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arXiv2020

Statistical tools and precision of searching for the Higgs boson at the LHC

Statistical tools have been developed to quantify the agreement between a hypothesis or a model and the observed data for probabilistic phenomena. In this work, we define statistical methods used to measure the properties of the higgs boson in the LHC on the one hand, but also to evaluate the uncertainty and precision on these measurements. They are based on the definition of a likelihood function whose construction will be detailed below. The challenge of HEP is to generate tons of data and to develop powerful analyses to tell if the data indeed contains evidence for the new particle, and confirm it's the expected Higgs boson.

physics.pop-ph↗

arXiv2020

A Changing Dichotomy: The Conception of the "Macroscopic" and "Microscopic" Worlds in the History of Physics

This short essay traces the conceptual history of micro- and macroscopicity in the context of physical science. By focusing on three distinct episodes spanning five centuries, we show the scientific and philosophical meanings of this antonym pair, despite never being far from "the small" and "the large," have been evolving as the frontier of science advances. We analyze the intellectual and material impetus for these movements, and conclude that this conceptual history reflects the changing interaction between the natural world and humankind.

physics.hist-ph↗

arXiv2019

Searching for a standard Drake equation

In the 20th century the scientific search for extraterrestrial intelligence began, and the Drake equation was proposed to estimate the number of extraterrestrial species humanity could attempt to detect, N. This paper discusses the need to update and standardize this equation. A new and more accurate expression is deduced which contains the classic equation as a particular case, and its advantages are discussed. A necessary condition is also stated for its use in scientific contexts: if N is defined as the total number of civilizations like ours then N = 1, given that we exist, and consequently the working hypothesis of the SETI project can be expressed as N>1. In this case, the Drake equation is being applied in a scientific way, because it is trying to test a hypothesis based on evidence.

physics.pop-ph↗

arXiv2019

To beer or not to beer: does tapping beer cans prevent beer loss? A randomised controlled trial

Objective: Preventing or minimising beer loss when opening a can of beer is socially and economically desirable. One theoretically grounded approach is tapping the can prior to opening, although this has never been rigorously evaluated. We aimed to evaluate the effect of tapping a can of beer on beer loss. Methods: Single centre parallel-group randomised controlled trial. 1031 cans of cans of beer of 330mL were randomised into one of four groups before the experiment: unshaken/untapped (n=256), unshaken/tapped (n=251), shaken/untapped (n=249), or shaken/tapped (n=244). The intervention was tapping the can of beer three times on its side with a single finger. We compared tapping versus non-tapping for cans that had been shaken for 2 minutes or were unshaken. Three teams weighed, tapped or did not tap, opened cans, absorbed any beer loss using paper towels, then re-weighed cans. The teams recorded the mass of each can before and after opening with an accuracy of +/-0.01 grams. Main outcome measure: The main outcome measure was beer loss (in grams). This was calculated as the difference in the mass of the beer after the can was opened compared to before the can was opened. Results: For shaken cans, there was no statistically significant difference in the mass of beer lost when tapping compared to not tapping (mean difference of -0.159g beer lost with tapping, 95% CI -0.36 to 0.04). For unshaken cans, there was also no statistically significant difference between tapping and not tapping. Conclusion: These findings suggest that tapping shaken beer cans does not prevent beer loss when the container is opened. Thus, the practice of tapping a beer prior to opening is unsupported. The only apparent remedy to avoid liquid loss is to wait for bubbles to settle before opening the can.

physics.pop-ph↗

arXiv2019

Autonomous Robot Swarms for Off-World Construction and Resource Mining

Kick-starting the space economy requires identification of critical resources that can lower the cost of space transport, sustain logistic bases and communication relay networks between major nodes in the network. One important challenge with this space-economy is ensuring the low-cost transport of raw materials from one gravity-well to another. The escape delta-v of 11.2 km/s from Earth makes this proposition very expensive. Transporting materials from the Moon takes 2.4 km/s and from Mars 5.0 km/s. Based on these factors, the Moon and Mars have the potential to export material into this space economy. Water has been identified as a critical resource both to sustain human-life but also for use in propulsion, attitude-control, power, thermal storage and radiation protection systems.There is also important need for construction materials such as aluminum, iron/steel, and titanium. Based upon these important findings, we have developed an energy model to determine the feasibility of developing a mining base on the Moon and Mars. These mining base mine and principally exports water, aluminum, titanium and steel. Our designs for a mining base utilize renewable energy sources namely photovoltaics and solar-thermal concentrators to provide power to construct the base, keep it operational and export water and other resources using a Mass Driver. Using the energy model developed, we will determine the energy per Earth-day to export 100 tons each of water, titanium, aluminum and low-grade steel into escape velocity of the Moon and Mars. We perform a detailed comparison of the energy required for construction of similar bases on the Moon and Mars, in addition to the operating energy required for regolith excavation, processing, refining and finally transport off-the-body.

cs.RO↗

arXiv2019

Toward a Comprehensive Model of Snow Crystal Growth: 6. Ice Attachment Kinetics near -5 C

I examine a variety of snow crystal growth measurements taken at a temperature of -5 C, as a function of supersaturation, background gas pressure, and crystal morphology. Both plate-like and columnar prismatic forms are observed under different conditions at this temperature, along with a diverse collection of complex dendritic structures. The observations can all be reasonably understood using a single comprehensive physical model for the basal and prism attachment kinetics, together with particle diffusion of water vapor through the surrounding medium and other well-understood physical processes. A critical model feature is structure-dependent attachment kinetics (SDAK), for which the molecular attachment kinetics on a faceted surface depend strongly on the nearby mesoscopic structure of the crystal.

cond-mat.mtrl-sci↗

arXiv2019

Why SETI Will Fail

The union of space telescopes and interstellar spaceships guarantees that if extraterrestrial civilizations were common, someone would have come here long ago.

physics.pop-ph↗

arXiv2019

The colours of Newton's Opticks: an advanced project for excellent students

We describe in detail an advanced project devised for outstanding High School (or undergraduate) students with appropriate abilities in physical reasoning (rather than with a good standard preparation), centered around the well-known historical case of Newton's theory of light and colours. The different action lines along which the project is developed are aimed to let the students involved to: 1) think as Newton did, by building step by step all his knowledge and reasoning; 2) work as Newton did, by performing the whole series of his original experiments with prisms; 3) deduce as Newton did about the nature of light and colours; 4) present the results of their activity (including physics demonstrations) to the general public, in order to test abilities in communicating what learned and discovered (including video realization published on YouTube youtube). Such didactic aim is complemented by the purpose to realize a historically informed activity, given the potential key role of the History of Physics in promoting science at a deeper level, especially when no particular training in mathematics or advanced education is required. The highly favourable reception of the project by the students involved, as well as that deserved by the uneducated people to the activities demonstrated by the students in public events, testify for the success of such work.

physics.ed-ph↗

arXiv2019

Gravitational Waves from merging binaries

We discuss gravitational waves from merging binaries using a Newtonian approach with some inputs from the Post-Newtonian formalism. We show that it is possible to understand the key features of the signal using fundamental physics and also demonstrate that an approximate calculation gives us the correct order of magnitude estimate of the parameters describing the merging binary system. We build on this analysis to understand the range for different types of sources for given detector sensitivity. We also consider known binary pulsar systems and discuss the expected gravitational wave signal from these.

physics.pop-ph↗

arXiv2021

There's No Place Like Home (in Our Own Solar System): Searching for ET Near White Dwarfs

The preponderance of white dwarfs in the Milky Way were formed from the remnants of stars of the same or somewhat higher mass as the Sun, i.e., from G-stars. We know that life can exist around G-stars. Any technologically advanced civilization residing within the habitable zone of a G-star will face grave peril when its star transitions from the main sequence and successively enters sub-giant, red giant, planetary nebula, and white dwarf stages. In fact, if the civilization takes no action it will face certain extinction. The two alternatives to passive extinction are (a) migrate away from the parent star in order to colonize another star system, or (b) find a viable solution within one's own solar system. It is argued in this paper that migration of an entire biological population or even a small part of a population is virtually impossible, but in any event, far more difficult than remaining in one's home solar system where the problem of continued survival can best be solved. This leads to the conclusion that sub-giants, red giants, planetary nebula, and white dwarfs are the best possible candidate targets for SETI observations. Search strategies are suggested.

physics.pop-ph↗

arXiv2019

From Solar Eclipse of 1919 to the Spectacle of Gravitational Lensing

A century after observing the deflection of light emitted by distant stars during the solar eclipse of 1919, it is interesting to know the concepts emerged from the experiment and the theoretical and observational consequences for modern cosmology and astrophysics. In addition to confirming Einstein's gravitational theory, its greatest legacy was the construction of a new research area to cosmos science dubbed gravitational lensing. The formation and magnification of multiple images (mirages) by the gravitational field of a compact or extended lens are among the most striking phenomena of nature. This article presents a pedagogical view of the first genuine gravitational lens effect, the double quasar QSO 0957 + 561. We also describe the formation of rings, giant arcs, arclets and multiple Supernova images. It is also surprising that the Hubble constant and the amount of dark matter in the Universe can be measured by the same technique. Finally, the lensing of gravitational waves, a possible but still not yet detected effect, is also briefly discussed.

physics.pop-ph↗

arXiv2020

Beyond Boltzmann: The Potential Energy Distribution of Objects in the Atmosphere

Estimates of the number and potential energy of molecules, aerosols, cloud droplets, insects, birds, planes and satellites in the atmosphere yield a distribution which is for potential energies below 10^2 kBT described by the Boltzmann distribution, but for the range from 10^2 kBT to 10^33 kBT by a power law with an exponent of approximately -1. An explanation for this surprising behavior is not found.

physics.pop-ph↗

arXiv2020

Banjo Break Angle Tension Modulation as Parametric Oscillation

The motion of the floating bridge of the banjo, in conjunction with the break angle of the strings over that bridge, produces string tension modulation that is first order in the amplitude of the string motion. This note refines a previous suggestion regarding the impact on the frequencies of the strings' and bridge's motion. For a given mode frequency pair of string and bridge, the resulting tension modulation produces a new, additional motion characterized by the sum and difference of the original ones. Strictly speaking, this corresponds to canonical "frequency modulation" only in the limit of modulation slow compared to the string frequency. The more general result is precisely an example of what is known as "parametric oscillation," first analyzed by Rayleigh. The qualitative impact of tension modulation on banjo timbre remains as suggested previously. It is only the precise math and physics that warrants this correction.

physics.pop-ph↗

arXiv2020

"Heat Flowing from Cold to Hot without External Intervention" Demystified: Thermal-Transformer and Temperature Oscillator

A recent Science Advances paper by Schilling et al, claiming "flow of heat from cold to hot without intervention" with "oscillatory thermal inertia" are fundamentally misplaced and dramatized as miraculous, even though compliance with the Second Law of thermodynamics is acknowledged. There is nothing "magical and beyond the proof-of-concept" as claimed. It could have been achieved by any work generating device, stored by any suitable device (superconductive inductor was beneficial but not essential as claimed), and such stored work used subsequently in any refrigeration device to sub-cool the body. Cooling devices work by transforming temperature to desired level by work transfer (thermal transformer and temperature oscillator), by non-thermal, adiabatic processes. However, the "direct heat transfer" is always from higher to lower temperature in all refrigeration components, without exception - it is not to be confused by "net-transport of thermal energy by work" from cold to hot ambients. The unjustified claims are critically analyzed and demystified here.

cond-mat.stat-mech↗

arXiv2020

On the approximation of D.I.Y. water rocket dynamics including air drag

If you want to get accurate predictions for the motion of water and air propelled D.I.Y rockets, neglecting air resistance is not an option. But the theoretical analysis including air drag leads to a system of differential equations which can only be solved numerically. We propose an approximation which simply works by the estimate of a definite integral and which is even feasible for undergraduate physics courses. The results only slightly deviate from the reference data (received by the Runge-Kutta method). The motion is divided into several flight phases that are discussed separately and the resulting equations are solved by analytic and numeric methods. The different results from the flight phases are collected and are compared to data that has been achieved by well explained and documented experiments. Furthermore, we theoretically estimate the rocket's drag coefficient. The result is confirmed by a wind tunnel experiment.

physics.pop-ph↗

arXiv2020

The physical leaky tank car problem, revisited

An exhaustive analysis of the leaky tank car problem is presented, pointing out its intriguing physical properties, which well serve to students and teachers for illustrating standard Newtonian mechanics in a highly non-standard fashion. Calculus (at a leading undergraduate level) is effectively required only to examine some details concerning the solution of the equation of motion and interesting limiting cases. Instead we let any student to appreciate all the physical content of the problem, within a proper simple model and its generalization, ranging from the motion of the leaky tank car to that of the water flowing from the car with their peculiarities. Generalizations of the problem to more than one draining hole (even with different sizes), as well as to "two-dimensional" geometries, reveal further intriguing results, culminating into a no-rotation theorem and its corollaries, thus rendering unique the problem at hand for allowing students to fully recognize the power of physical analysis.

physics.class-ph↗

arXiv2020

Maxwell's Demon and its Fallacies Demystified

A demonic being, introduced by Maxwell, to miraculously create thermal non-equilibrium and violate the Second law of thermodynamics, has been among the most intriguing and elusive wishful concepts for over 150 years. Maxwell and his followers focused on 'effortless gating' a molecule at a time, but overlooked simultaneous interference of other chaotic molecules, while the demon exorcists tried to justify impossible processes with misplaced 'compensations' by work of measurements and gate operation, and information storage and memory erasure with entropy generation. The illusive and persistent Maxwell's demon fallacies by its advocates, as well as its exorcists, are scrutinized and resolved here. Based on holistic, phenomenological reasoning, it is deduced here that a Maxwell's demon operation, against natural forces and without due work effort to suppress interference of competing thermal particles while one is selectively gated, is not possible at any scale, since it would be against the physics of the chaotic thermal motion, the latter without consistent molecular directional preference for selective timing to be possible. Maxwell's demon would have miraculous useful effects, but also some catastrophic consequences.

physics.hist-ph↗

arXiv2020

How Many Simulations Do We Exist In? A Practical Mathematical Solution to the Simulation Argument

The Simulation Argument has gained significant traction in the public arena. It has offered a hypothesis based on probabilistic analysis of its assumptions that we are likely to exist within a computer simulation. This has been derived from factors including the prediction of computing power, human existence, extinction and population dynamics, and suggests a very large value for the number of possible simulations within which we may exist. On evaluating this argument through the application of tangible real-world evidence and projections, it is possible to calculate real numerical solutions for the Simulation Argument. This reveals a much smaller number of possible simulations within which we may exist, and offers a novel practicable approach in which to appraise the variety and multitude of conjectures and theories associated with the Simulation Hypothesis.

physics.pop-ph↗