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Kilogram to be redefined by 2011


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Vijay B
Oh!
by Vijay B on Mar 01, 2008 11:03 PM  | Hide replies

Typical rediff! The kg isn't getting any lighter or heavier, so the headline is totally misleading!

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Meow
RE:Oh!
by Meow on Mar 02, 2008 05:49 AM
They redefined the kilometer in absolute terms too, it is now defined as a fraction of the distance traveled by light. In case you are not aware of it, the weight of a body increases and the size decreases in proportion to the speed in which it is traveling. The Lorentz Fitzgerald equation gives you the amount by which the size of a body contracts at speeds. There is no way to measure this because the measuring instrument will also have to move at the same speed to measure it exactly and the measuring instrument would contract too. Any student of physics will tell you this.

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Albert Pinto
RE:Oh!
by Albert Pinto on Mar 02, 2008 09:11 AM
You are confusing the kilogram; unit of mass with kilogram; unit of force. Kilogram; unit of force is also the kilogram weight we are all familiar with. It is what is used in measuring dal-chawal-sabji and just about everything else in the local supermarket. The kilogram this article refers to, and is of primary importance to the scientific community, is the kilogram; unit of mass. It is one of the seven univerally standard SI units and is thus one of the corner stones of physics and engineering. Being such a fundamentally important concept, it needs to be accurately measurable and reproducible - neither of this is the case with the current definition (as the mass of a block of alloy kept in a museum in Paris). They did the same thing with length some years ago - it was redefined from the then existing similar definition - as the length of a rod of a specific alloy in a museum in Paris, to being defined as the distance travelled by certain electromagnetic rays in vacuum.

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Meow
RE:RE:Oh!
by Meow on Mar 02, 2008 05:55 AM
In continuation to my previous post - the earth is traveling around the sun and the solar system itself is moving. The earth is also rotating on its axis and it is expected to become faster as the moon moves away from the earth (which it is). All this movement will have an effect on the kilogram, it is not corrosion that is the cause for re-definition of the kilogram. The effect of corrosion is a very tiny factor, but that has nothing to do with the definition of a kilogram. They will most probably redefine the kilogram as a computational mass of hydrogen atoms at a specific force of gravity and/or the movement of earth at a specific speed. Why hydrogen? Because it is the first element in the periodic table and also because it can be easily produced in a pure form like anything else.

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ben hur
RE:Oh!
by ben hur on Mar 02, 2008 12:37 AM
rediff is not misleading. its scientifically correct. in fact, its good to see rediff reporting scientifically important articles unlike the rubbish articles on divisive lines ckt/bollywood/politics n sensationalised by them.

'the kilogram is the only base still defined by a physical object.' so kilogram is the weight of that standard object kept by them in the lab, weight of the said object can get affected due to atmospheric conditions, corrosion, etc.
dont just criticise anybody. thanx.

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Vijay B
RE:Oh!
by Vijay B on Mar 02, 2008 08:42 PM
You don't get it do you? Two points -

1. "The idea is to replace the single master kilogram with something based on physical constants, rather than an artifact that could be damaged accidentally,"

2. "In addition, *copies* of the kilogram have changed over time by either gaining or losing weight as compared to the standard kilogram."

You have to start with *some* value of the kg right? And *then* define it using universal constant standards right? Now what will the *initial* value? The base alloy kg sans the dust? Or with the dust/atmospheric conditions/latitude/longitue induced gravity? Or what?

Answer that first, then criticise me. Or *ask* me again if you didn't understand what I meant.

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asdfgh
RE:Oh!
by asdfgh on Mar 03, 2008 06:45 AM
Vijay, It is really re-defining KG. We are mostly used with Kg as a measurement usit which is 1000gm etc. But as you asked correctly, what is that base for Kg or a sample to show Kg? Lot of people uses pounds to measure weight, right? So the physical measurable definition or if you want to feel the actual, original Kg, it is the weight of that alloy rod mentioned in the article. That is the actual definition of Kg. Now this alloy is pro to changes or destruction, so they will re-define it to some thing which is not destroyable...We study this definisiotn in our school books, now they have to change it.

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Ajit Birdi
RE:RE:Oh!
by Ajit Birdi on Mar 02, 2008 01:13 AM
Vijay B kilo gram does change and can change in many ways.
Dust on kilogram can add few micro grams to it so can polishing it can either add to it or remove some of it it all depends.
Moisture in the air can add to it while corrosion can decrease it.
A micro gram or two may not be of any significant value to you and me but it is a big and heavy weight for scientific world.


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Vijay B
RE:RE:RE:Oh!
by Vijay B on Mar 02, 2008 08:44 PM

In addition to my reply above to "ben hur", read this quote from the article -

"According to Tran, the kilogram will remain the kilogram; it's only the way it will be defined that will change."

So - the kg, dear Ajit, doesn't change. If it did...

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