heard it, anyway) who pointed out that the ounce/ pound system is more 'logical' than the metric system if you are just starting out.

hardly our number system is based on powers of 10. I wa sbrought up on both syetms and I see nothing logical about imperial measuremnts at all!

[papageno]

hardly our number system is based on powers of 10. I wa sbrought up on both syetms and I see nothing logical about imperial measuremnts at all!

Think of using a piece of string as a length standard.
It is very easy to take the half of that length by hand, and then take the half of that half, and so on.
That gives a series of fractions with powers of two in the denominator.

Of course, now we have rulers for this.

[A Thousand Pardons]

For weight and volume, English units are based on powers of two, sort of, which makes as much sense as powers of ten.

I think it was Philip Morrison (where I first heard it, anyway) who pointed out that the ounce/ pound system is more 'logical' than the metric system if you are just starting out.

hardly our number system is based on powers of 10. I wa sbrought up on both syetms and I see nothing logical about imperial measuremnts at all!

We've tried metric systems before. A mile used to be a thousand paces, a year had ten months, etc. They evolved.

[Disinfo Agent]

Now there's a whole other minefield, over here that's a "metre" (the French spelling), and a "meter" is a measuring device.

[nitpick] The French spelling is mètre. That's the British spelling. [/nitpick] :P

[Bob B.]

Here in the USA we use what is called the U.S. Customary System, which was inherited from, but is now different from, the British Imperial System. I think people often use the term English System when refering to the U.S. Customary System because they don't realize (1) is it not called the "English" system, and (2) the systems are not the same.

[Eta C]

On one level, converting between cgs and mks metric units is trivial since it's just a matter of powers of 10. However, cgs units, as used by scientists set c (the speed of light) and h-bar (planks constant divided by 2pi) equal to one. This simplifies the math since these constants pop up all over the place and it can be a chore to keep track of where they belong. So you do the calculations without them and then plug in the proper combination at the end to make the units come out right. The main place this pops up in in electromagnetism where you can enounter the cgs unit of charge called the electrostatic unit (or esu) instead of the mks metric unit of the Coulomb.

Then again, you can run into some very odd units when working with the military. One particularly odd one I've come across is the "kiloyard," which is just another way of saying one thousand yards. The Navy uses this unit of range a lot since one nautical mile is 2 kiloyards within one percent. I once encountered a computer simulation (not written by me!) that measured depths in feet, ranges in kiloyards, and sound speeds in meters per second. Talk about mixed units!

[Bad jcsd]

The vast majority of scientist use the SI system of units which is based on mks units.

There are other units sytems which use natural units, for example c = 1 is pretty much universally used among relativists, it's only when you need a numerical answer that you'd bother to put c back into the equation.

[weatherc]

We graphic designers have our own fun systems of measurement.

Type size is measured in points. 1 point is 1/72 of an inch.

Line length is measured in picas. 1 pica is 12 points, or 1/6 of an inch.

There is also the really obscure cicero, but I've never used it, nor do I know anyone else personally who has used it.

Kerning (the spaces between individual pairs of letters) and tracking (the overall spacing between the letters of a line of type) is measured using units loosely based on the letter "M." These units are referred to as ems. This is a flexible measurement, and it is dependent upon the type size (measured in points). Kerning and tracking are measured in thousandths of an em (but they are not referred to as "milliems").

Standard US paper sizes are measured in inches. Some examples are Letter (8.5 x 11 inches), Legal (8.5 x 14 inches) and Tabloid (11 x 17 inches).

Standard European paper sizes are measured in millimeters. Some examples are A4 (210 mm x 297 mm), A5 (148 mm x 210 mm), and A3 (297 mm x 420 mm).

And then, there is the "weight" of the paper, which is measured in pounds. Examples would be 28 lb. text, 40 lb cover and 80 lb card stock.

Fun, huh?

[A Thousand Pardons]

I once encountered a computer simulation (not written by me!) that measured depths in feet, ranges in kiloyards, and sound speeds in meters per second. Talk about mixed units!

I think I have you beat there. A worldwide bathymetric database we received at Lockheed, in the early eighties, had depth in fathoms, and x-y location in inches.

The x-y was a measurement in inches from the lower left hand corner of the standard nautical charts.

[Paul Mitchell]

And then, there is the "weight" of the paper, which is measured in pounds. Examples would be 28 lb. text, 40 lb cover and 80 lb card stock.

Fun, huh?

I'm sure in the UK we measure paper weight in grammes per centimetre squared.

[worzel]

If only we had evolved with 16 fingers, our number base would be hexadecimal, our units would have the convenience of the metric system and be based on powers of two, and bit twiddling would be a dodle.