Feels like a chicken and egg senario. Let’s say I get my torque wrench from work sent off to be calibrated, and that’s calibrated with something itself needs to be calibrated, and so on and so fourth. How’s that figured out?
In: 430
2147_m has a great explanation. However, one thing I want to point out that they didn’t mention, is that the “highest level” standard you can compare against is not based on a physical object. All measurements are derived from concepts. 1 meter (the standard unit of length, even feet are derived from meters) is defined as the distance light travels in a vacuum in 1/299,792,458 seconds. 1 second is defined as the amount of time it takes the energy level in a cesium atom to oscillate 9,192,631,770 times. And so on, all units of measurement are based on concepts, not physical items. This means that, in principal (not necessarily in practice) anyone can perform a calibration without having to send their equipment to compare it to other equipment. It also means the measurements will never change over time, which is something that will happen to any physical object.
Veritasium has three great videos on how the kilogram went from being defined as a physical object, to being defined as a concept. The first two videos are about how scientists were attempting to use two different methods to acheive this, the last is how they actuall went about acheiving it and how it’s defined today. They are well worth a watch if you’re interested:
Feels like a chicken and egg senario. Let’s say I get my torque wrench from work sent off to be calibrated, and that’s calibrated with something itself needs to be calibrated, and so on and so fourth. How’s that figured out?
In: 430
2147_m has a great explanation. However, one thing I want to point out that they didn’t mention, is that the “highest level” standard you can compare against is not based on a physical object. All measurements are derived from concepts. 1 meter (the standard unit of length, even feet are derived from meters) is defined as the distance light travels in a vacuum in 1/299,792,458 seconds. 1 second is defined as the amount of time it takes the energy level in a cesium atom to oscillate 9,192,631,770 times. And so on, all units of measurement are based on concepts, not physical items. This means that, in principal (not necessarily in practice) anyone can perform a calibration without having to send their equipment to compare it to other equipment. It also means the measurements will never change over time, which is something that will happen to any physical object.
Veritasium has three great videos on how the kilogram went from being defined as a physical object, to being defined as a concept. The first two videos are about how scientists were attempting to use two different methods to acheive this, the last is how they actuall went about acheiving it and how it’s defined today. They are well worth a watch if you’re interested:
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