"discovering an increased value for Planck's constant"
Isn't that the kind of thing that has an impact on just about everything concerning the history of the Universe ?
Massive news indeed.
While business around the world closed out a financial quarter or a financial year ahead of June 30, US boffins were working to a different deadline: linking the kilogram to electromagnetism. Part of the world of metrology's long project to redefine the world's fundamental measurements, the aim is to define the kilogram in …
Planck's constant has a small amount of uncertainty associated with it - we don't know the exact value. If in the course of creating the Watt balance kg they found Planck's constant was higher than previously believed, while simultaneously shrinking the uncertainty so it still fell within the bounds of the previous constant +/- uncertainty, there's no real impact other than on ultra-precise measurements that take the "value" as input, without the associated uncertainty.
This is where many people get confused and throw the baby out with the bath water. Some things we don't know, and can be discovered to be entirely different. Some things we know, and can never be undiscovered. Other things we know with some accuracy, and can only get more accurate.
"Many other key cosmological values are know only approximately - Hubble's 'constant' to just two significant figures, for example."
I think the significance of this is in moving towards a definition of the unit of mass which is independent of a specific physical object. This has already been done for length and time.
PM offered, "...impact on just about everything [WE KNOW] concerning the history of the Universe ?"
The history of the Universe is fixed, because it's in the past. (As far as we know.)
It's our *understanding* of the past that is in constant flux.
Looks interesting. Could go off the deep end though with quotes like "Our need for references is nothing but a comfort answer"... as reference is how we communicate, experience and exist. Yes our obsession could be a problem, or other parts of it. But "reference" and "confirmation" are entirely required and part of our existence and experience.
Without them we would be nothing... and hence why I both love and hate "art" films. For being both beautiful, and self destructive in their musings.
For most usages, we round it to 238mJ (milliJubs), or when talking in non scientific circles, one tenth of an adult badger.
This planks and 'Kilograms' thing confuses me, why try to make it all complicated? All the changes in units lately have me stumped. I know that my car does 1,000 double decker busses to the grapefruit, and frankly that's all I want to know!
I thought the kilogram already had a very precise definition, it's in their in its name:
A kilogram is not the basic unit of mass/weight, the gram is, with a kilogram being equal to 1000 grams.
Therefore, shouldn't they be trying to determine precisely the mass of 1gram? Multiplying that by 1000 gives you a kilogram.
"A kilogram is not the basic unit of mass/weight, the gram is, with a kilogram being equal to 1000 grams."
The cgs system was replaced by the SI system quite a long time ago - I was just at the end of using cgs in schools.
The kilogram has been the standard mass unit since the standard kilogram mass was made and placed in Paris. It's just an unfortunate bit of history; the gramme was too small a unit to be useful for standardisation, just as the dyne and the erg gave rather awkward powers of 10 for everyday measurements.
Though rather a side issue here, that does come very close to explaining why in the UK we still use mixed measures. Litres of petrol but miles per hour and pints of beer, even milk for many people's thinking . Food weight in Kg, human weight in lbs and ozs height in ft and inches, distance in cm and Metres etc. Many metric units work better in maths but poorer on a human scale. And in human terms multiples of 1 and 1000 have a nasty habit of being either too big or too small. A litre is too small for petrol, but there's no useful equivalent to the gallon. A gramme too small for food ( where a Kg is too large). And intermediate 10x units (100gm etc.) have almost unuseably long names Even decimalisation was hampered by this until inflation took control. £1 was too big for many small transactions and the 1p too small. In reality there was no reason to get rid of the intermediate units ( A shilling becoming worth 5p instead of 12d). If they'd had a sensible human name for 10l or 100gm the whole system would be much less unwieldy in everyday life.
"Even decimalisation was hampered by this until inflation took control. £1 was too big for many small transactions and the 1p too small."
1p was actually too big compared with 1d. For small value items rounding up to the nearest d (and when did prices ever get rounded down?) represented quite an inflationary step. Put that together with the dislocation in people's thinking - e.g. how does 16p really compare with 2 / 10d? enabled prices to be put up still further.
It wasn't decimalisation being hampered without inflation, it was decimalisation enabling inflation
That sort of sums up at least part of the issue. For mathematical accuracy and calculation decimal every time. But in everyday life Imperial measures relate to human scale. A metre works well because it's about a yard. But saying "about 30cm" doesn't mean as much to humans as "about a foot". And it's easier to get a handle on eight gallons than 40 litres. And so on.
"1p was actually too big compared with 1d. For small value items rounding up to the nearest d (and when did prices ever get rounded down?) represented quite an inflationary step."
That's probably why the 1/2p was also introduced at decimalisation (and only phased out in the 1980s), worth the equivalent of 1.2 old pence. Inflation was pretty high at the time anyway, so it's not clear how much could be attributed to decimalisation.
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When I started this hare it wasn't about which is best. It was just an observation on the reasons for our rather mixed up systems. I do think the metric systems could have been better organised in terms of human use. Units with simpler names and appropriate values. Imperial units grew up from practical uses, metric units were defined and applied retrospectively to practical uses.
Unfortunately, what counts as a convenient unit rather depends on what you're measuring: an ounce is good for cookery, perhaps, a pound for retail, and a bushel or something for industrial use. An inch is a good unit for measuring the length of something you hold in your hand (such as another body part), a furlong is good for horse-powered agriculture, and so on. Using the same metric units for all things in all contexts is slightly less convenient from the point of view of pure and simple measurement but it's much easier when you want to do a calculation. For example, if I tell you how many ounces of grain a man needs per day, how many bushels you can produce per acre per year, and how many square miles of usable land are in a certain province, calculating how many people can be fed off the land requires more effort for converting the units than for doing the real calculation. Similar thing for calculating how much wallpaper you need: width in inches, length in yards, area in square feet; the measurements are nice, but the calculations are unnecessarily complicated.
Of course, even without imperial/US units there are still a rather large number of units for measuring energy...
You could always start using deca/deci hecto/centi for the ones that are just in between the straight unit and it's kilo or milli notation.
So decalitres for gallons, deca or hectogrammes for food and such..
As for body sizes, metres or centimetres works perfectly well, as does the kilogram. It's just a matter of getting used to it. 6'7" isn't any better than 1.92m Or 19dm if the exact measurement isnt very important, as with the inches.
In sweden, the kilometer is too short to measure distances comfortably, solved by adding a swedish mil, which is 10 km. So, it's a weird and confusing name, but it's still adhering to the metric system.
You could always start using deca/deci hecto/centi for the ones that are just in between the straight unit and it's kilo or milli notation.
Try saying it. "The car took 8 decalitres of..." people seldom use words of more than two syllables. And consciously avoid them over three. Think; feet inches pints gallons mile yard pound ounce ( furlong fathom rod pole and perch fwiw, too). Add to that the confusing similarity between deca- and deci-
The metric system is one designed for machines, not people.
"The metric system is one designed for machines, not people."
I call bullshit.
It's just what you are used to. To me 8 gallons is about as clear as mud. I have no feeling for a gallon, since I've never used that measurement in my daily life. 30 liters on the other hands is about 3 standard household bucket fulls. 1 and a half if it's larger builders/contractors mixing buckets.
I also don't really see why saying 80 liters isn't clear, or why 21 gallons would be any easier to understand.
grammes and kilogrammes work perfectly well for food stuffs if that is what you are used to. And most people don't really use grams for anything over 200 or so. It becomes a half kilogram or a quarter kilogram for instance. And 200 grams is perfectly comprehensible, again if you are used to it. (About the weight of 2 average apples).
You need to realise any measurement system becomes easy and intuitive if it's what you've used for all your live. To me imperial measurements make no sense. To you metric sucks. Whatever. Get over it. Metric has won already anyway.
"Many metric units work better in maths but poorer on a human scale."
Utter nonsense. Are you seriously suggesting that we still use miles instead of kilometres to measure distance because a factor of 5/8 somehow makes the numbers incomprehensible on a human scale? Having to drive 160 km instead of 100 miles, or weigh 80 kg instead of 176 lb somehow makes everyone's brain's explode from trying to deal with the crazy numbers? And it's somehow too difficult to read "100 g" instead of "3.25 oz" when cooking? As for litres being too small for petrol, you must really suffer when trying to fill your car up given that petrol has been sold by the litre for a few decades now.
No, some people still stick with stupid imperial measurements out of habit, nothing more. When you've been thinking in one system all your life, trying to change to a different system is a lot of effort and most people just don't have much incentive to actually make that effort. Of course, things like the change to kg for food show that it's not actually all that much effort at all and such changes can easily be done quickly and painlessly, but since people are fundamentally lazy creatures of habit here we are.
As for litres being too small for petrol, you must really suffer when trying to fill your car up given that petrol has been sold by the litre for a few decades now.
Which sums up the paucity of your reasoning here. Few people actually think about the number of litres ( or gallons) they buy. They talk about a tank full or £10 worth etc. Or miles to the gallons .
And we prefer saying "miles" to "Kilometres" because it's a bloody sight easier to say.
Seriously guys arguing about better or worse in a Units System? It depends what you grew up with, period. If you grew up with Imperial Units like Terry6 then you're going to think Imperial is better, if you grew up with SI Units like i did, then your going to think SI makes a hell of a lot more sense.
Whether you think miles per gallon is a useful measurement or a ludicrous throwback to medieval times comes entirely down to what in your head makes sense. So accept that others will think differently based on their life experiences.
The only place where it makes an actual difference is when you get to Science and perfoming experiments. Anyone who does science expeirments using anything but SI Units should be tarred and feathered and forced to walk the plank (insert other medieval punishment as you see fit)!
"If you grew up with Imperial Units like Terry6 then you're going to think Imperial is better, if you grew up with SI Units like i did, then your going to think SI makes a hell of a lot more sense."
I'm largely neutral. I grew up with Imperial (Dad was a joiner by trade), used cgs at school and SI later. It doesn't really matter although I note that some aspects of Imperial are actually binary - lbs & ounces and the common divisions of an inch (until you get to thous).
I did some evening classes in furniture restoration. It got my pragmatic back up when a tutor would want to measure in metric an item whose maker had worked in Imperial.
"And we prefer saying "miles" to "Kilometres" because it's a bloody sight easier to say."
"Click" is even easier, and the military use that as shorthand for kilometers. We already use "kilo" for kilogram. As for fluids, where is the pint and gallon actually specifically important in real world usage?
@ Terry 6
How right you are.
Basically, to all the pedants here, yes, the metric system is a truly wonderful thing. But humans aren't robots. They use what's familiar, comfortable, *and relevant under the circumstances *.
The reason we don't pop down to the pub for a *shudder * 0.5 litre of beer is because we're British, and we still have pint glasses. When the EU (or whatever it was called at the time) cheese-eating surrender monkeys suggested making the litre the standard unit for measurement of alcoholic drinks, there was uproar, and we and the Germans made them an offer they couldn't refuse!
And yes, I've got used to car tanks being in litres, because it doesn't matter what that measurement is.
All that's pertinent there is if it's full or not. But we use MPG because we've spent our lives getting to instinctively know how far away various places are in miles, all our signposts are in miles, as are our speedos, and so MPG is obvious.
My (foreign) mother was brought up on the metric system and although she lived in the UK from the mid 50s onwards, she could never quite get the hang of 'miles' and was always happier describing places as being so many kilometres away.
As for engineering, we always used metric. When we first came across American stuff we were having trouble with it all until we realised they were the ones using imperial measurements - and if NASA's various mishaps are anything to go by, they still seem a bit schizophrenic about it.
In England I want to drink pints and drive cars using MPG (not in that order!) and have a back yard.
In Germany I want to drink out of steins, have bratwurst of indeterminate weight, size, or origin.
In short, you pedants are arguing about nothing. I know most of you are just being jocular, but for those of you who aren't, I would simply say, get a fucking life.
For important stuff, of course you need SI. For everything else then, as the above - mentioned surrender monkeys would say, 'vive la difference, Rosbif'
Mine's the one in 2XL size, UK 48. Allegedly.
"When we first came across American stuff we were having trouble with it all until we realised they were the ones using imperial measurements"
Actually, no. The Americans went their own way before "Imperial" measurements were a thing, which is why their gallons are the wrong size. I'm not sure what the correct name is for their system -- probably "English".
@ Ken Hagen,
Sorry, I should have been more specific.
I was actually thinking of length measurements (where they were using feet and inches, etc) rather than volumes, which we didn't use.
And while I'm here, someone in an earlier post said that a ton was 2000 lbs. When the hell did they change that?
A 'ton' was 2240 lbs (we learnt all these at school by rote, like the times tables).
I think the 'short ton' became 2000 lbs, to make calculation easier.
And then when the EEC came along we used 1000 kilos, which was very close to the British ton, and called that the 'metric ton' and spelt it 'tonne'.
But the ordinary original 'ton' was only ever 2240 lbs.
"And while I'm here, someone in an earlier post said that a ton was 2000 lbs. When the hell did they change that?"
AFAIK, Americans have ONLY known the ton as 2,000 pounds since they never got accustomed to the stone and hundredweight, which was the basis for the long ton's 2240 (= 20 hundredweight @ 8 stone each @ 14 pounds each).
"Utter nonsense. Are you seriously suggesting that we still use miles instead of kilometres to measure distance because a factor of 5/8 somehow makes the numbers incomprehensible on a human scale?"
Most of the measurements came from PRACTICAL consideration. Like the foot: the length of a person's foot, give or take, meaning a rough estimate of length could come from simply WALKING (also the pace, the length one makes in two steps, starting and ending on the same foot). As for the mile, blame the Romans for the name (the name comes from them defining it as a thousand paces) and farming for its current length, as it was last set based on the furlong, and that measurement didn't come from horse racing but rather how far an ox plow team could work in a day. Not to mention the mile relates well to a human's normal walking pace (about 2mph) and horizon distance (about 3 miles).
"A litre is too small for petrol, but there's no useful equivalent to the gallon."
We could use a decalitre and shorten it to dec (deck), though that would have a similar issue to pounds and kilos. Filling up would cost about £12 a dec, but at least the mpd would be over twice as good as mpg. Perhaps even kpd would become popular as it would give useable number ranges.
I'd go with that. it's not the most attractive word "dec" with two hard consonants. But it'd do. "Mil" works better in speech terms, but is usually a tiny unit and confusable out of context. Kilo has already caught on pretty well for groceries. It has a softer sound and is a reasonable size. But that then pre-empts it being used for distance, ( people will say "5k" though instead).
The point is that people are asked to adjust to metric, but Imperial was adjusted to people..
Many metric units work better in maths but poorer on a human scale
See also "Which Units of Length?" (Pamela Anderton, A Random Walk in Science, pp69-70)
In laboratory testing, their panel found that the millimetre provided excellent reliability of measurement - but when assessing its convenience in use, found it to be about 25.4 times too small.
For general use - Rule of Thumb
For scientists and for others whose arithmetic is weak - Metric
Absolutely, despite the assumptions of the (surprisingly few) metric warriors here, I'm happy using most Metric units and struggled with the yards in half a mile stuff in primary school ( I prefer calculation to rote). But in general discussion I have to use Imperial for most people; even the kids I meet often use miles and gallons, and many will give people's heights in ft and inches and weight in stones just like us older folk. Or come to that a surprising number still use the inch side of the ruler if it has one.
If it were the standard unit, it would not be prefixed but have a unit of its own, as the meter, the liter, and so on. The true standard should be the base, unprefixed form (in this case, the gram). If this is inappropriate, then a new base unit should be declared that equals 1,000 grams (not unheard of; 1 Sv = 100 rem). So instead of calling it the kilogram, call it say the Higgs (Hg), after Peter Higgs after which many supported connections between mass and energy are named.
"If this is inappropriate, then a new base unit should be declared that equals 1,000 grams "
Why not do it like they did the ton?
1 ton = 2000 pounds, a very convenient measure for shipping.
So 1 Tonne = 1000 kilograms was adopted, near enough to fit in the average intellect.
So why not Pounde* = 500 grams?
*Poundde just looks silly. ☺
"Why not do it like they did the ton?"
I'm surprised they haven't made a metric Pint 500mL already. A metric Fifth is already 750mL, and they call the 1500m race the "Metric Mile". Meanwhile, yards and meters (and quarts and liters) are close enough as makes little difference unless you need specifics. Making metric analogues to Imperial measurements is one way to ease metrication, and many of them already exist. Now, some of them will take some stretching (say make a metric Stone 6kg, a bit smaller than it should be but easier to calculate).
Roughly 3:1 in 1 iteration of the measurement procedure.
The potential revision in the Planck constant is also intriguing, given its intimate involvement in a lot of astrophysics.
BTW I had thought Kibble was also a brand of cat food, but it's actually for dogs. :-( .
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I feed my Black Labrador on Kibble. If a Lab got into the lab and saw a huge piece of Kibble, no wonder the balance is missing a few decimal places. it's a well known fact that all Labradors are surrounded by a food event horizon. Once anything even vaguely resembling food gets close it's gone.. .
To measure something with an accuracy of 13 parts per billion, how accurate do the parameters used to make the measurement have to be?
I'm thinking of the current in the current balance for instance. Is it possible to measure a current to a sufficient accuracy? Or the velocity of a moving coil in a known magnetic field. How accurately is it possible to measure both the coil's velocity and the magnitude of the field?
Actually I was wondering... Is it a matter of averaging (which, of course, can only help with random errors rather than systematic errors) or of intersecting ranges (error bars) which can give smaller error bars than any individual measurement (but relies on all the error bars being correct)?
I know that (at least some) time protocols rely on intersection: if clocks always report the time as a range ("I know the time is currently between 12:55 and 13:07") and you ask several clocks, you can get a more accurate value for the time than any one clock can report by intersecting the ranges (as long as all the clocks are really right in their range reporting, of course).
How does a force balance a mass?
Serious question. I assume the electromagnetic force is really balancing the force of gravity on the 1kg mass. So they must need to know the local acceleration due to gravity to a similar level of precision. How do they get that? The obvious way would be to weigh a known mass, but then you've got reference masses all the way down.
You measure 'g' with a gravity meter. They work by dropping a small ball bearing in a vertical vacuum column and measuring the time taken to fall a certain distance. Since you can measure time and distance amazingly accurately you get a very good (<1 ppb) measurement of gravity.
Since everythign falls at the same rate in vacuum you don't need to know the mass dropped.
They are used in oil and gas industry to find underground reservoirs (oil is lighter than rock) so are a well developed bit of kit
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Is that there are so many Imperials from which to choose. Many seem to overlook this wider issue.
Ounces, pounds and tons seem to have endlessly variable meanings in various parts of the world. Makes international commerce too complicated. A kilogram is internationally agreed.
New Theory: The invention of containerized shipping eventually caused SI.
Or perhaps it's vice versa.
Physicists, darn physicists, and scheming whinging dastardly cursed rubbish eating physicists!!
What you say am I talking about? The filthy lowlifes want to literally make Planck's Constant a constant-- i.e., a fixed number. No more of this "any time some busy body experimentalist discovers a more accurate value for Planck's Constant will our perfectly spherical (to a first approximation) august bodies have to recalculate our equations". Rubbish that, make Planck's Constant a true fixed number! Let the rest of the physical world recalculate everything when a more accurate underlying value is determined (our pristine Physicist's Planck's Constant is invariant by axiomatic definition completely regardless of the real world!).
Oh yes, all those metrology measurements are trashed, each time a more accurate Planck's Constant is found, recalibrate the instruments and keep a table to convert the past into the present. But the physicists won't have to lift a finger to scrub the numbers on the chalkboard.
It is a plot I say! Heaven help you if you use Planck's Constant (as a fixed number) in your orbital mechanics, you'd probably miss geosynch by at least 10's of meters because all those bits built into the spacecraft subtly change as "fixed Planck's constant" deviates further from its origins...
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