a measured response
March 2, 2007 1:17 AM Subscribe
Redefining Avogadro's Number. A mole is the number of molecules in a gram of water: ~6.022 x 1023. Unfortunately "a gram" is defined by a chunk of metal in a vault in France, the last of the seven SI units still defined by a physical artifact. Since the reference mass (known as "Le Gran K") is actually changing over time (due to cleaning, handling, etc), the definition of a gram is currently temporally unstable. Now a new proposal has been put forward to explicitly define the number to be a known integer: 602,214,141,070,409,084,099,072, which would fundamentally change the way we define a gram. Le Gran K could become a historical curiosity like the original platinum meter stick.
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