How To Measure Planck’s Constant Using Lego

Watt balance

Planck’s constant is one of the most important numbers in science. It describes the relationship between the energy and frequency of an electromagnetic wave in an equation known as the Planck-Einstein relation: E = hv (where E is energy, v is frequency and h is Planck’s constant).

This constant is set to become even more important because physicists are about to change the definition of mass so that it depends on Planck’s constant rather than on the mass of a lump of metal in a vault in Paris.

So it’s not surprising that physicists need various ways to measure mass based on Planck’s constant or, conversely, finding a value of Planck’s constant based on a known mass. Today, Leon Chao at the National Institute of Standards and Technology in in Gaithersburg, Maryland, and a few pals, explain how to do this using an experiment built out of Lego. Continue reading How To Measure Planck’s Constant Using Lego

Can GPS find variations in Planck’s constant?

Read more: physicsworld.com/cws/article/news/49135

Artist's impression of a GPS satellite (Courtesy: NASA).

Global Positioning System Test of the Local Position Invariance of Planck’s Constant
J. Kentosh and M. Mohageg
Phys. Rev. Lett. 108, 110801 (2012)
Published March 15, 2012

Pinpointing Planck’s Constant with GPS
GPS is helping drivers find their way and parents track their kids and pets. But now a pair of researchers—reporting in Physical Review Letters—has used the same technology to put new limits on variations in Planck’s constant.

Certain theories allow physical constants, such as the speed of light or the gravitational constant, to vary, and some astronomical observations have been interpreted as suggesting the electromagnetic coupling was different in the past. Testing these hypotheses often requires sophisticated instruments. But James Kentosh and Makan Mohageg of California State University, Northridge, have found a way to use the ubiquitous global positioning system, or GPS, to evaluate the constancy of Planck’s constant, h.

GPS relies on atomic clocks, which are sensitive to Planck’s constant through their ticking frequency, f=E/h, where E is the energy of a specific atomic transition. For a clock orbiting in one of the 32 GPS satellites, this frequency can shift with respect to ground-based clocks because of well-known relativistic effects. The GPS system keeps track of this frequency drift and broadcasts a clock correction with its signal.

Kentosh and Mohageg looked through a year’s worth of GPS data and found that the corrections depended in an unexpected way on a satellite’s distance above the Earth. This small discrepancy could be due to atmospheric effects or random errors, but it could also arise from a position-dependent Planck’s constant. Assuming the latter, the authors derive an upper limit on Planck variation. –

Michael Schirber – physics.aps.org/synopsis

Quantum Theory without Planck’s Constant

Excerpt from the minutes of Society for Physics and Mathematics
(Lund, Sweden) of November 5th 1888, showing Rydberg’s formula. From Lund
University Physics

John P. Ralston
Planck’s constant was introduced as a fundamental scale in the early history of quantum mechanics. We find a modern approach where Planck’s constant is absent: it is unobservable except as a constant of human convention. Despite long reference to experiment, review shows that Planck’s constant cannot be obtained from the data of Ryberg, Davisson and Germer, Compton, or that used by Planck himself. In the new approach Planck’s constant is tied to macroscopic conventions of Newtonian origin, which are dispensable. The precision of other fundamental constants is substantially improved by eliminating Planck’s constant. The electron mass is determined about 67 times more precisely, and the unit of electric charge determined 139 times more precisely. Improvement in the experimental value of the fine structure constant allows new types of experiment to be compared towards finding “new physics.” The long-standing goal of eliminating reliance on the artifact known as the International Prototype Kilogram can be accomplished to assist progress in fundamental physics……
Read more: arxiv.org/pdf