I'm Canadian, and as such, I've lived a life where I'm bombarded by both SI and imperial units. The more I think about it, the more angry I get about it.

As a technician, I've spent thousands on tools I should never have needed because imperial units are so common here. It's actually difficult to find metric fasteners in a lot of cases.

Our culture is even affected, people use a mixture of the two in daily life. I get offended when people try to use imperial units.

Perhaps I shouldn't be getting upset, but it's not about the units. It's about the stubbornness of certain countries. Almost the entire human race uses SI units, but because of a few holdouts, we're stuck with a mess. It smacks of arrogance to me. Some might say I'm no better, but the difference here is I have most of the world on my side so to speak.

That's all, just a vent.

I'm american and every time I google metric scale or ruler its always both. Amazon keeps showing my thousands of inch scales. I'm honesty pissed off it doesn't pop right up with how much metric is used across the world.

Let’s say you’re writing an email and you need to tell somebody that the existing ⌀220 [8.661] diameter needs to be increased to ⌀240 [9.449]

Would you write ⌀220 or ⌀220mm. None of the technical drawings I see in my role show units which is rarely a problem, I’ll guess because a mm is 25 times smaller than an inch, but once I’m writing the dimensions it’s slightly more ambiguous.

Final boss: How do you call out a metric thread for a shop that uses inch tooling?

DRILL ⌀0.203 BY .750 DEEP
TAP M6X1 BY .563 DEEP

Probably this is better:

DRILL ⌀0.203”BY 0.750” DEEP
TAP M6X1.0 BY 0.563” DEEP

This is another example of how the U.S. healthcare industry has still not fully adopted metric units, continuing to create unnecessary confusion. The instructions contain no metric units, while the actual bottles use only metric units. It's no surprise that this contributes to medical errors.

https://preview.redd.it/qrnr2bz7q60h1.png?width=1374&format=png&auto=webp&s=e21db16777f8776943c3c1eeb49ce5e21587f64f

https://preview.redd.it/puhi60sfq60h1.png?width=481&format=png&auto=webp&s=7847956fa981b07114ebfc62b84cb420fe37abac

Trying to find a metric tape measure in US that meets Class I or II approved measuring tape in accordance with European Weights and Measures regulations?

Astronomers continue to use several non-SI units, though they have decided on SI values for nominal values of these units.

Sources:

• IAU Website: Units (at Internet Archive)
• The re-definition of the astronomical unit of length: reasons and consequences
• NOMINAL VALUES FOR SELECTED SOLAR AND PLANETARY QUANTITIES: IAU 2015 RESOLUTION B3 - IOPscience

Units:

• Angle:
  • degree = (pi/180) radians
  • arcminute = (1/60) degrees
  • arcsecond = (1/60) arcminutes
• Time:
  • minute = 60 SI second
  • hour = 60 minutes
  • day = 24 hours (~ Earth solar day)
  • year = 365.25 days (Julian year, ~ Earth year)
• Distance:
  • astronomical unit (AU) = 149597870700 meters (~ Earth-Sun distance)
  • parsec (parallax second: pc) = (astronomical unit) / (arcsecond/radian)
• Sun:
  • radius = 6.957*10^8 m
  • light flux at 1 AU = 1361 W/m^2
  • luminosity = 3.828*10^(26) W
  • temperature = 5770 K
  • G*mass = 1.3271244*10^(20) m^3/s^2
• Earth:
  • equatorial radius = 6.3781*10^6 m
  • polar radius = 6.3568*10^6 m
  • G*mass = 3.986004*10^(14) m^3/s^2
• Jupiter:
  • equatorial radius = 7.1492*10^7 m
  • polar radius = 6.6854*10^7 m
  • G*mass = 1.2668653*10^(17) m^3/s^2

The G in these definitions is the Newtonian gravitational constant. It is combined with the masses because this combination is sometimes measured to much greater accuracy than G itself.

Also, of planet radii, the equatorial radius is used unless specified otherwise.

Turning to the very small, we find non-SI units there also.

The angstrom (Å, A circle) is 10^(-10) m = 0.1 nm, and most elements' atoms have radii within a factor of 2 of an angstrom.

The fermi (fm) is 10^(-15) m, a femtometer, so "fermi" is another name for a SI unit, like "metric ton" or "tonne" for a megagram. It's around the radius of a nucleon; a proton and a neutron.

The barn is 10^(-28) m^2 or 100 fm^2. Reaction cross sections are often expressed in barns, often with SI prefixes.

The atomic mass unit or dalton (Da) is roughly the average mass per nucleon of light elements' atoms, like carbon or oxygen. It is currently defined as 1/12 the mass of a carbon-12 atom. "Dalton" is often given SI prefixes, and masses of biomolecules, like proteins and nucleic acids (DNA, RNA), are often reported in kilodaltons (kDa) or megadaltons (MDa).

The electron volt (eV) is the energy that an electron will gain when dropping through an electric-potential difference of 1 volt. It's not just an electron; it's anything with elementary charge 1, like a proton.

It is often given SI prefixes, and it is often used in atomic, nuclear, and particle physics. With the help of Einstein's famous equation, it is also used as a mass unit. Electrons have mass 511 kiloelectron volts (keV), protons have mass 938.3 megaelectron volts (MeV), (neutrons 939.6 MeV, dalton 931.5 MeV), top quarks have mass 173 gigaelectron volts (GeV), and the Large Hadron Collider can accelerate protons to energies around 6.8 teraelectron volts (TeV).

I am following the usual custom of omitting the Einstein mass-energy factor, (1/c^2).

Name-brand kilogram-sized kettlebells at the local sporting goods store. Per Google, "They are considered the 'standard' in the broader fitness community."

https://preview.redd.it/bit0xk0kbmzg1.jpg?width=1792&format=pjpg&auto=webp&s=de7b8cdfd5d9a38680aeef61ea2127b7835d37c2

One thing that I think about as I prepare to move to a metric country is how time, both the calendar and watches are not in base ten.

Would a system of base ten time be something people who are used to metric be down for? I remember reading that the French attempted to implement a metric time but that didn't get off the ground.