[pfbtgom]

How would you use the new definition to calibrate instruments? My current understanding is that there is a lineage of artifacts calibrated against another artifact until one of those was calibrated against the one true artifact. So how would NIST or another certifying source say that my 1kg standard is 1kg +/- tolerance?

Is it anyone with a kibble balance can now certify calibrations? How do you know your kibble balance is as accurate as the next guy's kibble balance?

https://www.nist.gov/si-redefinition/kilogram-kibble-balance

Edit: Found some information explaining this from NIST: https://www.nist.gov/si-redefinition/kilogram-disseminating-...

[simcop2387]

Essentially this brings it one more step away from using another artifact for calibrating things. Instead this lets us define the kilogram against what we believe are universal constants, in this case properties about the electromagnetic force.

It's much simpler to understand looking at it with a watt balance, even though it's not going to be as precise or accurate as a kibble balance [1]. Basically now anyone with access to a kibble balance and the right set of numbers/information can make an exact 1kg object.

[1] https://www.youtube.com/watch?v=ewQkE8t0xgQ

[mjevans]

Or potentially more usefully, ascertain an accurate measurement of how closely a given measuring device is to the target to calibrate it's use in actual measurements (outside of the expensive validation mechanisms).

[coder543]

I'm pretty sure a watt balance and a Kibble balance are the same thing. Regardless, that YouTube video is so good! I was just about to post the same link.

[mabbo]

It will still mostly work the same way, except that instead of someone having the "one true artifact", anyone with enough equipment can measure their kilogram against natural constants and know it's correct.

It means the right answer is freely available to anyone (with a bunch of scientific equipment).

[ChuckMcM]

The pictures in that article about NIST reminds me of the adage, "The smaller the measurement, the bigger the lab."

I like to use metrology labs as an example of something people often take for granted (measuring things) and showing how deep that invisible rabbit hole goes.

[jonah]

Don't miss the video for the DIY Lego watt balance.

https://www.nist.gov/si-redefinition/nist-do-it-yourself-kib...

[jimworm]

The NIST explanation of Kibble balance calibration includes this:

> Everything on the right side of that equation can be determined to extraordinary precision: The current and voltage by using quantum-electrical effects that are measurable on laboratory instruments; the local gravitational field by using an ultra-sensitive, on-site device called an absolute gravimeter; and the velocity by tracking the coil's motion with laser interferometry, which operates at the scale of the wavelength of the laser light.

Current is measured in amperes, derived from the charge (in coulombs, defined from the charge of a proton) and time (in seconds, defined from the vibration of a Cs atom). Gravitational acceleration is measured in ms^-2, derived from length (in metres, defined from the distance travelled by light in a vacuum in a second) and time. Velocity is also derived from length and time.

With these new defined constants (including the Planck constant), all of the instruments could now be calibrated by observing natural phenomena and a whole lot of counting.

[azernik]

To abbreviate - these definitions change the means by which those calibration artifacts ("transfer standards") are created.