Weights and Measures

When teaching physics, I always teach people that a quick way to remember a formula, or a good way to check your work, is to take a look at the units.

Units are a fundamental thing in physics, as it's related to the concept of quantity. Ultimately, the idea of units is totally bogus. In most cases, they are just completely arbitrary objects that have withstood the test of time.

So, it comes with no surprise that the kilogram (the one that all kilograms are based upon, held in a vault) is losing it's mass. The best part, is that the nerds can't figure out why.

So now, the race is on to quantify a kilogram to natural phenomena. For example, there was once a metre stick that defined what exactly a metre was. Say that friggin metre was stolen or warped or something, we'd all be screwed. So now, it's defined as the distance travelled by light in a vacuum in 1/299,792,458 of a second. Speed of light is a universal constant, so good job. Wait.

We've defined a unit in terms of another arbitrary unit, the second. Well, a second is now defined as the amount of time it takes for 9,192,631,770 transitions between two levels of the ground state of Cesium 133.

The kilogram, me thinks, will have to be defined by something on the atomic level, perhaps related to the number of atoms in some element. It really could decades for the nerds and politicians to agree on this.

But, when it's all said and done, most other units are just combinations of metres, seconds and kilograms so we need to get this right.

UPDATE: For rather fascinating insight into the whole units thing, read the wikipedia article on Fundamental Units