It"s probably good idea to replace the old-fashion platinum-iridium plum, with something more precise.
Personally, I like the idea of "levitating" mass
http://www.physorg.com/news3178.html
It"s probably good idea to replace the old-fashion platinum-iridium plum, with something more precise.
Personally, I like the idea of "levitating" mass
It"s probably good idea to replace the old-fashion platinum-iridium plum, with something more precise.
Personally, I like the idea of "levitating" mass
I'm not a graduate chemist, and I don't pretend to know all the ins and outs of chemistry by a long chalk... but would not basing a system of measurement on a block of meterial which can change mass by as much as 1 part in 1800 with the simple application of an electric current be kind of, well, dangerous? What I'm saying is, why not base the system yes on a fixed number of atoms, ok, but let's make this new benchmark based on a totally unreactive material. It needn't even be solid. Helium, anyone? Surely easier to purify than, say, gold?
just my 2p worth
just my 2p worth
The trick is to be able to count all the atoms without dropping any on the floor
Best to revamp the ISO weights and measures all together... our current system is based on arbitrary values which they have had to come up with precarious ways to indirectly relate to natural phenomena.
Better to KISS and start with nature as the base measurement, such as the "Helius" being the atomic weight of one helium atom * 100,000,000.
Better to KISS and start with nature as the base measurement, such as the "Helius" being the atomic weight of one helium atom * 100,000,000.
This is a tricky one because mass is basically something you can hold in your hand and feel it. So far I can only think of 2 ways to redefine it without making use of anything other than time and distance which are defined very accurately already.
The first way is by the force needed to give a mass (which will be 1 kgm) an acceleration of precisely 9.80665 m/s/s. The problem with this is that G is very hard to determine more accurately and it's based on the equivalence of mass and inertia.
The second way is to use what's already a universal constant and that's the rest mass of a proton which is already known to high accuracy. This would define a Kgm as being 5.9786386E+26 protons (to however many decimal places as is deemed necessary, my spreadsheet only allows up to 7 decimal places). This would call for constant revision as experimental accuracy increases and would cause a flow on to other definitions but this already happens with G anyway.
Better still would be to show the equivalence to the number of neutrons which would be 5.9704089E+26 because any half smart alien would see immediately that this was the mass ratio between protons and neutrons and then know what the natural base units were.
Using a system like this (and knowing the affect of electron mass and binding energies) you could work out exactly how many atoms of any element you'd need for a 1 Kgm mass.
I think..............
The first way is by the force needed to give a mass (which will be 1 kgm) an acceleration of precisely 9.80665 m/s/s. The problem with this is that G is very hard to determine more accurately and it's based on the equivalence of mass and inertia.
The second way is to use what's already a universal constant and that's the rest mass of a proton which is already known to high accuracy. This would define a Kgm as being 5.9786386E+26 protons (to however many decimal places as is deemed necessary, my spreadsheet only allows up to 7 decimal places). This would call for constant revision as experimental accuracy increases and would cause a flow on to other definitions but this already happens with G anyway.
Better still would be to show the equivalence to the number of neutrons which would be 5.9704089E+26 because any half smart alien would see immediately that this was the mass ratio between protons and neutrons and then know what the natural base units were.
Using a system like this (and knowing the affect of electron mass and binding energies) you could work out exactly how many atoms of any element you'd need for a 1 Kgm mass.
I think..............
Why not just base the kilogram on the volume of the object it currently is measured against? The object's mass, taken today, would be agreed upon as being the definitive "kilogram" and its volume would be calculated. Then the basis could be ___ cm^3 of platinum iridium alloy.
Possible deficiencies with this method could be, how accurate can you calculate volume?
Simplistic, I know, someone please shoot the idea full of holes.
Possible deficiencies with this method could be, how accurate can you calculate volume?
Simplistic, I know, someone please shoot the idea full of holes.
Apart from the fact they want to get away from having just a lump of metal in a vault...it's an alloy of platinum and iridium so the % of each would have to be strictly controlled. Also, both elements come in several isotopes so for strict accuracy the isotope mixture of each needs to be specified. Then the temperature it's measured at for a specific volume.
Good point on the alloy %. However, what are some downfalls of using density of a more "pure" substance? What's the most pure substance achieved? Can temperature be controlled to a great enough degree of accuracy? (0C?)