# Boffin says Astronomical Unit should be binned

An astronomer based in Canada has published a paper arguing that distances within the solar system should no longer be measured using Astronomical Units (AU), which is currently standard practice. An AU is approximately equal to the distance between Earth and Sun, but the International Astronomical Union actually defines it …

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1. #### "Metres"?!

I was with him until that last part. What the hell's wrong with furlongs?

Original scientific definition of the metre as dictated by Napoleon to his Minister for Science:

"Give me a rationale for a measurement close enough to the yard as to make no real inconvenience for people but slightly bigger than the English one."

2. #### Reg Units?

Where are the Reg Standard Units? How many Bulgarian Funbags are being lost by the sun every minute?

3. #### Surely they should use...

the linguini, double-decker bus, or brontosaurus....

4. #### Wikipedia explains why astronomical units are still used

According to http://en.wikipedia.org/wiki/Astronomical_unit: "While the value of the astronomical unit is now known to great precision, the value of the mass of the Sun is not, because of uncertainty in the value of the gravitational constant. Because the gravitational constant is known to only five or six significant digits while the positions of the planets are known to 11 or 12 digits, calculations in celestial mechanics are typically performed in solar masses and astronomical units rather than in kilograms and kilometres."

5. #### Solar mass loss

Well, actually the Sun is losing mass ... but far more is lost via the solar wind than by the conversion of mass into energy. Still not very much in comparison with the total mass of the Sun, though.

6. #### The inaccuracy of decimal places

I'm with the "testy boffin" on this one.

A conversion of "Testy boffin" from AUs to clicks, would come out something like "Testis boffer". Close but no Clinton.

...and should be known as "The Paris probability"

7. #### 149,597,870,691 metres it is then

Then again, perhaps the AU is easier to remember.

8. #### SOL

just redefine AU's in terms of the speed of light through a vacuum and be done with it.

Something around 1AU = 8 lightminutes or similar.

9. #### Ultra efficient

Only 60 aircraft carriers mass equivalent consumed per second?

That's an unbelievably small loss compared to the thermal output we feel 1AU away (gotta use AU before it's banned).

Hurry up someone and get some fusion power plants working!

10. #### Eh?

I've never been a fan of the AU just because it's a stupid unit*, but all real units (as in those based on the distance between two actual points in space) change. I seem to recall a story a little while ago about the length of the metre changing (well, the piece of metal that determines its length anyway)

By my very poor maths the Sun will lose half of its mass in the next 95 billion millenia at that rate, although as it only has another few million years of fuel left I think that theory has its limitations :)

Whilst the AU may change by a tiny, possibly immeasurable distance I don't see that as the reason it should be binned. It sucks - isn't that reason enough?...

*totally personal opinion - not scientific fact :)

11. #### The question has already been resolved

in favour of the brontosaurus. http://www.theregister.co.uk/2007/08/24/vulture_central_standards/

12. #### No more global warming. Eventually.

Burn that coal chaps - we're going to need the extra CO2.

13. #### Future problems

And just think of the chaos that'll be caused when the sun becomes a red giant and engulfs the earth and 1AU is -238547km

14. #### Beeny's

Is that preggers or not?

15. #### Metres

"He proposes using metres instead."

Even allowing for our US friends who can't spell properly...

That's presumably quite a lot of metres, then.

16. #### Beenies

"...or 80-million-odd international adjusted Sarah Beenys completely annihilated."

Of course, even the international adjusted Satah Beeny mass is not a constant...

17. #### standard unit for the masses.

surely they should use the "football field" so "science" magazines and blogs can save time converting the units.

18. #### Meters and not yards ?

"The testy boffin reckons variance in the AU could account for the so-called "Pioneer anomaly", in which NASA's Pioneer space probes have wandered off their calculated courses since heading out into interstellar space."

Interesting. Would have been good to elaborate on this one, though, even if it could become a bit technical. Never could get used to AU, myself, as an astronomy student, too odd to be trusted. Same goes for the parsec which derives from AU. Ligh-year is better since defined by physics.

"He proposes using metres instead. ®"

Really ? Not yards, inches and miles ?

</sarcasm aimed at imperial units (all of them)>

19. #### What a load of tosh

Complete garbage.

AU are never used for serious scientific measurement, and anybody who does should be sacked.

They exist for illustrative/comparitive purposes, i.e. Mars is aprox 1.5 AU means it orbits 50% further form the sun than the Earth. Mars orbitting at 220 billion meters from the Sun doesn't mean anything to anybody.

20. #### The AU is merely a handy comparison unit...

....used only for estimation.

No-one would ever use it "for scientific and engineering usage".....

Surely he's not suggesting that scientists and engineers would use such strange units as AUs per millenium, rather than m/s?

21. #### Re: Wikipedia explains why astronomical units are still used

Wikipedia's argument is weak. Our uncertainty of big G hasn't stopped us measuring the distance to the moon to the nearest centimetre. Now that satellites have orbited most of the major bodies in the solar system, we probably know just about every distance to surprisingly high precision.

It seems to me that the AU remains in use because distances quoted in AU are less of a mouthful than those quoted in metres or km and because Gm and Tm just haven't found their way into common usage. The idea that anyone might use it for precise calculations in celestial navigation is, er, surprising since the velocity of spacecraft probably aren't measured in AU/century so you'd have to include a AU-to-metres conversion somewhere in your program anyway. Still, if you are still using body parts to measure size (fnarr fnarr), anything's possible.

22. #### Pioneer anomaly

No it's not. The Pioneers know better than the Luciferians that the Creator does not live in the Sun and are accelerating onwards and outwards to meet Him all the sooner like the pure and noble (aka innocent and naive) creations that they are.

Or to meet Her. (That would be cool - after all, the Creator is the max. So he/she/it has got to be Max cool. Not excepting that the singular could be a plural masquerading under a collective noun - like a Hive Mind. That would be even cooler). So, Hers even.

The idea that the Sun's miniscule loss of mass is causing the Pioneers not to be where boffins thought they should be is outlandish and preposterous but par for the course. So what else could make the solar wind defy gravity apart from disgust with Luciferianism?

23. #### @ Ross

The length of a metre is no longer defined by a piece of French metal. Instead, it is taken to be the distanced travelled by light in a vacumm in 1/299,792,458 s.

You're thinking of the international standard kilogram, which IS still a piece of French metal whose mass appears to be diverging from its official copies stored elsewhere around the world.

24. #### AU may be flawed, but Mach numbers are even more ridiculous

Especially when (as recently seen in the press) they are used to describe the speed of a (paper) space shuttle reentering the earths atmosphere.

So what exactly is the speed of sound in vacuum?

25. #### Re: "I've never been a fan of the AU just because it's a stupid unit"

I think Fahrenheit must be the king of stupid units. I can't remember the exact details, but this is really a "made up on the back on an envelope" job. It has no relation to any physical constant (Celsius is (or was until a more precise definition was invented), of course, linked to freezing/boiling point of water). I do know that Fahrenheit was based on some previous scale though and Mr. Fahrenheit added 2 to that old scale just to make it different. Yes, really - it's THAT random!

Goodness knows why the Americans still use the damned scale - it's rubbish!

26. #### The Reg's own measurement flaw

You say 60 US Navy Aircraft carriers, however which class of carrier there are several with different displacements?

27. #### Does he want to redefine years?

Since the orbital period of the Earth is changing, why not change that too? How about Days? Those are slowing as well!

28. #### It is..

all guess work, theory and speculation.

Gravity does not exist. Space is bent and bent space causes deviation from a straight path not gravity. Wind would not exist without air. Gravity would not exist without bendy space. Gravity is like the wind or a Sarah Beeny fart.

Dark matter and dark energy do not exist, all the virtual particles popping in and out of existence are causing the accelerating expansion of the Universe, a kind of reverse Casimir effect. The Universe expands into nothing, and that nothing cannot fight the pressure caused by the elusive virtual particles that survive the sucking into black holes that their partners that they would normally mutually self destruct with undergo. Because of the accelerating expansive nature of the Universe the metre is also meaningless and is varying over time.

Our brains work on a quantum level so not only is the Universe out there, it is part of our minds' inner function, this explains why logic is beyond the understanding of many individuals. Especially Tom Cruise and the superficially gorgeous Paris.

The best measure of spacial distances is the Dirac constant which is the length of a plank divided by 2 pies. As most of us, myself included are as thick as a plank when it comes to such things, this seems highly appropriate.

29. #### Re: wikipedia

well anyone not using SI units for everything, is probably being payed by the hour, and thinks they will be employed again when it all goes tit's up.

and, there really are a lot of problems in the basic physics stuff on wikipedia, what i'm guessing is happening is that since the factual stuff and current events seem very good, is that the consensus mechanism used there, is self-reinforcing common misconceptions, and as a wild guess, this is concentrated in the physics sections because there are a lot of chemists in the US with time on their hands and who have developed the same high level of, unchecked, confidence in their physics understanding.

30. #### "Not supposed to change"

"Units are not supposed to change," [Noerdlinger] told New Scientist, describing the situation as "quite a nuisance".

...reported the author of the line "three millionths of a quadrillionth goes every second if we've got our sums right; or three billionths of a trillionth if you prefer"!!!

Well, it amused me.

(In deference to my appreciation that Lewis /is/ writing for an international audience, here a reference [for everyone else] to what he means by "prefer": http://en.wikipedia.org/wiki/Long_and_short_scales)

31. #### Fahrenheit

was based on freezing point of salt water (assumed to be the coldest you could go), 0, with body temp at 100 but for some reason was out.

32. #### Taking this to its (il)logical conclusion

The yard should be scrapped as it is based on the length of Henry VIII's arm, and that arm has now withered away;

the mile because it is 1000 double paces of a Roman Legionnaire, and there aren't too many of those marching around;

and the metre was originally based on 1/10,000,000th the distance from the pole to equator, and we all know the Earth is not a sphere so that is not a standard distance.

The point is, many units are (or were) based on things that are no longer available/accurate/realistic, so a new basis of measurement is agreed, e.g. the wavelength of light at a particular frequency, or a bar of Invar in a laboratory, and we carry on as usual - this "issue" is much ado about nothing.

(Of course frequency is based on time being constant, whereas time can be bent, so nothing is 100% accurate.)

btw, good to see MfM firing on all cylinders - straight to the point as usual.

33. #### Fahrenheit

I seem to remember Mr Fahrenheit used the coldest temperature he had encounterd as 0, and used the highest temperature of a feverish body as 100, and then scaled between them.

Fahrenheits thermometers were more accurate then the ones made by Mr Celcius though

34. #### Re: Re: "I've never been a fan of the AU just because it's a stupid unit"

i think all the old 'units' are now referenced to SI ones anyway, or have been forgotten, so Fahrenheit is 'measured' in Kelvin, Fahrenheit isn't a 'real' unit anymore, its just a different way to read the SI units.

BTW i heard that, zero Fahrenheit has something to do with all life stopping, and one hundred Fahrenheit was people/blood/core/life temperature, guess the guy might of been a biologist.

but does it really matter whats on your thermostat, i think hot and cold would probably do it for people still using that scale.

35. #### Honestly...

How many people that _really_ care about this don't have beards? I bet it's a very low number...

36. #### Mr Fahrenheit @Rich

Hear, Hear,

I was bought up with Fahrenheit and have now managed to almost forget it.

Apparently Fahrenheit based zero degrees on the lowest temperature he could get - his equivalent of absolute zero - a salt and ice mixture, and 100 (Wikipedia says 96) was that universal constant, the temperature of the human body - he must have had a fever (or a chill). The freezing and boiling points of water were just extrapolated from there. (I was taught this at school, so it must be right!)

Anyway, 0 for freezing, 20 for a nice spring day and room temperature, 30 for a hot summer's day, 40 for a heat wave or a hot bath, and 100 for boiling water. What could be simpler?

37. #### Re: Taking this to its (il)logical conclusion

things have to be in relative motion for time to run at different speeds, so unless your MI5 eavesdropper is in a van, he should be able to gauge the level of stress in your voice accurately.

38. #### @Robert Long

Actually, a meter isn't that arbitrary, it is 10 times longer than the size of a cube that holds a liter of water which weighs a kilogram.

Besides, what is so silly about using meters to measure things in space? You just need to measure in Megameters, Gigameters, etc. I mean my hard disk contains 320,062,062,592 bytes, but that doesn't stop me from measuring it as 300GB, forget the unnecessary precision.

39. #### Metres!

The tool of the devil! My car gets 40 rods to the hogshead and that's the way I likes it.

40. #### F/C

"The length of a metre is no longer defined by a piece of French metal. Instead, it is taken to be the distanced travelled by light in a vacumm in 1/299,792,458 s."

1/299,792,458?? Fahrenheit doesn't seem so odd after that!

My coat's the North American 'large' not the Made in China 'large'.

41. #### Google Calculator sez:

1.0 Astronomical Unit = 8.79057469 × 10^10 Smoots

42. #### RE:F/C

Sorry, of course I meant fahrenheit and the rest of the IMPERIAL lot. I was distracted trying to use my 3.4 sided ElReg ruler.

43. #### @ Brent Gardner

Is your hard drive measured in binary or decimal bytes?

Also I'm cool with Mars at 227 Gm's from the sun and the Moon at 348 Mm's from Earth etc.

Also... try to remember... from wikipedia (stop laughing!)

"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom." and "at rest at a temperature of 0 K"

to calculate your seconds, which define the speed of light, which defines the meter. Try not to sneeze on your caesium, as the change in pressure might alter the speed of light, and the distance to to Mars... or anyone on it.

44. #### @Brent Gardner

"...forget the unnecessary precision"

If precision isn't necessary can we just carry on using AUs please.

45. #### @Claus P. Nielson

The speed of sound in a vacuum is slightly slower than the speed of the valuable object you think you've just accidently hoovered and slightly faster than that sinking feeling when you search through the dust bag and find it was just a penny. It's certainly a lot slower than the speed of a mobile phone thrown by a super-model at a domestic servant after hoovering said valuable object.

Paris, coz there's no Naomi icon

46. #### AUs cancelled - world about to end

Without the AU, I am never going to be able to play "Frontier Elite" ! This is a complete disaster. I often wondered if the AU was different in each solar system... and by the way I don't have a beard!

47. #### Imperial?!?

Farenheit is not an imperial measurement. Never was. The whole farenheit vs celcius thing is completely independent to metric vs imperial. I mean, at least imperial measures are based on things that matter (Elizabeth the first and her new miles notwithstanding) and have a logical progression of sorts. Farenheit is just *weird*.

48. #### re: 149,597,870,691 metres it is then

CURRENTLY, yes. But with the expansion of the universe this isn't actually all that accurate either.

49. #### No.. not meters!

No we should measure the whole chummin bit in lengths of a Paris Hiltion Jail sentnece! Damn folks its called TIME SPACE for a reason!

50. #### [Title]

@Joe: "The length of a metre is no longer defined by a piece of French metal. Instead, it is taken to be the distanced travelled by light in a vacumm in 1/299,792,458 s.

You're thinking of the international standard kilogram, which IS still a piece of French metal whose mass appears to be diverging from its official copies stored elsewhere around the world."

The second is definied in terms of specific properties of a Caesium atom*. The metre is defined in terms of the second, as above. 1 gram = 1cm^3 of pure water.

All the SI units link back to measurable and reproducible natural quantities - I thought that was the point! I cannot believe the kilogram is still defined as a mass of metal... Then again, the French always like to think they're better than the rest of us...

@GrahamT: "(Of course frequency is based on time being constant, whereas time can be bent, so nothing is 100% accurate.)"

As an object travels closer to the speed of light, to an outside observer their time appears to run slower, their mass appears to increase, etc, etc. However, within said object, no increase in mass or change in time is perceived and all the normal physical rules hold. The definition of "second", "kilogram", etc should be constant as long as you are stationary with respect to your test apparatus. Or, at least, not moving at a significant fraction of light speed with respect to it.

Though, if you were, I imagine it would be quite hard to read the output anyway...

* Second, the SI base unit of time, is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom ( 133 Cs). (http://www.ktf-split.hr/periodni/it/abc/s.html)

51. #### On stupid units

regadpellagru, the parsec is DAMN handy as an astronomy observer. How man arcseconds will the star image move? Answered by asking "how many parsecs away is it?".

And Celsius is more stupid than farenheit. Celsius depends on pure water, which is hard to get hold of (and impurities change things quickly), whereas IIRC the farenheit zero point was where 100% saline (which since it is already so impure doesn't change much and is REAL easy to make: keep puttin salt in until it doesn't dissolve, then decant off).

Add to that, the altitude makes a difference. And how often do we care when water boils? We want to know whether it's hot enough to get a case of the Betty's out there.

Oh, and Brett, rather ironic in a topic where someone says "scrap it because it isn't accurate" you use an example where you've truncated the accuracy so you can actually say it... Hah!

52. #### @ Luther Blissett

Have you been taking lessons from amanfrommars?

53. #### In defense of the old units

The conversion is only a problem because people use them stupidly.

The yard was a stride. A league how far you could march your soldiers in an hour. A furlong was how long you could have your ox plough before it needed a rest (so why not turn around), a rod was the width of the plough's effect and so the acre was how much you could plough in a day (being X rods by one furlong, and the most efficient shape to give to your peasant to farm).

The ounce was a good size for spices, herbs, etc and the pound a weight you can "feel" is correct. A hundredweight the bigges bag you could spend all day loading on a cart, a tonne how many bags you can get on a cart drawn by a drey. grains were good for precious items (and about the same size as a rice grain, I think, so you had a rough check).

You can drink a pint and spirits a gill was better than a small fraction of a pint.

But you had uses for these IN THEIR NICHE. You didn't really care how many gills in a pint because you never DRANK a pint of spirits.

You don't say "8 leagues, 4 furlongs, 2 rods a yard , two feet and three inches to London" so converting them doesn't make a lot of sense. And so the odd conversion ratios DON'T matter. They were fiddled about so they became an integer number and (like in the case of yards and miles) were chivvied to make them wildly divisible so you could get as many of them adding up evenly so it looks seamless.

It wasn't meant to be seamless.

And when you say "but conversions in metric are so much easier", this is either untrue (you need the density of a fluid to turn litres into cubic m, so what's a different number?) or because there's NO conversion (so why not use kiloyards, megayards, milliyards? How many milliyards are in a yard? A thousand!!!).

The old units are appropriate in their sphere. That they don't scale up matters nothing to almost all humans.

However, engineers need to make a mix of cable thickness in ~cm/in and lengths in 100'sm/furlongs so conversions that are decimal changes ARE better.

And isn't it a SIMPLER concept to say 1AU and 1.5 AU rather than 227Gm and 348GM? Longer to say and you have to think what the ratios are. How many times is 348 bigger than 227? Is that harder to work out in your head than how many times bigger is 1.5 than 1?

Hence the multitude of old units. With maths nowhere near the standards even today, a complex series of units that don't interact but give small numbers in everyday use is a lot better than a simple set of a few units that can easily interact but produce unweildy numbers.

Paris would understand that...

54. #### @Jon: the kg

Yup, the problem is that to be REALLY accurate, it boils down to counting atoms and making sure they are pure.

And avogadro's number being so inconveniently awkwardly large this means we have no chance in hell of counting out one..two... so it really turns out to get the perfect count, we need the perfect shape. I think the sphere was chosen because it's supposed to be regular under any rotation, so that makes a good check on whether it's an egg shape or a sphere. A cube sounds great but there aren't many materials that will form a regulr square and all of those don't have other characteristics we need (like purity, stability, etc).

Until then, we've got one lump of rare metal (palladium, I think) in a cylinder shape that is held in a paris vault and taken out to be compared with all the other world references (with the expense and risk (what would the luggage handlers do to it?!?!) ) that entails.

55. #### Stupid people ...

… do you not realise that even the speed of light is not a true constant? It is, however, constant enough for the purposes of creatures shaped like us.

AU's are like all “fixed” units subject to the ultimate effects of entropy.

In the real world, however, none of that matters as change happens over such and long time and so slowly that all the dearly held absolutes of which we are so fond don't amount to a hill of beans.

As Father Dyer and Kinderman say:

Kinderman: In the meantime, we have cancer and mongoloid babies and murderers, monsters prowling the planet, even prowling this neighborhood. Father... right now, while our children suffer, and our loved ones die, and your god goes waltzing blithely through the universe like some kind of cosmic Billie Burke.

Father Dyer: Bill, it all works out right.

Kinderman: When?

Father Dyer: At the end of time.

Kinderman: That soon?

Or something.

56. #### Avagadro's Number and Prototypes

Actually, there was an article in El Reg a couple of months ago where a group of (Australian?) scientists were trying to do exactly that: count the number of atoms in a given sample of ultrapure silicon. Once complete, the sample would be the new standard for the mole and Avagadro's number would be derived from that sample.

If instead Avagadro's number is fixed by convention, then that sample would also be standard for mass.

57. #### History

The AU was tremendously important back before we knew the size of the solar system in absolute units. A planet's orbital period is a function of distance. By comparing the orbital period of a body with an earth year, we know the distance form the sun in AU, without actually knowing that distance - if that makes sense.

58. #### The problem with old units...

"The yard was a stride. A league how far you could march your soldiers in an hour. A furlong was how long you could have your ox plough before it needed a rest (so why not turn around), a rod was the width of the plough's effect and so the acre was how much you could plough in a day (being X rods by one furlong, and the most efficient shape to give to your peasant to farm)."

The problem with old units is that they're barely better than nothing. They varied _massively_ between people "measuring" them, and over time too.

E.g., the acre was already getting obsolete around 800 AD, when someone figured out how to use a _horse_ to plough. It worked out entirely differently than the ox-driven plough that the old acre was based on. So although it would be centuries before most peasants could afford horses, already a gradually increasing number of people were stuck with a unit which, used exactly how the original logic behind it went, ended up with decimals. "How much you can plough in a day" was no longer 1 acre, and fields divided into 1 acre plots became more of a pain in the arse than something anywhere near useful. Which is one of the many reasons why they gave up on that system.

Second, soil type? Plough type? And are/were all oxen created that identical to each other? Etc.

Stride... Whose stride? The average person's hight rose gradually over time, partially because kids get better food. But even at any given time, two persons of different height would "measure" a very different "1 yard". Heck even the same person at two different times, you can bet on a bit of variation.

Etc.

Which is why even the imperial system gave up on those vague definitions and came up with standardized yards, inches, gallons, tonnes, etc. They're just as artificial definitions as the French metre or kilogram. But you need some standardized pound, inch and foot to do any kind of trade or engineering work. If you rely on noting the sizes in strides, the tolerance is too bloody huge for any practical use.

Even very early, well, let's just say you have words like yardstick -- and the metaphorical expression that something is the yardstick for some domain -- because they really used that kind of crude standardizations. They didn't actually measure in strides, they had a stick cut to the value they had defined as 1 yard. (And similar "standards" for everything else. E.g., for liquid units they had containers of standardized capacities.)

Basically, no, the old units, as they originated, weren't fine even back then. (Otherwise, see above, they wouldn't have needed yardsticks.) And then got standardized to some arbitrary, but uniform value. It doesn't matter if it's one stride, it matters that 1 yard is 1 standardized yard. Whether or not it fits your stride (most likely not), is irrelevant.

And at that point, if you're using some arbitrary standardized unit anyway, you might as well pick one which also gets conversions right.

59. #### The matter with the Metre

Graham T-

The length of the metre is based on the semi-meridian of the meridian that passes through Paris (Not That Paris !)

Viva la Frogs

Bruce ( a Kiwi)

60. #### Fahrenheit - not eccentric

As other correspondents have noted the 32F was chosen for the triple point of water (melting ice) because the 0F was the coldest that you could easily get in the 18th century (a mixture of ice, water, and ammonium or sodium chloride).

The difference between the freezing point of water (32F) and the boiling point of water (212F) was defined by him as 180 degrees for a practical reason. In those days (before decimal took over), most trades counted in 12s (dozens for older readers). Hold up your dominant hand, then using your thumb on that hand, count all the joints on your opposing fingers - four fingers, three joints each gives 12. A dozen is divisible by 1, 2, 3, 4 and 6. The scale of 180 was chosen because it is easily divisible by 1, 2 , 3, 4, 5, 6, 9,10 and 12. The 96, 98 or 100 bit for blood temperature was a lucky approximation for human blood temperature which reinforced his 180 degree scale.

That was what I was told in the 1950s, but then that was before the internet, so it is old fashioned, and possibly incorrect (Well, highly technical, requiring degree level education or above.).

Mine is the old, comfy, frayed coat with the dinner stains down the front.

61. #### Hans, you forget this wasn't for engineering

If you know it's half an hour walk to the shops, you don't CARE if one specific stride is smaller than the others. Knowing that the next town is three leagues away means it'll take three hours to walk there. Given that you can say "is that edge to edge, centre to centre, or church to church?" and the answer changes whether it's 3 or 3.1 leagues don't matter.

When you're buying cloth, you don't really need to know that a yard is PRECISELY this big: people didn't HAVE tape measures, so they ran cloth fromhand to chin and called it a yard.

Precision is needed nowadays, but then we've defined the yard precisely, so that's not a problem. Odd scaling units aren't a problem as I just described.

What was needed was something that allowed you to ignore having to know advanced mathematics (decimals) for daily use.

Metric only has ONE unit of length (metre) so MUST require fractions or decimals. And a decimal system has very few divisors.

Imperial has a crapload (metric) of units so you can use unitary figures (requiring no maths training, just fingers to count on) and where you DID want to use fractions, the divisors are multituninous, so they work down to two integers again. Decimals don't get used because they aren't needed.

PS we change the length of a metre because the original was "this stick". We will change the weight of a kilo because at the moment it's "this lump". These were hardly better than "the length of King James' arm".

62. #### Anyone found using Wikipedia...

... as a reference for scientific debate in the comments of El Reg should be mocked mercilessly for their folly, followed by public flogging in the stocks.

There's being a fool, then there's shouting from the rooftops that you are one...

63. #### Magazine Lengths and Temperature

I just love the football pitch measurement, now I know that UEFA have a standardised minimum pictch size fo their competitions but beyond that football pictches vary wildly in size.

Double Decker busses is another classic, is that an AEC Routemaster (8.4m long) or a Neoplan Jumbo cruiser (11m long) whats that in Reg Units?

20 for a nice spring day and room temperature, Agree on Room temperature, but when the temp gets past 10 up here it is officially a heat wave

64. #### The metre v the AU

The AU is for descriptive purposes only (or should be). It helps to visualise relative distances in the Solar system - but that's all. It is not suitable as a proper standard. We have the SI for that purpose which should be used just like in all other disciplines.

The metre may seem a small unit for measuring interplanetary distances but we do have scientific notation. Furthermore it makes no sense to use the kilometre when we have other more suitably sized units such as the gigametre and terametre, e.g. 1 AU ia approximately 150 Gm and the distance to Pluto is 4.4 Tm.

65. #### @Mark

[Oh, and Brett, rather ironic in a topic where someone says "scrap it because it isn't accurate" you use an example where you've truncated the accuracy so you can actually say it... Hah!]

Nooooooooo!!!!!!!!!!!!!!

Accuracy does NOT equal precision. NOT NOT NOT!!!!!

If I were to say Barking is 12.5436458786637832532 inches from Pluto that would be precise, but obviously not very accurate. If I were to say that Barking is closer to the Earths magnetic north pole than Pluto that would be accurate, but not at all precise.

Truncating an accurate measure still produces an accurate (to a specified level) measure, you just lose precision. In fact too much precision will get you looked down upon. For example if you measure two sides of a square and come up with measurements of 10.5cm and 10.3cm then tell me that the area is 108.15cm^2 most of the scientific community will beat you with sticks until you accept that the correct answer is in fact 108.2cm^2. Creating extra precision from nowhere is BAD!

I'm sorry, but the whole accurate/precise thing is a pet hate of mine :o(

66. #### @Mark

Mark, actually you'll find that most people _did_ care if they got sold less cloth or grain than they paid for.

You can find various laws, going as far back as Hammurabi, where they tried to standardize stuff and/or punish people using faked units. So I'm guessing at least _some_ people cared.

Or you can see back in the roman empire days that people did care when the value of the gold Solidus went down. Being just a little less gold in a coin actually made enough of a difference as to be one of the causes of the decline.

Cloth? Well, quality cloth was very expensive in the middle ages, and one of the most lucrative trades. Do you genuinely believe that people went and bough a generous extra, to cover for the seller's having shorter arms? Or do you believe that people whose living depended on it, were content with the result of their work being only very approximately defined? No offense, but I'm thinking you haven't thought very much about it then.

It's not engineering, it's trade and taxes. You'd be surprised the kind of effort, including legislative, that went into both.

And, yes, it doesn't matter that much when you're thinking "how long it would take to walk to the pharmacy." But, for example, when you have a plot of land and have to divide it into acres for the peasants, you start to want more clear units than "until the ox gets tired."

Not the least because your own wealth and military power as a lord depended on it. Being that, say, 1 hide was the land needed to support 1/5 of a knight, darn right you cared about how many knights you can have.

67. #### Density of water

Why isn't the density of water 1g/m³ ?

Now that would be simple.

(yes a gramme would be equal to a tonne)

Why isn't a litre equal to 1m³ ?

Why isn't an are equal to 1m² ?

Why isn't 1km² equal to 1000m² ? (it would follow algebra rules, which would be nice)

68. #### A title is required??? OK TITLE,... Is that OK now?

Oh what the hell, let's use Cubits, it worked well enough 5 Millennium ago for a conscripted bunch of OJT non union tomb builders. It makes about as much sense as employing Metric. I always wanted to know the distance in mm!

AU is simply a convenience approximate measurement for guesstimates, kinda like the guy at the carnival guessing your weight.

Find this guy something useful to do!

OK eh

69. #### @ Tim

Grandpa Simpson, is that you?

70. #### Fahrenheit - 100F

IIRC, from a children's "why is world world like that" type book form the late 60s...

100F was supposed to be blood temperature, but Mr Fahrenheit didn't realise that different organisms have different body temperatures.

He used an Ox to calibrate 100F

71. #### @Hans

You'll find that what they did was similar to the bakers' dozen.

And that would be where there's no "horse-trading" i.e. bargaining or trade ("I'll give you this chicken for that much wool cloth" "Nah, that chicken and this piece here that's slightly smaller").

I'm not saying the values are worth it today, but they were VERY worth it then. Now is not then. Even I can see that.

But stupid arguments wind me up. And saying "How many rods to the league!?! lolz! That's so much more difficult than metric!". Cos that really IS a stupid argument. Like saying "how many yards in a kiloyard".

Stupid stupid arguments.

Good ones are "we have too many units in imperial". It's true. And it's true because they weren't originally designed to be mixed like that. Because nobody can measure a mile to the inch, so how many inches to the mile is a silly question, only useful for teaching kids to multiply. But comlpining that conversion in metric is easier is only true when you're converting between one unit and the same unit (cm and km, for example).

We still use barrels...

72. #### Confused by units...

... so is Sarah Beeny supposed to be lighter or heavier than an aircraft carrier?

73. #### Re: Confused by units...

Yes.

:-)

PS Ross, are you saying that 1,073,741,824 ISN'T 1 GB? 'cos the example givenwas on the surface supposed to be about his 300GB HDD (which people dont' call a "three hundred and twenty billion, four hundred and ..... hard drive" because accuracy isn't important: you're not going to return a hard drive that says 320GB and it's a thousand or so bytes short. In the same way you don't need exactly four yards of cloth to make a dress: *about* four yards is good enough, because people aren't all the same height. Ballpark figures are good enough when you can haggle: if it's slightly less or more, you can change the price you're asking. It's when your price isn't open for negotiation you want what you've paid for. And that is the world we are in today.

It isn't "bah! imperial roolz" it's that there's merely a choice on whether you use metric or imperial, metric is a MUCH simpler system (one length unit, one weight unit, etc) but that makes everyday use where you aren't using scales or tape measure difficult.

a 10 stone man is average. Is it 72kg average? 6ft is tall, that's about 1.7m. which is the easier measurement to work with everyday? 10 or 72? 6 or 1.7? most people would say the former. But metric is more useful when you aren't in everyday situations. E.g. A one mile span or 1600m length gap must be crossed by a bridge made of sections. Each sectin can be 220 yards or 200m long. How many spans do you need? Metric is easier there, but that's hardly an everyday question, is it.

And that ease of everyday use is why some people like to keep imperial. Not because they like a stupid system, but because they have a better handle on the figures because there's a unit appropriate for their use that keeps the numbers manageable without needing a calculator. And some people would prefer the metric system not because they're idiots but because a simpler system is trivially solved when you have a calculator (and they're cheap) where the varying units is less manageable in imperial because a calculator isn't meant to change units.

All I ask is that people wanting imperial realise that the units grew out of a human need when measuring before maths and science really cared about it (note: ergs isn't used much but it made working with electricity a DAMN sight easier, in the same way as uing mols in chemistry helps keep things simple to handle: they see the benefit of variable units).

deal?

74. #### Use SI units

There are plenty of prefixes to use for the VAST distances.

Consider yottametre (Ym).

75. #### Fahrenheit

Fahrenheit is ultimate proof why you really, really should keep your inventions away from marketing department until they are tested and ready.

As for this AU thing- This astro-boffin seems to forgot, that distance of AU has changed more in last 30 years thanks to boffins like him who keep changing the basic units, than because all those aircraft carriers disappearing in the sun.

76. #### silly brits

thank you for the cheeky article. I now have a new nickname for my father: 'testy boffin'

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