121–130 of 589 posts
I can imagine that in 100-200 years we'll have to adjust some unit because our understanding of some constant was just slightly wrong.
Earlier quoted context omitted.
I've never heard anyone claim that as the reason for its superiority. Metric is superior because it makes sense as a system .
1/2 m = 50.00 cm, 1/2 ft = 6 in 1/3 m = 33.33 cm, 1/3 ft = 4 in 1/4 m = 25.00 cm, 1/4 ft = 3 in 1/6 m = 16.67 cm, 1/6 ft = 2 in This is why imperial makes more sense to me than metric. If we had a base-12 number system, metric would be perfect, but base-10 is terrible under division. For practical divisors like these, imperial shines. If you're doing science, metric makes more sense because units work out. But most a…
Can anyone tell this poor ignoramus whether the kg is getting heavier or lighter - and how much by (approximately, I know it's not going to be an exact figure given the reason they are changing it)?
> "[...] the size of these units will not change (a kilogram will still be a kilogram) [...]"
Earlier quoted context omitted.
I've never heard anyone claim that as the reason for its superiority. Metric is superior because it makes sense as a system .
1/2 m = 50.00 cm, 1/2 ft = 6 in 1/3 m = 33.33 cm, 1/3 ft = 4 in 1/4 m = 25.00 cm, 1/4 ft = 3 in 1/6 m = 16.67 cm, 1/6 ft = 2 in This is why imperial makes more sense to me than metric. If we had a base-12 number system, metric would be perfect, but base-10 is terrible under division. For practical divisors like these, imperial shines. If you're doing science, metric makes more sense because units work out. But most a…
Something is 3m x 0.3cm, what area is that?
If that's one internal face of a container what width will hold a pint/litre respectively?
This is probably the dumbest thing I'll type on HN. In university I just gave up trying to understand why we even needed the Avogadro constant / mole as a fundamental constant. It still confuses me. Why have a difference between molar mass and mass? Why couldn't it just be "1" and everything else change around it?
The one that made it click for me as incredibly useful was Avogrado's Law (now part of the Ideal Gas Law): > Equal volumes of all gases, at the same temperature and pressure, have the same number of molecules. This law, for example, explains why hot air rises. Take two equal quanties of the same gas at the same pressure. They will have the same volume. Now, heat one quantity of gas. By this law, that gas will have a…
The law as quoted doesn't say what happens when the temperature change. Maybe it gets more dense? Be more specific.
Earlier quoted context omitted.
I've never heard anyone claim that as the reason for its superiority. Metric is superior because it makes sense as a system .
1/2 m = 50.00 cm, 1/2 ft = 6 in 1/3 m = 33.33 cm, 1/3 ft = 4 in 1/4 m = 25.00 cm, 1/4 ft = 3 in 1/6 m = 16.67 cm, 1/6 ft = 2 in This is why imperial makes more sense to me than metric. If we had a base-12 number system, metric would be perfect, but base-10 is terrible under division. For practical divisors like these, imperial shines. If you're doing science, metric makes more sense because units work out. But most a…
Using the metric system you'll rarely write 1/2m, as fractions are not what a person used to metric would default to. That is why 1/6m looks so weird as no one would use it like that, but if you write it 0.5m now it's obvious we are talking about 50cm, or 500mm.
BUT,
In those examples you are not using the system, you are just using one unit. If the question were, for example, what is the mass of the water contained in a 1m x 1m x 1m box, then the answer is obvious which system is by far the most sane one.
Maybe I interpreted it wrong (non-native English speaker), but does it say that the Kilogram will be equal to the Planck constant? Shouldn't it be that the definition of the Kg will be based on the Planck constant?
>Although the size of these units will not change (a kilogram will still be a kilogram)
Are our current measurements of the IPK that exact so the old kg is exactly equal to the new Kg? How can they measeure it with 0 error?. It doesn't make any sense to me.
How would you use the new definition to calibrate instruments? My current understanding is that there is a lineage of artifacts calibrated against another artifact until one of those was calibrated against the one true artifact. So how would NIST or another certifying source say that my 1kg standard is 1kg +/- tolerance? Is it anyone with a kibble balance can now certify calibrations? How do you know your kibble bala…
It means the right answer is freely available to anyone (with a bunch of scientific equipment).
> a cylinder of a platinum alloy stored at the BIPM in France, will now be retired. It will be replaced by the Planck constant – the fundamental constant of quantum physics. I thought they did that long time ago.
I wonder how much the cylinder will auction for.
Can anyone tell this poor ignoramus whether the kg is getting heavier or lighter - and how much by (approximately, I know it's not going to be an exact figure given the reason they are changing it)?
It used to literally be defined as the mass of "IPK" - the international prototype kilogram. https://en.wikipedia.org/wiki/Kilogram#International_prototy...
This switch now defines it in terms of the force equivalent of the energy exerted by a single photon - if my understanding is correct.
Theoretically a more scientifically sound way of keeping 1 kg a constant permanently.