#units

[todays-xkcd]

169 is a baker's gross.

Baker's Units [Explained]

Transcript Under the Cut

Baker's units

[A formation comprising of 13 items] - Baker's dozen [A ruler divided into 13 parts] - Baker's foot 1:00 PM - Baker's noon [A polyhedron with 13 faces] - Baker's dodecahedron January 31st - Baker's New Year's Eve [Two notes on a staff 13 half-steps apart] - Baker's octave [13 people standing in a row] - Baker's jury [A flag with 13 stars forming a circle] - Baker's EU flag Aluminum - Baker's magnesium

[fishcat076]

Yeah About a Hug's Worth

Think about it: If a kid is trying to measure their mood or love with their arms, saying "I love you this much" or "more than this much" it's an actual unit of measurement! If someone says "my love for you is unfathomable" they're saying "my love for you is more than which an embrace can convey." Sailors literally talk by saying "yeah this square knot takes about six hugs of rope" The words "fathom" "unfathomable" "fathomless" all relate to hugs! We have been measuring length in hugs for 5 centuries! I think that's beautiful.

[horsefigureoftheday]

Horse figure of the day: Units Horse

[o-craven-canto]

Idea to annoy the supporters of both Metric and Imperial units: make the foot the basic unit of distance, but reduced by 2% and redefined as one light-nanosecond

[hbmmaster]

outside of highly technical contexts, when converting between units there's a subtle risk of introducing "false precision". like, there's this old tumblr post saying like 500 miles sounds "more poetic" or something than 804.672 kilometers.

and it is true that 500 miles precisely equals 804.672 kilometers, but that conversion has introduced a level of precision that wasn't there in the original measurement! it would be less precise but more helpful to say 800 kilometers instead.

anyway I've been thinking a lot about the general problem of how exactly to decide what level of precision is appropriate for a conversion (assuming you're not in a context where you definitely always want the exact conversion). in particular, given one measurement given in feet, what metric unit should be used? I reckon that decimeters would work best (smaller than a foot by a large enough factor to give an accurate-enough conversion, but not so much smaller that they introduce too much false precision), but the problem is that decimeters aren't nearly "normal enough" of a unit to have the same vibes to metric users as things measured in feet do for imperial/us customary users.

so like, do you use centimeters rounded to the nearest ten, or meters with one digit after the decimal point? when exactly is one of these options better than the other? much to consider! I'd be interested in hearing other people's thoughts on this :)

[guerrerense]

One of the first passenger diesels on the Milwaukee Road . por Terry Spirek

[anonymouscapybara]

people say the worst SI unit is the mole. "ohhh but it's just a number it doesn't even have anything attached it doesn't deserve to be an official unit" BZZZ WRONG

the worst unit is the candela. the candela is stupid.

what's the candela, you ask? well, it measures the brightness of light

"oh that sounds reasonable" you say, "just measure the energy or power emitted!" nope. they would not do anything nearly so simple. a lightbulb emitting a watt of yellow light is more candelas than a lightbulb emitting a watt of red light.

"ok that's weird" you say, "but maybe they're adjusting for that somehow? maybe it measures number of photons?" again, that would be far too reasonable. a lightbulb emitting a fixed rate of yellow-light photons is more candelas than the same rate of purple-light photons.

but what are they even measuring then? what else is there to measure? clearly they ran out of ideas while making up units, because what they're actually measuring is the SUBJECTIVE BRIGHTNESS OF LIGHT TO THE HUMAN EYE. the candela is STUPID

a reasonable question to ask is: how would you even measure the brightness of light to the human eye? aren't a lot of human eyes different? don't different things look bright in different circumstances? aren't there colorblind people in the world?

surely the General Conference on Weights and Measures, which spent millions precisely calibrating magnetic quantum flux to avoid basing the kilogram on a random block in France, has a clever solution!

no. no they don't. the candela is stupid.

as far as I can tell, what you do is you first measure how much light of each wavelength comes in. Then you multiply each measurement by a "luminosity function", which measures brightness to the human eye:

you will notice that there are multiple functions shown in this diagram. the SI system has five of these, for different lighting conditions. do your lighting conditions not exactly follow one of the Five Official Standardized Lighting Conditions? guess you're out of luck then.

and whose eye are we using? why, the Official Standardized CIE Photometric Observer, of course: the "ideal observer having a relative spectral responsivity that conforms to a CIE-defined spectral luminous efficiency function for human vision"

(and no I can't show you this function because the fine people of the ISO put it BEHIND A PAYWALL. who puts measurements determining a fundamental SI unit BEHIND A PAYWALL. the candela is stupid)

all right, so we're measuring a fundamental unit using a (nonexistent) idealized observer in one of five random lighting conditions. how did they find the values for this? i'm...not entirely sure. but here's a glimpse, based on a few of the most recent studies I found used for this:

"...heterochromatic (minimum) flicker photometric data obtained from 40 observers (35 males, 5 females) of known genotype..."

"To obtain an estimate of the mean L-cone fundamental, we weighted [weird variables] according to the ratio of 0.56 L(S180) to 0.44 L(A180) found in the normal, male Caucasian population...and averaged them together"

that's right, our Official Objective Brightness Unit is probably sexist and racist. none of the other SI units have a chance to be sexist and racist. a meter is a meter in every country on Earth. 6.022*10^23 For Women is still 6.022*10^23. but the candela is-- probably-- the white man's candela, because you can absolutely bet that genetic drift around the world gives different values for this stuff.

in summary: my opinion, as you might have guessed, is that the candela is stupid. hopefully you agree with me after reading this that we need to completely eradicate it from the planet. failing that could we at not give it the same level of officialness as the meter or the kilogram?