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Banjo Ring from Stretching String: A Zero Break Angle Demo

A novel bridge and tailpiece design allows direct comparison of the sound of zero break angle with same banjo (and all its parts) configured to have an angle of 13 degrees. This lends additional support to the 2014 proposal that a key element in banjo sound is the frequency modulation produced by string stretching due to a floating bridge, break angle, and head with substantial motion. When playing a banjo tune in the 0 degree configuration, there are enough audio clues that it still sounds like a banjo. The comparison allows you to judge for yourself to what extent it's lost its ring or sparkle.

physics.pop-ph↗

Searching for Technosignatures: Implications of Detection and Non-Detection

The search for technosignatures from the Galaxy or the nearby universe raises two main questions: What are the possible characteristics of technosignatures? and How can future searches be optimized to enhance the probability of detection? Addressing these questions requires an interdisciplinary approach, combining i) the study of Anthropocene as a planetary transition and thus a possible proxy also for other planets, ii) the active search for technosignatures in the radio/optical and infrared range, and iii) the statistical modelling of technosignatures and Bayesian inference methods to learn from both detection and non-detection. This strategy (combining modelling and observations) offers the best scientific opportunity in the next decade to discover the possible existence of technological civilizations beyond Earth.

astro-ph.EP↗

A Brief history of mangnetism

In this article an overview of the historical development of the key ideas in the field of magnetism is presented. The presentation is semi-technical in nature.Starting by noting down important contribution of Greeks, William Gilbert, Coulomb, Poisson, Oersted, Ampere, Faraday, Maxwell, and Pierre Curie, we review early 20th century investigations by Paul Langevin and Pierre Weiss. The Langevin theory of paramagnetism and the Weiss theory of ferromagnetism were partly successful and real understanding of magnetism came with the advent of quantum mechanics. Van Vleck was the pioneer in applying quantum mechanics to the problem of magnetism and we discuss his main contributions: (1) his detailed quantum statistical mechanical study of magnetism of real gases; (2) his pointing out the importance of the crystal fields or ligand fields in the magnetic behavior of iron group salts (the ligand field theory); and (3) his many contributions to the elucidation of exchange interactions in d electron metals. Next, the pioneering contributions (but lesser known) of Dorfman are discussed. Then, in chronological order, the key contributions of Pauli, Heisenberg, and Landau are presented. Finally, we discuss a modern topic of quantum spin liquids.

physics.pop-ph↗

Looking for Lurkers

A recently discovered group of nearby co-orbital objects is an attractive location for extraterrestrial intelligence (ETI) to locate a probe to observe Earth while not being easily seen. These near-Earth objects provide an ideal way to watch our world from a secure natural object. That provides resources an ETI might need: materials, a firm anchor, concealment. These have been little studied by astronomy and not at all by SETI or planetary radar observations. I describe these objects found thus far and propose both passive and active observations of them as possible sites for ET probes.

astro-ph.IM↗

The Roman Colonia Marciana Ulpia Traiana Thamugadi (Timgad) and Trajan's Birthday

It is told that the Roman Colonia Marciana Ulpia Traiana Thamugadi, that is Timgad in Algeria, had been oriented to the sunrise on the day of Trajan's birthday, that is 18 September 100 AD. Here we use software CalSKY to investigate the sunrise azimuth and compare it to the direction of the decumanus of the Roman town.

physics.pop-ph↗

Solving the Fermi paradox without assumptions

This paper suggests that a universal solution to the Fermi paradox exists and can be derived directly from the definition of life and/or intelligence, therefore eliminating the need for any questionable assumptions and even for the anthropic principle. The proposed solution puts an upper limit on the growth of civilizations that is independent of resource availability or biological factors.

physics.pop-ph↗

The Long Night: Modeling the Climate of Westeros

Many previous authors have attempted to find explanations for Westeros's climate, characterized by a generally moderate, Earth-like climate punctuated by extremely long and cold winters, separated by thousands of years. One explanation that has been proposed is that the planet orbits in a Sitnikov configuration, where two equal-mass stars (or a star and a black hole) orbit each other on slightly eccentric orbits, and the planet moves along a line through the barycenter perpendicular to the primaries' orbital plane (Freistetter & Grützbauch 2018). We modify an intermediate-complexity GCM to include the effects of such an orbit and integrate it for thousands of years to determine whether such an orbit can a) be habitable and b) explain the climatic variations observed by the inhabitants of Westeros, in both double-star and star-black hole configurations. While configurations with low primary eccentricity and initial conditions that permit only small excursions from the ecliptic plane are habitable, these orbits are too stable to explain Westerosi climate. We find that while orbits with more bounded chaos are able to produce rare anomalously long and cold winters similar to Westeros's Long Night, huge variations in incident stellar flux on normal orbital timescales should render these planets uninhabitable. We note that the presence of an orbital megastructure, either around the planet or the barycenter, could block some of the sunlight during crossings of the primaries' orbital plane and preserve Westeros's habitability. While we find that bounded chaotic Sitnikov orbits are a viable explanation for Westeros's Long Night, we propose that chaotic variations of the planet's axial tilt or semimajor axis, potentially due to torques from nearby planets or stars, may be a more realistic explanation than Sitnikov orbits.

physics.pop-ph↗

Worlds in Migration

In this paper we discuss an alternative track for migration that can explain the existence of Hot Jupiters observed in close orbits around their stars based on a novel interpretation of established work. We also discuss the population of sub-Earth rogue planets that would be created via this migration method, which would be on the order of 2 to 40 billion, many of which would still be present in the Galaxy and potentially detectable.

physics.pop-ph↗

Forecasting Future Murders of Mr. Boddy by Numerical Weather Prediction

Despite a previous description of his state as a stable fixed point, just past midnight this morning Mr. Boddy was murdered again. In fact, over 70 years Mr. Boddy has been reported murdered $10^6$ times, while there exist no documented attempts at intervention. Using variational data assimilation, we train a model of Mr. Boddy's dynamics on the time series of observed murders, to forecast future murders. The parameters to be estimated include instrument, location, and murderer. We find that a successful estimation requires three additional elements. First, to minimize the effects of selection bias, generous ranges are placed on parameter searches, permitting values such as the Cliff, the Poisoned Apple, and the Wife. Second, motive, which was not considered relevant to previous murders, is added as a parameter. Third, Mr. Boddy's little-known asthmatic condition is considered as an alternative cause of death. Following this morning's event, the next local murder is forecast for 17:19:03 EDT this afternoon, with a standard deviation of seven hours, at The Kitchen at 4330 Katonah Avenue, Bronx, NY, 10470, with either the Lead Pipe or the Lead Bust of Washington Irving. The motive is: Case of Mistaken Identity, and there was no convergence upon a murderer. Testing of the procedure's predictive power will involve catching the D train to 205th Street and a few transfers over to Katonah Avenue, and sitting around waiting with our eyes peeled. We discuss the problem of identifying a global solution - that is, the best reason for murder on a landscape riddled with pretty-decent reasons. We also discuss the procedure's assumption of Gaussian-distributed errors, which will under-predict rare events. This under-representation of highly improbable events may be offset by the fact that the training data, after all, consists of multiple murders of a single person.

physics.pop-ph↗

Human Mars Mission Architecture -- Plan to Settle the Red Planet with 1000 People

Exploration is one of the attentive endeavor to mankind and a strategy for evolution. We have been incessantly reconnoitering our planet and universe from Mesopotamian era to modern era. The progression of rocketry and planetary science in past century engendered a futuristic window to explore Mars which have been a source of inspiration to hundreds of astronomers and scientists. Globally, it invigorated space exploration agencies to make expedition for planetary exploration to Mars and Human Mars Missions. Scientists and engineers have portrayed numerous Human Mars Mission proposals and plans but currently the design reference mission 5.0 of NASA is the only mission under study. Here we propose a mission architecture for permanent Human Mars Settlement with 1000 peoples with multiple launch of sufficient cargoes and scientific instruments

physics.pop-ph↗

Introduction to Regge Calculus for Gravitation

With the theory of general relativity, Einstein abolished the interpretation of gravitation as a force and associated it to the curvature of spacetime. Tensorial calculus and differential geometry are the mathematical resources necessary to study the spacetime manifold in the context of Einstein's theory. In 1961, Tullio Regge published a work on which he uses the old idea of triangulation of surfaces aiming the description of curvature, and, therefore, gravitation, through the use of discrete calculus. In this paper, we approach Regge Calculus pedagogically, as well as the main results towards a discretized version of Einstein's theory of gravitation.

gr-qc↗

Does it Swing? Microtiming Deviations and Swing Feeling in Jazz

Jazz music that swings has the fascinating power to elicit a pleasant sensation of flow in listeners and the desire to synchronize body movements with the music. Whether microtiming deviations (MTDs), i.e. small timing deviations below the bar or phrase level, enhance the feeling of swing is highly debated in the current literature. Studies on other groove related genres did not find evidence for a positive impact of MTDs. The present study addresses jazz music and swing in particular, as there is some evidence that microtiming patterns are genre-specific. We recorded twelve piano jazz standards played by a professional pianist and manipulated the natural MTDs of the recordings in systematic ways by quantizing, expanding and inverting them. MTDs were defined with respect to a grid determined by the average swing ratio. The original and manipulated versions were presented in an online survey and evaluated by 160 listeners with various musical skill levels and backgrounds. Across pieces the quantized versions (without MTDs) were rated slightly higher and versions with expanded MTDs were rated lower with regard to swing than the original recordings. Unexpectedly, inversion had no impact on swing ratings except for two pieces. Our results suggest that naturally fluctuating MTDs are not an essential factor for the feeling of swing.

physics.pop-ph↗

Ensuring Uninterrupted Power Supply to Lunar Installations Through an Organic Rankine Cycle

We propose using the temperature gradients between the Moon's surface and the soil at a certain depth to power an Organic Rankine Cycle that could supply a permanent installation, particularly at night, when solar power is not available. Our theoretical and engineering considerations show that, with existing working fluids and quite feasible technical requirements, it is possible to continuously yield $25\,{\rm kW}$ to sustain a 3 member crew.

astro-ph.IM↗

Oumuamua and Scout ET Probes

Numerous advantages may accrue to ET from the use of probes for the conveyance of information relative to the alternative of beaming information electromagnetically from its home star system. However, probes would benefit from a trans-galactic communications network to transmit information back to their progenitor civilization(s) and throughout the Galaxy. A model for such trans-galactic communications has previously been proposed, comprised of probes linked together by relay nodes. The current paper refines that model, specifying two types of probes or nodes, both part of a communications lattice. The first type of cellular probe (CP) is statically associated with individual stars, and the second type is a scout CP that traverses the galaxy surveying successive star systems rather than permanently residing within any one of them. CPs would communicate with adjacent CPs and, ultimately, through the network of CPs, with their progenitor civilization(s). The question of whether Oumuamua is such a flyby scout CP is considered. Search strategies for CPs are suggested.

physics.pop-ph↗

Physics of rowing oars

In each rowing sport, the oars have their very own characteristics most of the time selected through a long time experience. Here we address experimentally and theoretically the problem of rowing efficiency as function of row lengths and blades sizes. In contrast with previous studies which consider imposed kinematics, we set an imposed force framework which is closer to human constraints. We find that optimal row lengths and blades sizes depend on sports and athletes strength, and provide an optimisation scheme.

physics.pop-ph↗

Construction of a Model of the Solar System with Temperature Control for Visually Impaired Students

In this work, we present a study carried out to develop a didactic kit based on the use of touch and thermal receivers for the teaching of Astronomy. The proposal arose in the face of the difficulties encountered in the search for experiments capable of presenting the best concepts involved in the teaching of Astronomy for visually impaired people. The equipment consists of the use of a model with hemispheres with Peltier pellets for simulation of temperature scale of planets of the Solar System. The research was based on the use of accessible and low-cost materials. All the materials used and the assembly of the equipment are described in this work, since the design until the application of the final product for students. This experiment was part of a set of pedagogical equipment presented at a scientific exhibition for the visually impaired during the 15 a National Science and Technology Week in the city of Juazeiro do Norte in the State of Ceará.

physics.ed-ph↗

Science Communication a New Frontier of Researcher's Job

In the world of communication, nobody can be out of the fray! Since many years science communication and more in general the ability of a researcher to communicate his/her work to founding agency, policy makers, entrepreneurs and public at large, starts to be a fundamental skill of the researchers job. This skill is needed and requested to access funds and successfully disseminate the research outcome, as well as to engage society in understanding science and its benefits. Moreover, due to the large decrease of research funds and of people starting scientific carrier, researchers must be in the front line to promote the scientific culture in order to invert the dreadful trend of last years. Where are we and where are we going to? We try to answer such questions introducing successful models that can be used without huge overloads for our job. This paper reports on the experience of one of the largest and oldest project in Europe of the Marie Sklodowska-Curie Actions European Researchers' Night and describes how this project followed the evolution in science communication.

physics.pop-ph↗

Measuring Mountains on the Moon

Following a technique of Galileo we compute the height on a mountain on the Moon. It is based on a simple observation that precisely on a half Moon day, the Earth, the Moon, and the Sun form the vertices of a right triangle with the Moon at the 90 degree vertex.

physics.pop-ph↗