You can measure mass (as opposed to weight) using angular momentum and torsion springs.
By 1785, those were already so sensitive that Charles-Augustin de Coulomb could use one to measure electrostatic forces, and came up with
Coulomb's law.
By 1798, Henry Cavendish used one to directly measure the gravitational attraction between two masses in a laboratory experiment, the famous
Cavendish experiment, although geologist John Michell designed the experiment (Coulomb following his plans), sometime before 1783, but alas, kicked the bucket too early. (Michell was 69 when he died, though.)
With commercially available load cells, a turbo pump for pumping a good vacuum, some glass jars and such, you can definitely measure for example the gravitational attraction between say two marbles, in a freshman physics experiment. The most expensive thing is getting precise mechanics nowadays. A couple of hundred years ago there were watchmakers and others happy to help produce interesting scientific apparatuses, but now, you're better off with old mechanisms and new sensors!
1. Please stop calling g a physical constant, in the sense that G (universal gravitational constant) is a constant.
Hey, I blame the language! We need a word describing a variable that is not being varied in this particular context.
For differential calculus, we use "derivative" and "partial derivative"; so would "partial constant" work?
Yesterday, I spent a couple of hours admiring the concept and word
geodesic.
Let me waffle on a bit once again, but this time, as a hopefully entertaining but informative musing on how precise, exact terms make life interesting, and mushy overloaded ones a misery. (I am thinking of making a T-shirt with
"Why don't you just use pastel tones to reduce gravity?, too.)
As a background,
geodesic is when you extend the concept of "straight line distance between two points" to surfaces; and from its name, one of the most used one is the "straight line distance" between two points on the surface of a sphere or geoid, like the Earth. On a perfect sphere, that distance is the shorter arc of the great circle – a circle passing through those two points, with its center at the center of the sphere.
What happens, if you ask your Californian friend what the distance between LA and Las Vegas is?
My bet is that the most common answer is something like "Oh, about four hours, at this time of day."
Bitch, I asked you distance, and you gave a time interval. What sort of mindfuck is this?
(If you happen to have the cultural context, you'd know that because primary transport in that region is via personal automobiles, and the physical distance is less relevant than the actual travel speeds achievable, it makes more sense to describe distances using the typical time taken to drive that distance, than anything else. Just like we include the completely unrelated inertial term in our "average acceleration on Earth due to gravity", because we don't have any better place to put it, and keeping it there takes care of it very nicely, thank you.)
In a different cultural context, that friend might ask for clarification, say "As the crow flies, or?".
Bitch, I ain't an ornithologist or an ornithopter; how the hell would I know how corvids fly anyway? They may do so ass first for all I care.
Now, let's get to "geodesic".
Let's say you're driving from LA to Las Vegas with your friends' kid on the back seat, thinking about normal kid stuff, like how many hydrogen bombs in the 50 to 100 kiloton range would they need to carve a canal from Los Angeles to Las Vegas.
The kid asks, "Do you know what the geodesic between Los Angeles and Las Vegas is?"
Why, you just looked that up a few days ago for this very thread, so you answer "About 368 km, but there is also an elevation difference of about 525 meters."
SEE? No confusion. Straight, unambiguous answer unrelated to ornithology, free of oddities like trying to measure distances using time units, and so on.
The kid happily takes the added cratering depth into account, you both smile, and have a nice car drive. Everybody wins.
If you try to be physically or geometrically correct but do not know the term, the mistakes and confusion one gets mired in are endless.
For example, let's say you ask "What is the distance between Los Angeles and Las Vegas?", I ask for clarification, for which you say "in a direct line, but ignoring the curvature of Earth and the difference in elevation". My answer, not to be snarky but maximum helpfulness, could likely be "Either 368 km or 39707 km, depending on which way you measure it."
I know, I'd get bitch-slapped for that (if I wasn't driving, and I don't). But I lack the context necessary to give the "straight answer"; I either have to make assumptions (which are often wrong), keep asking for clarifications, or give an answer that outlines the possible set so the asker can determine what the hell they were trying to find out in the first place.
And no, I don't really like "partial constant". But I'm used to it, because I use
const every day, and it does not mean that something is constant, just that in that particular context
I (or the C code I write that uses that) promises to the compiler to not try and modify that value. And
volatile does not mean "flames or vapours are imminent, get your fire extinguisher ready!", it means "hey compiler, that value may change at any point, so make no assumptions about it okay?". And I have to talk about stuff like "immutable string literals" to get new programmers to understand you really don't get to modify them; that if you do, you broke a promise, and the kernel gives you a segmentation fault in confusion.
But I
perfectly understand the frustration with mushy and misused concepts and terminology. If we'd have a better set, one with say posters or web pages intended for different levels of complexity/understanding, that I could point others to and say "using
these" ..., I would do exactly that. And I'd be darn happy; I'd buy it as a dozen posters and lovingly put them on my walls and give out as gifts; they'd make that much a real-world measurable difference.
But scientists and their insistence of attaching peoples surnames to things yielding undescriptive (or in the case of original discoverer being someone else, sheer misleading history-twisting self-aggrandizement) words one has to learn by rote by the dozen and use "correctly" (read differently) in every single little domain, and science becomes a Black Magic only those versed in the Old Powerful Names of Power and History and Power have the sheer single-mindedness to delve into.
I mean, I can say something like
"My mother in law was being a sheer Cheney this week visiting us. Thank Dog her Trumpy sister could not come! Dealing with those two is like trying to watch The Kardashians and Dr. Phil at the same time. I don't know... I think I might be getting a bit Biden in my old age or something; I've been acting like a complete Dubya." and people would just get it.
But use "mass" and "constant", and people start getting more confused and even angry... No, this is not sane or right. Yet, it is the world we have.
So, what is one to do? Even writing about this like I've decided to do in this thread gets me flak about wasting others time, and gets me added to new ignore lists.
I don't know. I just pick a topic at a time, think hard about it, and especially all the ways I know and think of it can be misunderstood, and if I decide it seems possible/worthwhile/useful, construct something that hopefully helps others wade through the word salad but with new mental tools and understanding at their disposal.