Do Americans use metric system?

A few conversions I do are gallons to litres and kms to miles and how to work out distance and time to create mph.

My car displays mpg but petrol is sold in litres so if I do 234 miles and my car does 50mpg average and petrol is £1.24 per litre, how many apples do I have?

I remember reading that cannabis dealers could be prosecuted for selling drugs in ounces rather than actually selling illegal drugs. Probably just another stupid story.

Problem is when is a litre a litre? A litre of petrol at 30 degrees Celsius is very different than at 0 degrees. So always buy petrol at night when it's cooler as you're getting more petrol!

A pressurised suit is needed at altitude such as the U-2 pilots because the boiling point of water can become lower than the human body temperature so the water in your blood can turn to gas. That's not good!

So boiling point of water is 100'C. OK... What type of water? Sea water? Is this at altitude? On the planet Mars?

The boiling point of water originally defined by the Celsius scale is 100°C at 1 standard atmosphere pressure. I don't know the water composition.

Since the '50s the Celsius scale has been defined in terms of absolute zero and the triple point of a standard water composition at 1 standard atmosphere.

Since a couple of days ago, SI units have all been redfined in terms of physical constants.
BIPM - measurement units

I read that when the folks at China Lake were developing the Sidewinder missile that they found that passive IR sensors could find when the various female employees were having their periods. When the girls found out about that they made a list of the data, gave it to the men and told them to cut it out.

So the phrase "hot girls" has some scientific basis.

swampyankee said:

I do physics (which I teach) in SI

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I wondered if anyone would make this point. The so called METRIC system ended officially way back in 1960 when the International System of Units, universally abbreviated SI (from the French Le Système International d'Unités), was established by the 11th General Conference on Weights and Measures (Conférence Générale des Poids et Mesures). The term METER/METRE derives from Old English, reinforced in Middle English by Old French metre, from Latin metrum, from Greek metron meaning 'measure'. You might recall that the term is/was in use prior to being taken over by the scientific community. Poetry and music have a rhythmic pattern of beats which is called their Meter/Metre. It can also be used to simply mean 'measure' as in "There is no metre to happiness"
Not to mention Water METERS; Gas METERS; Electricity METERS; and Parking METERS.
But I digress. The original idea behind the Metric System was born during the French Revolution. The New French Republic wanted to remove any and all vestiges of the monarchy. The French system of weights and measures was, at the time, like the English system, based on plethora of objects with no relationship to each other and like the Pied du roi, the Royal Foot. As long as they were starting over from scratch several well-known French scientists petioned to have the "New" system be based on 'imperishable' objects that were eternal and that any and everyone who wanted to had access to. In other words abandoning things like a bar of metal stored in a vault somewhere. The new system would also be a decimal system AND most importantly all units would relate directly to one another.
Starting with the unit of length the METRE defined as 1/10,000,000 the distance from the equator to the north pole along the Paris meridian. Which the French actually measured (at least most of the accessible parts that were on land). The result was the METRE divided up into base 10 units. Volume was defined by constructing a CUBIC DECIMETER which is/was a LITRE. The the cubic decimeter/litre was filled with the Earth's most common substance WATER. One CUBIC MILLIMETER of pure water became the GRAM. Since a decimeter = 10 millimeters the cubic decimeter is 1000 cubic millimeters of one gram each or a cubic decimeter of pure water is one KILOGRAM.
As the Metric system gained in acceptance, the growing scientific community began to add more and more units of measure, Ampere, Henry, Weber, Torr, Atmosphere, Tesla, amu, lumen, angstrom, etc. As a result the 1960 conference ended the Metric system replacing it with the SI system decreeing that any and all measurements HAD to be derived from just seven base units: the metre for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. Interesting to note that the former GRAM and LITER are no longer SI units.
This SI rule leads to simplification BUT forces the use of non-usable/inconvenient units of measure like the PASCAL for pressure. Under SI rules the unit of pressure, the PASCAL has to be FORCE per unit of AREA. In SI one NEWTON (Kilogram / s^2) of force / area of one square meter. A unit so tiny as to be totally impractical except maybe to measure mouse farts. The Earth's atmosphere exerts a pressure of 101,325 Pascals. The weather Guys who used to use the BAR ( one atm) and millibar now use hPa or hectoPascals. 100 hPa = 1 millibar. Materials and engineering are forced into Mega and even GigaPascals for the most common of substances.

I wish the U.S. would change because most science is done in scientific units. But if you don't know this store it is worth looking up:

Gimli Glider

It's the simple things in life......

Metric is just so much more logical to me.

vikingBerserker said:

It's the simple things in life......

Metric is just so much more logical to me.

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Entirely agree.

A propos of absolutely nothing, Alan Turing made a compelling argument that humans should adopt base 12 number system because of the ease of counting using the knuckles and tips of the fingers as the numerals, with the thumb being the counting pointer. While I admire the idea, I think it would drive me nuts!

Just to pick a nit: a triple point is where solid, liquid, and vapor are in equilibrium; this happens at a specific temperature and pressure.

The Basket said:

Problem is when is a litre a litre? A litre of petrol at 30 degrees Celsius is very different than at 0 degrees. So always buy petrol at night when it's cooler as you're getting more petrol!

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Most petrol tanks are stored underground, so end up without enough diurnal temperature variation to make a difference.

I once bought a set of combination wrenches Made in India.

As near as I could tell they must have used the same forgings for the Metric and the SAE ones, because none of them with either exactly metric nor SAE.

MIflyer said:

I once bought a set of combination wrenches Made in India.

As near as I could tell they must have used the same forgings for the Metric and the SAE ones, because none of them with either exactly metric nor SAE.

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Whitworth?

buffnut453 said:

Entirely agree.

A propos of absolutely nothing, Alan Turing made a compelling argument that humans should adopt base 12 number system because of the ease of counting using the knuckles and tips of the fingers as the numerals, with the thumb being the counting pointer. While I admire the idea, I think it would drive me nuts!

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The problem with people like Turing is that they cant imagine not being like they are. I am sure he could work in any base you care to mention, it doesn't mean the general public can. In fact the Chinese count to ten on one hand.

gumbyk said:

Whitworth?

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Tiawanese and Chinese toolsets had a combination of Metric, SAE and Whitworth sizes, too.

mikewint said:

Materials and engineering are forced into Mega and even GigaPascals for the most common of substances.

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We used Mega Pascals which is the same as N/mm2 but easier to use for the same reason as it is easier to write MPa. than N/mm2 on here. It is just how the metric system is used 6,000 Km is just another, more convenient way of saying 6,000,000 metres.

I hope you all realize that where it concerns electricity, you have always been in metric/SI country exclusively, including all the modifiers: MilliVolt, MegaWatt, KiloOhm, MicroFarad and so on.

By the way, the IJAAF used metric, because they were established with the aid of a French technical mission, while the IJNAF used British haphazard, because they were tutored by Brits. That led to otherwise identical engines not being exchangeable between services, because the mounting and connecting hardware was incompatible. And while both Kawasaki (Army) and Aichi (Navy) license-built the DB601, you couldn't put an Aichi engine into a Ki-61 (that was considered when the Kawasaki factory was bombed), because all the screws, nuts, bolts and washers in the engines had different sizes. And while the Navy continued to use the British 7,7x56R cartridge, the Army developed a 7,7x58 in rimless AND semi-rimmed, just to be contrary, I guess.

mikewint said:

This SI rule leads to simplification BUT forces the use of non-usable/inconvenient units of measure like the PASCAL for pressure. Under SI rules the unit of pressure, the PASCAL has to be FORCE per unit of AREA. In SI one NEWTON (Kilogram / s^2) of force / area of one square meter. A unit so tiny as to be totally impractical except maybe to measure mouse farts. The Earth's atmosphere exerts a pressure of 101,325 Pascals. The weather Guys who used to use the BAR ( one atm) and millibar now use hPa or hectoPascals. 100 hPa = 1 millibar. Materials and engineering are forced into Mega and even GigaPascals for the most common of substances.

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1 bar = 100kPa

1 bar does not equal 1 atmosphere. 1 atmosphere is, in fact, 1.01325 bar.

Funny thing about MPa is that if you use mm for length units and N for force units you directly end up with MPa. You don't have to work with N and m to calculate Pa and then figure out how many MPa that is (not that that would be difficult).

Wurger said:

Actually the flight levels are nothing more but the altitude measured in thousands feet. Eg.. FL 100 = 10000 feet, FL80 = 8000 feet,.

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Well, sort of. In North America anyway (the rest of the world does weird stuff) altitudes lower than 18,000 feet are defined in feet referenced on local surface barometric pressure, while above that the Flight Levels are based on a constant 29.92 " HG standard atmospheric pressure. If we could only survive the transition, we'd be way better off to go with the rest of the world and switch the whole system over to "metric" units. It's only us brontosaurs that would be inconvenienced, the younger folk with more flexible minds would adapt readily.

Cheers,
Wes

buffnut453 said:

In British English, a meter is a device used for measuring something (eg speedometer, gas meter, electric meter etc)

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And a meter is a mental device used for measuring a linear distance.
And speaking of the confusion of tools needed to work on today's "global" machinery, I remember maintaining a fleet of Netherlands manufactured Fokker F27s of varying vintages with RR Dart engines made from 1947 to 1977, with Dowty props of varying ages, Lucas electrics, Maxaret antiskid, and Goodyear and Dunlop brake assemblies. SAE and metric tools weren't enough. You had to have British Standard and Whitworth as well. Sometimes you would get an older Dart with newer accessories on it and you'd wind up using Whit, BS, and metric all on the same job. Newer combustion cans on an older engine might have "updated" hardware installed...or not.
Cheers,
Wes

Many years ago I was involved in a big job, and one of the consultant structural Engineers was a Canadian.
Discussing about the stresses in a column I noticed that he was mentally translating data from Imperial to SI and he noticed that I was doing the same but from ST ( Sistema Tecnico, used by italian Engineers until twenty years ago).
"D***n SI" was our mutual agreement "could not things have stayed as they were, we Engineers were working so well, with that units…"