41–50 of 90 posts
There is an alternate definition using a sphere of silicon with N atoms: https://www.nist.gov/physical-measurement-laboratory/silicon... What's really need though is a universal, stable over eons, single standard for time, length, and mass. I believe time is N cycles of an excited sodium (light) emission. Length is N wavelengths of that same emission in a vacuum. Mass would be N atoms. So why are they not using a sin…
https://youtu.be/JKHUaNAxsTg?t=591
The other parts are a bit "woo" and I'm sure would be laughed at by the HN crowd. But his points about fundamental "constants" changing, and the metrologists' dogmatic (really, anti-scientific) response, are worth pondering.
There is an alternate definition using a sphere of silicon with N atoms: https://www.nist.gov/physical-measurement-laboratory/silicon... What's really need though is a universal, stable over eons, single standard for time, length, and mass. I believe time is N cycles of an excited sodium (light) emission. Length is N wavelengths of that same emission in a vacuum. Mass would be N atoms. So why are they not using a sin…
What is the problem that would be solved by switching to a single element?
Ha, the irony! The USA 's NIST defines a SI unit to the rest of the world; meanwhile, most of citizens don't know what it is.
...except actually it's the International Committee for Weights and Measures.
However I will help you retain your justifiable sense of ironic superiority: the US is one of the 17 original signatories to the metre convention (in May 1875: http://www.bipm.org/en/about-us/member-states/original_seven...). Also all the US conventional units have been based on the SI metre and kilogramme since 1959. And of course the metric system is familiar to any American in the military and/or who uses illegal drugs.
Although its not part of the BIPM, my favorite such standards organization is the International Earth Rotation Service (justified paying my taxes -- what if they stopped???). Sadly they recently renamed themselves "International Earth Rotation and Reference Systems Service"
Apropos of little: I used to live quite close (a couple of hundred metres) to an official metre, as there is one on the wall across the street from the French Senate. When the system was originally promulgated, markers were erected around France; you could bring something (piece of string or whatnot) and make your "own" metre to bring home and measure things. There are two or three of them still extant.
There is an alternate definition using a sphere of silicon with N atoms: https://www.nist.gov/physical-measurement-laboratory/silicon... What's really need though is a universal, stable over eons, single standard for time, length, and mass. I believe time is N cycles of an excited sodium (light) emission. Length is N wavelengths of that same emission in a vacuum. Mass would be N atoms. So why are they not using a sin…
Turns out they know that :-)
The problem isn't definition, its the accuracy of reproducibility. You need a mechanism that can be built from scratch and can be believed to produce identical results. You can pull that off counting wavelengths of an unknown number of a known pure atom. Counting actual numbers of atoms is quite difficult. Typically we do it statistically...via mass! We could get it precisely by using a small number, but then actually measuring the mass (rather than calculating it) would be difficult.
There is an alternate definition using a sphere of silicon with N atoms: https://www.nist.gov/physical-measurement-laboratory/silicon... What's really need though is a universal, stable over eons, single standard for time, length, and mass. I believe time is N cycles of an excited sodium (light) emission. Length is N wavelengths of that same emission in a vacuum. Mass would be N atoms. So why are they not using a sin…
A second (time) is already defined on cesium transition, a meter (length) is defined as a fraction of the distance light travels in a second. Both things which we can accurately measure for some time now, and which universal and stable over eons. What is the problem that would be solved by switching to a single element?
Interesting fact: this is important for US too, because pound is defined as exactly 0.45359237 kg ( https://en.wikipedia.org/wiki/Pound_(mass)#Current_use )
It's kind of not important because nobody measures the kinds of things that require the level of precision applied to the kilogram definition using pounds.
The kilogram is not the only unit that will be redefined based on universal constants. The seven base units[0] will transition to being based on elementary charge and the Planck, Boltzmann, and Avogadro constants[1]. [0] https://en.wikipedia.org/wiki/SI_base_unit#Seven_SI_base_uni... [1] https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_ba...
Four of the seven physical constants used to define the seven base SI units will change, so a bunch of physical constants that currently have exactly defined values will start being subject to measurement uncertainty. So μ_0 will no longer be exactly 4π × 10^-7 H/m, k_C = 1/4πε_0 will no longer be exactly 8,987,551,787.3681764 N m^2/C^2, and 1 mol of carbon-12 will no longer have a mass of exactly 12 g.