one reason why we can't take the plank constant as the definition of this mass is because the planck constant can be expressed in terms of the kilogram and to other units that's why we were able to establish a relationship between the value of the cube a gram and the plant constant. this can be done using a watch balance for example it's a highly complex instrument that's been used since the 1980 s. to measure the planck constant as precisely as possible. there are only a handful of these scales worldwide this one is in the united states at the national institute of standards and technology. the high precision scale is based on the principle of electromagnetic force compensation this is how it works the gravitational force of a test mass is balanced with an electromagnetic force the magnetic field is provided by a permanent magnet a coil of wire is immersed in that field. it's like

a coil in a loudspeaker the coil is in the permanent magnetic field and electrical current is run through it to generate a force that force is used to balance the downward force of the weight it's a way to measure weight using an electrical current. mission in other words the electrical current is adjusted until the upward force on the coil perfectly balances the downward force of the weight the 2nd step is called the velocity mode of precision laser called an interferometer shown here in green is used to measure the position and velocity of the coil. the aim is to measure the voltage that is created in the process. then we need gravitational acceleration small g. 9.81 meters per 2nd per 2nd if you know all these things very precisely you can

calculate the numerical value for h. the math isn't complicated in reverse if you know the value of h. the planck constant you can specify a kilogram. the planck scales from germany will work in exactly the same way they're basically all what about alan's on the left is the laser interferometer on the right is the balance based on the principle of electromagnetic force compensation but it's a lot smaller than its american counterpart. if i reverse the principle of the water balance and say i know the value of h. then i can use my plank scales to calibrate any weight. i simply lay my object on the one side and then relate the electrical values to the plank constant and from that i can calculate the mass on the scale of. the 2 planck scale prototypes from the technical university ill man now will eventually be put to

industrial use currently they can be used to determine weights in the range between one milligram and 100 grams but it will be another 3 to 5 years before the 1st planck scale goes to market the paris kilogram meanwhile has already lost its status as the international benchmark and is now being consigned to a museum. along with the kilogram the 2nd and the meter they are all sorts of the units of measurement we asked our viewers what units of measurement do you. separate the indigenous people of mexico use them a data which is equal to the volume of an empty sardine can. from indonesia says in java we often use the volume of an empty coconut shell to measure rise maize and other goods one shell usually holds one kilo. this unit of

measurement is still in use today. in argentina eduardo says we use the meter kilo celsius liter and hector best skill or we eyeball it that always works. says our says farmers in colombia use the key to the distance you can travel while smoking a cigar so where is the farm one and a half to go from danya is stuck here as farm lands for your comments. that's all for today and next week we head to colombia as we continue our journey in the footsteps of humbugs he wrote that slavery was the greatest of all evils to have before then humankind we visit the town of palenque a established by scared slaves 400 years ago until then good bye.

the powerhouse turns 100. 100 years of modern struggle to actually. 100 years of functionalism n.p.r. isn't. what's behind the legend. we asked the experts about the. coming up on d w. a a fine dining moves tradition to move to reconstruct the list go and make love. to see some rain sleet are good to. find the memories of what's behind the about. 30 minutes body double.

in the streets rising people fight for some kind of money to set up and when there's a flood the water comes up to your waist going to close faster everyone but. the lack of water is an equally dangerous. sank you can see people not self so they can plant crops and trying to meet the system. floods and droughts will climate change become the main driver of mass migration you could not write any going to night if you want and probably most of the bill. for climate exodus starts september 5th on d w. i was here when i arrived here i slept with 6 people in a room as. it was hard i was fair. i even got white hairs that.

language and not a lot this gets me and they go but you need to entrap it's the same.