That's actually the reasoning behind the Watt Balance another potential method for defining the kilogram.
Keep in mind that the Joule is a composite SI unit, and is itself dependent on the mass of the kilogram. Unless you can calibrate the energy measurements (exactly what they are trying to do) you end up with a circular definition.
Actually, it does way exactly 12 grams. It is defined to weight 12 grams. Neutrons weigh slightly more than protons, but the mass of a proton is not 1 amu (it is actually ALSO more than 1 amu). You can't just add the mass of the constituent protons, neutrons and electrons to get the mass of an atom because when you combine them, you get binding energy. Energy = mass, therefore the combined mass is less than the sum of its parts (less, because the binding energy corresponds to the energy needed to separate them).
They are measuring the sphere using interferometry - not possible with a cube.
I'm not sure if you were being facetious or not when you were talking about pi being irrational, but its value is known to billions of decimal places. I doubt it will introduce any additional uncertainty.
Sort of... we don't know the mass of one atom of Silicon to a precise enough degree, but "atomic mass" is generally measured in atomic mass units - i.e. relative to the mass of carbon-12.
A mole of carbon-12 atoms weighs exactly 12 grams, but we just don't know how many atoms are in a mole (i.e. we don't know Avogadro's number).
The mass of silicon-28 relative to carbon-12 is actually quite precisely known.
It is rather confusing, I know... probably why "psychopath" is obsolete. People just kept confusing psychopathy and psychosis, when the two have very little in common.
Actually, sociopath and psychopath are pretty much synonymous. Psychosis, on the other hand, is where one loses contact with reality.
Neither psychosis nor sociopathy are subsets of one another.
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That's actually the reasoning behind the Watt Balance another potential method for defining the kilogram.
Keep in mind that the Joule is a composite SI unit, and is itself dependent on the mass of the kilogram. Unless you can calibrate the energy measurements (exactly what they are trying to do) you end up with a circular definition.
Note to self: If you misspell "weigh" twice in two sentences, you may need more sleep.
Actually, it does way exactly 12 grams. It is defined to weight 12 grams. Neutrons weigh slightly more than protons, but the mass of a proton is not 1 amu (it is actually ALSO more than 1 amu). You can't just add the mass of the constituent protons, neutrons and electrons to get the mass of an atom because when you combine them, you get binding energy. Energy = mass, therefore the combined mass is less than the sum of its parts (less, because the binding energy corresponds to the energy needed to separate them).
They are measuring the sphere using interferometry - not possible with a cube.
I'm not sure if you were being facetious or not when you were talking about pi being irrational, but its value is known to billions of decimal places. I doubt it will introduce any additional uncertainty.
recursion, n.
1. see recursion
I like it...
Sort of... we don't know the mass of one atom of Silicon to a precise enough degree, but "atomic mass" is generally measured in atomic mass units - i.e. relative to the mass of carbon-12.
A mole of carbon-12 atoms weighs exactly 12 grams, but we just don't know how many atoms are in a mole (i.e. we don't know Avogadro's number).
The mass of silicon-28 relative to carbon-12 is actually quite precisely known.
It is rather confusing, I know... probably why "psychopath" is obsolete. People just kept confusing psychopathy and psychosis, when the two have very little in common.
I prefer to do my 'social networking' in the real world.
If you assume Facebook users don't, you've almost comletely missed the point.
Wrong. Psychopathy has nothing to do with psychosis or a grounding in reality.
It, along with sociopathy is an obsolete term for what the DSM-IV classifies as antisocial personality disorder.
Actually, sociopath and psychopath are pretty much synonymous. Psychosis, on the other hand, is where one loses contact with reality. Neither psychosis nor sociopathy are subsets of one another.