Upper limit on the Stiffness of space-time

stiffnessAdrian Melissinos
From the recently observed propagation of gravitational waves through space-time an upper limit can be deduced for the stiffness of space-time through which the gravitational wave propagates. The upper limit is extremely weak, implying that the stiffness of space-time is at least 14 orders of magnitude weaker than that of jello.


Physics Needs Philosophy. Philosophy Needs Physics

Carlo Rovelli
Contrary to claims about the irrelevance of philosophy for science, I argue that philosophy has had, and still has, far more influence on physics than is commonly assumed. I maintain that the current anti-philosophical ideology has had damaging effects on the fertility of science. I also suggest that recent important empirical results, such as the detection of the Higgs particle and gravitational waves, and the failure to detect supersymmetry where many expected to find it, question the validity of certain philosophical assumptions common among theoretical physicists, inviting us to engage in a clearer philosophical reflection on scientific method.

Investigation of Skyscraper’s Feat

(original version with an addendum)

Costas Efthimiou
Skyscraper is a Hollywood action film directed and written by Rawson M. Thurber scheduled to be released on July 13, 2018. We present an exhaustive analysis of the feat shown in the recently released teaser poster and trailer of the film. Although the feat appears to be unrealistic at first glance, after close investigation using back-of-the-envelope calculations, it is seen to be within human capabilities.
This article is the original version of an abridged article published in Physics Education. It was written very soon after the poster and clip were released by Universal Pictures.


Emergence of Benford’s Law in Classical Music

Azar Khosravani, Constantin Rasinariu

The histograms represents the digit distribution of time
intervals for each piano key played for the 32 piano sonatas by
Beethoven vs. the theoretical (Benford) distribution

We analyzed a large selection of classical musical pieces composed by Bach, Beethoven, Mozart, Schubert and Tchaikovsky, and found a surprising connection with mathematics. For each composer, we extracted the time intervals each note was played in each piece and found that the corresponding data sets are Benford distributed. Remarkably, the logarithmic distribution is not only present for the leading digits, but for all digits.

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.