[HN Gopher] Coke can planimeter
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Coke can planimeter
Author : lambdatronics
Score : 66 points
Date : 2024-05-24 06:28 UTC (1 days ago)
(HTM) web link (durealeyes.com)
(TXT) w3m dump (durealeyes.com)
| 082349872349872 wrote:
| My favourite field-improvised planimeter consists of (a) tracing
| out the figures and cutting them out of paper, then (b) weighing
| the paper shapes with an analytical balance and dividing out by
| the weight of a unit area's worth of paper.
| emmelaich wrote:
| Not surprisingly, this technique is used for numerical
| integration of complex graphs.
| mensetmanusman wrote:
| My advisor's thesis had an entire section on that for computing
| complex integrals.
| lupire wrote:
| That's Galileo's method of integration.
| mauvehaus wrote:
| I can't pass up this opportunity to mention "How Round is Your
| Circle". It's nerd shit about geometry applied to, among other
| things, steam engines.
|
| There's a chapter or three about planimeters, the introduction to
| which is the hatchet planimeter.
|
| Worth a read if you're into geometry and Industrial Revolution
| stuff, and honestly, probably worth working through with pencil
| and paper, though I never have.
| theyinwhy wrote:
| I can't pass the opportunity to post https://neal.fun/perfect-
| circle/
| jasomill wrote:
| Nice. After five minutes: 95.6% with a mouse; 96.2% with a
| Wacom tablet; trackpad (Apple Magic 2), hopeless.
|
| As for opportunistically relevant posting: see the first
| chapter of Felix Klein's _Elementary Mathematics from an
| Advanced Standpoint: Geometry_ [1] for a bit on the geometric
| theory behind the planimeter.
|
| [1]
| https://archive.org/details/elementary_mathematics_geometry/
| ggm wrote:
| 3 bar linkage computing by Svoboda. MIT rad labs, ww2. Cams and
| drums did a lot of work plotting bomb angle, gunnery, rate of
| descent.
| foehrenwald wrote:
| Computing Mechanisms and Linkages By Antonin Svoboda
| https://archive.org/details/computingmechani00anto
|
| "He shows that with two basic mechanisms, the harmonic
| transformer and the three-bar linkage, it is possible to
| perform the fundamental operations of arithmetic, addition,
| subtraction, multiplication and division, and to generate
| ballistic functions." - JOHN WOMERSLEY
| (https://www.nature.com/articles/162085a0.pdf)
| ulnarkressty wrote:
| An experiment from an old physics textbook: trace a convex shape
| on a piece of paper, wet its contour with a brush and drip some
| water on it until it beads up. You then place the paper on a
| still water surface and touch the surface of the bead with a
| needle. The surface tension will move the shape under the needle
| until it points at the geometric center of the shape.
| itronitron wrote:
| Am I correct in thinking that the wet contour is made within
| the boundaries of the convex shape?
| ithkuil wrote:
| I always trip on the ability of English has to turn nouns into
| verbs so after my first parse of the sentence I thought "w.t.f
| does the verb to planimeter mean?". Then I realized that "can" is
| not a verb here....
| lupire wrote:
| Right. Coke can can planimeter
|
| What's the difference between a piano and a fish?
|
| You can tune a piano, but you can tuna fish.
| rahimnathwani wrote:
| You can tune a file system, but you cannot tune a fish.
| toast0 wrote:
| I mean, we verb nouns all the time, but this is just a homonym,
| can and can are different words that sound and spell the same.
| ithkuil wrote:
| Yes I was referring to the verbing of "planimeter" which
| wasn't
| HPsquared wrote:
| Proper capitalization would have made it clearer.
| veloxo wrote:
| "Coke can" is a phrasal adjective here and ought to be
| hyphenated, which removes the ambiguity: "Coke-can planimeter"
| ajb wrote:
| I don't think that's mandatory.
|
| Noun phrases can be arbitrarily long in English and don't
| require connecting words or hyphens. This can be very
| confusing to people whose first language doesn't have this
| feature. Classic example: "Heathrow airport customer car
| park", a five word noun phrase (IE, noun noun noun noun noun)
| that native speakers find completely normal.
| NegativeLatency wrote:
| This YouTube channel is worth a peek if you find physical
| computation interesting: https://www.youtube.com/@ChrisStaecker
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