sharpiefan

11-14-2018, 09:32 PM

Finally, 130 years after it was established, the kilogram as we know it is about to be retired. But it's not the end: a new definition will be put in place - one that's far more accurate than anything we've had until now.

Tomorrow, on 16 November, the General Conference on Weights and Measures (CGPM) in Versailles is going to vote to officially make the change. Le kilogramme est mort, vive le kilogramme.

Most people don't think about metrology - the science of measurement - as we go about our day. But it's vastly important. It's not just the system by which we measure the world; it's also the system by which scientists conduct their observations.

It needs to be precise, and it needs to be constant, preferably based on the laws of our Universe as we know it.

But of the seven base units of the International System of Units (SI), four are not currently based on the constants of physics: the ampere (current), kelvin (temperature), mole (amount of substance) and kilogram (mass).

"The idea," explained Emeritus Director of the International Bureau of Weights and Measures (BIPM) Terry Quinn to ScienceAlert, "is that by having all the units based on the constants of physics, they are by definition stable and unaltering in the future, and universally accessible everywhere."

For example, a metre is determined by the distance light travels in a vacuum in 1/299792458 of a second. A second is determined by the time it takes for a caesium atom to oscillate 9,192,631,770 times.

A kilogram is defined by… a kilogram.

No, literally. It's a kilogram weight called the International Prototype of the Kilogram (IPK), made in 1889 from 90 percent platinum and 10 percent iridium, and kept in a special vault in the BIPM headquarters.

In fact, the kilogram is the only base unit in the SI still defined by a physical object.

(CONT'D AT LINK)

The Definition of The Kilogram Is About to Change. Here's What That Really Means (LINK) (https://www.sciencealert.com/after-130-years-the-definition-of-the-kilogram-is-finally-going-to-change)

#include [ std-disclaimer ]

Tomorrow, on 16 November, the General Conference on Weights and Measures (CGPM) in Versailles is going to vote to officially make the change. Le kilogramme est mort, vive le kilogramme.

Most people don't think about metrology - the science of measurement - as we go about our day. But it's vastly important. It's not just the system by which we measure the world; it's also the system by which scientists conduct their observations.

It needs to be precise, and it needs to be constant, preferably based on the laws of our Universe as we know it.

But of the seven base units of the International System of Units (SI), four are not currently based on the constants of physics: the ampere (current), kelvin (temperature), mole (amount of substance) and kilogram (mass).

"The idea," explained Emeritus Director of the International Bureau of Weights and Measures (BIPM) Terry Quinn to ScienceAlert, "is that by having all the units based on the constants of physics, they are by definition stable and unaltering in the future, and universally accessible everywhere."

For example, a metre is determined by the distance light travels in a vacuum in 1/299792458 of a second. A second is determined by the time it takes for a caesium atom to oscillate 9,192,631,770 times.

A kilogram is defined by… a kilogram.

No, literally. It's a kilogram weight called the International Prototype of the Kilogram (IPK), made in 1889 from 90 percent platinum and 10 percent iridium, and kept in a special vault in the BIPM headquarters.

In fact, the kilogram is the only base unit in the SI still defined by a physical object.

(CONT'D AT LINK)

The Definition of The Kilogram Is About to Change. Here's What That Really Means (LINK) (https://www.sciencealert.com/after-130-years-the-definition-of-the-kilogram-is-finally-going-to-change)

#include [ std-disclaimer ]