The kilogram is dead, long love the kilogram

[Dicknose]

Well it seems this week could be the end of the current kilogram standard - a lump of metal that has defined the amount of mass that is called a kilogram.
It’s being replaced by a definition based on Planks constant and measured using a special balance that uses electromagnetic force.
This is pretty big news. Mass was the last of the units that had a single physical object defining it, the others such as length and time had all changed to a definition based on a physical property that in theory could be measured by anyone.


The existing lump of metal was created in 1889, replacing another one made in 1799 - so this is a change in technology to replace something that’s been used for over 200 years. Amazing that it’s the last to change and taken so long.

The change won’t actually happen for a while, this week is the vote to decide if this change should happen. Still it’s pretty important and marks a new era in measurements.

[MR2 Fan]

so they're changing what weight the kilogram is? but why?

[Godson]

For a more accurate measurement I suppose.

[Crazed_Insanity]

Just redefining it with something much better..., not really changing its weight I don’t think.

https://www.npr.org/2018/11/13/66631...d-the-kilogram

[Dicknose]

so they're changing what weight the kilogram is? but why?

Changing it so its defined by a property, rather than a single reference lump!

So they will have an experiment that you can do to measure your own kilogram.
At the moment they only way is to compare it to a single sample held in France (and its changing its mass!)

[Rare White Ape]

A kilogram will still be a kilogram.

But rather than define it by comparing to an object, they’re going to link its mass to an intrinsic property of the universe, so that anyone around the world who is so equipped can do the comparison without relying on that single object.

It’ll help drug dealers around the world when they’re offloading their product.

[Cam]

I always thought the kilogram is based on the mass of one cubic litre of water.

[Dicknose]

I always thought the kilogram is based on the mass of one cubic litre of water.

The problem is defining the temp of the water as the density varies. Also the purity of the water. Technically you would also have to specify the amounts of heavy water (water using a different isotope of hydrogen)
Thats still considered the original definition and a very useful day-day one.
But it wasnt accurate enough for science.

[G'day Mate]

"Cubic litre" ... Your imperial is showing

[Cam]

Whoops, yeah.