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An old artifact kept in a vault outside Paris is no longer the standard kilogram

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101–110 of 155 posts

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#101
post #4

Defining a unit of weight in terms of a unit of time and a unit of length. Explain that to your grandma! :)

Unit of weight in terms of time and length? It's the unit of mass in terms of action (time and energy). It's very easy to explain https://ichef.bbci.co.uk/news/624/cpsprodpb/AE6A/production/...

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#102
post #97

I'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.

Such a choice might get you removed as emperor of the world -- the number related of engineering, scientific, and medical errors might be high. Generations of scientists would remember such an emperor, but not in a positive light. I share your consternation with the kilogram's name, but it is almost as fundamental to our units as Franklin's implicit, and perhaps unfortunate, choice to call the charge of the electron…

I'm aware of that, but had I given the value in another mass unit like AMU my meaning would have been less apparent.

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#103
post #77
post #4

Defining a unit of weight in terms of a unit of time and a unit of length. Explain that to your grandma! :)

Or to me. So I guess a weight = some number of square meters per second. I'm trying to think of a intuitive idea why it should be thus.

It's actually the unit of mass in terms of action (time and energy). You can think of it as "how much of something is required to balance a scale where I'm pulling this much" https://ichef.bbci.co.uk/news/624/cpsprodpb/AE6A/production/...

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#105

Earlier quoted context omitted.

>The definition of units are done in the most convenient and precise way possible. testing my scale with a mirror that contains a kg of photons doesn't sound very convenient.

You were also never going to test your scale with a weight that is stored in a vault in Paris. So far you would test with a replica of a replica of that weight, in the best case (getting a copy directly from the local standards body). With the new definition in principle anybody can create an object that weighs exactly one kg and sell it to you.

It's actually really hard to imagine an actual physical apparatus for producing a "reference" Kg mass using the new definition of Kg.

I get the feeling this just changes the definition of "Kg", but not how reference Kg's are actually produced?

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#106

Earlier quoted context omitted.

How about we keep the current name and use it as a basis for prefixing? gram -> millikilogram milligram -> microkilogram metric ton -> kilokilogram ...never mind.

It's almost a crime that a metric ton isn't called a "megagram". Aside, are the mega and giga prefixes ever used for anything except bits and bytes? (Edit: OK, OK. I forgot about megaohms, megahertz, megawatts. Also megapixels and Megadeth.)

Physicists studying the sun and effect on its surface use megameter as a length scale quite a bit.

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#107
post #4

Defining a unit of weight in terms of a unit of time and a unit of length. Explain that to your grandma! :)

The unit of length is also defined in terms of the unit of time (distance travelled by light in a specific interval of time) ;)

Re: An old artifact kept in a vault outside Paris is no longer the standard kilogram

#109

Change is scheduled for 20 May 2019. checks date fake news... the artifact is still the official reference for the standard kilogram for another 72 hours... ;)

Yeah, jokes aside I think _technically_ the post title should be changed. (Even the article's title is wrong. Though, it wouldn't be the first time NH's title is more accurate than that of the article it points to.)
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