My bathroom scale is accurate to within 15kg. I wouldn’t make a good scientist.
Scientists around the world are finding themselves facing a bit of a problem: the kilogram is losing weight.
Originally the kg was planned out to be the mass of 1L of water. It proved too difficult to measure an exact litre. In 1875, the International Committee on Weights and Measures was formed to safeguard precise measurements. A goldsmith was commisioned to create a model that would be used to measure everything else against. He cast a platinum alloy cylinder. For decades it’s been kept under lock and key in France (only three people on earth have the key) and is brought out of the safe once a year to be measured.
The problem happened and continues to happen when the cylinder is measured. It turns out that the accurate little cylinder is getting lighter. 50 whole micrograms lighter. 50 micrograms is the weight of a fingerprint, or slightly less than a grain of salt. Sounds tragic, doesn’t it? Apparently it doesn’t really matter except for the fact that certain electrical calculations are based on mass.
80 copies of the original cylinder have been copied and sent to folks who were original signers of the treaty back in the 1800’s. Amazingly enough, they’ve remained constant. So what’s wrong with the first little guy? Scientists aren’t really sure, but some have come up with solutions. One involves creating a nearly perfectly round ball of perfectly pure silicon crystal. The theory being if you know the atomic weight of silicon, the distance the atoms are from each other, etc. you could calculate the mass of one ball. Apparently one of the balls they’ve put together is:
a) so round that if the Earth was as round, Mt. Everest would be 4 m tall.
b)so smooth they can’t actually tell if it’s spinning or sitting still. If a mote of dust lands on it, they have something the eye can follow, but that would affect the mass then wouldn’t it?
The good news is that scientists believe this is a solvable problem. Based on their track record, they’re probably right. Consider:
– The metre used to be a linear measurement based on a portion of the circumference of the Earth but now is calculated by determining distance light travels in one-299,792,458th of a second
– The second used to be considered a portion of a 24 hour day, but is now calculated by knowing the time it takes for a cesium atom to vibrate 9,192,631,770 times
The above examples are important, because they can be calculated ‘easily’, ‘anywhere’ on earth. Yeah, like my workbench, where I have just the tools.