There’s also no such thing as an inch. It’s defined by the meter, there isn’t an official yardstick.
The only reason the UK, Canada and USA used the same inch is because they needed to interchange parts for weapons and machines during WW1. Despite all thinking they used the same measurement system the definition had drifted between them. Metric was defined by enlightenment people with better methods of reproducing the standard. So it was easier to adopt a inch definition based on 25.4mm.
The UK and US inch only match because of WW1. The imperial volumes are still different.
By that logic, there’s also no such thing as a meter either. It’s defined as a distance light travels in a time interval proportional to the inverse of a frequency related to the caesium-133 atom. Definitions don’t mean there’s “no such thing” as something, it’s just a matter of if the units are useful in a given context. And meters are more useful in most everyday contexts.
In timekeeping, there are so called stratums to describe how correct a clock is.
Stratum 0 is a physical process, an inherent property of the universe. An atomic clock would be stratum 0.
Stratum 1 is a clock defined based on a stratum 0 clock. For example, GPS clocks are usually stratum 1, so are timeservers at universities with atomic clocks.
Stratum 2 is a clock defined based on a stratum 1 clock, for example, your router’s ntp server if it syncs its time based on gps or a university’s timeserver.
So if we adopt this jargon for units:
Meter is a stratum 1 unit, defined based on the stratum 0 properties of lightspeed and cesium resonance.
Inch is a stratum 2 unit, defined based on the stratum 1 meter.
There’s also no such thing as an inch. It’s defined by the meter, there isn’t an official yardstick.
The only reason the UK, Canada and USA used the same inch is because they needed to interchange parts for weapons and machines during WW1. Despite all thinking they used the same measurement system the definition had drifted between them. Metric was defined by enlightenment people with better methods of reproducing the standard. So it was easier to adopt a inch definition based on 25.4mm.
The UK and US inch only match because of WW1. The imperial volumes are still different.
By that logic, there’s also no such thing as a meter either. It’s defined as a distance light travels in a time interval proportional to the inverse of a frequency related to the caesium-133 atom. Definitions don’t mean there’s “no such thing” as something, it’s just a matter of if the units are useful in a given context. And meters are more useful in most everyday contexts.
In timekeeping, there are so called stratums to describe how correct a clock is.
Stratum 0 is a physical process, an inherent property of the universe. An atomic clock would be stratum 0.
Stratum 1 is a clock defined based on a stratum 0 clock. For example, GPS clocks are usually stratum 1, so are timeservers at universities with atomic clocks.
Stratum 2 is a clock defined based on a stratum 1 clock, for example, your router’s ntp server if it syncs its time based on gps or a university’s timeserver.
So if we adopt this jargon for units:
Meter is a stratum 1 unit, defined based on the stratum 0 properties of lightspeed and cesium resonance.
Inch is a stratum 2 unit, defined based on the stratum 1 meter.