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Topic: Kilogram shrinks, oh noes (Read 4562 times)
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Yegolev
Moderator
Posts: 24440
2/10 WOULD NOT INGEST
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Why am I homeless? Why do all you motherfuckers need homes is the real question.
They called it The Prayer, its answer was law
Mommy come back 'cause the water's all gone
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Morat20
Terracotta Army
Posts: 18529
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I thought they'd already gotten around to defining the gram as some number of carbon molecules, just like they did with the meter (distance light travels in a vaccuum in a certain amount of time, with time defined as oscillations of something or other -- another physical constant). |
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Yegolev
Moderator
Posts: 24440
2/10 WOULD NOT INGEST
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I had thought so, too, but apparently not considering the discussion of using a silicon sphere as a replacement. In my view, if you have a fomulaic definition then you don't need a physical object at all. However, I am not a scientist.
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Why am I homeless? Why do all you motherfuckers need homes is the real question.
They called it The Prayer, its answer was law
Mommy come back 'cause the water's all gone
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Morat20
Terracotta Army
Posts: 18529
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I had thought so, too, but apparently not considering the discussion of using a silicon sphere as a replacement. In my view, if you have a fomulaic definition then you don't need a physical object at all. However, I am not a scientist.
People like shit to hold? According to wikipedia, it's the last of the SI units to be defined by an artifact and not a constant (and the only one to be fixed to a prefix definition -- defining kilogram, not gram). The silicon sphere is actually an attempt to fix it to a constant (a fixed number of silicon atoms). According to wikipedia, looks like they're also looking at using Planck's constant (how they get mass from current is beyond me, but apparently it's a leading contender because they can almost get precise enough measurements standard off that method), fixed number of carbon atoms, electron mass and elementary charge. Seems like they're moving towards it, they're just waiting for the development of a useful measurement system. (Apparently with meter, they use a helium laser and a fixed number of wavelengths -- easy enough to do in a lab to the requisite precision). |
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Yegolev
Moderator
Posts: 24440
2/10 WOULD NOT INGEST
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Laser for meter seems easier to do, as far as a "thing", so maybe that's it. Still, if you know how many atoms of silicon then you don't need to actually constuct a sphere. I think.
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Why am I homeless? Why do all you motherfuckers need homes is the real question.
They called it The Prayer, its answer was law
Mommy come back 'cause the water's all gone
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Morat20
Terracotta Army
Posts: 18529
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Laser for meter seems easier to do, as far as a "thing", so maybe that's it. Still, if you know how many atoms of silicon then you don't need to actually constuct a sphere. I think.
There was something in the wikipedia article about "why a sphere". I think because their tolerance for "Easily constructed measure of weight" is something like 25 picugrams. Whatever the funky lower-case u means in metric. |
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Murgos
Terracotta Army
Posts: 7474
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μ
It's a mu, it's for micro or 1 millionth i.e. E-6.
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"You have all recieved youre last warning. I am in the process of currently tracking all of youre ips and pinging your home adressess. you should not have commencemed a war with me" - Aaron Rayburn
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Morat20
Terracotta Army
Posts: 18529
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μ
It's a mu, it's for micro or 1 millionth i.e. E-6.
Damn Frenchies and their SI. :) |
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Nebu
Terracotta Army
Posts: 17613
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Perhaps the kilogram went swimming in cold water.
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"Always do what is right. It will gratify half of mankind and astound the other."
- Mark Twain
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Mrbloodworth
Terracotta Army
Posts: 15148
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Does this means everyone is now fatter?
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Samwise
Moderator
Posts: 19324
sentient yeast infection
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Can't you already define a gram as being the mass of 1 mole (the Avogadro constant) of neutrons, or something like that? Of course, the Avogadro constant is currently strictly defined in terms of the gram rather than an exact numerical value, but it seems better to just pick a number than to base the mass on a hunk of metal that is apparently evaporating as we speak.  |
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Morat20
Terracotta Army
Posts: 18529
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Can't you already define a gram as being the mass of 1 mole (the Avogadro constant) of neutrons, or something like that? Of course, the Avogadro constant is currently strictly defined in terms of the gram rather than an exact numerical value, but it seems better to just pick a number than to base the mass on a hunk of metal that is apparently evaporating as we speak. As I said upthread -- they're working on it. :) The problem isn't "definition" so much as it is "definition that can easily be created and measured in a given lab, and known to be precise within 25 micrograms" or something to that effect. |
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WayAbvPar
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Perhaps the kilogram went swimming in cold water.
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When speaking of the MMOG industry, the glass may be half full, but it's full of urine. HaemishM
Always wear clean underwear because you never know when a Tory Government is going to fuck you.- Ironwood
Libertarians make fun of everyone because they can't see beyond the event horizons of their own assholes Surlyboi
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Nebu
Terracotta Army
Posts: 17613
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That was exactly the image I was thinking of WAP. Exactly.
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"Always do what is right. It will gratify half of mankind and astound the other."
- Mark Twain
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Righ
Terracotta Army
Posts: 6542
Teaching the world Google-fu one broken dream at a time.
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Christ, first the wars, then the Euro cup 2008 qualifier to Scotland, and now bits of the kilo. The bloody French can lose anything.
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The camera adds a thousand barrels. - Steven Colbert
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Ironwood
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Posts: 28240
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:-D
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"Mr Soft Owl has Seen Some Shit." - Sun Tzu
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