Topic: Now That's a Standard!

[meandean]

  Here it is, the one and only International Prototype of the Kilogram (IPK). This unit of mass was orginally based on the mass of 1 liter of water at its densest temperature (about 4C), but the water definition was impractical to reproduce to high precision in a lab, so back in the late 1800's scientists took their best guess and made 40 cylinders of 90% platinum 10% iridium (for hardness, as platinum is soft) measuring just over 1.5" in diameter and height to match that value. The alloy used is nearly twice as dense as lead and over 10% more dense than gold. The first cylinder (pictured) in this set (housed in a vault near Paris) is decreed to be THE reference for the kg itself; the others in the set match to within about 2 parts in 10^8, and these replicas were distributed to many countries- the US uses kg#20 as its reference. In their history, all of the prototype kg's have returned to France 3 times for dilligent comparison to the original, (last time in 1999) and the results have drifted around a bit, causing a problem for scientists. Interestingly enough, the metric system is French based, but the cylinders were made in England. Here we are in 2010, and the kg is the only unit left in the SI measurement system that is based on the properties of a specific artifact, rather than a natural property. The exact value of the kg is important in physics, as so many other measurements such as Amperes, Coulombs, Planck's constant and others depend on its value. There are some alternative ideas in the works, but the next meeting of the big wigs is scheduled for 2011.

  Notice that the IPK is adorned with 3 nested bell jars- it remindes me of the triple tiara worn by the big guy in Rome for centuries before Paul VI 86'd it in the 1960's (party pooper!). 

[James]

Yea, big deal. I got one of those.

James. 

[drlava]

Good historical fun, thanks.

What! they protect the weight in nitrogen under 3 jars but don't protect the tongs that hold it!?

[James]

Have any idea what it's value is?

2.2 lbs. of Platinum Iridium is HEAVY! 

James. 

[BlinkenLights]

would make more sense to create an atom based measurement where a few million carbon atoms were counted one by one then weighed ..

however weight is subject to change as the major masses on out planet, our solar system, and to a lesser extent, the universe, move.

earths mass changes daily.

If you consider that weight is based on gravitational pull, and that a Kg would "weigh" less on the moon, then its not hard to understand that when the earths mass changes, weight also changes.

more to follow....

[James]

We should measure Newtons in micro gravity but that is still based on a volume of some Earthly mass.

Oh well..... I guess we just have to get busy and find that pesky Higgs Boson. Then all we have to do is count them all.

James. 

[Lazerjock]

would make more sense to create an atom based measurement where a few million carbon atoms were counted one by one then weighed ..

however weight is subject to change as the major masses on out planet, our solar system, and to a lesser extent, the universe, move.

earths mass changes daily.

If you consider that weight is based on gravitational pull, and that a Kg would "weigh" less on the moon, then its not hard to understand that when the earths mass changes, weight also changes.

more to follow....

Don't seem very accurate to me either. At least by todays standards.

[Fanny Pack]

Weight is just a measurement of mass.  As long as mass doesn't change then weight doesn't change.  The perceived value might change as your measurement instruments are affected by different environments but weight stays the same as long as you are always comparing to the exact same object.  That's the purpose of the standard.  As long as you compare what you are measuring to the standard then it doesn't matter if you do it on the moon or in James' basement.  The ratio of mass will be constant and that is what the indicated weight will be.

[James]

Weight is just a measurement of mass.  As long as mass doesn't change then weight doesn't change.

Weight is absolutely NOT mass!

Weight is the force of gravity that pulls masses together.

Gravity is nowhere near constant anyway you look at it; not even on Earth!

It's just like magnetism; the distance between the masses has everything to do with its strength.

Mass is accounted for by the number of heavy particles, like protons and neutrons, in an object made of matter.

Before you go nit-picking the phrase "heavy particles", consider what "heavy water" is.

Calling it "massive water" just doesn't make sense on Earth.

I wonder how they deal with the fact that these 1Kg samples might have more or less electrons at any given time. Electrons have some mass. They are anything but fixed in place and constant! These things are metal! They conduct!

Somehow I think the accuracy of any weight is eventually going to come down to the Heisenberg Uncertainty Principle and can never be know. It really is not a constant! It is the combination of an uncertain amount of matter being pulled by an incalculable force.

James. 

[Fanny Pack]

I said weight is the measurement of mass.  Geez.  First you argue with a MS expert and MS and now you want to argue with an ex-nuke about mass. 

[James]

Sorry. I guess I still had my monster boots on from stomping you down about MS! 

http://en.wikipedia.org/wiki/Newtons

http://en.wikipedia.org/wiki/Fig_Newton

James. 

[meandean]

Sorry. I guess I still had my monster boots on from stomping you down about MS!

 You have monster boots! Are they anything like Gene Simmons famous set?

[Fanny Pack]

I used to split atoms (literally) before I was a computer programmer.  I only got back into computer science because I got tired of operating a reactor control panel in the middle of the night.  I think my next job might be fixing up old cars.  Seems more rewarding, except for the grease stains.

[James]

Oh good. I'll prepare to debate you on foreign or domestic! 

I don't really care which side you take.

You're WRONG! 

And your view (still unknown to me) is pure evil. 

That seems reasonable.

James. 

[James]

Sorry. I guess I still had my monster boots on from stomping you down about MS!

 You have monster boots! Are they anything like Gene Simmons famous set?

No. These are ferry boots; steel toed, ruby sequined, combat style. They still have blood and guts in the tread of the soles from stomping Bill Gates into the dirt.

James.