An old artifact kept in a vault outside Paris is no longer the standard kilogram
1–10 of 155 posts
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#2I wonder if there is a process that has to be gone through to now update the pound avoirdupois. It is defined as 453.59237 grams but given the formal definition of the gram has changed could there be a need for a formal acknowledgement, or does the law encompass changes in methods so it just happens automagically?
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#3I wonder if there is a process that has to be gone through to now update the pound avoirdupois. It is defined as 453.59237 grams but given the formal definition of the gram has changed could there be a need for a formal acknowledgement, or does the law encompass changes in methods so it just happens automagically?
I don't know about US, but this does need formal amendment to Weights and Measures Act 1985 (current UK standard in force) Schedule 1 Part V, see http://www.legislation.gov.uk/ukpga/1985/72/schedule/1/part/....
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#4Defining a unit of weight in terms of a unit of time and a unit of length. Explain that to your grandma! :)
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#5This article sounds like it got written by a scientist but got butchered through a PR department.
It talks about the "Mass of a photon" and weighing them directly, rather than the energy-equivalent mass, which is presumably what they are intending to talk about?
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#6And with that, I mourn the obsolescence of my last remaining "absolute unit" joke and will have to develop something equally satisfying based on dressed lumber to replace it.
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#7I wonder if there is a process that has to be gone through to now update the pound avoirdupois. It is defined as 453.59237 grams but given the formal definition of the gram has changed could there be a need for a formal acknowledgement, or does the law encompass changes in methods so it just happens automagically?
I think the US is not affected by this change, as the NIST didn't define what kilogram actually is back in 1959 [1].
[1] https://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.p...
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#8Confused, so how do they measure 1 kilo of something now when they need to calibrate the most precise instruments? They count 10^40 photons? How? And how does that translate into a physical mass they want to carry around?
Edit: Seems I completely missed a paragraph somehow. Thanks!
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#9I've always been mildly irritated that the name of the SI mass base unit has a prefix. Second, liter, meter, Newton, kilogram. Were I emperor of the world I would slide the name scale up so the mass equal to 2.205lbs was called a gram.
Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram
#10Confused, so how do they measure 1 kilo of something now when they need to calibrate the most precise instruments? They count 10^40 photons? How? And how does that translate into a physical mass they want to carry around? Edit: Seems I completely missed a paragraph somehow. Thanks!
The term of art is "realisation". The article mentions two realisations but does not elaborate: "In practice, there are currently two known methods for measuring such masses with great precision. These are known as the Kibble balance and the single-crystal silicon sphere". You should be able to google from that.