Gravitational waves without general relativity

strainRobert C. Hilborn
This tutorial leads the reader through the details of calculating the properties of gravitational waves from orbiting binaries, such as two orbiting black holes. Using analogies with electromagnetic radiation, the tutorial presents a calculation that produces the same dependence on the masses of the orbiting objects, the orbital frequency, and the mass separation as does the linear version of General Relativity (GR). However, the calculation yields polarization, angular distributions, and overall power results that differ from those of GR. Nevertheless, the calculation produces waveforms that are very similar to the pre-binary-merger portions of the signals observed by the Laser Interferometer Gravitational-Wave Observatory (LIGO-VIRGO) collaboration. The tutorial should be easily understandable by students who have taken a standard upper-level undergraduate course in electromagnetism.

Read more at https://arxiv.org/ftp/arxiv/papers/1710/1710.04635.pdf

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A brief history of physics education in the United States

HS physicsIn order to provide insight into current physics teaching practices and recommended reforms, we outline the history of physics education in the United States—and the accompanying pedagogical issues and debates—over the period 1860–2014. We identify key events, personalities, and issues for each of ten separate time periods, comparing and contrasting the outlooks and viewpoints of the different eras.

This discussion should help physics educators to (1) become aware of previous research in physics education and of the major efforts to transform physics instruction that have taken place in the U.S., (2) place the national reform movements of today, as well as current physics education research, in the context of past efforts, and (3) evaluate the effectiveness of various education transformation efforts of the past, so as better to determine what reform methods might have the greatest chances of success in the future…
… Read more at physicseducation.net

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