61–70 of 155 posts
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As the article correctly states, photons have a finite mass that could in principle be measured by putting an optical cavity on a scale.
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?
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> Aside, are the mega and giga prefixes ever used for anything except bits and bytes? Sure, few examples of the top of my head: - Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit! - Similarly, energy consumption/production. Commonly used units MWh, GWh, TWh. Again, the proper unit would be J, not Wh. Or Mtoe, for Million tons of oil equivalent.
> Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit! That’s what is odd about it? It should be teragrams.
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.
Related to this is the fact that the Avogadro constant, 6.02214076×10^23 mol^-1, is equal to 1.
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.
The reason the mole is in the SI puzzled me too. It seems that the reason is that chemists don't care how many atoms there are in their reactions. It would be inconvenient: fractions of atoms don't make sense, and the numbers are far from human scale. They just want an agreement, so that even if they don't know the exact number of atoms in their test tube, they know they all have the same number. That's what units ar…
testing my scale with a mirror that contains a kg of photons doesn't sound very convenient.
Earlier quoted context omitted.
The reason the mole is in the SI puzzled me too. It seems that the reason is that chemists don't care how many atoms there are in their reactions. It would be inconvenient: fractions of atoms don't make sense, and the numbers are far from human scale. They just want an agreement, so that even if they don't know the exact number of atoms in their test tube, they know they all have the same number. That's what units ar…
>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.
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> Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit! That’s what is odd about it? It should be teragrams.
It's a measure of energy, hence the unit should be J (with some appropriate prefix).
Confused, 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.
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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If you were emperor of the world, I would implore you to finance a multibillion dollar project to measure the gravitational constant to higher percision so that we could move to units that actually make sense. https://en.wikipedia.org/wiki/Planck_units
Shpx, gung'f n shpxvat terng vqrn.
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.