Some other sources have suggested that the *length of the coil* is difficult to measure accurately enough, but the beauty of the Kibble balance is that length cancels out (along with the strength of the magnetic field, 'B'). I'm curious therefore about the comment at 1:17 that the coil is of a known length..?!
Anthony Kernich - No. It uses what is known about light. There is no choice to be made on that question. Light exhibits properties of each in different circumstances.
I don't get it. If kg is unstable and source of that instability are changes in Earths gravity field then how that "counterweight" method could help keep it stable? Not even mention that there are probably zero researches that evaluates influence of gravity field on magnetic fields...
@@aleksandersuur9475 I'm no scientist but I'd like to know if this new definition of 'h', 1 decimetre of water at 4°C will still weight exactly 1Kg - as it should - and not 0.999999999923 Kg ?
@@stephanesonneville think carefully for a second now. Accuracy of all your measurements depends on how precisely you can measure definition of your unit. Your measurement cannot be any more accurate than your ability to compare it to your definition. Never mind that the water definition is circular reasoning. Density of water depends on pressure, definition of pressure depends on definition of force and definition of force depends on definition of mass, which the french initially tried to define in terms of density of water. It was a convenient starting point for the era, but it's a piss poor definition by 21th century standards.
@@stephanesonneville 1L of water is not exactly 1kg, it's about 25mg short and has been for over 200 years, catch up would you. Besides, what kind of water? How pure? what isotopic composition? At what pressure?
Such a historic moment!
Some other sources have suggested that the *length of the coil* is difficult to measure accurately enough, but the beauty of the Kibble balance is that length cancels out (along with the strength of the magnetic field, 'B'). I'm curious therefore about the comment at 1:17 that the coil is of a known length..?!
so the new definition assumes that light is a particle not a wave
Anthony Kernich - No. It uses what is known about light. There is no choice to be made on that question. Light exhibits properties of each in different circumstances.
I don't get it. If kg is unstable and source of that instability are changes in Earths gravity field then how that "counterweight" method could help keep it stable? Not even mention that there are probably zero researches that evaluates influence of gravity field on magnetic fields...
No one knows why the kg isn't stable, but it doesn't have anything to do with gravity.
Hymeleon - Gravity is not the source of the instability. Mass does not depend on gravity.
Will they use le grand k to come up with the constant?
Adrian - Yes, in part.
Did you forgot that the kilogramme was already define by physical constants since its creation? 1 litre - 1 dm³ - of water at 4°C.
That definition was tossed out ages ago, like in 18th century. For the very simple reason that you can't measure it all that accurately.
@@aleksandersuur9475 You don't have to measure it as you already know that it's weight exactly 1Kg !
@@aleksandersuur9475 I'm no scientist but I'd like to know if this new definition of 'h', 1 decimetre of water at 4°C will still weight exactly 1Kg - as it should - and not 0.999999999923 Kg ?
@@stephanesonneville think carefully for a second now. Accuracy of all your measurements depends on how precisely you can measure definition of your unit. Your measurement cannot be any more accurate than your ability to compare it to your definition.
Never mind that the water definition is circular reasoning. Density of water depends on pressure, definition of pressure depends on definition of force and definition of force depends on definition of mass, which the french initially tried to define in terms of density of water. It was a convenient starting point for the era, but it's a piss poor definition by 21th century standards.
@@stephanesonneville 1L of water is not exactly 1kg, it's about 25mg short and has been for over 200 years, catch up would you. Besides, what kind of water? How pure? what isotopic composition? At what pressure?