I have always had one question about defining measurements in terms of universal constants. Perhaps it is a silly one.<p>What if universal constants are, in the long run, variable? What if over the course of 500 years the speed of light, or the strength of gravity, changes?<p>If the measurements used to define these constants are defined in terms of the constants themselves, how would we see change? Perhaps this is a silly question in practice. If so, I would be interested in the 'theoretical' or hypothetical answer for a world where traditional measures of the kilogram and second have been forgotten.
The most interesting takeaway from this article for me isn't the kilogram, which is obvious and makes sense, but that the <i>mole</i> is being redefined.<p>A "mole" is a unitless quantity. Literally it's just a number. I'm just dumbfounded that when they defined it, they didn't just pick an actual number but referenced an experiment to define it. Now it's a number.
So if I understand correctly, this is saying that we would be formally redefining the kilogram, mole, ampere and Kelvin units (or prototypes?) as some quantifiable relation to immutable, measurable constants instead of the arbitrary and self-referential "this is a kg because it's how much this block of metal weighs and we decided that's what a kg is". Is that correct?<p>Not being a scientist myself, I'm struggling to understand the impact of these changes being made. Is it just a matter of increasing the precision of base units?<p>Say they redefine the mole to be based on that 1kg sphere of silicon-28. What is the real-world impact of doing so? Presumably one mole will still be one mole and not all of a sudden e.g. 6.03x10^23.<p>Does anyone have an example of where a change like this would be important?
<i>"For the scale that's in your grocery store or bathroom, nothing's going to change," Dr. David Newell of NIST said.</i><p>Was <i>really</i> hoping my Intent to Deliver charges would drop to simple possession, but I guess that's not going to happen...
While this is a good thing, I can't help but be a little bit sad. I liked the idea that while meters and seconds were defined by some natural process or law, the Kilogram was something that physically existed, that you could see or even theoretically hold in your hand.
Interesting read I saw a similar post about this from July:<p><a href="https://www.washingtonpost.com/news/speaking-of-science/wp/2017/07/05/scientists-are-about-to-change-what-a-kilogram-is-thats-massive/?utm_term=.d8dff516db82" rel="nofollow">https://www.washingtonpost.com/news/speaking-of-science/wp/2...</a><p>Redefining mass based on an idea as opposed to a physical object took me some time to get my head around.
IANAS... Is it possible that these adjustments could mean the difference between someones work needing a "magic number" to be correct and not? I've heard stories about physicists who needed to add some "correcting" variables to make their math totally correct, which is why I thought of this.
You know what's kinda funny: In order to make the changes to "define" these physical constants, we first make equipment using the old definitions. XD (Not that it changes the outcome, mind you.)