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Fahrenheit was invented first in 1724. The United States started using Fahrenheit. Celsius was proposed in 1742. Celsius was selected by the Metre Convention in

Fahrenheit was invented first in 1724. The United States started using Fahrenheit. Celsius was proposed in 1742. Celsius was selected by the Metre Convention in 1875 as the international standard (mostly because France was already using it). Everyone else except the United States and Liberia has slowly switched to the international/scientific standard (now known as SI) because having multiple standards is an ongoing cost but switching standards is a one-time cost. The United States is sentimentally attached to its pre-SI units more than they care about international inter-operability – so they continue to endure the ongoing cost of juggling a separate system of units while also using SI units in most science and some engineering work.

roryisok 8y ago
The UK still uses imperial for road signs I think
- pebers 8y ago
  Yes, we do. I assume the cost of changing them all (and the resulting confusion and potential danger) was deemed too high.
- orf 8y ago
  We use imperial for long distances, but SI for short ones. We use imperial for human weights, but SI for food and drink weights (excluding the pint!). Height is in imperial as well, mostly. Temperature is in SI. It's all quite confusing when you explain it, but pretty natural when you live there
  - roryisok 8y ago
    I live just next door in Ireland. We're officially metric but people still talk in miles, feet (and yards), acres, stone, pints, etc
    - orf 8y ago
      Oh yes I forgot about acres!
      - roryisok 8y ago
        Last car I owned had all the trip counters in Mph and the fuel efficiency in Mpg. New one is km and lpk, I'm totally lost
  - dogma1138 8y ago
    There is also plumbing and engineering which uses both depending on the case and the discipline. My old flat had a faucet that was a pain to update to a mixing tap because the hot water used inch threads and the cold used metric....
r00fus 8y ago
I'd say it has more to do with the US industry's ability to dominate the imperial standard and use it like Apple uses the "lightning" port... to prevent interoperability and endure a protected market for US manufacturers.
- dogma1138 8y ago
  Imperial units have a lot of advantages when you need to do accurate calculations and produce good measurements. Since everything is fractions you don’t get irrational numbers and calculations are super easy even without calculators case and point say you need to square a measurement squaring 3/16th of an inch is something any fifth grader can do in their head or simply look it up in an easy table. Squaring 4.7625mm on the other hand requires a calculator and since you get an irrational number you can’t easily accurately measure it with common tools in the real world.
  - Aardwolf 8y ago
    Who says one has to use fractions with one unit and real numbers with another? Both units are just a different multiplier. What stops one from using 3/16th of a meter? (I admit I rarely see SI units with fractions, but if one finds them so useful, why not? Personally I prefer non-fractions by the way, it's much easier to rank and compare numbers in your head if they're all given as real numbers. E.g. can you tell quickly if 5/17 is bigger or smaller than 8/30?) And how will you square 2.829 inch? Not everything you measure will happen to be some perfect fraction
tzs 8y ago
What I don't understand is why nearly everyone switched when it comes to temperature. For the other metric units, such as meters and grams, the new units had a clear advantage over the old: decimal based subunits. That was an advantage that you could not simply add on to your existing units without making a total mess of things. This does not apply to temperature, because we very rarely use subunits with temperature. Furthermore, the other base units are frequently used together in very commonly used derived units. For example, force is length x mass / time^2, pressure is mass / length / time^2, and energy is mass x length^2 / time^2. Those are all important enough that they have their own names. There are no commonly used named derived units that are based on temperature (and I can't actually offhand think of any named derived units based on temperature). In short, a government can make a pretty good case to its citizens to switch to meters and grams, despite the costs of dealing with that obsoleting a whole bunch of existing rulers, scales, and written records, because it is actually a better system. But as far as I can tell, meter+gram+F would work as well as meter+gram+C, so it is hard to make a good, let alone compelling, case to your citizens that it is better. All they've got is "everyone else is doing it". For meters and grams, "everyone else is doing it" might be good enough, even if meters and grams were not actually better than the old system, because of international trade. People choose dimensions and weights of goods to come out nicely in the units they use, and they want to buy goods with nice dimensions and weights, so if you are trading internationally in goods, you have to deal with length and mass units of your trading partners. Length and mass cross borders in trade. For temperature, that is generally not the case. If I'm importing stuff from, say, France to the US, for almost all goods it does not make one bit of difference if France and the US use different temperature units. Temperature does not cross borders in trade.
- dogma1138 8y ago
  I used to diss imperial units until I’ve started doing a lot of DIY and I can see some advantages using them. Everything is essentially always divided by two 1 inch, 1/2 inch, 1/4 inch etc, or by 1000 when very fine precision is required. You never get numbers that are hard to add up, divide or multiply when this especially comes into play when calculating derived units like PSI, clamping torque etc. And more importantly it makes calculating squares which are often used quite easy it’s much easier to square 3/16th of an inch than 4.7625.... mm Metric only really allows for easy conversion between magnitude of scale but when it comes to other calculations you get numbers which are hard to accurately calculate in your head and irrational numbers much more often than when using imperial units. And irrational numbers can’t be measured. It’s very easy to make a measurement tape that does 1/16th of an inch increments and measuring 3/16th of an inch is a breeze measuring 4.76251784744823823... mm on the other hand is eyeballing it.

roryisok 8y ago

The UK still uses imperial for road signs I think

pebers 8y ago
Yes, we do. I assume the cost of changing them all (and the resulting confusion and potential danger) was deemed too high.
orf 8y ago
We use imperial for long distances, but SI for short ones. We use imperial for human weights, but SI for food and drink weights (excluding the pint!). Height is in imperial as well, mostly. Temperature is in SI. It's all quite confusing when you explain it, but pretty natural when you live there
- roryisok 8y ago
  I live just next door in Ireland. We're officially metric but people still talk in miles, feet (and yards), acres, stone, pints, etc
  - orf 8y ago
    Oh yes I forgot about acres!
    - roryisok 8y ago
      Last car I owned had all the trip counters in Mph and the fuel efficiency in Mpg. New one is km and lpk, I'm totally lost
- dogma1138 8y ago
  There is also plumbing and engineering which uses both depending on the case and the discipline. My old flat had a faucet that was a pain to update to a mixing tap because the hot water used inch threads and the cold used metric....

r00fus 8y ago

I'd say it has more to do with the US industry's ability to dominate the imperial standard and use it like Apple uses the "lightning" port... to prevent interoperability and endure a protected market for US manufacturers.

dogma1138 8y ago
Imperial units have a lot of advantages when you need to do accurate calculations and produce good measurements. Since everything is fractions you don’t get irrational numbers and calculations are super easy even without calculators case and point say you need to square a measurement squaring 3/16th of an inch is something any fifth grader can do in their head or simply look it up in an easy table. Squaring 4.7625mm on the other hand requires a calculator and since you get an irrational number you can’t easily accurately measure it with common tools in the real world.
- Aardwolf 8y ago
  Who says one has to use fractions with one unit and real numbers with another? Both units are just a different multiplier. What stops one from using 3/16th of a meter? (I admit I rarely see SI units with fractions, but if one finds them so useful, why not? Personally I prefer non-fractions by the way, it's much easier to rank and compare numbers in your head if they're all given as real numbers. E.g. can you tell quickly if 5/17 is bigger or smaller than 8/30?) And how will you square 2.829 inch? Not everything you measure will happen to be some perfect fraction

tzs 8y ago

What I don't understand is why nearly everyone switched when it comes to temperature. For the other metric units, such as meters and grams, the new units had a clear advantage over the old: decimal based subunits. That was an advantage that you could not simply add on to your existing units without making a total mess of things. This does not apply to temperature, because we very rarely use subunits with temperature. Furthermore, the other base units are frequently used together in very commonly used derived units. For example, force is length x mass / time^2, pressure is mass / length / time^2, and energy is mass x length^2 / time^2. Those are all important enough that they have their own names. There are no commonly used named derived units that are based on temperature (and I can't actually offhand think of any named derived units based on temperature). In short, a government can make a pretty good case to its citizens to switch to meters and grams, despite the costs of dealing with that obsoleting a whole bunch of existing rulers, scales, and written records, because it is actually a better system. But as far as I can tell, meter+gram+F would work as well as meter+gram+C, so it is hard to make a good, let alone compelling, case to your citizens that it is better. All they've got is "everyone else is doing it". For meters and grams, "everyone else is doing it" might be good enough, even if meters and grams were not actually better than the old system, because of international trade. People choose dimensions and weights of goods to come out nicely in the units they use, and they want to buy goods with nice dimensions and weights, so if you are trading internationally in goods, you have to deal with length and mass units of your trading partners. Length and mass cross borders in trade. For temperature, that is generally not the case. If I'm importing stuff from, say, France to the US, for almost all goods it does not make one bit of difference if France and the US use different temperature units. Temperature does not cross borders in trade.

dogma1138 8y ago
I used to diss imperial units until I’ve started doing a lot of DIY and I can see some advantages using them. Everything is essentially always divided by two 1 inch, 1/2 inch, 1/4 inch etc, or by 1000 when very fine precision is required. You never get numbers that are hard to add up, divide or multiply when this especially comes into play when calculating derived units like PSI, clamping torque etc. And more importantly it makes calculating squares which are often used quite easy it’s much easier to square 3/16th of an inch than 4.7625.... mm Metric only really allows for easy conversion between magnitude of scale but when it comes to other calculations you get numbers which are hard to accurately calculate in your head and irrational numbers much more often than when using imperial units. And irrational numbers can’t be measured. It’s very easy to make a measurement tape that does 1/16th of an inch increments and measuring 3/16th of an inch is a breeze measuring 4.76251784744823823... mm on the other hand is eyeballing it.