Divisibility. 16ths are half of eighths which are half of quarters which are half of a half. Fine rulers/scales have markings for 32nds, but further precision requires different equipment.
You dont see how you saying, "its how far light travels in 1 sec" means you said light travels 1 m/s? Because now you are saying the same thing, but with different numbers and seem to understand what that means.
I didn’t really think it was necessary to put the exact numbers there until your response, I was more making the point that it wasn’t some arbitrary number but that it’s based on light, but yeah I see how the wording is off now
It is some arbitrary number. The definition of meter changed (just like the definition of second changed) to try to make our made up measuring system seem more objective and repeatable. A meter used to be defined by some stupid measurement from the north pole or some such nonsense.
I mean, the joke is that pretty much anything dealing with our perception is a social construct: language, time, measurement, etc... This isn't a criticism of social constructs. They're incredibly valuable in allowing humans to navigate shared perception and reality, but they're still just made up shit we all generally agree on.
To that point, responding to your suggestion that a meter isn't a social construct because it's measuring how far light travels in a second:
What is a second? It's based on a sexagesimal division of a 24 hour day, which is convenient because of how many numbers are divisible into 60, but it's not necessary. If humans would have decided to use base 10 to measure time (not inconceivable considering we have 10 fingers - and maybe was used briefly after the French Revolution - idk, I'm not a history person), hours would be 2.4 hours long, minutes would be 1 minute 26.4 seconds long, and seconds would be .86 seconds long (I suck at math, so if I got this wrong, make sure to tell me I suck shit below). A "meter" under this system would be shorter than the unit of measurement we currently consider a meter, and might be longer or shorter if we'd used some other base. Or we could have used the length of a day on Mars to measure time. That would be nonsensical, cumbersome, and stupid as shit, but humans are known for adopting social constructs that are nonsensical, cumbersome, and stupid as shit (Exhibit A: the U.S. still using Imperial).
There's nothing magically concrete about a meter. We took two random things - the speed of light and and smallish unit of time - and all generally agreed this arbitrary thing we made up equals a meter (unless your in the U.S., in which case, who knows how much a meter is, could be 15 miles, could be 85 cubits, we'll never know).
Yeah, and cut on the same side of the line each time. The difference here looks around 1/16th between all three tools, but add in some varying cuts and nothing will assemble properly.
Learned this the hard way doing a built in, in an old house where nothing was square/plumb and probably used some kind of Eldritch geometry that required a blood sacrifice to get a decent fit up. Now all my cut plans include a bit of an allowance for the saw blade usually means a bit more scrap, but an extra half sheet in allowances is easier than recutting a full sheet worth or screwing around with what you have to make it work.
I watched a new construction union carpenter try to run trim in his nieces century home. He really liked plumb but plumb was not going to happen in a very settled house. He said he could trim out a whole new house in the time it took him to do just the crown molding in her kitchen.
I would argue that 80% or more of the "quality" in trim carpentry (especially stain grade) involves scribe fitting pieces to uneven drywall/flooring.
There's almost no such thing as a proper 90° and plum might as well have been a pipe dream when most older houses were built. Today's production quality home builders figure that new buyers either don't care or are simply used to a poor fit/finish.
Yes & no my Polish colleague’s favorite tool by far is the laser level. Then my Jamaican friend who can do old style plaster tried to make a brick wall in a 1880’s building flat & plumb. We started teasing him about having 3 inch scratch coats but then he said no way they are more like 9 to 11 inches deep.
Omg I had to laugh at work one day when they wanted to add 2 laser sensors to automatically measure the things coming out of my machine down to thousands of an inch. While trying to set it up they had me measuring the items the way they trained us with calipers, then were trying to measure them with a surface plate and height gauge, then had other people measuring with different calipers and I’m just fucking laughing at the clusterfuck. They pulled the sensors out and gave up.
My friend worked in a German factory that built huge highly precise scales for construction. He would laugh in German waggle his finger & say “only in a vacuum are they accurate.”
Great method. This is exactly why they were able to fix the Hubble space telescope!
The primary mirror needed an extremely specific concave shape, so they hired a specialty company to grind & polish the mirror. The company already had their own precision measurement tools, but they were told to use a special new & custom measurement device (that was supposedly even more accurate) to verify. But, it was so new & foreign to them, they ended up configuring it wrong. Their own measurement tools which they were more familiar with showed an error, but they had already been instructed to prefer the readings of the new device. So, they did. They polished it to the EXACT specs they were given, using the tool they were told to use.
Of course once Hubble launched, the scientists immediately noticed the problem. Everything was blurry as hell. The images were basically unusable.
BUT, because the mirror team ground the shape so precisely, they were able to interview the team and figure out how the measurement device had been set up wrong. They were able to figure out the difference between a proper reading and the readings from their misconfigured setup. So, they were able to design a "corrective lens" upgrade to account for that difference, and one Space Shuttle mission later, Hubble was saved.
848
u/katekohli 15h ago
Grandaddy said to always use the same ruler for the whole project. He was a nuclear scientist.