4 ms·
There are actually a fair few problems with SI units. The candela is fairly ridiculous, the kilogram needs to not depend on a physical object (it's also a littl
by sethrin 10y ago
There are actually a fair few problems with SI units. The candela is fairly ridiculous, the kilogram needs to not depend on a physical object (it's also a little silly to have a prefixed base unit). The ampere is not practical to measure with its current definition, and apparently with the current definitions of Hz and radians, 1 Hz = 1/s = 1 radians/second. Other people take issue with the mole, as well.
SI is an improvement but it is not quite perfect. As long as we have a choice of imperfect systems, we have to pick which is most convenient.
- 3chelon 10y ago> it's also a little silly to have a prefixed base unit I somewhat agree with that - I had the exact same conversation with my kids very recently. Re. physical object: well, whatever physical reference artefact is used, to all intents and purposes the physical stuff is water, with the basically sensible equivalence 1L = 1kg = 1000cc. As you point out, it's not perfect because of the somewhat arbitrary scales (kg, cc), and it gets worse when you bring temperature into it (I believe it's supposed to be measured at 4 degrees C, but I'm not totally sure of that). You're right in that it is not perfect, but at least it is a fair attempt at coherence.
- tremon 10y agoI believe it's supposed to be measured at 4 degrees C Correct; it's because at that temperature water is at its densest: https://en.wikipedia.org/wiki/Water#States https://en.wikipedia.org/wiki/Water#States
- auxbuss 10y agore: the kilogram issue: Redefining the Kilogram with the DIY Watt Balance: https://www.youtube.com/watch?v=ewQkE8t0xgQ https://www.youtube.com/watch?v=ewQkE8t0xgQ