I’ve often wondered why the kilogram was not called the gram when the former is commonly cited as the official unit of mass? I guess it doesn’t really matter much since it’s easy to convert between units. That’s sort of the point of metric, but still…
Fair enough. But it’s interesting right? Like the litre lines up with the kilogram (for fluid measures) but they don’t call it a kilolitre for consistency’s sake?
This is one of two “warts” that I know of in SI. They wanted a coherent set of units, coherent meaning that no nuisance constants are required to convert between dimensions in the set. The system at the time was gram-centimeter-second. To expand things to all dimensions I suppose it was simpler to use the larger units, like J = kg m^2 / s^2 rather than trying to make a new unit for energy, etc. You’d think they’d have just come up with a new name for mass units and defined it as 1 kg, something like 1 prot = 1 kg, then all of the coherent units would be ones without prefixes. Someone must have really being going to bat for the word “gram” though, because now we have this pretty stupid rule that the coherent units are all of the ones without prefixes, except mass, which has the coherent unit of kg. And then also, prefixes are used to scale the coherent units by appending the appropriate letter to the coherent unit symbol, except for mass, for which g is treated as the coherent unit, even though it’s not.
It’s not the worst thing, but it’s pretty stupid to explain.
until you realize, that “second” is also not the base unit. it’s not at obvious because it isn’t metric, but second is just the second subdivision of an hour (the first being the minute)
I’ve often wondered why the kilogram was not called the gram when the former is commonly cited as the official unit of mass? I guess it doesn’t really matter much since it’s easy to convert between units. That’s sort of the point of metric, but still…
Apparently it was going to be, but they chose the kilogram instead.
Fair enough. But it’s interesting right? Like the litre lines up with the kilogram (for fluid measures) but they don’t call it a kilolitre for consistency’s sake?
This is one of two “warts” that I know of in SI. They wanted a coherent set of units, coherent meaning that no nuisance constants are required to convert between dimensions in the set. The system at the time was gram-centimeter-second. To expand things to all dimensions I suppose it was simpler to use the larger units, like J = kg m^2 / s^2 rather than trying to make a new unit for energy, etc. You’d think they’d have just come up with a new name for mass units and defined it as 1 kg, something like 1 prot = 1 kg, then all of the coherent units would be ones without prefixes. Someone must have really being going to bat for the word “gram” though, because now we have this pretty stupid rule that the coherent units are all of the ones without prefixes, except mass, which has the coherent unit of kg. And then also, prefixes are used to scale the coherent units by appending the appropriate letter to the coherent unit symbol, except for mass, for which g is treated as the coherent unit, even though it’s not.
It’s not the worst thing, but it’s pretty stupid to explain.
until you realize, that “second” is also not the base unit. it’s not at obvious because it isn’t metric, but second is just the second subdivision of an hour (the first being the minute)