How to make measurement standards better?

--------- #1412 - Measurement Accuracy as Good as your Standards?

- Attachments : cantilever force measurement

- Any measurement is only as good as the standard used Measurement is a comparison with something and you want that something to be as stable, and consistent, and as accurate as possible. The International Standards (SI) are kept in Paris, France. There seven (7) of them that all of science depends on. Metrologists would like to make today’s standards even better by tying them to nature’s constants.

- The length of the meter , the duration of a second and the mass of kilogram are tied to SI standards. The ratios of two of these is the speed of light which is one of the natural constants. The speed of light is 299,792,458 meters per second. But, what is a meter and what is a second?

-------------- (1) A second is 9,192,631,770 oscillations of a vibrating Cesium atom

-------------- (2) A meter is the distance light travels in 1/ 299,792,458^th of a second.

- The measurement of the speed of a falling object by Galileo was the start of the modern science of measurement. Later a metal rod in a vault in Paris became the standard for the meter. A refinement made later was to scribe two marks on a metal rod which were less likely to get damaged. Today we measure length by the distance light travels at its constant speed.

- -------------- (3) A kilogram is a platinum-iridium cylinder kept in a vault in Paris. Science would like to improve this standard. There is too much uncertainty in its weight. It could have some dust on it. Could its surface oxidize. Science would like to see the kilogram measured in Planck Constants. That is a natural constant = 6.6260755 * 10^-34 Joule- seconds.

-------------- A Joule is a unit of energy = 1 Newton * meter.

--------------- Energy = Force * distance

-------------- A Newton is a unit of force = kilogram * meter / second / second

--------------- Force = Mass * acceleration.

-------------- (4) An Ampere is a unit of electric current = a current in 2 parallel conductors 1 meter apart producing a force of 10^-7 Newtons. Science would like to see the Ampere defined in terms of the elementary electron charge.

------------- (5) A Kelvin is a unit of temperature = 1 / 273.16 to the triple point of freezing of water. Science would like to see the Kelvin defined in terms of Boltzman’s constant. Boltzman’s Constant is another natural constant = 1.380658 * 10^-23 Joules / Kelvin.

-------------- (6) A Mole is he amount of a substance counting atoms or molecules. It is Avogadro’s Number of 6.0221367 * 10^23 atoms per mole.

------------ (7) A Candela is a unit of measurement of luminous intensity. It is 1 / 600,000^th of the light produced by a square meter cavity of freezing platinum ( 2,032 Kelvin) Science would like to see the Candela defined by a luminosity of monochromatic radiation at a specific frequency.

-------------- A watt is a unit of power = 1 Joule / second

--------------- Power is Energy consumed per second.


-------------- A Coulomb of electricity = flow of 6.25*10^18 electrons

- A of these recommended changes in the standards of measurement are designed to improve the accuracy of measurements. Technology is getting so precise in can tolerate the uncertainty of measurement . For example: If you raise a clock one meter off the floor , it experiences less gravity, it will run faster. How much will it speed up = 1 part in 10,000,000,000,000,000 ( 1 part in 10^16) . If you could measure time that accurately you could measure your altitude using the Theory of Relativity.

- We have come a long way since 1892 when Albert Abraham Michelson made the first measurements of the speed of light. 300,000 kilometers per second has been refined many times since. Today it is 299,792,458 meters per second. And, Science would even like to see it measured in centimeters per second. When it comes to accuracy we are never satisfied. An announcement will be made shortly, stay tuned.

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(1) See Review #784 - Spacetime, Energy and Calculus

(2) See http:www.onlineconversion.com where all of these units are easily converted between other units of measurement.
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707-536-3272, Thursday, February 23, 2012