A whole bunch of scientists are meeting today in France to decide on something absolutely fundamental to our understanding of the world: how much does a kilogram weigh?
No, I promise you that actually makes sense. Obviously we know how much a kilogram weighs, but that’s only because the concept of a ‘kilogram’ is baked into the measuring instruments we use every day like scales and computers. A kilo is a thousand grams – but how much is a gram? How much is a microgram, a nanogram? You could drive yourself crazy that way.
Turns out we actually do have something to determine how much a kilogram is: a literal kilogram of metal, sitting in a vault just outside Paris. It’s called the Big K, and it’s been there for 130 years. Here’s a replica of what it looks like:
The thing is, basing your measurements on an actual physical object is pretty unreliable. There are minor fluctuations and variations happening in literally every object that exists in the universe at all times, so that lump of metal is not always going to weigh exactly one kilogram. Scientists have already made lots of changes to how they measure other things: for example, a metre is now measured as a precise fraction of the speed of light, which is always constant.
So, scientists are meeting today to make a similar change to how we measure the kilogram. I absolutely will not delve into the specific technical aspects of this change – because I simply do not understand them in detail – but the vibe that a kilogram will now be defined using another fundamental law of nature called the Planck constant. What that means is that anyone with the right equipment could work out what a kilogram is without having to refer to an actual physical object.
Obviously, this isn’t the sort of thing any old idiot could just measure, but it’s a vastly more precise definition than a lump of metal sitting in a French vault.
Representatives from a number of countries, including Australia, are going to vote on the change today. It’s expected it will sail through, which will no doubt excite a whole bunch of nerds. Excellent!
