American Reacts to Who Invented The Metric System, & Why It's NOT Perfect 

We know earth is spherical since 600-500bc.

1795? Eratosthenes in ancient Greece did it with less than 2% error over 2100 years ago :)

I didn't say that they discovered the Earth was spherical in 1795, just that they calculated its dimensions at that time.

@@benoit6026 I know, and I also didn't say that they discovered that it was spherical 2100 years ago, they calculated the dimensions to a 2% accuracy 2100 years ago. aka the flat earthers are even sillier.

@@Henrik_Holst Although this only 2% error is kind of lucky. Erathosthenes made mutually compensating errors.

It was one gram of water one degree C. That's one calorie.

To be honest it is not exactly 1000kg. And it's more like a coincidence, than a part of the system. Same as normal atmospheric pressure is roughly 1 kg / cm2.

I vaguely remember something about it originally being one cubic decimeter of water heated from 15°C to 16°C and such a cubic decimeter weighing 1 kilogram. However, some tiny errors in the measurement resulted in two almost similar units: A cubic decimeter of water (Not weighing exactly 1 kilogram) and a liter (weighing 1 kilogram!)

​@@FelisLeopard That explains the difference between mass and weight. It would rather be a step back into way before the the Middle Ages using 9.80665.🤷‍♂👴

@@darkiee69 In fact, in science, calories are no longer used. It's Joule.👴🧐

The thing is, the US agreed to it, back in 1875, and all customary units are based on metric. In 1890, the US received two of the kg prototypes (it's a weight that weighs 1kg). All weight measurements in the US are traceable to those two prototypes in NIST.

​@@georgH So not only metric is not perfect, US customary units includes this definition error too. But it is under the discernment of the imperial system. (0,2mm - 0.0078740157 Inch)

@@Kyk_cz Equivalency: 0.5669291304 points

@@georgH No, Customary Units are not "based" on metric. They are "defined" via inheritance. eg; 1 inch is defined as 2.54 cm. 1 cm is defined as 1/100 of a meter. 1 meter is defined as the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second. SO...therefore the Customary Unit is defined by the same light speed as the metric meter. BUT, the meter was "based" on the length of a meridian, and the foot was "based" on well...a foot.

Europe: Join me and I will complete your training. With our combined strength we can end this destructive conflict and bring order to the world! US: I'll never join you! Europe: If you only knew the power of the metric system. Your teachers never told you the truth. US: They told me enough! They told me to listen to my dad. Europe: I AM your father. US: No.. No.. It's not true! That's impossible!! Europe: Search your feelings. You KNOW it to be true. US: Nooooo!! Nooooo!!! Europe: US, you can destroy the imperial system. It is your destiny!

Consistency in radix allows easier calculations. It's why decimal currency caught on practically everywhere.

Trust someone to bring violence into it. Why? there's nothing fun about guns, unless you're American.

America made a perfect meeter stick and it shoots!? Merica! 🇺🇸 🦅 🎉

So that's why ever American has a gun, it's not to shoot people or protect themself, it's so they can measure things. Free guns for everyone!

Well, it is more important to know where the good and the bad end of this meter is.

And even here it's off. Measure it coming right out of a freezer against right out of a hot oven.👴🤷‍♂

And the UK. Partly.

Um, you’re mixing up the conversion to decimal currency, which occurred in 1966, and the conversion to metric which happened in the 70s. It took longer than a year…. It took almost 20 years..

The one thing we still seem to use imperial for (INFORMALLY) is the height of a person. Do you think that's true?

@@EL_Duderino68 Oh indeed, and for baby weight as well.

@@sammidee4713 Yeah I think you're right in that. Funny old world isn't it.

I remember when hot weather was Fahrenheit and cold Celsius 😂

@@llljustcallhimdave I remember when Celcius was 'centigrade'...

I still make some recipes with solids measured in ounces and liquids measured in millilitres - and YT's stupid spellchecker is trying to tell me I spelled that wrong...

Send them to Germany. We use liters per 100 kilometers.

@@eisikater1584 And in the Netherlands, we use km per liter.

🤣

Does not. In fact, a yard is defined as the length of the path travelled by light in vacuum in ⁠1/299792458⁠ of a second * 0.9144

@@Kyk_cz No a yard but 1 Meter.

...and to minimize the number of basic units! So, except for use of the factors with base 10: Lenghts, areas and volume are all based on m, weight is water in a particular volume, etc...

@@la-go-xy That is especially really important when you get to derived units like force, acceleration, energy, electrical tension etc. You know that if you apply 1 N of force on a 1 kg object during 1 s, it will be accelerated to a speed of 1 m/s, with no strange constant, thanks to the definition of the Newton (unit of force). Then again, integrating the acceleration, you get that the object has travelled 0.5 m during that time (the half factor is not due to a poor definition of the units, it appears when integrating, its origin is purely mathematical, not physical). It would also have received from you 0.5 J of energy. Therefore the power of the force you applied was on average 0.5 W during that second (though it was 0 W at the beginning and 1 W at the end). And I could go on and on. The consistence of all this structure is really essential whenever you do physics. It's already difficult enough not to add multiple traps and sources of mistakes from our own definitions.

The big Negative of the metric system is the up and downscaling by factors of 10. It is very simple to make an error in scale that will not be noticed. In a system that uses different scaling factors dependant on the overall size any scaling issue would give a wildly different number. When different estimates are based on wildly different scaling factors you are more likely to notice these in estimates.

@@stephenlee5929 when you convert miles to feet for adding two measurements and then convert yards back to miles, you have huge numbers and easily can miss that small factor of 3 that you introduced when converting down with feet and up with yards. and you need to do lots of those conversions even for the smallest calculations, eg when someone is 4 inches taller than someone else and you add 5'9 and 0'4 to get 5'13 or erroneously 6'3 if you look at that 13 as a decimal (instead of being a factor 12, to get 6'1). A house with 5 floors of 3.5m each is 15+2.5=17.5 m tall. what about an almost identical house at 5 floors of 11'6 each? 5x11'5x6 = 55'30 = 55'+(30/12)' = 55'+2.5' = 57'6 ? when doing calculations and estimates with large numbers, i usually do the numbers and prefixes separately, eg 60x10^9 / 5x10^3 = 60/5 x 10^(9-3) = 12x10^6 and for the estimate i can just do the calculation with the exponents, while the numbers don't have to be converted at all ! in contrast to this, how many conversion errors can you add to a calculation when you add (miles+yards+feet+inches) with (miles+yards+feet+inches) to get (miles+yards+feet+inches) with [miles+yards+feet+inches = 63360*miles+36*yards+12*feet+1*inches, possibly also fractional inch/8, inch/16, inch/32, inch/64, etc], instead of (xxxyyyzzz mm) and (xxxyyyzzz mm) to get (xxxyyyzzz mm) [with xxxyyyzzz m = xxx km + yyy m + zzz mm, optionally simply concatenating eg micrometers which simply are 0.001 mm each]

@@stephenlee5929 - An error made with the metric system is easy to notice, because the number will either be too large or too small. Unless you're incompetent.

US system is basically Metric, but with a conversion filter on top. Same as the rockets NASA used to send people to the moon. Hardware worked on metric calculations, but the pilot displays had a conversion filter because the astronauts were used to imperial units.

Correct, i wouldn't even have a problem if 1 meter would be 1 foot and we took the foot of Abe Lincoln for that. The important thing is that its based on 10 and not on random numbers like 1 mile = 63360 inches, 1 yard = 36 inches, 1 foot = 12 inches .. so 1 yard = 3 feet ?? where we don't even are in the 12x system anymore.

@@Real_MisterSir This is a lot like the real world, serious work is done in metric and then the results are converted to show to the "civilians" that are still using imperial.

There are two issues, really. The decimal system - units, tens, hundreds etc. - is simply because we have 10 digits, and we count in base 10. We could count in any base, and the metric system (using that base) would still work, but instead of 10 cms in a meter, we could have 8 (or whatever the base is) cms in a meter. Or 16, or 12. Any of those would be better than 10 (because they have more divisors than 10 does, which has only 10, 5 and 2 as its divisors, and 5 and 2 are both prime numbers. 16, for instance, as 8, 4 and 2 (and 8 and 4 are not prime), 12 has 6, 3 and 2 and so on. So whatever base you use, it would be just as good, in many cases better, than base 10. What is clever about the metric system is not so much that it is decimal (that is good, given we use base 10) but that wherever possible it uses natural measures. The meter was based on the size of the earth (sort of), but is now based on the distance that light will travel in a vacuum in 1/299792458 seconds (yeah, rather strange number, but it was a certain number of wavelengths of one of the emission lines in Krypton-80). But then we get the clever parts. Volume is defined in terms of cubic metres. Mass (weight, if you like) is defined in terms of the mass of a certain volume of water - 1 gram is the weight of 1 cubic centimetre of pure water. Atmospheric pressure is the weight of 1 square centimetre of air as high as the atmosphere - in terms of kilograms (or grams, whichever you prefer). Time is defined in terms of the vibration of caesium 133. And so on. So on the one hand we have the definition of the basic units of mass, time, length, volume etc., and on the other hand we have the number of divisions on the basic units. For the most part it is 10 and multiples thereof (time is different, using 60 for the most part). It would work just as well if we had chosen 8, 12, 16, or any other number. We chose decimal, unfortunately - but naturally we did, given our 10 digits. ⁠

@@steveknight878 I sort of agree, except, I think we use base 10 due to numbers we took from Arabic, a base 3 numbering system seems to be used in Wales. Why would a number system be based on the digits of both hands be preferred, its not actually good for counting. The base 5 system implied by roman numbers seems better (to me). I can count to 30(decimal) using my hands easily, I believe the base 3 option goes higher, but I don't understand it. The reason we use 10 digits on fingers to count to 10 is because we want to count to 10 not the other way round (I suggest), base 4, 5, 8 or 9 would make more sense based on our physical attributes, though I think if we had 6 fingers per hand base 12 may have been more widely used.

@@stephenlee5929 Base 3 is possible, of course, but not particularly good because 3 is prime. Similarly base 5. With base 2 (binary) you can count to 31. As for a link between number of digits and 10, why did the Arabs use base 10? Using your fingers for counting is commonplace, because it is quite easy. I suggest that the Romans used base 10 (X) if you look at the words for numbers in Latin (0 to 10 ends in decim (from which we get decimal) then it undecim (11), duodecim (12), tredecim (13) etc. to viginti (20), viginti unus (21) etc.

@@steveknight878 That's how the French count: in vigesimal taken directly from Latin.

Yes but the problem was always how to make it the same length for all people at all times, e.g metal bars extend and contract with temperature, even the speed of light varies according to the quality vacuum one can create here on Earth. Of course this limitation apples to all measurement systems, a point conveniently ignored in this video.

@@vtbn53hmmmmm, this problem doesn’t solve imperial ether

1/32" ≈ 0.44… points

... and for landing rovers on Mars.

Bizarre ? They invented great techniques and tool to estimate that. It prooved to be pretty accurate... Only a small mistake and en error on the exact shape (poles are flatter than expected)

They could even measure astronomical distances and changes around 5000 BC.

Fun fact: this accuracy shrank France. King Louis the Whatevernumber got a surveyor and his son to properly map France. They used the same technique. It took three generations (literally grandfather, father, son) and it turned out France was a lot smaller than people had assumed for a long time. Map Men did a great video about this.

@@Belaziraf Changes, sort of. Distances, no. That took a very, very long time.1838 to be exact, by a man called Friedrich Beesel. Ancient people could map the starts moving across the sky as the earth goes around the sun, but not the distance to those stars from earth, nor the distance between them.

I mean people calculated the earth dimensions several time throughout ancient history, that's where the story of the well comes from.

Old buildings at market places still have engraved e.g. the correct size of a loaf etc..

In some cases from city to city.

@@peregreena9046True, but what would I care as a resident in a city, how some other city handled its trade, that was an issue for 'traders', so long as they used our measurements here, how does it concern me?

@@stephenlee5929 when a trader from the UK tries to sell you a gallon of oil or fuel in the USA, would you assume that he uses US gallons (3.78 liters) or UK gallons (4.55 liter)? maybe he would tell a price per gallon and then give you a US gallon for that price when selling, but give the same price when buying a UK gallon from you? in those old times, most people had difficulty calculating something themselves or even couldn't read and thus they easily could be scammed. you would need to trust the traders as well as your local craftsmen to use the correct values when you can't look it up yourself. btw : Since many conversions can be done with "round even numbers" and still mostly 10% or less error, i often understand measurements on the internet, eg in youtube videos, as 1 gallon = 4 liters, 2 pounds = 1 kg (btw: on german farmer markets, you still can find pounds, but ours are 0.5kg = 500g), 1 m = 1 yard = 3 feet, 1 m² = 10 feet², 1 $ = 1 €, 1 mi = 1.6 km, 1 km = 0.6 mi, etc. but of course i will use a calculator when i would buy or sell internationally. those problems were one of the reasons why tables of prices and weights were created, where people (bakers as well as customers) could easily see (only read without calculating it themselves) eg how much flour needed to be used for a bread of a specific price, or what price to ask for a bread of a specific weight. Those tables surely were not created over and over again for each single town or little village that used different measurements. btw : in germany, when people do some calculations, they sometimes say "Das macht nach Adam Riese xxx" ("according to Adam Riese, this is xxx"). he was probably the most famous of those who made these tables.

@@stephenlee5929because over the centuries better modes of transport have made cities, provinces, countries, and the world interconnected. Any economy would collapse if there was no import and export. Nobody lives in isolation anymore.

Sorry it's "treaty of the Meter" it's hard on a phone, and doesn't allow editing comments...

even much much longer ago, the first of those kilogram prototypes got lost when the ship that transported it to the USA was stopped by pirates. would it have been delivered to be able to show it to the givernment, maybe the usa would be fully metric today :-)

@@georgH when i use the YT app on my phone, i can click the three dots to the right of my own comments to edit them, and on other comments to report them, etc..

Its metre not meter omfg

@@Anson_AKB I use it in a browser, Firefox, which allows me to use extensions 👍

Here's the thing: American exceptionalism trumps common sense and logic. Also, capitalism existed centuries before the U.S. was founded.

Strangely it is the UK gallon which does not make sense. A pound is 16 ounces. In US a pint is 16 fluid ounces, but in UK it is 20 fluid ounces. In both a gallon is 8 pints. Just remember that the official definition of an inch is now 25.4 mm, so all distances are based on the metric standard.

Law makers in democratic (and sometimes even non democratic) countries often follow the wind anyway (or more precisely, the people that do vote for them, not to lose them), for better or for worse.

Imperial is more precise, that's why building industry and finance still use it. Try express fractions into metric, and you will see.

​​​@@fredshred5194please understand: The precision has nothing to do with the units you use, but with the number of digits you give. In metric, instead of doing so behind the decimal point, you can scale down to milli, nano, mycro, pico, femto... Since our arithmetic is decimal, that's ever so simple.

@@la-go-xy I9f you are an architect or work in finance, the bond market, precision has a lot to do with it. Can you build the pyramids in Egypt using decimal ? They used a royal cubit, "a foot" as measurement. Yes it's more simple, but that's it.

@@fredshred5194 The old Egyptians were quite good in geometry, without use of numbers...

@@la-go-xy but their unit of measure was still a cubit/foot, which was used to build. So I don't really see your point, if you can't measure or have a system to measure geometry is useless in that respect. They needed good geometry to divide land, not build, although it does help ...... a lot.

Netherlands: duimstok (folding stick) = thumb stick… a thumb being the old measure that gave way to the inch: the width of a man’s thumb.

The name was officially changed, exactly because it does not measure inches any longer. - Becoming one of the bulky compound words, makes it even harder for old habits to die.

Und "Maßstab" hat auch schon eine andere Bedeutung, eher ist es ein "Messstab" Der "Faltstab" aus NL gefällt mir :D

and that was during Canadia's conversion from imperial to metric. they calculated fuel needs by volume in metric, and then had to convert it into imperial weights, and got the formula wrong, or something like that.

That was the Gimli Glider and the mix-up was between pounds and kilograms. The fuelling crew were so used to filling by the pound that they assumed pounds when the number they were given was in kilograms. The pilot's calculations didn't help matters, being all over the place in their conversion of a volume measurement to a weight measurement.

Every one on this planet is using metric excerpt two countries. Metric is not used by about 3% of population, maybe less.

@@sinisatrlin840 I'm not sure about that. There are many indigenous populations who probably don't use metric since they live in a self-chosen isolation from the rest of the world.

@@McGhinch You may be right, there are probably some cannibals around Jawa that use chiefs grandfathers bone for measure, and few guys in central Sahara that measure with horse tail😄 China, Japan, India (whole Asia basically), whole Europe, whole south America, whole Africa and Australasia, middle and far east, basically all excerpt Myanmar and US, about 1% of population.

I find it interesting that everyone is refering to it as the "metric system". Here in Finland we call it the"SI system", but perhaps I am living in an academic bubble.

@@FLindroos You are 100% correct. 'Metric' is an 'English Speaking' thing.

@@MichaelRogers-et8dq In engineering we would specify "SI units", to distinguish from CGS, especially in fields where CGS is still used.

Well the Tories tried to do that to appeal to boomers wanting to relive the glory days, then people pointed out how pointless that would be. Go British exceptionalism!!!

Simple. makes sense. Makes sense as UK politics in last 14 years.

😳😂😂😂😂😂

1 inch = 72 points

And a pint's a pound the world round. Perhaps we should rethink what we base our measurements on. The pint looks like a good candidate for that 🙂 Cheers!

when I take a pint it's 0.44lt.... I bring another but it's 0.88..😢 So... For make my liter it's mandatory the third....😮 But it's again out measure...😢 And... I've to start again🍻🍺🍺🍺😂😂😂😂 You English thinked I'm wrong?????😂😂 An Italian former mountain trooper Alpini 🇮🇹 🇮🇹 🇮🇹

🤣👍

I love how proud the Americans are of their imperial system. But they don't realise that the name literally means from the Empire... (And yes I know the US system is no longer the same as the UK).

Certain circles use furlongs (1/8 miles).

nobody says its perfect. everybody says the imperial is stupid

No stones?

You're referring to the Gimli Glider-the fuelling crew took a number and being used to getting their orders in pounds, assumed pounds over kilograms. 1 lb ≈ 0.46 kg hence the crash almost halfway to the destination.

U.K. Real Estate Agents sell land in acres and floor space in square feet because they sound like more than the SI units.

​@@MichaelRogers-et8dq Theme parks do that sh*t as well. use whatever is the bigger number to make their rides seem more impressive like Rita in Alton towers when it opened the park claimed it does 100 mph when it actually does 100 km/h 😂

@@MichaelRogers-et8dq 4356 square feet = 1 square chain = 1/10 of an acre.

Try to calculate how far you get with your car, if you refuel it with liters but measure the use of fuel in miles/gallon. Do you define a distance in miles or kilometer? So you are permanently recalculating the values. While that got easier with the distribution of calculators in the phones, still each calculation inherits the risk of wrongly tyoed numbers and throwing of the whole calculation. Simple typos and thinks like: I've got a kilometer, do i hav to multiply it to get a mile or must I divide - what, if that kilometer is under the hrizontal line in a fraction .... Do you know from the top of your head?

We still prefer the imperial measure of PSI for tyre pressure over kPa as 32 PSI is easier to say in conversation than 220 kPa.

That's everywhere (and it also says cm in parentheses sometimes)

@@markomesaric5460 In the days of CRT TVs, some people used cm to make the item look bigger than the equivalency in inches.

Though pilots and medical staff might really have a direct understanding of their units, still, having inches given for e.g. plumbing, tyres or screens does not mean that we understand that unit. It's more like a name plus that the thing with the bigger number is the bigger thing. To really understand the size, we'd convert it to metric. Just because material is partly available in backward compatible dimensions (e.g. for plumbing) it does not mean that they are defined applying old units, they are defined in mm.

'The rim diameter is also always in inches' and then there is the case of the rims and tyres on older BMW 525, rim size 390 and tyre size 230/55/ZR390

@@carlosalbuquerque5672 I said most of those points in the video, I agree with you

@@IWrocker 👍 Actualy your are one of the lucky ones, your hight is a very simple wround number 1,9m☺

​@@IWrockerhi, in France we have a historical figure who surpasses all others. He is our pride, our national hero. A certain Mark Twain wrote that he is the most extraordinary human being that our planet has ever known. Please can you react "Joan of Arc, savior of kingdom of France" of thecajun cutthroat channel and you will understand what it means to "be proud to be French and what's more, you will do honor to the French people. THANK YOU👍🤞🤞

​@@IWrockerhi, in France we have a historical figure who surpasses all others. He is our pride, our national hero. A certain Mark Twain wrote that he is the most extraordinary human being that our planet has ever known. Please can you react "Joan of Arc, savior of kingdom of France" of thecajun cutthroat channel and you will understand what it means to "be proud to be French and what's more, you will do honor to the French people. THANK YOU

So true. And its really being a system with as few base units, and the others derived, simply using arithmacy.

It wasn’t adopted because manufacturers lobbied to keep imperial so they wouldn’t have to pay to change their factories and machines

​​​@@RBernsCarterWhich actually is no reason, since you can keep the machinery and just give the measurements in different units. And if units are displayed on the machines, you only need to add the new scale. Costs for ressources calculating with various factors (are 6.250 feet = 6 feet 3 inches = 2.0833 yards = 0.00118... miles?) - and waste due to miscalculations not considered...

@@la-go-xy it’s a stupid reason but money always talks 🤷‍♂️

​@@RBernsCarterMaybe they really believed it was cheaper, but I very much doubt it was

the fact that what I measure is in even units in Customary units and not in even units in SI units means what is objectively true to you is objectively false for me. when it comes to the US customary system - you can measure in cm, and I can measure in inches. and unless we are collaborating directly, there's no need to quibble over units.

Meaning, measuring something analogue and putting it into numbers. The easy part in the metric system being that you can choose the precision simply by giving as many digits behind the decimal point as you need - and given that our arithmetic is decimal.

@@la-go-xy and the easy part in the customary system is that you can express parts of a unit in fractions or in decimals. allowing you to choose the precision using your choice of two methods. plus it has multiple base units available, allowing you to select a base unit in a convenient scale for what you are measuring, but the greatest strength of the customary system is that it doesn't attempt to ban SI units, so they are also fully available for use. but probably the reason Americans love it so much is it terrifies europeans.

@@kenbrown2808 Well, it seems difficult to explain... The whole range of arithmacy can be applied to metric, of course... So you can write fractions like 1/3 m or digits like 0.33 m or 0.333333...m. Sorry the term decimal was maybe not the correct translation for it. And having so many base units means you have to converse within your system with various factors you have to know by heart. So, seemingly, you weigh one person in stones? What is the unit for all the people in a full bus? What is the unit for the bus? What is the unit for beer kegs? What if they are in the same bus and the bridge ahead has a weight limit??

@la-go-xy if you want to know what they weigh in pounds, you weigh them in pounds. But since a stone is 20 pounds, and a us ton is 2000 pounds, you can calculate it's 100 stone to a ton. But a bus operator knows the loaded weight of his bus, to the next highest ton. So if he knows the loaded weight of his bus is under 25 tons, he knows he can cross any bridge rated 25 tons or more.

Yes it was pretty painless. It was a process of years behind the scenes though. The three months was only the most public facing things, like price labels in supermarkets.

when do you switch from inch to feet? and from feet to yard?

@@Gr8Buccaneer I havent used inches, feet and yards since 1972. My comment was clarity to Ian who thought a Yard was longer that a Meter.

@@MrClovek1 1 Meter is 100 centimeters, 1 centimeter is 10 millimeters, 1000 meters are 1 kilometer.

@@MrClovek1 1cm=100mm? 100m=1km? LUL

@@MrClovek1 1 correct 2 wrong

How to upset non-Americans. Freezer set to 0 deg F and hot tub set to 100 deg F. ( and one fl oz weighs 1 oz. 1 pint weighs 1 lb )

Finland is inside ring-3 . everything outside that might aswell be iceland. no1 lives there

You also used stones (14 pounds).

@@JamesDavy2009 And Hundredweight.

No, you are thinking of a Calorie. It would be 4.19J. And all of a sudden, metric loses it's shine. Look, the formula is the same in either system, only the constants change. In metric you have to know the "Heat Capacity" of water in J/(kg⋅°C) and in Imperial you have to know BTU. (heat energy to raise 1 pound of water by 1 degF) But the formulas are the same. And for visualization, 1 BTU is about the heat energy from a regular match.

For some reason though, the legal unit for mass is kg, not g, even though kg has a prefix.

Really? Where do you live? I assume then the speed posted everywhere on roads is in m/s?

Yanks hate change.

There is no error since the speed of light is defined in metre or km, If 1 light year = Y kilometers then 89547000 light years = 89547000 x Y kilometers, they could have chosen the length of their head to define metre it change nothing.

1 AU is defined as 8 light minutes.

It seems, the reason that the US populus is so keen on dividing by 3 is, that artists, architects and carpenters like to apply the golden ratio 1.618... : 1 resp. 3.236... : 2 and that 3 : 2 is considered near enough (and you start off with the lenghts representing the 3× part). If the golden ratio is only approximated, why would you want thirds in more precision than a chosen number of decimals offer? And how precise could you measure, anyways?