A Changing Standard

Did you hear a bell toll mid-November in 2018? You should have because a longtime king died! Norbert, you're being melodramatic. It was no king.No, it wasn't a person, BUT, it was le Grand K which is a pretty big deal!

Le Grand K is a shiny cylinder of platinum-iridium alloy that has been locked away for one hundred thirty years. Every forty years, this one-kilogram cylinder was taken out at the International Bureau of Weights and Measures in France so that we could be sure that one kilogram was still a kilogram. It was a physical calibration for the world's standard measurement of mass. But now, instead of using this cylinder, the kilogram will be defined by something called Planck's constant.

It's a mainstay of quantum mechanics and has a value of six point six two six zero seven zero one five times ten to the negative thirty-four kilogram meters squared per second. Wow, that was a mouthful.

So, basically, to find a kilogram, you'd use something called the kibble balance which determines mass as a balance to a defined electric force. It's complex, much harder than getting out a cylinder but it's way more precise. We already do this with the meter. We now tie the meter to the speed of light.

Since light travels some two hundred ninety-nine million meters every second, then one divided by this number defines a distance that we call a meter. Since the speed of light never wavers, the length of a meter is precise. Now that the new definition of the kilogram has been approved by scientists from sixty nations, next is the second which has long been defined by emitted radiation from a radioactive Cesium clock.

What?? Don't worry. It's complicated.