2.75 Cm On A Ruler

Your Body Ruler - A User's Transmission

(Now part of A View from the Back of the Envelope.)

The idea: you tin can measure with your body.
Length, angle, time, etc. This page deals with length.
And... you volition never forget to bring your bodyruler with you lot. :) Though sometimes I forget my calibration...

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Your Body Ruler
A User's Transmission

Congratulations on being a human ruler!
Throughout history, people have been using themselves to measure length. Y'all can too!

An instance

How large is the screen/newspaper in front of you?
My screen is virtually 4.five palms by 3.5 palms.
(Yes, there are now fingerprints on my screen. :)
Having calibrated myself, I know my palm is 0.07 meters (7 cm, 2.75 in).
So my screen is something like 0.31 past 0.24 chiliad (12.four past 9.six in).
Measuring with an "ordinary ruler", I get 0.32 m and 0.25 chiliad. (12.5 by 9.5 in.)
And so my palms apace gave a nice measurement.

Calibrating Yourself

A first pace is to cull your measures, and measure your choices.

Many trunk distances can be used every bit measures, simply you dont need all of them. Many accept similar size (for example, paw and palm), so yous can just cull ones you prefer, perchance ones with numbers easier to remember. As well, some are related (i palm tin be iv fingers). Feel free to use other measures, or to change these (like using little finger rather than middle finger). The important thing is consistency, using them the same way each time.

Earlier using any new measuring instrument, one needs to calibrate it by comparing it with something else, something of known measure. For your bodyruler, you lot tin use an "ordinary ruler". Averaging can be used to reduce fault. For case, mensurate out 3 palms and divide by 3, rather than merely measuring a unmarried palm.

Here are some measures yous might use. I've highlighted my favorites, and included some roman names.

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Measure	Caption	my personal scale Your'due south will differ.
finger	finger width (digitus)	2 cm, three/4 in
"boom"	width of thumb'southward nail. (Information technology's almost finger width.) ("nail" historically likewise names some longer units.)	1.5 cm, 5/8 in
inch	thumb width, "mesouret at the rut of the nayll"	ii.5 cm, 1 in
half finger	fingertip to (center of) second joint (cull a finger (historically, information technology was middle))	5.v cm, 2 1/eight in
finger length	fingertip to knuckle	11 cm, four 1/4 in
palm	width of 4 extended fingers (palmus) ("palm" is besides know every bit "hand".)	vii cm, 2 3/4 in (at eye articulation) eight cm, 3 in (at knuckles)
hand length	mitt length, heel to fingertip	nineteen cm, 7.5 in
hand span	manus width, from outspread pollex to fiddling-finger (Convenient, but because stretch varies, a chip less consistent than these others.)	22 cm, eight.5 in
foot	foot length, heel to toe (pes) Skilful for walking curt distances.	27 cm, 10.5 in (bare) thirty cm, 12 in (sneakers)
cubit	elbow to fingertip (cubitus)	47 cm, xviii.v in (~0.5 meter)
yard	nose to fingertip, with arm straight out to side, head facing front Good for measuring rope and fabric.	92 cm, 36 in (3 ft) (i meter if I turn my head)
fathom	fingertip to fingertip, arms out stretched	178 cm, 68 in
acme	the usual	182 cm, 72 in
step	ane step	~80 cm, ~30 in (~3 ft)
footstep	two steps (passus) Good for walking long distances.	~150 cm, ~sixty in (~1.5 meter)

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Stuff

Leonardo da Vinci (1452-1519) writes of Roman builder-engineer Vitruvius Pollio (1st century B.C.):
"... Vitruvius declares that Nature has thus arranged the measurements of a man: four fingers make one palm. and four palms make 1 foot; six palms make i cubit; iv cubits make once a homo's top; iv cubits make a footstep, and twenty-four palms brand a homo's height..." [Klein, pg 68]

It would be nice to talk over measurement error and techniques, usage hints, historical notes on the units, averaging to create standards, perhaps also calibrate precision/errorbars, ...

Bending

Encounter as well Measuring bending & distance with your thumb.

The visual acme of your fist, held out in forepart of you, is virtually 10 degrees.

Y'all tin check this by starting with your arm straight out, and than walking you fists upwards, hand over mitt. At 9 fists, you should exist pointed at the ceiling.

        +                    +  f          +            f Eye ddddddddddddddddd f       +      

A brief elaboration: together, the distance from heart to outstretched fist, and the pinnacle of the fist, grade two sides of a right triangle, and thus make up one's mind an angle. (say 58 cm and 9 cm, "opposite over adjacent" is 9/58, with arctan(ix/58) = 9 degrees).

Information technology would be nice to have some notes on usage, on sensitivity to fist distance, on measuring the distance to objects of known size (shipping, people), on measuring the top of a building by walking towards information technology, on ...

References

The Science of Measurement : A Historical Survey / Herbert Arthur Klein. 1988 (Under another title in 1974). Especially pages 53-73.

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Comments/questions/thoughts encouraged. - mcharity@lcs.mit.edu.
[Elevation] [Musings]

History: 1997.May.05  Added link to A View from the Back of the Envelope. 1997.Mar.25  Added "hand bridge", and "measuring distance due west thumb" link.              There has been no comment, and thus no further work here. 1996.December.17  Fleshed out draft. 1996.December     Occasional puttering.        

2.75 Cm On A Ruler,

Source: http://www.vendian.org/mncharity/dir3/bodyruler/

Posted by: scottwhounces1938.blogspot.com

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