4 ms·
>Despite the greatest of precautions, every time the standard kilo was handled — for example, to compare it to another unit that could then be used to calibrate
by dwighttk 7y ago
>Despite the greatest of precautions, every time the standard kilo was handled — for example, to compare it to another unit that could then be used to calibrate instruments — it would shed some atoms and its mass would be slightly changed. Over its lifetime, that standard kilo is estimated to have lost about 50 micrograms.
Why did the standard kilo ever need to be handled? Just store it on a balance and only handle the comparison unit.
- hiccuphippo 7y agoI think they needed to take the replicas from other countries like the US to the master one in Paris for comparison every year. Edit: see this Veritasium episode https://youtu.be/SmSJXC6_qQ8 https://youtu.be/SmSJXC6_qQ8
- forgot-my-pw 7y agoAlso relevant: https://www.youtube.com/watch?v=ZMByI4s-D-Y https://www.youtube.com/watch?v=ZMByI4s-D-Y
- rough-sea 7y agoThe balance still would need to be balanced.
- dwighttk 7y agoright...
- thenewwazoo 7y agoand then left...
- petschge 7y agoAt this precision you weigh things twice. Once with the reference on the left arm of the balance and the test object on the right and another time with objects swapped.
- ISL 7y agoThe standard kilo was/is stored in a vault inside several bell jars and only removed once every ~30 years to compare with the world's national reference/transfer standards. As far as I know, the mechanism by which Le Grand K is drifting with respect to all of the national references is not known. To leave it on a balance (which must be operated/checked/maintained) would expose the K to much more risk.