Kilogram Reference Losing Weight 546
doubleacr writes "Ran across a story on CNN that says the "118-year-old cylinder that is the international prototype for the metric mass, kept tightly under lock and key outside Paris, is mysteriously losing weight — if ever so slightly. Physicist Richard Davis of the International Bureau of Weights and Measures in Sevres, southwest of Paris, says the reference kilo appears to have lost 50 micrograms compared with the average of dozens of copies.""
Re:The Kilogram is not losing weight (Score:3, Insightful)
The object which defines the Kilogram is getting lighter (the fact that it is getting lighter is independent of this object's role in defining the Kilogram), ergo the definition of Kilogram is getting lighter. We all weight the same, we'll just use a slightly bigger number to describe how heavy we are.
Re:The Kilogram is not losing weight (Score:5, Insightful)
Re:Mass? (Score:4, Insightful)
According to the back of this envelope here, the weight change from raising a kilogram by one metre would be
about equivalent to reducing its mass by about 3 parts in 10^7, i.e. 300 micrograms. The article says the measured loss was around 50 micrograms. So I guess there is equivalent sensitive enough to measure that.
Unless I was off by a few orders of magnitude...
Re:Bogus story, I think (Score:3, Insightful)
50 micrograms is just the right weight (Score:2, Insightful)
WARNING: Measurements are approximate
Problem solved.
They should redefine a kilogram (Score:3, Insightful)
The planck mass is defined as the mass for which the Schwarzschild radius is equal to the Compton wavelength over Pi.
The Schwarzchild radius is 2Gm/c^2, while the Compton wavelength = h/mc = 2*pi * dirac's constant/(mc). (I'll refer to dirac's constant as d, since I don't know how to type the proper character).
Setting the two equal yields 2Gm/c^2 = 2d/mc => m= sqrt(dc/G). Then, we could define 1 kg as 45940892.447777 planck masses. The only thing's we're assuming as constant are the speed of light, the universal gravitational constant, and planck's constant.
It must not lose mass! (Score:5, Insightful)
Re:hmmmm (Score:1, Insightful)
Re:Sublimation? (Score:3, Insightful)
They are, but not at identical rates.
Re:They should redefine a kilogram (Score:2, Insightful)
I agree, redefine...but it seems easier to redefine it by fixing Avogadro's number and then saying that the mass of one mole of C12 divided by 12 equals one gram.
Maybe to a physicist/mathematician it seems inelegant to base the definition of mass on an arbitrary number (Avogadro's) rather than on a physical constant. But are we absolutely, positively sure that physical constants are constant throughout the space-time continuum and that we've got them exactly right?
Re:The Kilogram is not losing weight (Score:3, Insightful)
You've got a strange definition of world there.
On this side of the pond:
"A pint of water weighs a pound and a quarter"
I'm ashamed to have to say that it appears the majority of my countrymen would prefer to use "fundamental" units that have rhyming mnemonics rather than units that make all the calculations simple and consistent across the world.
http://news.bbc.co.uk/1/hi/uk/6637587.stm [bbc.co.uk]
Tim.
Re:The metre must be shrinking then... (Score:2, Insightful)
I had this explained to me in the mid '90's by someone who was involved in printing. With variable width fonts, you are no longer supposed to use two spaces, the typeface is supposed to leave an adequate gap. Two spaces is left over from the days of typewriters.