mathmannix wrote:OK, I know roughly what a liter of water is (I picture a quart, ha!)

But even if I have it established really well in my head what a liter is, that doesn't really give me a good idea of what a hundredth or thousandth of a liter is, or even what ten liters is. OK, the math is great for SCIENCE and all that, but not really for everyday life (such as measuring for cooking or whatnot.)

That is not a sufficient reason.

With use (the same way you can visualize a teaspoon or cup), the metric units will become equally familiar. The advantage (and arguably, the only advantage) is that metric units easily convert, whereas cups and quarts and teaspoons and barrels don't. There are a lot more conversion factors to memorize and multiply/divide by.

The problem is really twofold:

One is that ten is a horrible number system base. Twelve is far superior (almost all common fractions are easily expressed past the "decimal" point). Commonly needed arithmetic in base twelve will almost always lead to pretty numbers; this is not true of base ten. We use base ten because we

~~were designed with~~ haphazardly evolved with ten fingers. It's too late to go back now, but commonly needed arithmetic is why so many measuring systems have factors of two and three and four built into them, but rarely five or seven.

Two is that different sized units are "best" for different fields, and they also arose haphazardly, without any thought for an overarching unit system. Moving to metric (or any other universal system) makes each of these fields more awkward, for the benefit of easily switching between them. There once was a

wonderful website which described the history and usefulness of various systems (such as why "chain" is used for surveying, and why it's so much better than anything else

for that purpose, but I don't remember the URL and cannot find it any more. It may have gone to the Bit Bucket in the Sky; searches reveal other sites but not any as awesome as that one.

Even money fights this. Ten is an awkward number for splitting subsets, but since we have adopted base ten, anything else is awkward for universal systems.

As for temperature, Farenheit and Centegrade are superior to Kelvin because at least with the former, you can have something that has "absolutely no temperature", thus defeating quantum mechanics at its own game.

Jose