Hello Covers,

Here is a question.

HOW MUCH IS A KILOGRAM??

Please do not discard this question as naive or a joke.It's neither.

The answer is: 'That nobody can say for sure'

The official Kilogram-a cylinder cast 118 years ago from platinum and iridium,and known as the 'International Prototype Kilogram' or "le Gran K"-has been loosing mass,about 50 micrograms at last check;despite careful storage at a facility near Paris.

It is ridiculous or even ludicrous for a standard to define mass.

There is a campaign launched to redefine the Kilogram.

Full story is available in Inside Metrology at the link given below:

http://qualitydigest.com/IQedit/QDarticle_text.lasso?articleid=12480

/Umang :D

Major standards institutes around the world including NIST and NPL have been working for many years on redefining the kilogram. They welcome new ideas but unless Professors Hill and Fox are misreported in these articles I cannot see how this is one of them. It sounds like something that could have been wished for 118 years ago and anytime since.

A new artefact must be created somehow to match the original with an uncertainty of 1 in 10^8 or a little better. Then and only then can the kilogram be traceable to length/time standards with zero uncertainty and zero drift using electromagnetic radiation or electric force. Its definition will be related to an exact integer.

Now we will not be able to eliminate uncertainty in making artefact copies and there will be very few of them, but if there is any drift we will know its true value.

I always thought that a kilogram was equal to the weight of 1,000 cc of distilled water somewhere around 4degrees C.

I know that loss of mass has to do with motion.

Interesting article ..... will it affect my weight too :confused:

Interesting article ..... will it affect my weight too :confused:

Only if you are in motion I guess...so start running real fast:lol:

Hello Covers,

Here is a question.

HOW MUCH IS A KILOGRAM??




I work on the principle of a bag sugar in the UK (2.2lbs), can I claim under weights and measures that I am not recieving the stated amount of sugar as loses mass during storage, the bag I buy may well have been there for 2 weeks!! :rolleyes:

I always thought that a kilogram was equal to the weight of 1,000 cc of distilled water somewhere around 4degrees C.


It was true for much of the 19th century but there was for a long time a platinum kilo as the practical standard until the international prototype Pt/Ir kilogram (IPK) re took over as the primary artefact in 1889. The figure now is 0.999974 g/cc give or take the last decimal. Water as a reference artefact has its problems, like gas content.

Some kilogram copies gain weight, some lose weight relative to the IPK. Cleaning makes a difference. There are microscopic surface defects that can adsorb gases or offgas, but they could all be gaining weight, some less than others. We don't know.

I think the Wikipedia entry http://en.wikipedia.org/wiki/Kilogram is reliable. The article in the first post is mentioned in reference 17.

The Wikipedia entry has a neat way of describing the idea of Professors Hill & Fox. It calls it an imaginary realization. Try imagining your traceability chain in standards compliance.

Do distance and time have zero error ? Are there any true absolutes ?

I read that time moves more slowly the higher you are, therefore its not an absolute is it ?

Also if distance is measured in light years, another time derivative, it must also be subject to such variance.

In some sense, definitions of base units are exact. A second 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."

There is the secondary question of how well you can measure those 9 192 631 770 periods and what effect there might be from other factors like temperature. At the moment, NIST claims to be able to measure this to within 1 second in 60 million year.

And yes, time DOES change with position. the higher you go, the faster clocks run. (Time itself changes - NOT just the clocks!) For GPS satellites, it is about 40 micoseconds per day. This doesn't sound like much, but it must be accounted for or GPS systems would be useless.


Tim

I almost forgot.......it's 1000 miligrams.

Thanks Tim

Yes I remember now that GPS satelites have some correction because of this time problem.

And thats why its funny when people say the Imperial system isn't all that great. Sure its not based on some very accurate measurement of light but how accurate is that measurement anyways. :biglaugh:

The meter has changed quite abit, after all it was defined orignally in 1791 as 1⁄10,000,000 of the distance between the Equator and a pole which puts it at 1.001879m in todays terms.

On the other hand the Inch "yard stick" from Queen Elizabeth's time (1588) is not "inaccurate" to todays standard by much more, its only off about 0.010" verses the meter which is off by 0.0074" which isn't all that bad considering its also 200 years older. :)

Dimitri