Would you like to touch his ball?
Perfect silicon sphere to redefine the kilogram: Securely tucked away inside a French vault is a lump of metal known as the International Prototype. A mixture of platinum and iridium, it was made in the 1880s to define the mass of a kilogram.
But work by a team of Australians could help pave the way for the retirement of this century- old prototype, as weight and measurement experts across the globe work towards a more scientific definition of the kilogram.
The project requires the development of perfect silicon spheres, and optical engineers at CSIRO’s Australian Centre for Precision Optics — considered world leaders in the craft — are doing their part.
Scientists will use the spheres to determine how many silicon atoms make up a kilogram, and this will be used as the new definition — bringing the kilogram into line with other base units such as the metre and the second, which are all defined by physical constants.
Silicon is such a sexy element too…
None of this means anything to Americans who will avoid joining the rest of the metric world – on their merry way to Armageddon. After all, it wasn’t used by Noah.
Actually, U.S. joined the metric party long ago — it just hasn’t filtered down to the rest of the populace, is all. All U.S. “English” measurements are defined based on their metric counterparts. For example, 1 inch is defined as exactly 2.54 cm. So, yeah, U.S. weights would be affected by the definition change for kg.
Thats kinda interesting. Setting a standard measurement to a physical restraint. That should make things logical and rational.
Metre: Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent 1/10,000,000 of the distance from the equator to the north pole through Paris. Today, it is defined by the International Bureau of Weights and Measures as the distance travelled by light in absolute vacuum in 1/299,792,458 of a second.
I like round numbers, but that earth distance thing must vary by atleast 5 factors?
What would be a “natural physical restraint?” While we want something close to 2.2 pounds–I would favor something like the weight of a cube of water 100 Centimeters per side? –ie, should be tied into the standards already agreed upon. And that distance thing should be so many wave cycles of light of some frequency.
#2
Hmmm, I’m an American and have used the metric system for many years with no significant trauma.
Where the heck are you that you are so ignorant?
In the UK we have a similar confused mix of metric and imperial. Legally everything should be in metric but road signs are still in miles and yards but with regard to shorter distances I measure in centimetres and metres but if I’m describing someone’s height I’ll still say 6′ 2″. Being born in 1972 I am a product of the confusion and lack of commitment to metric that all governments in the UK have allowed to go on since its inception.
And really, this is just an exercise in intellectual masturbation anyway. Who cares is a standard is arbitrary, as long it is defined and consistent.
Crazy thing here in Honduras, weight is measured in pounds but distances are measured in kilometers.
Frankly I dump all english measures and use the metric in all my work, and my engineering readership hasn’t complained yet. Having said that, the general populace is shockingly ignorant about the metric system.
Too bad it will role right off the scale.
I saw a parts catalog that had a length listed in inch-centimeters once.
#9 – If you can get Joe Twelvepack straight about the metric system, you immediately have to move to level two and explain the difference between mass and weight.
When you’re working with CAD/CAM systems, mixing english and metric can be a real PIA.
Also, you can now get silicon balls implanted after your dog is altered so that your dog still looks manly… or dogly as the case may be.
Actually, you can get them for yourself as well.
http://tinyurl.com/2ov58c
I’ve wondered how scientists were going to redefine the Kg, since the Earth’s gravity varies from place to place (and altitude is a factor) and mass is not weight. Seems arbitrary at first, but having the Kg defined by a discrete number of atoms of an element instead of some “standard ball in a vault” should improve the definition by orders of magnitude.
Way cool. Now if we could just figure out why fundamental constants like the mass of the electron and unit charge are what they are, we could rule the universe – bwahahaha.
Actually I think metric familiarity is increasing in the US. I quote range on wireless networks and cabling in meters all the time and i’ve had very few people ask me to define it.
Also, I notice that people are increasingly doing printer cartridges in milliliters instead of however many hundredths of a fluid ounce each one is.
There’s an upcoming deadline of 2010 that the EU is enforcing after which it will be illegal to sell anything in the EU without it being labelled in SI only units. No dual labels. Forty eight of the fifty states already permit this at the state level but the federal law needs to be amended to permit metric only if the company wants to. Many companies including Proctor and Gamble and lots of others have expressed a desire to do so as soon as the law is put in, and it looks like it will be even if the EU extends the deadline. I think that will increase the familiarity a lot more.
Even crazier, my in-laws live in Puerto Rico, where distances are measured in kilometers, but speed limits are in miles-per-hour.
It has been a long time since I studied the metric system. The kilogram is a measure of mass, not weight, right? We really should really say something weighs, say, 9.8 Newtons instead of 1.0 Kg, correct?
So, how do these guys know they have exactly one kilogram when the Earth’s gravitational pull varies depending on your location? By that, I mean that the sphere will weight less at sea level than it would on top of Mount Everest (or on the exact opposite side of the planet from Mount Everest, for that matter). Is there a metrically-precise repeatable way to measure 1g?
And how, exactly, are they supposed to “count” the number of atoms in these “virtually perfect” spheres so that they can determine what a kilogram is equal to?
I was always a little confused by pounds (pound-mass) and slugs (pounds-force). Another good reason to use metric.
Someone please enlighten me.
Forget it. We’re all just as confused as you are.
So, how do these guys know they have exactly one kilogram when the Earth’s gravitational pull varies depending on your location?
Comment by Mark T. — 6/15/2007 @ 4:19 pm
That’s the beauty of the new definition – mass is mass, not weight. An exact number of atoms of an pure element (arbitrarily chosen to be very close to current 1Kg) will have the same mass anywhere in the universe (according to general relativity), and will require the same exact force to accelerate that mass from [frame] rest to an arbitrary [frame] velocity. Pretty cool, isn’t it?
Bubba, yep, mass is mass no matter what velocity. I am just thinking that you cannot measure the exact mass unless you can induce an exact acceleration and exactly monitor the induced weight (m=f/a). The level of precision needed to measure this thing seems like it is unattainable on Earth.
I would think that you could only get a truly exact mass measurement by using a frictionless centrifuge suspended in a pure vacuum while in a zero g environment, i.e. in outer space.
I can imagine a planet sized cyclotron or superconducting supercollider in deep space to accelerate these 1kg balls in lieu of the usual ions or sub-atomic particles. Sounds like a sci-fi novel. I would think that anything else would only get you very, very close to exact.
Of course, it doesn’t sound like these guys would settle for very close. Anyway, you still couldn’t count the atoms. It all seems rather academic to me. Anything they come up with will still be an approximate, unlike the scientifically defined metric units of length and time which are tied to the wavelength and speed of light, respectively.
Fun to think about, though.
#19, Mark T.,
If an object at [frame] rest has a mass M, moving at a speed v it will have a mass M/sqrt(1 – v²/c²). This is an undetectably small effect at ordinary speeds, but as an object approaches the speed of light, the mass increases without limit. Tough to select an “at rest” reference frame, but the insignificant gravity well of 1G here on the good ol’ Earth wrt the center of the our local galaxy cluster (Virgo) will just have to suffice.
But I’d really like to see the solar system sized super collider — just think of the theories it could prove or disprove!
#21, HBear, precisely. And now even more accurately defined with the no. of atoms in an elemental reference mass which isn’t dependent on velocity or time. The technique of mfg. looks much like the technique for polishing a mirror for astronomical use (surface accuracy to 1/100 wavelength of visible light — nanometers). To figure a mirror, interferometric tools such as a ronchigram are available. Wonder what kinds of tools are used for creating a near perfect sphere?