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At least 523 records · Page 29Linked to original sources

arXiv2019

Analysis of the Indian ASAT test on 27 March 2019

On March 27, 2019, India tested its first anti-satellite (ASAT) missile against its own "live" satellite, Microsat-R, launched on 24 January, 2019, as part of "Mission Shakti". The test parameters were chosen with extreme caution to minimize the hazard of post-impact debris predicted to re-enter the earth`s atmosphere within 45 days. Of the 400 pieces of debris identified by NASA, more than 60 were large enough to be tracked by the US Air Force`s Space Surveillance Network and US Strategic Command`s Combined Space Operations Center. Much of the information provided in the press about the ASAT missile and Microsat-R was inaccurate or misleading and did not appear to be based on scientific analysis of the data available to the public. To better understand the circumstances of this event, this paper will calculated and present detailed analysis of the tracked post-impact orbit debris from Microsat-R. All results in the current paper are based on orbital data, in the form of the NORAD two-line element (TLE) dataset from space-track.org and the own calculations of the CoLiTec group.

physics.space-ph↗

arXiv2019

The naval battle of Actium and the myth of the ship-holder: the effect of bathymetry

A myth of antiquity is explained with modern science in the context of an ancient naval battle. A legend was invoked by the admiral Pliny the Elder to explain the defeat of Antony and Cleopatra against Octavian at the naval battle of Actium. A fish, called echeneis or remora, is said to have the power to stop ships or to delay their motion by adhering to the hull. Naturalists have since studied how the fish sucking-disk with its typical pattern of parallel striae sticks to its host. Here we show the pattern of the free surface measured in a towing tank in the wake of an ancient galley is similar to the striae pattern of the fish. We have measured the bathymetry at the mouth of the Ambracian Gulf that influenced the physical environment of the battle. The computations demonstrate the increase of wave resistance of a galley as a function of the draft to the water depth ratio in shallow water corresponding to the appearance of a particular wake pattern: the echeneidian free surface pattern.

physics.class-ph↗

arXiv2019

Acoustics of Margravial Opera House Bayreuth

The Margravial Opera House Bayreuth, built between 1745 and 1750, is a well preserved Baroque court theatre designed by Giuseppe Galli Bibiena [1]. It provides an opportunity to experience not only the visual but also the acoustic design of opera theatres in the 18th century, as the bell-shaped auditorium along with the decoratively painted canvas remains intact. Using balloons and hand-claps as sound sources, we characterize the impulse response of this opera house after its recent renovation. The reverberation time (RT), early decay time (EDT) and clarity factor are characterized and discussed in comparison to historical Italian theatres of a similar age.

physics.pop-ph↗

arXiv2019

A quick how-to user-guide to debunking pseudoscientific claims

Have you ever wondered why we have never heard of psychics and palm readers winning millions of dollars in state or local lotteries or becoming Wall Street wolfs? Neither have I. Yet we are constantly bombarded by tabloid news on how vaccines cause autism (hint: they do not), or some unknown firm building a mega-drive that defies the laws of physics (nope, that drive does not work either). And the list continues on and on and on. Sometimes it looks quite legit as, say, various natural vitamin supplements that supposedly increase something that cannot be increased, or enhance something else that is most likely impossible to enhance by simply swallowing a few pills. Or constantly evolving diets that sure work giving a false relieve to those who really need to stop eating too much and actually pay frequent visits to a local gym. It is however understandable that most of us fall for such products and news just because we cannot be experts in everything, and we tend to trust various mass-media sources without even a glimpse of skepticism. So how can we distinguish between baloney statements and real exciting scientific discoveries and breakthroughs? In what follows I will try to do my best to provide a simple how-to user guide to debunking pseudoscientific claims.

physics.pop-ph↗

arXiv2019

Modeling Consonance and its Relationships with Temperament, Harmony, and Electronic Amplification

After briefly revising the concepts of consonance/dissonance, a respective mathematic-computational model is described, based on Helmholtz's consonance theory and also considering the partials intensity. It is then applied to characterize five scale temperaments, as well as some minor and major triads and electronic amplification. In spite of the simplicity of the described model, a surprising agreement is often observed between the obtained consonances/dissonances and the typically observed properties of scales and chords. The representation of temperaments as graphs where links correspond to consonance (or dissonance) is presented and used to compare distinct temperaments, allowing the identification of two main groups of scales. The interesting issue of nonlinearities in electronic music amplification is also addressed while considering quadratic distortions, and it is shown that such nonlinearities can have drastic effect in changing the original patterns of consonance and dissonance.

cs.SD↗

arXiv2019

Bosons, Fermions, Spin, Gravity, and the Spin-Statistics Connection

Satyendra Nath Bose's attempt to describe the quantum statistical aspects of light consistently in terms of particles, and Einstein's generalisation, lead to the concept of Bosons as a class of quanta obeying `Bose-Einstein statistics'. Their identity as a class came in sharp contrast when the Pauli exclusion principle and the Dirac equation revealed the other class called Fermions, obeying `Fermi-Dirac statistics'. Spin, and spin alone, is the determining factor of the multiparticle behaviour of fundamental quanta. This is the basis of the Spin-Statistics Connection. While it is known that the overall theoretical picture is consistent, the physical reason for the connection is unknown. Further, the class difference is sensitive only to the total spin in a quantum aggregate, as spectacularly seen in superconductivity and superfluidity, and in the Bose-Einstein condensation of neutral atomic gas. Can we grasp the true reason behind the difference in the collective behaviour of Bosons and Fermions? An explorer's journey demanding logical and physical consistency of what we already know takes us to the hidden factors in the relation between spin and the statistics of quanta. The surprising answer is in the domain of gravity, that too, on a cosmic scale.

physics.pop-ph↗

arXiv2019

The increasing importance of Ashi Waza, in high level competition. (Their Biomechanics, and small changes in the form)

In this paper we are interested, both: at the description of Biomechanics of the Ashi Waza techniques, with precision of few of them, members of the Japanese, so called, Ko Waza group; and at the biomechanical analysis of the small changes in the applicative form of them. These small changes, from the basic movement defined by Kodokan and show in thousand books, probably born from practical competitive situations. They are today become the usual applicative form, not only present among the various National Federations, but also in Japan itself among Universities dojos and the Kodokan. Among the Ko Waza techniques, we will select for our analysis only the following: Ko Uchi Gari , Ko Soto Gari, Ko Uchi Barai, Ko Soto Barai, Ko Soto Gake , Ko Uchi Gake That are considered by Japanese followers different throwing techniques, as the different names show us. But from the Biomechanical point of view all these Kodokan throws are based on the same physical principle and practically on the same movements.

physics.pop-ph↗

arXiv2019

Pedagogical Materials and Suggestions to Cure Misconceptions Connecting Special and General Relativity

Many professional physicists do not fully understand the implications of the Einstein equivalence principle of general relativity. Consequently, many are unaware of the fact that special relativity is fully capable of handling accelerated reference frames. We present results from our nationwide survey that confirm this is the case. We discuss possible origins of this misconception, then suggest new materials for educators to use while discussing the classic twin paradox example. Afterwards, we review typical introductions to general relativity, clarify the equivalence principle, then suggest additional material to be used when the Einstein equivalence principle is covered in an introductory course. All of our suggestions are straightforward enough to be administered to a sophomore-level modern physics class.

physics.ed-ph↗

arXiv2019

The Scientists' Experience in Participated Science Communication

Since 2006 a small group of researchers from the Italian National Institute for Nuclear Physics started to realized one of the first European Researchers' Night in Europe: a one night-event, supported by the European Commission, that falls every last Friday of September to promote the researcher's figure and its work. Today, after thirteen editions, the project has evolved by involving more than 60 scientific partners and more than 400 events/year spread from the North to the South of Italy in 30 cities, captivating more than 50.000 attendees with a not negligible impact on the people and the press. During the years, the project has followed and sometimes anticipated the science communication trend, and BEES (BE a citizEn Scientist) is the last step of this long and thrilling evolution that brought to a huge public engagement in our territory. The experience, the methodology, and the major successful examples of the organized events are presented together with the results of the long term project impact.

physics.ed-ph↗

arXiv2019

Searching for Extraterrestrial Intelligence by Locating Potential ET Communication Networks in Space

There have been periodic efforts in recent decades to search for extraterrestrial intelligence (SETI), especially by trying to find an extraterrestrial (ET) radio signal or other technosignature in space. Yet, no such technosignatures have been found. Considering the vastness of space, finding such technosignatures has been described as trying to find a needle in a cosmic haystack. To help resolve this, two hypotheses are proposed to aid SETI researchers in narrowing the search for ET technosignatures, based on a network analysis approach to locate where in space potential ET communication networks would most likely be. A potential ET communication network can use exoplanets as communication access points (e.g., placing a communication satellite into planetary orbit, or an antenna on a planetary surface). The approach uses a topology where exoplanets are represented as nodes, and the lines of average distance (generalized communication paths) between adjacent exoplanets are represented as edges; the nodes and edges form local and wide planetary networks. Using the approach and data visualization on exoplanet databases can highlight locations of potential ET communication networks in space. The first hypothesis posits that an ET technosignature would more likely appear in a potentially habitable solar system containing a high concentration of planets, wherein the planets function as communication access points to facilitate a potential ET communication network. The second hypothesis posits that an ET technosignature would more likely appear in a highly concentrated cluster of potentially habitable solar systems. Contributions to the SETI field can be increased accuracy in finding ET technosignatures, increased accuracy in reaching a Schelling point (a mutual realization of how we and an ET intelligence can find each other), and promoting interdisciplinary SETI research.

physics.pop-ph↗

arXiv2019

The Breakthrough Listen Search for Extraterrestrial Intelligence

The discovery of the ubiquity of habitable extrasolar planets, combined with revolutionary advances in instrumentation and observational capabilities, have ushered in a renaissance in the millenia-old quest to answer our most profound question about the Universe and our place within it - Are we alone? The Breakthrough Listen Initiative, announced in July 2015 as a 10-year 100M USD program, is the most comprehensive effort in history to quantify the distribution of advanced, technologically capable life in the universe. In this white paper, we outline the status of the on-going observing campaign with our primary observing facilities, as well as planned activities with these instruments over the next few years. We also list collaborative facilities which will conduct searches for technosignatures in either primary observing mode, or commensally. We highlight some of the novel analysis techniques we are bringing to bear on multi-petabyte data sets, including machine learning tools we are deploying to search for a broader range of technosignatures than was previously possible.

astro-ph.IM↗

arXiv2019

Climate Modeling and Bifurcation

Many papers and monographs were written about the modeling the Earth climate and its variability. However there is still an obvious need for a module that presents the fundamentals of climate modeling to students at the undergraduate level. The present educational paper attempts to fill in this gap. To this end we collect in this paper the relevant climate data and present a simple zero and one dimensional models for the mean temperature of the Earth. These models can exhibit bifurcations from the present Earth climate to an ice age or a "Venus type of climate". The models are accompanied by Matlab programs which enable the user to change the models parameters and explore the impact that these changes might have on their predictions on Earth climate.

physics.pop-ph↗

arXiv2019

Extremophiles: a special or general case in the search for extra-terrestrial life?

Since time immemorial life has been viewed as being fragile, yet over the past few decades it has been found that many extreme environments are inhabited by organisms known as extremophiles.Knowledge of their emergence, adaptability, and limitations seems to provide a guideline for the search of extra-terrestrial life, since some extremophiles presumably can survive in extreme environments such as Mars, Europa, and Enceladus. Due to physicochemical constraints, the first life necessarily came into existence at the lower limit of lifes conceivable complexity.Thus, the first life could not have been an extremophile, furthermore, since biological evolution occurs over time, then the dual knowledge regarding what specific extremophiles are capable of, and to the analogue environment on extreme worlds, will not be sufficient as a search criterion.This is because, even though an extremophile can live in an extreme environment here-and-now, its ancestor however could not live in that very same environment in the past, which means that no contemporary extremophiles exist in that environment.Furthermore, a theoretical framework should be able to predict whether extremophiles can be considered a special or general case in the galaxy.Thus, a question is raised: does Earths continuous inhabitability represent an extreme or average value for planets? Thus, dependent on whether it is difficult or easy for worlds to maintain this inhabitability, the search for extra-terrestrial life with a focus on extremophiles will either represent a search after dying worlds, or a search after special life on living worlds, where one focus too narrowly on extreme values.

physics.bio-ph↗

arXiv2019

An estimation of the Moon radius by counting craters: a generalization of Monte-Carlo calculation of $π$ to spherical geometry

By applying Monte-Carlo method, the Moon radius is obtained by counting craters in a spherical square over the surface of it. As it is well known, approximate values for $π$ can be obtained by counting random numbers in a square and in a quarter of circle inscribed in it in Euclidean geometry. This procedure can be extend it to spherical geometry, where new relations between the areas of a spherical square and the quarter of circle inscribed in it are obtained. When the radius of the sphere is larger than the radius of the quarter of circle, Euclidean geometry is recovered and the ratio of the areas tends to $π$. Using these results, theoretical deviations of $π$ due to the Moon radius $R$ are computed. In order to obtain this deviation, a spherical square is selected located in a great circle of the Moon. The random points over the spherical square are given by a specific zone of the Moon where craters are distributed almost randomly. Computing the ratio of the areas, the deviation of $π$ allows us to obtain the Moon radius with an intrinsic error given by the finite number of random craters.

physics.pop-ph↗

arXiv2019

Upper limit on the fraction of alien civilizations that develop communication technology

We re-examine the likelihood for alien civilizations to develop communication technology on the basis of the general assumption that life elsewhere could have a non-carbon chemical foundation. We particularized the discussion to a complex silicon-based biochemistry in a nitrogen solvent, and elaborate on the environment in which such a chemistry is feasible, and if so, on what scales. More concretely, we determine the region outside the habitable zone where such organisms can grow and flourish and after that we study how our findings impact the recently derived upper limit on the fraction of living intelligent species that develop communication technology $\langle ξ_{\rm biotec} \rangle$. We also compare this new restriction on $\langle ξ_{\rm biotec} \rangle$ with that resulting from the extension of the habitable zone to accommodate subsurface exolife, originating in planets with subsurface (water) oceans.

physics.pop-ph↗

arXiv2019

Control of habitat's carbon dioxide level by biomass burning

Consider a free-space settlement with a closed ecosystem. Controlling the habitat's carbon dioxide level is a nontrivial problem because the atmospheric carbon buffer per biosphere area is smaller than on Earth. Here we show that the problem can be solved by burning agricultural waste. Waste biomass is stored and dried, and burned whenever plant growth has lowered the atmospheric carbon dioxide level so that replenishment is needed. The method is robust, low-tech and scalable. The method also leaves the partial pressure of oxygen unchanged. In the initial growth phase of the biosphere, one can obtain the carbon dioxide by burning sugar or carbon, which can be sourced from carbonaceous asteroid materials. This makes it possible to bootstrap the biosphere without massive biomass imports from Earth.

physics.pop-ph↗

arXiv2019

Detection of symmetry using a crystallographic image processing algorithm

This article presents an automated method to quantify and detect symmetry elements in 2D patterns by means of image processing. Escher's woodcuts, a widely recognized didactic tool for crystallographic education of students, were used to demonstrate this approach. We also discuss peculiarities in the detection of black and white symmetry, color symmetry, and detection of the "hidden" and "broken" symmetry elements by means of the phase origin map approach.

physics.pop-ph↗

arXiv2019

The Sounds of Music : Science of Musical Scales I -- Human Perception of Sound

Both, human appreciation of music and musical genres, transcend time and space. The universality of musical genres and associated musical scales is intimately linked to the physics of sound and the special characteristics of human acoustic sensitivity. In this series of articles, we examine the science underlying the development of the heptatonic scale, one of the most prevalent scales of the modern musical genres, both western and Indian.

physics.pop-ph↗