71–80 of 155 posts
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It always feels a little grating when I hear someone say some number of "thousand kilometers".
Yes, describing my old car's odometer as "250 megameters" is oddly satisfying to let roll of the tongue.
For the next revision: remove the mole from the SI. It's completely pointless. A number is not a unit! Instead replace it by the bit, the fundamental unit of information.
If we identify the entropy formula
S = kB ln W
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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.)
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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.
I never understood why a sphere was even in the discussion of a standardized atomic count. Any rational fractions using pi = pi atoms or molecules. And that's absurd to have r=(3V/4pi)^1/3 . No matter how you mess with it, it's irrational to the extreme! Now.. Face-centered or ody-centered cubic follows a nice quadratic expansion for integer based counting. We don't need no steenkin pi's!
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I know that zero is a finite number, but since the photon is a massless particle, wouldn't it be impossible to get a kilogram worth of photons bouncing around in an optical cavity?
No, it’s entirely possible in principle. If you build a perfect optical cavity, weigh it, pump a bunch of light in, and weigh it again, you’ll find that the weight went up by ghf/c^2 summed over each photon added to the cavity. Divide by g and you get the sum of the masses of the photons. 1 kg of photons would be enough to destroy your lab and the rest of your city, so only a very advanced civilization would ever do…
For the next revision: remove the mole from the SI. It's completely pointless. A number is not a unit! Instead replace it by the bit, the fundamental unit of information.
Dear Lord no, the "mole removal" jokes in mainstream press would be too much.
Defining a unit of weight in terms of a unit of time and a unit of length. Explain that to your grandma! :)
And 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.
Why did the standard kilo ever need to be handled? Just store it on a balance and only handle the comparison unit.
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>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.