5 ms·

All the motivating examples but one are about mixing units from different system. And of those, all but one are about errors in mixing US Customary units with t

All the motivating examples but one are about mixing units from different system. And of those, all but one are about errors in mixing US Customary units with the metric system. Maybe Americans should just stop using the US Customary Units as a start?

throwaway5959 3y ago
[flagged]
- amphitheatre 3y ago
  Actual scientific institutions like NASA already do, and all of the imperial units have metric backings and definitions now, so it’s just ignorance, stubbornness, or apathy at this point.
  - throwaway5959 3y ago
    Oh boy, NASA, a scientific organization using metric. Lemme know when you’ve converted every recipe, ruler and wrench to metric. So ridiculously out of touch.
WJW 3y ago
Yes that would work, but why stop there. Having hundreds of different spoken languages is wasteful, so why not standardize everyone on Esperanto while we're at it, unify all electric plug standards to the one used in the EU and change the last few countries over to driving on the right side of the road. Don't even get me started on all the duplicate work being done on text editors, programming languages, web servers and databases. /s of course.
smitty1e 3y ago
Practicality over purity. How are we to divide a meter into whole number thirds? Easily done with yards. Get stuffed, Talleyrand.
- chriswarbo 3y ago
  > How are we to divide a meter into whole number thirds? We can't divide a metre into whole number anythings; and likewise a metre doesn't itself divide evenly into anything else. That's because the metre is the only unit of distance in metric/SI; so there's nothing else to divide into. That's a feature, not a bug, since it makes metric "coherent" https://en.wikipedia.org/wiki/Coherence_(units_of_measurement) https://en.wikipedia.org/wiki/Coherence_(units_of_measuremen...
  - hedora 3y ago
    You can divide a meter into four 25 centimeter pieces, or five 2 decimeter pieces. Alternatively, you could restrict US units to just yards if you wanted, and get nearly the same inconvenient behavior as meters. Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio.
    - kevindamm 3y ago
      A meter is three 1/3-meter pieces.
    - chriswarbo 3y ago
      > Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio. There is one metric unit for distance (the meter). Likewise, there is one unit for force (the Newton); one for energy (the Joule); one for mass (the kilogram); one for electric charge (the Coulomb); etc. > You can divide a meter into four 25 centimeter pieces, or five 2 decimeter pieces. The parent specifically asked for "whole numbers". The term "centi" means hundredth, and "deci" means tenth, so your examples are 25/100 metres and 2/10 metres, which are not whole numbers. If we allow fractions (which we should!) then sure, we can make any rational ratio we like. > Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio. All ratios between units in metric/SI are 1, by design. You're probably referencing power-of-ten ratios between prefixes, like "centi", "kilo", "mega", "micro", etc. Those are not units, they're just an alternative way of writing numbers. For example, 2km = 2000m because 2k = 2000 (by definition of k); nothing to do with units, which in both cases are meters. Likewise, both "2 dozen meters" and "24 meters" are in units of meters; the first isn't in a separate unit of "dozen meters". > Alternatively, you could restrict US units to just yards if you wanted I've never seen anyone restrict to using yards; usually the restriction is to feet, like the foot-pound-second system https://en.wikipedia.org/wiki/Foot%E2%80%93pound%E2%80%93second https://en.wikipedia.org/wiki/Foot%E2%80%93pound%E2%80%93sec... > and get nearly the same inconvenient behavior as meters The explicit convenience of using meters (rather than the implicit convenience of not having any length conversions) is that all of its conversion factors to combinations of other units are one, by definition. For example: Pushing a force over a distance takes energy (see https://en.wikipedia.org/wiki/Work_(physics) https://en.wikipedia.org/wiki/Work_(physics) ) so distance = energy / force. In metric, 1 meter = 1 Joule per Newton. In contrast, 1 yard = 0.968 calories per pound-force, which is less convenient. Newton's second law says force = mass × acceleration, so distance = force × time² / mass. In metric, 1 meter = 1 Newton second² per kilogram. In contrast, 1 yard = 2.978 pound-force second² per slug, which is less convenient. etc. I actually wrote a page about this on my blog a while ago http://www.chriswarbo.net/projects/units/metric_red_herring.html http://www.chriswarbo.net/projects/units/metric_red_herring....
frumiousirc 3y ago
Even in a metric monoculture, mixing code with different system of units poses a problem. Worse, mixing code with no system and just a convention for what units numbers are assumed to be in. Joining two simulation packages, on with length in mm and the other in cm provides a bounty of potential bugs. Sometimes this variation is happenstance but sometimes it can be important for precision. nm and ns are the relevant scales for particle physics while parsecs and seconds for astro and yet astro-particle physics is a thing.
- aragilar 3y ago
  Parsec is a unit of distance, not time, even if Star Wars is confused about that.
icegreentea2 3y ago
Switching costs would be very high. Just consider this library. There is no standard way to handle units in C++. This presumably means that every single piece of C++ software that was ad-hoc programmed to work in customary units needs modification, or some sort of shim/interface layer to become 'metric'. Or be saddled with decades of dual-systeming. As many of the examples point out, the very act of switching systems can cause problems (the Air Canada flight is the classic example). This is not to say that switching is a hopeless cause, but it's certainly not a cheap or easy task to perform. Maybe we can leverage Y2K38 as a breakpoint to help this transition along =P
owlstuffing 3y ago
We can’t because football fields are 100 yards and gun caliber is based on the inch. Changing those would result in civil war.
packetlost 3y ago
It's easy enough to mess up conversions between amplitudes of a unit (ex. milliamps vs amps) and having a standardized and well-tested way of doing so is important for reliability and safety critical systems IMO.
EnigmaFlare 3y ago
The need would still exist. TFA covers the often-overlooked issue of different "kinds" of quantity that have the same dimensions but shouldn't be mixed. Eg. Hz and radian/s for frequency and angular frequency. Both have dimensions of 1/time but they're different. You have to be an extreme purist to refuse to use Hz and only express frequencies as angular frequencies. And by the way, if the metric system is so great, why does Avogadro's constant still exist? Since 2019, it's fortunately been downgraded to an exact arbitrary number but it's an ugly legacy of even metric-users refusing to accept change.

throwaway5959 3y ago

[flagged]

amphitheatre 3y ago
Actual scientific institutions like NASA already do, and all of the imperial units have metric backings and definitions now, so it’s just ignorance, stubbornness, or apathy at this point.
- throwaway5959 3y ago
  Oh boy, NASA, a scientific organization using metric. Lemme know when you’ve converted every recipe, ruler and wrench to metric. So ridiculously out of touch.

WJW 3y ago

Yes that would work, but why stop there. Having hundreds of different spoken languages is wasteful, so why not standardize everyone on Esperanto while we're at it, unify all electric plug standards to the one used in the EU and change the last few countries over to driving on the right side of the road. Don't even get me started on all the duplicate work being done on text editors, programming languages, web servers and databases. /s of course.

smitty1e 3y ago

Practicality over purity. How are we to divide a meter into whole number thirds? Easily done with yards. Get stuffed, Talleyrand.

chriswarbo 3y ago
> How are we to divide a meter into whole number thirds? We can't divide a metre into whole number anythings; and likewise a metre doesn't itself divide evenly into anything else. That's because the metre is the only unit of distance in metric/SI; so there's nothing else to divide into. That's a feature, not a bug, since it makes metric "coherent" https://en.wikipedia.org/wiki/Coherence_(units_of_measurement) https://en.wikipedia.org/wiki/Coherence_(units_of_measuremen...
- hedora 3y ago
  You can divide a meter into four 25 centimeter pieces, or five 2 decimeter pieces. Alternatively, you could restrict US units to just yards if you wanted, and get nearly the same inconvenient behavior as meters. Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio.
  - kevindamm 3y ago
    A meter is three 1/3-meter pieces.
  - chriswarbo 3y ago
    > Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio. There is one metric unit for distance (the meter). Likewise, there is one unit for force (the Newton); one for energy (the Joule); one for mass (the kilogram); one for electric charge (the Coulomb); etc. > You can divide a meter into four 25 centimeter pieces, or five 2 decimeter pieces. The parent specifically asked for "whole numbers". The term "centi" means hundredth, and "deci" means tenth, so your examples are 25/100 metres and 2/10 metres, which are not whole numbers. If we allow fractions (which we should!) then sure, we can make any rational ratio we like. > Just because most metric unit ratios are a power of ten doesn’t mean there is no ratio. All ratios between units in metric/SI are 1, by design. You're probably referencing power-of-ten ratios between prefixes, like "centi", "kilo", "mega", "micro", etc. Those are not units, they're just an alternative way of writing numbers. For example, 2km = 2000m because 2k = 2000 (by definition of k); nothing to do with units, which in both cases are meters. Likewise, both "2 dozen meters" and "24 meters" are in units of meters; the first isn't in a separate unit of "dozen meters". > Alternatively, you could restrict US units to just yards if you wanted I've never seen anyone restrict to using yards; usually the restriction is to feet, like the foot-pound-second system https://en.wikipedia.org/wiki/Foot%E2%80%93pound%E2%80%93second https://en.wikipedia.org/wiki/Foot%E2%80%93pound%E2%80%93sec... > and get nearly the same inconvenient behavior as meters The explicit convenience of using meters (rather than the implicit convenience of not having any length conversions) is that all of its conversion factors to combinations of other units are one, by definition. For example: Pushing a force over a distance takes energy (see https://en.wikipedia.org/wiki/Work_(physics) https://en.wikipedia.org/wiki/Work_(physics) ) so distance = energy / force. In metric, 1 meter = 1 Joule per Newton. In contrast, 1 yard = 0.968 calories per pound-force, which is less convenient. Newton's second law says force = mass × acceleration, so distance = force × time² / mass. In metric, 1 meter = 1 Newton second² per kilogram. In contrast, 1 yard = 2.978 pound-force second² per slug, which is less convenient. etc. I actually wrote a page about this on my blog a while ago http://www.chriswarbo.net/projects/units/metric_red_herring.html http://www.chriswarbo.net/projects/units/metric_red_herring....

frumiousirc 3y ago

Even in a metric monoculture, mixing code with different system of units poses a problem. Worse, mixing code with no system and just a convention for what units numbers are assumed to be in. Joining two simulation packages, on with length in mm and the other in cm provides a bounty of potential bugs. Sometimes this variation is happenstance but sometimes it can be important for precision. nm and ns are the relevant scales for particle physics while parsecs and seconds for astro and yet astro-particle physics is a thing.

aragilar 3y ago
Parsec is a unit of distance, not time, even if Star Wars is confused about that.

icegreentea2 3y ago

Switching costs would be very high. Just consider this library. There is no standard way to handle units in C++. This presumably means that every single piece of C++ software that was ad-hoc programmed to work in customary units needs modification, or some sort of shim/interface layer to become 'metric'. Or be saddled with decades of dual-systeming. As many of the examples point out, the very act of switching systems can cause problems (the Air Canada flight is the classic example). This is not to say that switching is a hopeless cause, but it's certainly not a cheap or easy task to perform. Maybe we can leverage Y2K38 as a breakpoint to help this transition along =P

owlstuffing 3y ago

We can’t because football fields are 100 yards and gun caliber is based on the inch. Changing those would result in civil war.

packetlost 3y ago

It's easy enough to mess up conversions between amplitudes of a unit (ex. milliamps vs amps) and having a standardized and well-tested way of doing so is important for reliability and safety critical systems IMO.

EnigmaFlare 3y ago

The need would still exist. TFA covers the often-overlooked issue of different "kinds" of quantity that have the same dimensions but shouldn't be mixed. Eg. Hz and radian/s for frequency and angular frequency. Both have dimensions of 1/time but they're different. You have to be an extreme purist to refuse to use Hz and only express frequencies as angular frequencies. And by the way, if the metric system is so great, why does Avogadro's constant still exist? Since 2019, it's fortunately been downgraded to an exact arbitrary number but it's an ugly legacy of even metric-users refusing to accept change.