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NIST Wants An Electronic Kilogram
Dearing writes "According to the Global Engineering Journal, NIST, those not-so-standard standards people, want to give up the hunk of metal they've been calling a kilogram, even though it never weighs the same twice. In it's place, an electronic kilogram could act as the permanent standard."
They balance it against gravity to measure it? Wouldn't that be really, really inaccurate, since gravity varies by altitude, local density variations, etc? Did I misunderstand what I just read?
Sheeze, why not just define it as 1.498e20 atoms of carbon (or whatever number), and be done with it.
Sometimes it's best to just let stupid people be stupid.
If there isn't, then you're way smarter than most practicing physicists... gravity is hard.
The Mongrel Dogs Who Teach
Do you know how many states of water there are? Not to mention somewhere you are going to have to define a pressure, a temperature etc. You don't exactly want to end up with a circular reference in there....
Now, at CSIRO, they are researching into using a super spherical ball of silicon, about 8 cm across, and weighing 1kg. It is spherical to an accuracy of 8nm, and was built by the same glass grinders that build lenses for our precision instruments and telescopes. We have shipped one or two overseas (and have one or two in .au), so that people around the world can test 'em.
Pretty cool in all - I watched the guy pick it up with cottonwool, in the same room that I was in - no contaminant free clothes, either - it is pretty robust. It is all part of an international effort to produce new standards of mass etc - the platinum bar in Paris is getting a bit old. IIRC - CSIRO are researching another method, but can't remeber what it was....
You could even define it as the energy in some huge number of photons of a particular wavelength. :-)
Hmmm - which unfortunately comes back to a density of photons, and a length cubed, which unforteunalty comes back to that damn platinum bar in Paris. IIRC - it has a chip in the corner of it too - Ooops. I just dropped your metre - my, how you have just grown!
Wouldn't it make sense to measure the mass of something by accellerating it to a known speed, then measure the amount of energy it takes to stop it?
Or, conversely, the amount of energy it takes to get it to a certain speed?
That would/should provide you with a measurement that's truly gravity-independant, and a scale that
Another idea: Make a vacuum tube. Put the item you want to weigh inside the vacuum tube. (Again, don't put your pets in there!=) Point the tube straight up and down. (we're using gravity for this one) Throw the item to be weighed up the tube, like the ball in a pinball machine, with a known amount of energy. Measure how high up the tube it goes, how long it takes to get there, and how long it takes to fall back down to the bottom.
Should be simple computation to determine the actual mass of the object from there, no matter how much gravity is in effect... no?
That's odd, I don't understand how this question relates to an article about an electronic standard for mass. And before you flame me for nitpicking, let me remind you that Mars has some very expensive upper-atmospheric dust right now thanks to imprecise communication about units of force. Ordinary people can blithely confuse mass and weight without causing problems. Engineers can't, and this article appears in an engineering publication. When are we going to learn to be more precise about this sort of thing?
When all you have is a hammer, everything looks like a skull.