4 ms·

> In 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.304 8 meter exactly. We can thank one man for this: Carl Edvard Johan

by p1mrx 7y ago

> In 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.304 8 meter exactly. We can thank one man for this: Carl Edvard Johansson from Sweden. When making gauge blocks, he decided to round off the inch to exactly 25.4mm, and people around the world used his blocks to manufacture everything. The 1959 change just reflected what industry was already doing. - http://mitutoyo.com/wp-content/uploads/2013/07/E12016-History-of-The-Gage-Block.pdf#page=8 http://mitutoyo.com/wp-content/uploads/2013/07/E12016-Histor... - https://books.google.com/books?id=3rUaAQAAMAAJ&lpg=PA293&ots=hiqJuRiYSM&pg=PA293 https://books.google.com/books?id=3rUaAQAAMAAJ&lpg=PA293&ots...

analog31 7y ago
An interesting factoid is that if you rummage around in a machine shop, you will find a pair of gears in a drawer somewhere, with 50 and 127 teeth. Those are for converting an old fashioned manual lathe to cut metric screw threads.
- Svip 7y ago
  Just FYI, a 'factoid' is something believed to be true, when it probably isn't. I assumed you meant 'fact', but otherwise your comment could be confusing.
  - zamfi 7y ago
    That is indeed one sense of the word factoid, but in common North American usage it also can mean “small or trivial piece of information”, which is the sense I believe the parent poster is using.
beerandt 7y ago
For reference, a US survey foot is legally defined as 1200⁄3937 meters, which is ~0.304801 meters. The difference is usually written as 2ppm, for practical purposes. (To match units for survey equipment accuracy.)
samatman 7y ago
It frustrates my sense of aesthetics to no end that the inch isn't defined as 25.6 mm. That would make the imperial system a base-two variant of the SI system. This would have made the mile around 42 (current) feet longer, which is a non-starter; I just wish the foot had been a little longer, somehow.
- p1mrx 7y ago
  At least you can't blame Johansson for that; 25.6mm would've been so far off (0.8% versus 0.0002%) that people wouldn't have bought his product. Now I'm wondering how the ratio landed so close to 25.4 in the first place; 25.4000508 and 25.399977 have too many 0s and 9s for random chance.
  - beerandt 7y ago
    Johansson rounded the inches, but previous legal definition was in yards. The Mendenhall Order was the US agreeing to define it's units in terms of the metric pegs, instead of the UK's (which were unreliably changing). The US survey of the coast (today the national geodetic survey), defined conversion values for the yard and pound. 1 (survey) yard = 3600⁄3937 meters Reduces to: 1 (survey) foot = 1200⁄3937 meters 1 (survey) inch = 1/39.37 meters ~ 25.4000508 mm https://en.m.wikipedia.org/wiki/Mendenhall_Order https://en.m.wikipedia.org/wiki/Mendenhall_Order
- sdenton4 7y ago
  If it helps, the miles-to-kilometers ratio is approximately the golden ratio... (1.609 vs 1.618.) So, as a level N nerd, you can convert miles to kilometers by rounding to a nearby fibonacci number, and then finding the NEXT fibonacci number (and maybe fudging a bit in the direction of rounding). Then, as a Level N+1 Nerd, you can realize that the Fibonacci Base exists, in which any integer can be represented as a collection of distinct fibonacci numbers. (for example, 43 = 34 + 8 + 1, or, using a binary string to show which Fibs are involved, 42 = 10010001.) The conversion of miles to kilometers is then just a bit-shift operation. Well, almost, anyway.
  - 7y ago
askvictor 7y ago
Gauge blocks are quite interesting, particularly how they stick to each other: https://en.wikipedia.org/wiki/Gauge_block#Wringing https://en.wikipedia.org/wiki/Gauge_block#Wringing (mention on HN a few months ago IIRC)

by p1mrx 7y ago

analog31 7y ago

An interesting factoid is that if you rummage around in a machine shop, you will find a pair of gears in a drawer somewhere, with 50 and 127 teeth. Those are for converting an old fashioned manual lathe to cut metric screw threads.

Svip 7y ago
Just FYI, a 'factoid' is something believed to be true, when it probably isn't. I assumed you meant 'fact', but otherwise your comment could be confusing.
- zamfi 7y ago
  That is indeed one sense of the word factoid, but in common North American usage it also can mean “small or trivial piece of information”, which is the sense I believe the parent poster is using.

beerandt 7y ago

For reference, a US survey foot is legally defined as 1200⁄3937 meters, which is ~0.304801 meters. The difference is usually written as 2ppm, for practical purposes. (To match units for survey equipment accuracy.)

samatman 7y ago

It frustrates my sense of aesthetics to no end that the inch isn't defined as 25.6 mm. That would make the imperial system a base-two variant of the SI system. This would have made the mile around 42 (current) feet longer, which is a non-starter; I just wish the foot had been a little longer, somehow.

p1mrx 7y ago
At least you can't blame Johansson for that; 25.6mm would've been so far off (0.8% versus 0.0002%) that people wouldn't have bought his product. Now I'm wondering how the ratio landed so close to 25.4 in the first place; 25.4000508 and 25.399977 have too many 0s and 9s for random chance.
- beerandt 7y ago
  Johansson rounded the inches, but previous legal definition was in yards. The Mendenhall Order was the US agreeing to define it's units in terms of the metric pegs, instead of the UK's (which were unreliably changing). The US survey of the coast (today the national geodetic survey), defined conversion values for the yard and pound. 1 (survey) yard = 3600⁄3937 meters Reduces to: 1 (survey) foot = 1200⁄3937 meters 1 (survey) inch = 1/39.37 meters ~ 25.4000508 mm https://en.m.wikipedia.org/wiki/Mendenhall_Order https://en.m.wikipedia.org/wiki/Mendenhall_Order
sdenton4 7y ago
If it helps, the miles-to-kilometers ratio is approximately the golden ratio... (1.609 vs 1.618.) So, as a level N nerd, you can convert miles to kilometers by rounding to a nearby fibonacci number, and then finding the NEXT fibonacci number (and maybe fudging a bit in the direction of rounding). Then, as a Level N+1 Nerd, you can realize that the Fibonacci Base exists, in which any integer can be represented as a collection of distinct fibonacci numbers. (for example, 43 = 34 + 8 + 1, or, using a binary string to show which Fibs are involved, 42 = 10010001.) The conversion of miles to kilometers is then just a bit-shift operation. Well, almost, anyway.
- 7y ago

askvictor 7y ago

Gauge blocks are quite interesting, particularly how they stick to each other: https://en.wikipedia.org/wiki/Gauge_block#Wringing https://en.wikipedia.org/wiki/Gauge_block#Wringing (mention on HN a few months ago IIRC)