How the Planck Constant is Better than a Kilogram Artifact, or How the History of Measuring Physics Constants Will Lead to a “New” International System of Metric Units

dc.contributor.author Steiner, Richard en_US
dc.contributor.corporatename National Institute of Standards and Technology (U.S.) en_US
dc.contributor.corporatename Georgia Institute of Technology. School of Physics en_US
dc.date.accessioned 2013-10-02T19:55:33Z
dc.date.available 2013-10-02T19:55:33Z
dc.date.issued 2013-09-30
dc.description Presented on September 30, 2013 at 6:00 pm in the Clough Undergraduate Learning Commons - Room 144. en_US
dc.description Runtime:73:12 minutes. en_US
dc.description.abstract For over 200 years, the metric system has been the standard for comparing measurements in science and industry. Formal procedures were adopted about 125 years ago to create the International System (SI) of units, and it has been steadily improved. In the next few years, the SI will be completely redefined to make all units more reproducible for the foreseeable future. The base concepts of time, length, mass, charge, temperature, amount of substance, and luminosity will have SI units of seconds, meters, kilograms, coulombs, kelvins, moles, and candela, respectively, all linked to fundamental physical constants. Conducting tests to obtain consistent and better values for physics constants has a long history, going back to Galileo trying to measure the speed of light. Many physics constants now have values in SI units of 8 digits or more, but that accuracy improved slowly. The Planck constant h has the shortest history of them all, since it was only conceived in the modern quantum approach to atomic theory. This talk will use the Planck constant as an example of how the uncertainty in constants measurements decreases, but not without jumps and disagreements, even increasingly smaller ones, that still have significant effects. Change always involves controversy. The early Planck values “quickly” changed by one percent as physics itself developed. Even in the 1970's and 80's there was controversy over voltage units, arising in the changeover from standard chemical cells to the quantum-based Josephson effect. Today's hot topic concerns changing from the last artifact, a kilogram mass standard, to a Planck constant (or Avogadro constant) definition. The recent discrepancies over Planck and Avogadro results are a factor of 100 smaller than those over voltage, showing how electronic metrology is still progressing, and that research on accurate measurements is never complete. en_US
dc.format.extent 73:12 minutes
dc.identifier.uri http://hdl.handle.net/1853/49176
dc.language.iso en_US en_US
dc.publisher Georgia Institute of Technology en_US
dc.relation.ispartofseries Physics Public Lecture Series
dc.subject SI en_US
dc.subject Metric system en_US
dc.subject Planck constant en_US
dc.subject Kilogram redefinition en_US
dc.title How the Planck Constant is Better than a Kilogram Artifact, or How the History of Measuring Physics Constants Will Lead to a “New” International System of Metric Units en_US
dc.type Moving Image
dc.type.genre Lecture
dspace.entity.type Publication
local.contributor.corporatename College of Sciences
local.contributor.corporatename School of Physics
local.relation.ispartofseries School of Physics Public Lecture Series
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