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arXiv2015

Early Telescopes and Ancient Scientific Instruments in the Paintings of Jan Brueghel the Elder

Ancient instruments of high interest for research on the origin and diffusion of early scientific devices in the late XVI - early XVII centuries are reproduced in three paintings by Jan Brueghel the Elder. We investigated the nature and the origin of these instruments, in particular the spyglass depicted in a painting dated 1609-1612 that represents the most ancient reproduction of an early spyglass, and the two sophisticated spyglasses with draw tubes that are reproduced in two paintings, dated 1617-1618. We suggest that these two instruments may represent early examples of keplerian telescopes. Concerning the other scientific instruments, namely an astrolabe, an armillary sphere, a nocturnal, a proportional compass, surveying instruments, a Mordente's compass, a theodolite, etc., we point out that most of them may be associated with Michiel Coignet, cosmographer and instrument maker at the Court of the Archduke Albert VII of Hapsburg in Brussels.

astro-ph.IM↗

arXiv2015

Centennial of General Relativity (1915-2015); The Schwarzschild Solution and Black Holes

This year marks the 100th anniversary of Einstein's General Theory of Relativity (1915-2015). The first nontrivial solution of the Einstein field equations was derived by Karl Schwarzschild in 1916. This Note will focus mainly on the Schwarzschild solution and the remarkable developments which it inspired, the most dramatic being the prediction of black holes. Later extensions of Schwarzschild's spacetime structure has led to even wilder conjectures, such as white holes and passages to other universes. Penrose diagrams are introduced as compact representations of extended spacetime structures. Stephen Hawking's derivations of quantum effects in black holes might provide clues to an eventual "Theory of Everything" encompassing both general relativity and quantum mechanics.

physics.pop-ph↗

arXiv2015

Symmetries and the fundamental forces of Nature II

Lecture script of a one-semester course that aims to develop an understanding and appreciation of fundemental concepts in modern physics for students who are comfortable with calculus. This document contains the last part of the course where we introduce the concept of the quantum unit to describe the dynamic properties of subatomic particles and the interactions of matter and radiation.

physics.pop-ph↗

arXiv2015

Optimal Strategy in Basketball

This book chapter reviews some of the major principles associated with optimal strategy in basketball. In particular, we consider the principles of allocative efficiency (optimal allocation of shots between offensive options), dynamic efficiency (optimal shot selection in the face of pressure from the shot clock), and the risk/reward tradeoff (strategic manipulation of outcome variance). For each principle, we provide a simple example of a strategic problem and show how it can be described analytically. We then review general analytical results and provide an overview of existing statistical studies. A number of open challenges in basketball analysis are highlighted.

physics.soc-ph↗

arXiv2016

Depletion Gilding: An Ancient Method for Surface Enrichment of Gold Alloys

Ancient objects made of noble metal alloys, that is, gold with copper and/or silver, can show the phenomenon of surface enrichment. This phenomenon is regarding the composition of the surface, which has a percentage of gold higher than that of the bulk. This enrichment is obtained by a depletion of the other elements of the alloy, which are, in some manner, removed. This depletion gilding process was used by pre-Columbian populations for their 'tumbaga', a gold-copper alloy, to give it the luster of gold.

physics.pop-ph↗

arXiv2016

A novel flexible and modular energy storage system for near future Energy Banks

We considered a novel energy storage system based on the compression of air through pumped water. Differently from CAES on trial, the proposed indirect compression leaves the opportunity to choose the kind of compression from adiabatic to isothermal. The energy storage process could be both fast or slow leading to different configuration and applications. These novel storage system are modular and could be applied in different scales for different locations and applications, being very flexible in charge and discharge process. The system may offer an ideal energy buffer for wind and solar storage with no (or negligible) environment hazard. The main features of this novel energy storage system will be showed together with overall energy and power data.

physics.flu-dyn↗

arXiv2016

NEUTRINOS: Mysterious Particles with Fascinating Features, which led to the Physics Nobel Prize 2015

The most abundant particles in the Universe are photons and neutrinos. Both types of particles are whirling around everywhere, since the early Universe. Hence the neutrinos are all around us, and permanently pass through our planet and our bodies, but we do not notice: they are extremely elusive. They were suggested as a theoretical hypothesis in 1930, and discovered experimentally in 1956. Ever since their properties keep on surprising us; for instance, they are key players in the violation of parity symmetry. In the Standard Model of particle physics they appear in three types, known as "flavors", and since 1998/9 we know that they keep on transmuting among these flavors. This "neutrino oscillation" implies that they are massive, contrary to the previous picture, with far-reaching consequences. This discovery was awarded the Physics Nobel Prize 2015.

physics.pop-ph↗

arXiv2016

Econo- and socio- physics based remarks on the economical growth of the World

It has been shown that the long term evolution of the Gross Product of the World after World War II can be well portrayed by the exponential function with the crossover at the year 1973, cinsiding with the Oil Crisis onset. For the the Standard and Poor 500 index the single exponential behavior extends down to at least the mid of the nineteen century. It is notable that the detailed short-term insight focused on the last quarter of century revealed the emergence of the power like dependence. However, such dependences can be introduced only when taking into account the behavior at reference-baselines years. The possible relationship to the growth/death evolution of microorganisms is also discussed. The report proposes the new discussion of the past and nowadays time of the global economy. It recalls econonophysics and sociophysics as disciplines within which the effective parameterization of trends is possible. Finally, possible future trends are discussed.

q-fin.GN↗

arXiv2016

Much ado about Zero

A brief historical introduction for the enigmatic number Zero is given. The discussions are for popular consumption.

math.HO↗

arXiv2016

Les composantes obscures de l'Univers

This article is the detailed version of a paper on dark matter, dark energy, and modified gravity, published in the December 2015-January 2016 special issue of "La Recherche" (in French)

physics.pop-ph↗

arXiv2019

Scaling for speed on the water

Dimensional analysis combined with limited experimental data for the performance of fully submerged propellers have been available since the 1950s. I present two new scale-free hydrodynamic predictions for the relative performance of both submerged and surface-piercing propellers. Larger p/D (pitch to diameter ratio) are more favorable for peak peopeller efficiency and higher speeds; lower p/D are more favorable for carrying loads at low speeds. This conflicts with the common advice to swing as large a diameter as slowly as possible but diameter D has dimensions while p/D is dimensionless, and useful hydrodynamic recommendations must be given in terms of dimensionless variables. For the surface piercing case I compare my scaling predictions with empirical data using a single case in each class as a baseline. One scaling law allows propeller diameter to be predicted from an established baseline where shaft hp and shaft RPM are the variables. The second prediction is inferred from Froude nr. scaling and allows boat speed to be predicted based on shaft horsepower (shp) and weight, given a known baseline in the same class of drag coefficient. I also discuss the existing available data on surface piercing propellers and compare the data with both typical competition data and speed records. In the context of the p/D ratio I discuss the limits on both too high and too low gear ratios. I state for the first time a basic requirement for setting the leading edge camber of surface piercing propellers for optimal acceleration and top speed. I end by using the basic hydrodynamic ideas of circulation conservation and vortex stretching to provide a qualitative picture via the tip vortices of the physics of blade ventilation in surface piercing.

physics.pop-ph↗

arXiv2016

Uchi Mata family analysis for Coaches and Teachers

In this paper it is performed the biomechanical analysis of Uchi Mata family, the unifying vision of biomechanics let coaches and teachers to approach competition and lessons in different way. Uchi Mata and all throws that are in the biomechanical group of Couple applied by trunk - leg showed that these most effective techniques in high level competition, are in fact also energetically less expensive than those of the Lever group. The overview of the sportive judo books that show the different kind of Uchi Mata, for example, are in term of Biomechanics always the same movement. The Japanese different vision informed also the studies among the world that never analyzed the unifying vision. The complementary tools to increase the effectiveness are also analyzed and few New or Chaotic application of trunk-leg family. The Physical and biomechanical background is analyzed showing that these throws are also bio-mechanically simpler, relying only on closing the distance and apply Couple . GAI plus Couple. Their intrinsic simplicity, however, hides a different complexity from those of the Lever which, remember, they need a high motor coordination to be effective. In fact, being able to apply these techniques of Couple require a particular timing ability.

physics.pop-ph↗

arXiv2016

Variations on chaos in physics: from unpredictability to universal laws

The tremendous popular success of Chaos Theory shares some common points with the not less fortunate Relativity: they both rely on a misunderstanding. Indeed, ironically , the scientific meaning of these terms for mathematicians and physicists is quite opposite to the one most people have in mind and are attracted by. One may suspect that part of the psychological roots of this seductive appeal relies in the fact that with these ambiguous names, together with some superficial clich{é}s or slogans immediately related to them ("the butterfly effect" or "everything is relative"), some have the more or less secret hope to find matter that would undermine two pillars of science, namely its ability to predict and to bring out a universal objectivity. Here I propose to focus on Chaos Theory and illustrate on several examples how, very much like Relativity, it strengthens the position it seems to contend with at first sight: the failure of predictability can be overcome and leads to precise, stable and even more universal predictions.

physics.pop-ph↗

arXiv2016

Quantum Go

We introduce a new board game based on the ancient Chinese game of Go (Weiqi, Igo, Baduk). The key difference from the original game is that players no longer alternatively play single stones on the board but instead they take turns placing pairs of entangled go stones. A phenomenon of quantum-like collapse occurs when one of the stones in an entangled pair is directly in contact with at least one other stone. The player to whom the entangled pair belongs must then remove one of the stones in the pair from the board. The aim of the game is still to surround more territory than the opponent and as the number of stones increases, all the entangled pairs of stones eventually reduce to single stones. Quantum Go provides an interesting and tangible illustration of quantum concepts such as superposition, entanglement and collapse.

quant-ph↗

arXiv2017

General Relativity for Pedestrians -- First 6 lectures

The 2017 Nobel Prize in physics awarded to Rainer Weiss, Barry C. Barish and Kip S. Thorne has generated unprecedented interest in gravitational waves (GWs). These notes are based on my lectures on various occasions - in the University of Delhi as well as in different GW schools held in India following the exciting direct detection of GWs. I discuss GW flux and luminosity while pointing out a curious aspect associated with the latter - physical dimensions of $c^5/G$ as well as third time derivative of mass quadrupole moment are that of luminosity. Formation of primordial black holes in the early universe and progenitors of fast radio bursts could have generated GW luminosity comparable to the Planck luminosity, $c^5/G$. I also address the issue of black hole thermodynamics in connection with the GW150914 event, demonstrating that this event is consistent with Hawking's black hole area theorem. In the last section, as an illustrative exercise, I estimate the GW amplitude expected from the fast moving plasma bullets that have been shot out from the vicinity of the carbon star V Hydrae, as reported recently by Sahai et al. (2016).

physics.pop-ph↗

arXiv2016

Optimizing spectral distribution character of the LEDs to decrease discoloring of the collections in museum

For white LEDs used for lighting museums, it is possible to reduce their effects on the discoloration of exhibits to a great extent by regulating their spectral distribution so that less lights with 420~470 nm of wavelength which acts on increasing the span of preservation of exhibits, such as pictures, color paper and color cloth. For same illumination of radiation of 5000 lx of white LEDs with different color temperature of about 3000, 3200, 4200 and 6500 K, the density of radiation energy of 420 nm was 34.2, 71.8, 83.1 and 268.3 μW/cm2, respectively. The discoloration experiment shows that the effects of discoloration of cold white LEDs was much greater than those of warm white LEDs.

physics.pop-ph↗

arXiv2016

A Probabilistic Analysis of the Fermi Paradox

The fermi paradox uses an appeal to the mediocrity principle to make it seem counter-intuitive that humanity has not been contacted by extraterrestrial intelligence. A numerical, statistical analysis was conducted to determine whether this apparent loneliness is, in fact, unexpected. An inequality was derived to relate the frequency of life arising and developing technology on a suitable planet in the galaxy, the average length of time since the first broadcast of such a civilization, and a constant term. An analysis of the sphere reached thus far by human communication was also conducted, considering our local neighborhood and planets of particular interest. We clearly show that human communication has not reached a number of stars and planets adequate to expect an answer. These analyses both conclude that the Fermi paradox is not, in fact, unexpected. By the mediocrity principle and numerical modeling, it is actually unlikely that the Earth would have been reached by extraterrestrial communication at this point. We predict that under 1 percent of the galaxy has been reached at all thus far, and we do not anticipate to be reached until approximately half of the stars/planets have been reached. We offer a prediction that we should not expect this until at least 1,500 years in the future. Thus the Fermi paradox is not a shocking observation, and humanity may very well be contacted within our species' lifespan.

physics.pop-ph↗

arXiv2016

Why is there no von Neumann probe on Ceres? Error catastrophe can explain the Fermi-Hart Paradox

It has been argued that self-replicating robotic probes could spread to all stars of our galaxy within a timespan that is tiny on cosmological scales, even if they travel well below the speed of light. The apparent absence of such von Neumann probes in our own solar system then needs an explanation that holds for all possible extraterrestrial civilisations. Here I propose such a solution, which is based on a runaway error propagation that can occur in any self-replicating system with finite accuracy of its components. Under universally applicable assumptions (finite resources and finite lifespans) it follows that an optimal probe design always leads to an error catastrophe and breakdown of the probes. Thus, there might be many advanced civilizations in our galaxy, each surrounded by their own small sphere of self-replicating probes. But unless our own solar system has the extraordinary luck to be close enough to one of these civilizations, none of these probes will ever reach us.

physics.pop-ph↗