Unit conventions (SI versus others)

[JR Jonsson]

Can anyone explain to me how it comes that US not have accepted the use of SI ?
Do you not understand the benefits ?

Would it not be more effective if the new generation of students could concentrate on understanding fundamental physics relations rather than struggle whith old-fashioned and confusing unit transformations ?

As far as I know it is only US beside Liberia and Burma who has not understod the importance of this.
Why ?

 

[Choppy]

This is best answered by The Frantics.

 

[Student100]

Can anyone explain to me how it comes that US not have accepted the use of SI ?
Do you not understand the benefits ?

Would it not be more effective if the new generation of students could concentrate on understanding fundamental physics relations rather than struggle whith old-fashioned and confusing unit transformations ?

As far as I know it is only US beside Liberia and Burma who has not understod the importance of this.
Why ?

Struggle with confusing unit transformations? I don't think I ever had a physics class that didn't use SI, except the odd course that used Gaussian units. Certainty, no course ever asked me to convert foot pounds to Newton meters if that's what you mean.

So we do use SI primarily in science courses, and not Imperial units in the US.

 

[Vanadium 50]

But the US has been metric since 1866!

 

[Student100]

But the US has been metric since 1866!

Psh, we've done advanced from that: https://en.wikipedia.org/wiki/America_COMPETES_Act

 

[Dale]

Do you not understand the benefits ?

I don't understand the benefits. Scientists and engineers are already free to use SI if they want, and so are manufacturers. So what are the benefits?

 

[Ibix]

This is best answered by The Frantics.

Thank you for that.

Spoiler

"YARDS! What happened to CUBITS!?"

 

[jbriggs444]

I don't understand the benefits. Scientists and engineers are already free to use SI if they want, and so are manufacturers. So what are the benefits?

It would be nice not to have fifty bajillion sizes of sockets in my set.

 

[Dale]

It would be nice not to have fifty bajillion sizes of sockets in my set.

So auto mechanics could reduce the cost of their tools. That would be a benefit to them, but tool manufacturers would lose sales so that would be a disadvantage to them.

 

[jbriggs444]

So auto mechanics could reduce the cost of their tools. That would be a benefit to them, but tool manufacturers would lose sales so that would be a disadvantage to them.

Although you can run an economy by paying one batch of people to make holes and another batch of people to fill them in and while both groups of people will consider this to be to their benefit, there are better options.

 

[Vanadium 50]

Although you can run an economy

Run? I thought you said "ruin".

 

[256bits]

Some non-SI units are still very much common ex calorie ( or does any country with SI as the legal system of measurement just outright ban and fine usage ?? )
https://www.nist.gov/pml/nist-guide-si-chapter-5-units-outside-si

 

[russ_watters]

Can anyone explain to me how it comes that US not have accepted the use of SI ?

Inertia.

 

[fresh_42]

Some non-SI units are still very much common ex calorie ( or does any country with SI as the legal system of measurement just outright ban and fine usage ?? )
https://www.nist.gov/pml/nist-guide-si-chapter-5-units-outside-si

Would be interesting to know, where Joule is actually used instead of calories. I mean, they don't get even this right, as usually all talk about cal and mean kcal. And I can't remember a correct weather report. I usually don't get understood very well, if I complain about temperatures above 300. But °C is SI you could argue. Well, that's right, although not logical, but e.g. °mC isn't allowed here. I vote for Delisle!

P.s.: I counted 89 (sic!) different miles on the Wiki page!

 

[Mark44]

Can anyone explain to me how it comes that US not have accepted the use of SI ?
Do you not understand the benefits ?

Maybe you would like to volunteer to come here (U.S.) and change all of the millions of property descriptions, all of which are relative to some township (36 square miles), and one or more sections (1 square mile = 640 acres) within the township.

Here is an example property description for a place in the state of Florida. Care to take a crack at this one?

 

[Astronuc]

We have the benefit of hybrid units, e.g., kW/ft (linear power) and cal/g (specific enthalpy/energy), in one particular industry. Most of my reports have incorporated both units since they were used in the US, Europe and Asia. I much prefer SI/mks, or mixed units, e.g., W/cm.

 

[OCR]

Here is an example property description for a place in the state of Florida.

Well, at least that description didn't use chains...

Although, mostly related to wildland fires, the LMAs still do, to a certain extent...[COLOR=#black].[/COLOR]

And then... there's also the good old DBH measurement... so if you want somebody to cruise your timber for a sale, try to find a real short person ... lol

I'm not even going to talk about log scaling, and the Scribner Decimal C rule...[COLOR=#black].[/COLOR]

 

[Helios]

The drawback to the number 10, the basis of the metric system, is its lack of divisors. No one is complaining about a 24 hour day. One could invent a 10-part year, but then you'd lose the 4 seasons. Many things come in 12's. Some things come in 20's. When something is not metric, there's usually a very pragmatic reason to prefer that system of measure. I like inches and feet, also quarts and gallons. I hope they are not abolished.

 

[Astronuc]

The drawback to the number 10, the basis of the metric system, is its lack of divisors.

Except most engineering applications, particularly in manufacturing, use decimals even when using inches.

Using divisions like 1/16 inch or 1/32 inch might work for construction, or something similar, but it doesn't work well in precision engineering and manufacturing. When it comes to small parts, we often use mils, or fractions of mils, and sometimes micro-inches.

 

[Ibix]

Tenths are convenient because we use base ten because we have ten fingers. I always said we ought to have evolved an extra finger.

 

[fresh_42]

Tenths are convenient because we use base ten because we have ten fingers. I always said we ought to have evolved an extra finger.

A penny for your thoughts! The Sumerians used the base 60 ...

 

[JR Jonsson]

I know SI is in use in U.S as well as other units are common everywhere
As a step on the way you can use both old units and SI (as for "cal" and "J" on all food declarations in sweden)
My point is that physics is hard enough to understand without unit conversions.
I had a student some years back who went to U.S. For one year between the ordinary in Sweden (17-18 years old)
He was advised not to study physics because it was considered very difficult, but did so anyway because he liked it.
I asked how he had done when he was back.
"The physics was really easy", he said, "nothing new but all the conversions. But I just converted the given data to SI, solved the problem and gave the answer in the unit that was asked for. Nobody understod how I did, not even the teacher."

The benefits with SI is simply that physics (and offcourse all technical use of it) will be easier.

 

[Student100]

I know SI is in use in U.S as well as other units are common everywhere
As a step on the way you can use both old units and SI (as for "cal" and "J" on all food declarations in sweden)
My point is that physics is hard enough to understand without unit conversions.
I had a student some years back who went to U.S. For one year between the ordinary in Sweden (17-18 years old)
He was advised not to study physics because it was considered very difficult, but did so anyway because he liked it.
I asked how he had done when he was back.
"The physics was really easy", he said, "nothing new but all the conversions. But I just converted the given data to SI, solved the problem and gave the answer in the unit that was asked for. Nobody understod how I did, not even the teacher."

The benefits with SI is simply that physics (and offcourse all technical use of it) will be easier.

Again, no proper physics course in the US is using anything but SI or other metric type units.

At most there may be problems given in one set of units and you're asked to convet to SI, but that's only normally in the very beginning when students are learning conversions of all sorts.

I don't know where your student went, but it isn't normal. Also any physics teacher should be able to convert any type of units and understand unit conversions.

 

[SW VandeCarr]

But the US has been metric since 1866!

Yes, and the US Bureau of Standards redefined "customary" units in terms of metric standards. One inch is defined as exactly 2.54 cm. Congress allowed customary units to be used, probably thinking for the time being, but meaning metric units would never be used if it could possibly be avoided.

 

[vela]

My point is that physics is hard enough to understand without unit conversions.

What's the big deal? Unit conversions aren't difficult. They're annoying and, at times, tedious, but they're hardly difficult. And as others have pointed out, physics courses typically use SI units.

"Nobody understood how I did, not even the teacher."

I don't believe this for a second.

 

[Dale]

The benefits with SI is simply that physics (and offcourse all technical use of it) will be easier.

I disagree with this. SI is not particularly convenient for many physics disciplines. It is bad for both general and special relativity, it is bad for QM, it is not the best for electromagnetism, and it is not used without substantial modification for particle physics.

It works for medicine and biology. It works for engineering. It works for trade, but I think a blanket statement that it makes physics easier is excessive.

 

[SW VandeCarr]

Well, at least that description didn't use chains…

As Mark44 pointed out in post 15, land measure in the US is based on the acre and changing it would be very difficult. Chain-link measure in land measure is compatable with the acre.

From google headline:

"A chain (ch) is a unit of length. It measures 66 feet, or 22 yards, or 100 links, or 4 rods (20.1168 m). There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains (that is, an area of one chain by one furlong)."

 

[JR Jonsson]

I'm sorry if i expressed myself badly.
Offcourse you in this forum understand SI and it's benefits. That is why I am taking part in here.
What i meant was the uncovinience with the imperial units ( or what it's named) when dealing whith US technical matters, and US has some influence on the rest of world.

It is interessting that the question about units seems to be so emotional.

The history of SI started whith units for length, mass and time. When needed and an agrement was made, the units for other dimensions was introduced.
In the case of elektronics, chemistry and light I don't think there is so much to choose between, it is relative new fields so there is simply no old units to argue whith.

Regarding new disciplins in physics it's totaly meaningless to say that SI don't is good. There are totaly new dimensions so if needed the science comunity hopefully will agree on definitions for units if there are something to messure.

It's easy to convert units when you know how, that's wright, but it's so unconvinient and makes it harder to introduce understanding for the fundamental physics relations.

I am in the technical field as profession and countless examples of the problem whith different unit- systems.

Another aspect of this is the communikation between scientists and the craftsman. It's difficult to introduce new ideas when there is no common language.

I'm no liar, the story was true. It was some years ago but I'm afraid there still are some old units in school, in US as well as in the rest of this world.
And it will be some problems if technical students come's to the first employment with only SI in mind.

I started this thred in hope of ideas about how to overcome communikation problems and phasing out unnecessary old-fashioned systems where we can.

 

[Dale]

Offcourse you in this forum understand SI and it's benefits.

I am still not convinced that there are any particular benefits. So far all you came up with is that physics is easier, and I don't think that is particularly true.

SI is already used in the US where it is beneficial and not used where it is not beneficial.

 

[JR Jonsson]

I am still not convinced that there are any particular benefits. So far all you came up with is that physics is easier, and I don't think that is particularly true.

SI is already used in the US where it is beneficial and not used where it is not beneficial.

You make me confused.
For me it is physics to calculate f.ex. the heat loss in a building, equippment as pipes, pump's, radiators and heatpump needed to keep the house warm.
Compare the calculations needed whith SI resp. Imperial units; is there no difference ?

 

[OCR]

As Mark44 pointed out in post 15, land measure in the US is based on the acre and changing it would be very difficult.

Well, yes, that was my point... I thought, anyway... ??
I did say... "well, at least that description didn't use chains"… right ?

From google headline:

Oh!... maybe you didn't see my chain [COLOR=#black].[/COLOR]link ... lol.[COLOR=#black]..[/COLOR]

From Wikipedia:

"A chain (ch) is a unit of length. It measures 66 feet, or 22 yards, or 100 links, or 4 rods (20.1168 m). There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains (that is, an area of one chain by one furlong)."BTW, another nybble of information:

A rectangle, 8 feet wide and 1 mile long also has an area of one of 1 acre...[COLOR=#black].[/COLOR]

 

[Dale]

For me it is physics to calculate f.ex. the heat loss in a building, equippment as pipes, pump's, radiators and heatpump needed to keep the house warm.

Yes (I would lump that into engineering in my previous list). My point is that it is also physics to model collisions between galaxies and atomic spectra and orbits of comets and high energy particle collisions and electromagnetism. SI is not particularly beneficial for any of those.

In the USA, the SI system is already used where it is convenient and not used where it is not.

 

[SW VandeCarr]

A rectangle, 8 feet wide and 1 mile long also has an area of one of 1 acre...[COLOR=#black].[/COLOR]

8x5280=42240 sq ft, 1 acre=43560 sq ft (US)

 

[OCR]

8x5280=42240 sq ft, 1 acre=43560 sq ft (US)

OK, 8 feet wide in one mile is actually ‪0.969,697 acre... so it rounds to 1 acre...[COLOR=#black].[/COLOR]
You're right though...[COLOR=#black].[/COLOR][COLOR=#black]...[/COLOR]

A rectangle, 8 feet wide and 1 mile long also has an area of one of 1 acre...

That's an old rule of thumb in farming... used to estimate how many acres per hour you can do...
An example... our grain drills are each 8 feet wide, and we pull 5, hitched side to side, so that makes a 40 foot wide swath, or, about 5 acres in a mile.
If we go about 6 MPH, we can do about 30 acres per hour...[COLOR=#black].[/COLOR]

Lol, it does take some pretty big thumbs for that to happen though, considering overlap and the directional changes...

 

[SW VandeCarr]

The difficulties faced by the US in converting completely to metric units, let alone SI, go beyond land measure. Consider the economic impact of professional sports. It's a big deal for major US cities who compete for franchises. Football would be played on a 91.44 meter long field. A first down requires a gain of 9.144 meters after 4 downs. You could rescale the game to 100 meters, but that changes the game. In baseball, the impact of rescaling is even greater. Alternatively we could just use percents: the 50 % line for the coin toss and spotting the ball on the 20% line after the kickoff. It might take some getting used to distance gained or lost in percents rather than yards. In baseball, we could just mostly ignore the numbers and get used to 100 meter home runs.

Or we could just ignore the whole issue and use whatever units we want. That seems to have been the real intention of Congress way back in 1866 when the US became officially metric.

EDIT: For units used in commercial transactions, I believe these units are required to be those that are precisely defined in terms of metric units by the US National Institute of Standards and Technology (NIST).

https://en.wikipedia.org/wiki/United_States_customary_units