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Direct imaging of exoplanets will allow us to directly observe the planet in reflected light. Such a scenario may eventually allow for the possibility to scan the planetary surface for the presence of artificial structures made by alien civilizations. Detectability of planetary scale structures, called megastructures, has been previously explored. In this work, we show that it is possible to detect structures of much smaller scale on exoplanetary surfaces by searching for the specular reflection of host starlight from the corresponding structures. As the planet rotates, these reflections can manifest as an optical transient riding atop the rotational light curve of the planet. Due to the directional nature of specular reflection, the reflected signal is very strong, and it is comparable to the planetary flux for surfaces covering only few ppm (parts per million) of the total planet surface area. By tracking the planet around its orbit, it should be possible to scan the planetary surface for any such structures covering a size larger than a few ppm of planetary surface. The proposed method will aid in the search for extra-terrestrial intelligence in the era of direct imaging of exoplanets., Comment: 2 figures, 4 pages, published in Astrobiology

We survey some of the philosophical challenges and pitfalls within origins research. Several of these challenges exhibit circularities, paradoxes, or anthropic biases. We present origins approaches in terms of three broad categories: unlikely (life's origin was a chance event), construction (life's origin was a stepwise series of synthesis and assembly processes), and emergence (life was always an amalgam of many parallel processes from which the living state emerged as a natural outcome of physical driving forces). We critically examine some of the founding and possibly misleading assumptions in these categories. Such assumptions need not be detrimental to scientific progress as long as their limits are respected. We conclude by attempting to concisely state the most significant enigmas still remaining in the origins field and suggest routes to solve them.

The European Open Science Cloud aims to make all data Findable, Accessible, Interoperable and Reusable. By far the largest community of users of the European Open Science Cloud is the science-inclined public. These users need a more curated experience of open science than subject specialists, but nevertheless make very substantial research contributions in open science, especially in crowdsourced data mining, i.e. citizen science. This short, non-technical invited review presents applications of citizen science in the European Open Science Cloud, with a particular focus on astrophysics and astroparticle physics., Published in Europhysics News, vol. 54(2), 2023, pages 20-23. 4 pages, published version

This paper discusses how theories can be assessed within the epistemological viewpoint advanced by the Austrian physicist Ludwig E. Boltzmann. It builds upon, and further develops, the perspective of Boltzmann's thinking as advanced by Ribeiro and Videira (1998, arXiv:physics/9806011). Boltzmann's epistemological viewpoint accepts that reality is real and proposes that reality can be described by different points of view because his main philosophical thesis states that scientific theories are images of Nature. We present the historical context that witnessed the genesis of Boltzmann's ideas and expand Ribeiro and Videira's (Ibid.) perspective by arguing that later in his life Boltzmann realized the insufficiency of his thesis as justification for theoretical pluralism and avoidance of dogmatism. Consequently, his thinking went beyond epistemology, the nature of scientific knowledge, to include realism, the nature of the represented objects., 19 pages. New abstract. Sections 1 and 5 were slightly revised and enlarged. Version v1 was intended as a chapter of a book on Boltzmann, but the publisher cancelled it. This version matches the text appearing in "Interdisciplinary Science Reviews"

Armed with an astrolabe and Kepler's laws one can arrive at accurate estimates of the orbits of planets., Comment: 28 pages, 19 figures

This is an introductory review of Musical Excellence of Mridangam by Dr. Umayalpuram K Sivaraman, Dr. T Ramasami and Dr. Naresh, which is a scientific treatise exploring the unique tonal properties of the ancient Indian classical percussive instrument -- the Mridangam. This review aims to bridge the gap between the primary intended audience of Musical Excellence of Mridangam - listeners, artistes and makers -- and the scientific rigour with which the original treatise is written, by first introducing the concepts of musical analysis and then presenting and explaining the discoveries made within this context. The first three chapters of this review introduce the basic scientific concepts used in Musical Excellence of Mridangam and provides background to previous scientific research into this instrument, starting from the seminal work of Dr. CV Raman. This also includes brief discussions of the corresponding chapters in Musical Excellence of Mridangam. The next chapters all serve the purpose of explaining the main scientific results presented in Musical Excellence of Mridangam in each of the corresponding chapters in the treatise, and finally summarizing the relevance of the work.

As humanity embarks on an age of exploration, the question of whether we are alone in the universe remains unanswered. This comprehensive review reflects on the paradoxical nature of our existence in a seemingly lifeless cosmos, delving into the silence we encounter and the depths of our self-awareness. We embark on a journey that encompasses the search for life within our solar system, the mysteries of exoplanets, and the absence of technologically detectable life. Traditional definitions of life are challenged, especially in the context of artificial intelligence, as we strive to understand the complexities of existence. Contemplating our significance and insignificance in the vast cosmos, we grapple with the profound responsibility that accompanies being the only known life forms. Through introspection and contemplation, we capture the essence of our epoch -- an era defined by cosmic loneliness yet magnificent self-awareness.

In this article, we present several apparent paradoxes of special relativity and their respective solutions. These paradoxes have appeared since the advent of relativity in 1905, and in fact they are never paradoxes. From a didactic point of view, paradoxes are an excellent learning tool. They lead the student to confront, and abandon, several central concepts of Galilean theory, such as simultaneity and rigidity of extended bodies. In particular, we review a new and simple solution to the twin paradox, recently found by one of the present authors [1]. It does not need to consider reference accelerators or light signals, which are the solutions presented in the literature., in Portuguese language, paper accepted for publication in Revista Brasileira do Ensino de F\'isica

In this paper, a quantum variant of chess is introduced, which can be played on a traditional board without the need of using computers or other electronic devices. The rules of the game arise naturally by combining the rules of conventional chess with key quantum-physical effects such as superposition and entanglement. Niel's Chess is recommended for ages 10 and above, to everyone who wishes to play a creative game with historical roots and at the same time gain intuition about the foundational quantum effects that power cutting-edge technologies like quantum computing and quantum communication, which are poised to revolutionise our society in the coming decades., 16 pages, 42 figures

Several technosignature techniques focus on historic events such as SN 1987A as the basis to search for coordinated signal broadcasts from extraterrestrial agents. The recently discovered SN 2023ixf in the spiral galaxy M101 is the nearest Type II supernova in over a decade, and will serve as an important benchmark event. Here we review the potential for SN 2023ixf to advance ongoing techonsignature searches, particularly signal-synchronization techniques such as the "SETI Ellipsoid". We find that more than 100 stars within 100 pc are already close to intersecting this SETI Ellipsoid, providing numerous targets for real-time monitoring within ~3$^\circ$ of SN 2023ixf. We are commencing a radio technosignature monitoring campaign of these targets with the Allen Telescope Array and the Green Bank Telescope., 3 Pages, 1 Figure, Submitted to RNAAS. Collaboration welcomed

The Fermi paradox has given rise to various attempts to explain why no evidence of extraterrestrial civilisations was found so far on Earth and in our Solar System. Here, we present a dynamical model for the development of such civilisations, which accounts for self-destruction, colonisation and astrophysical destruction mechanisms of civilisations including gamma-ray bursts, type Ia and type II supernovae as well as radiation from the supermassive black hole. We adopt conservative estimates regarding the efficiency of such processes and find that astrophysical effects can influence the development of intelligent civilisations and change the number of systems with such civilisations by roughly a factor of 2; potentially more if the feedback is enhanced. Our results show that non-equilibrium evolution allows for solutions in-between extreme cases such as "rare Earth" or extreme colonisation, including scenarios with civilisation fractions between 10^{-2} and 10^{-7}. These would imply still potentially large distances to the next such civilisations, particularly when persistence phenomena are being considered. As previous studies, we confirm that the main uncertainties are due to the lifetime of civilisations as well as the assumed rate of colonisation. For SETI-like studies, we believe that unbiased searches are needed considering both the possibilities that the next civilisations are nearby or potentially very far away., 8 pages, 6 figures, 1 table. Accepted for publication in the International Journal of Astrobiology

The famous "Wow" signal detected in 1977 remains arguably the most compelling SETI signal ever found. The original Big Ear data requires that the signal turned on/off over the span of ~3 minutes (time difference between the dual antennae), yet persisted for 72 seconds (duration of a single beam sweep). Combined with the substantial and negative follow-up efforts, these observations limit the allowed range of signal repeat schedules, to the extent that one might question the credibility of the signal itself. Previous work has largely excluded the hypothesis of a strictly periodic repeating source, for periods shorter than 40 hours. However, a non-periodic, stochastic repeater remains largely unexplored. Here, we employ a likelihood emulator using the Big Ear observing logs to infer the probable signal properties under this hypothesis. We find that the maximum a-posteriori solution has a likelihood of 32.3%, highly compatible with the Big Ear data, with a broad 2 $\sigma$ credible interval of signal duration 72 secs < T < 77 mins and mean repeat rate 0.043 1/days < $\lambda$ < 59.8 1/days. We extend our analysis to include 192 hours of subsequent observations from META, Hobart and ATA, which drops the peak likelihood to 1.78%, and thus in tension with the available data at the 2.4 $\sigma$ level. Accordingly, the Wow signal cannot be excluded as a stochastic repeater with available data, and we estimate that 62 days of accumulated additional observations would be necessary to surpass 3 $\sigma$ confidence., Comment: Re-submitted to MNRAS after first review

We first recall fundamentals of elementary climate physics: solar constant, radiative balance, greenhouse effect, astronomical parameters of the climate (theory of Milankovitch). Without disputing the analyzes of climatologists and the famous Keeling curve revealing in an indisputable way the increase in CO$_{2}$ in the atmosphere since the industrial revolution, we nevertheless insist on the main contributor to the greenhouse effect which is, as we know, water vapor. Faced with the difficulties that there will be in imposing zero-carbon policies everywhere in the world (and especially in developing countries), we show that it would perhaps be in our interest to act on soil drought, which amounts, in fact, to being interested in the clouds. The decrease in cloud cover, due to a lack of water fixation in the soil, in fact increases the general temperature and therefore the greenhouse effect. Acting on CO$_{2}$ will always have, in this context, much less effect than acting on water vapor, even indirectly. Despite the difficulty of making this action sustainable, due to the balance of atmospheric water vapor and the oceans, it would be in our interest not to neglect this path and also possibly increase forest cover for this purpose, given the problems of setting up zero-carbon policy on a global scale. In desperation, one can also consider protecting the Earth with an artificial dust cloud., 34 pages, 10 figures

The sensitivity to deformation plays a key role in determining the applicability of stretchable metamaterials (MMs) to be used for conformal integration or mechanical reconfiguration. Typically, different unit designs are required to achieve the desired sensitivity, but this article proposes a block definition design for stretchable MMs that enables regulation of the MMs' response to deformation by defining various block arrangements with the same precursor structure. The article demonstrates a stretchable MM that employs the block definition design to show the mechanical reconfigurability of resonant frequency. Different block definitions result in modulation ranges of resonant frequency ranging from 39\% to 85\% when applying a 20\% tensile strain. Additionally, the proposed design is also used to realize another MM with contradictory sensitivity to the deformation and electromagnetically induced transparency (EIT) MMs with configurable transmission bandwidth to the deformation, indicating its potential for broader applications.

We outline the course of affairs in the experimental and theoretical fields of nuclear and particle physics which determined its finale, and give several fragmentary remarks on its present state. The essay tells about events and their participants, known from the literature, but presented here from the perspective of a person whose 50-year labor activity, 1972--2022, proceeded at the All-Union Scientific Research Institute of Experimental Physics, Sarov. In order to predict the fate of particle physics and related astrophysics and cosmology, it is useful to become aware of the facts about another branch of physics that has already gone through its decline $\sim 30$ years ago, the physics of nuclear weapons. These facts are important not in themselves, but as evidence of the growing problems of science and social life, which are not only far from a satisfactory solution, but have not even been the subject of any serious discussion., 50 pages, 1 figure

In this paper, we present a novel approach for the design of leaky-wave holographic antennas that generates OAM-carrying electromagnetic waves by combining Flat Optics (FO) and machine learning (ML) techniques. To improve the performance of our system, we use a machine learning technique to discover a mathematical function that can effectively control the entire radiation pattern, i.e., decrease the side lobe level (SLL) while simultaneously increasing the central null depth of the radiation pattern. Precise tuning of the parameters of the impedance equation based on holographic theory is necessary to achieve optimal results in a variety of scenarios. In this research, we applied machine learning to determine the approximate values of the parameters. We can determine the optimal values for each parameter, resulting in the desired radiation pattern, using a total of 77,000 generated datasets. Furthermore, the use of ML not only saves time, but also yields more precise and accurate results than manual parameter tuning and conventional optimization methods.

We present a physically appealing and elegant picture for quantum computing using rules constructed for a game of darts. A dartboard is used to represent the state space in quantum mechanics and the act of throwing the dart is shown to have close similarities to the concept of measurement, or collapse of the wavefunction in quantum mechanics. The analogy is constructed in arbitrary dimensional spaces, that is using arbitrary dimensional dartboards, and for for such arbitrary spaces this also provides us a ``visual'' description of uncertainty. Finally, connections of qubits and quantum computing algorithms is also made opening the possibility to construct analogies between quantum algorithms and coupled dart-throw competitions.

Elucidating the nature of Dark Matter (DM), which does not interact with light and which interacts with known matter primarily or only through gravity, is one of the principal quests in physics. Leading candidates for DM are weakly interacting massive particles (WIMPs) or ultralight bosons (axions), at opposite extremes in mass scales, that have been postulated by competing theories to solve deficiencies in the Standard Model of particle physics. Whereas DM WIMPs behave like discrete particles ($\varrho$DM), quantum interference between DM axions is manifested as waves ($\psi$DM). Here, we show that gravitational lensing leaves signatures in multiply-lensed images of background galaxies that reveal whether the foreground lensing galaxy inhabits a $\varrho$DM or $\psi$DM halo. Whereas $\varrho$DM lens models leave well documented anomalies between the predicted and observed brightnesses and positions of multiply-lensed images, $\psi$DM lens models correctly predict the level of anomalies left over by $\varrho$DM lens models. More challengingly, when subjected to a battery of tests for reproducing the quadruply-lensed triplet images in the system HS 0810+2554, $\psi$DM is able to reproduce all aspects of this system whereas $\varrho$DM often fails. The growing success of $\psi$DM in reproducing astrophysical observations tilt the balance toward new physics invoking axions., Comment: This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in Nature Astronomy, and is available online at https://doi.org/10.1038/s41550-023-01943-9 or https://www.nature.com/articles/s41550-023-01943-9. Please check out the final version on Nature Astronomy's website for the improved main text

The monostatic property of polyhedra (i.e. the property of having just one stable or unstable static equilibrium point) has been in a focus of research ever since Conway and Guy \cite{Conway} published the proof of the existence of the first such object. In the same article they also proved that a homogeneous tetrahedron has at least two stable equilibrium points. By using polar duality, the same idea has been used \cite{balancing} to prove that a homogeneous tetrahedron has at least two unstable equilibria. Conway \cite{Dawson} also claimed that among inhomogeneous tetrahedra one can find monostable ones. Here we not only give a formal proof of this statement and show that monostatic tetrahedra have exactly 4 equilibria, but also demonstrate a startling new aspect of this problem: being monostatic implies certain \emph{visible} features of the shape and vice versa. Our results also imply that mono-monostatic tetrahedra (having just one stable and just one unstable equilibrium point) do not exist. In contrast, we show that for any other legal number of faces, edges, and vertices there is a mono-monostatic polyhedron with that face vector., 12 pages, 7 figures

A long-standing issue in astrobiology is whether planets orbiting the most abundant type of stars, M-dwarfs, can support liquid water and eventually life. A new study shows that subglacial melting may provide an answer, significantly extending the habitability region, in particular around M-dwarf stars, which are also the most promising for biosignature detection with the present and near-future technology., 6 pages, 2 figures, Nature Communications

The application of the motion of a vertically suspended mass-spring system released under tension is studied focusing upon the delay timescale for the bottom mass as a function of the spring constants and masses. This ``hang-time", reminiscent of the Coyote and Road Runner cartoons, is quantified using the far-field asymptotic expansion of the bottom mass' Laplace transform. These asymptotics are connected to the short time mass dynamics through Tauberian identities and explicit residue calculations. It is shown, perhaps paradoxically, that this delay timescale is maximized in the large mass limit of the top ``boulder". Experiments are presented and compared with the theoretical predictions. This system is an exciting example for the teaching of mass-spring dynamics in classes on Ordinary Differential Equations, and does not require any normal mode calculations for these predictions.

The universe is composed of ordinary matter (for example, stars, planets, ourselves), dark matter and dark energy. The estimated percentage of dark matter is about $27\%$ of the entire universe, while $5\%$ is ordinary matter and the remaining part is dark energy. This article introduces the fundamental ingredients that led to conjecture the existence of dark matter and to study its properties. To this result have contributed, directly or indirectly, numerous female mathematicians and astronomers, who we quote to give them the right credit., 21 pages, in Italian language

The geocentric universe, in its most developed form as set out by Ptolemy, was a remarkably successful and coherent theory. It did not, however, specify the order of the planets, that is, which was closer to Earth and which farther away. One would naively think that seeing one planet pass in front of another would settle the matter. In practice such mutual phenomena happen too rarely for them to have been useful. Even in principle, it turns out that most naked-eye observations of a central event would show nothing conclusive, with the exception of some occultations by Venus that would demonstrate it to be the lowest (nearest) planet. However, if one's theory were good enough to allow conclusions from {\it not} seeing changes, one could find that Mars is probably lower than Jupiter and Saturn, and possibly that the overall order is Venus-Mars-Jupiter-Saturn-Mercury., 7 pages, no figures

A cryptocurrency is a digital asset maintained by a decentralised system using cryptography. Investors in this emerging digital market are exploring the profitability potential of portfolios in place of single coins. Portfolios are particularly useful given that price forecasting in such a volatile market is challenging. The crypto market is a self-organised complex system where the complex inter-dependencies between the cryptocurrencies may be exploited to understand the market dynamics and build efficient portfolios. In this letter, we use network methods to identify highly decorrelated cryptocurrencies to create diversified portfolios using the Markowitz Portfolio Theory agnostic to future market behaviour. The performance of our network-based portfolios is optimal with 46 coins and superior to benchmarks up to an investment horizon of 14 days, reaching up to 1,066% average expected return within 1 day, with reasonable associated risks. We also show that popular cryptocurrencies are typically not included in the optimal portfolios. Past price correlations reduce risk and may improve the performance of crypto portfolios in comparison to methodologies based exclusively on price auto-correlations. Short-term crypto investments may be competitive to traditional high-risk investments such as the stock market or commodity market but call for caution given the high variability of prices., Comments welcomed

Airborne transmission of SARS-CoV-2 via virus-laden aerosols in enclosed spaces poses a significant concern. Elevators, commonly utilized enclosed spaces in modern tall buildings, present a challenge as the impact of varying heating, ventilation, and air conditioning (HVAC) systems on virus transmission within these cabins remains unclear. In this study, we employ computational modeling to examine aerosol transmission within an elevator cabin outfitted with diverse HVAC systems. Using a transport equation, we model aerosol concentration and assess infection risk distribution across passengers' breathing zones. We calculate particle removal efficiency for each HVAC design and introduce a suppression effect criterion to evaluate the effectiveness of the HVAC systems. Our findings reveal that mixing ventilation, featuring both inlet and outlet at the ceiling, proves most efficient in reducing particle spread, achieving a maximum removal efficiency of 79.40% during the exposure time. Conversely, the stratum ventilation model attains a mere removal efficiency of 3.97%. These results underscore the importance of careful HVAC system selection in mitigating the risk of SARS-CoV-2 transmission within elevator cabins., 38 pages, 14 figures

Planetary effects have been attributed to biological processes without scientific rigor. Some generic invisible slow matter from the dark Universe in the form of streams or clusters with occasional large flux enhancements due to planetary gravitational focusing is the driving idea and the only explanation we have. This work extends previous observations regarding relationships of diagnosed cancer (melanoma), which may provide additional insight into previously unrecognized factors also affecting other biological processes. Biological measurements in vitro and mutation rates are promising., 13 pages, 4 figures

We observe neither life beyond Earth, nor moons around exoplanets, despite the prevalence of Earth-like planets across the galaxy. We suggest Moonfall as a possible mechanism to explain both simultaneously.

In what will likely be a litany of generative-model-themed arXiv submissions celebrating April the 1st, we evaluate the capacity of state-of-the-art transformer models to create a paper detailing the detection of a Pulsar Wind Nebula with a non-existent Imaging Atmospheric Cherenkov Telescope (IACT) Array. We do this to evaluate the ability of such models to interpret astronomical observations and sources based on language information alone, and to assess potential means by which fraudulently generated scientific papers could be identified during peer review (given that reliable generative model watermarking has yet to be deployed for these tools). We conclude that our jobs as astronomers are safe for the time being. From this point on, prompts given to ChatGPT and Stable Diffusion are shown in orange, text generated by ChatGPT is shown in black, whereas analysis by the (human) authors is in blue.

Astronomical images can be fascinating to the general public, but the interaction is typically limited to contemplation. Numerical simulations of astronomical systems do permit a closer interaction, but are generally unknown outside the research community. We are developing "Protoplanet Express", a video game based on hydrodynamical simulations of protoplanetary discs. In the game, the player visits several discs, finds its relevant features and learns about them. Here we present the current version of the game, discuss its reception, and consider its further development., 6 pages, 4 figures, submitted to the Proceedings of ASP 2022. Beta version of game available at https://questionablegames.itch.io/protoplanet-express

How many gravitational-wave observations from compact object mergers have we seen to date? This seemingly simple question has a surprisingly complex answer that even ChatGPT struggles to answer. To shed light on this, we present a database with the literature's answers to this question. We find values spanning 67-100 for the number of detections from double compact object mergers to date, emphasizing that the exact number of detections is uncertain and depends on the chosen data analysis pipeline and underlying assumptions. We also review the number of gravitational-wave detections expected in the coming decades with future observing runs, finding values up to millions of detections per year in the era of Cosmic Explorer and Einstein Telescope. We present a publicly available code to visualize the detection numbers, highlighting the exponential growth in gravitational-wave observations in the coming decades and the exciting prospects of gravitational-wave astrophysics. See http://www.broekgaarden.nl/floor/wordpress/elementor-967/. We plan to keep this database up-to-date and welcome comments and suggestions for additional references., 1 April submission, with fun videos for visualizing the landscape of gravitational waves! (they are awesome!) See http://www.broekgaarden.nl/floor/wordpress/elementor-967/

An analysis of barriers to women's participation in physics education is presented. It is expected that in undergraduate physics the most common situation for a women is that she is cisgender and one of a numerical minority in the classroom. The effects of other intersectional identities are not considered. The analysis is based on evidence from the author's lived experience as a transgender woman who transitioned as an undergraduate and on evidence from the literature on the effects of gender differences in academic disciplines. It is expected that the teaching philosophy and practice in physics classrooms favours men over women and these gender dynamics are partially responsible for the under-representation of women in physics. These expectations require further research to be substantiated., 5 pages, Opinion

The swinging counterweight trebuchet was at its full blossom in the Late Middle Ages an artillery piece of great importance that could destroy the defenses of castles under siege by bombardment with stones from considerable distances. The exact dimensions of these engines are unfortunately unknown, but would have been valuable for an assessment of the true significance of the weapon. Presumed dimensions derived from interpreted historical accounts must be tested and examined critically. This has been done by full-scale experimental reconstructions or by~\textit{ad hoc} theoretical estimates. A more systematic approach is made possible by the present theory, which is based on a mathematical quality function for the trebuchet. This function can be maximized and the maximizing design parameters are by definition the optimal parameters. A simple analytical expression for these optimal parameters is given., 20 pages, 4 figures

In this letter, we give a simple and analytical solution to the twin paradox. It relies just on Lorentz transformations and does not involve accelerated frames or any kind of signals exchanged between the twins. We expect that with this we can put a dead end to this century-old problem., Comment: Paper accepted for publication in The Physics Educator

Educational research highlights that improved careers education is needed to increase participation in science, technology, engineering, and mathematics (STEM). Current UK careers resources concerning the space sector, however, are found to perhaps not best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We, therefore, compile a more diverse set of space-related jobs, which will be used in the development of a new space careers resource.

It has been hypothesized that advanced technological civilizations will construct giant space colonies and supporting infrastructures to orbit about their home stars. With data from recent satellites that operate at infrared and optical wavelengths (Spitzer, WISE, TESS, Kepler), in company with a few modest assumptions, it is now possible to begin to constrain observationally the frequency of such space-based civilizations in our Milky Way Galaxy., Accepted for MNRAS

Now that we know that Earth-like planets are ubiquitous in the universe, as well as that most of them are much older than the Earth, it is justified to ask to what extent evolutionary outcomes on other such planets are similar, or indeed commensurable, to the outcomes we perceive around us. In order to assess the degree of specialty or mediocrity of our trajectory of biospheric evolution, we need to take into account recent advances in theoretical astrobiology, in particular (i) establishing the history of habitable planets' formation in the Galaxy, and (ii) understanding the crucial importance of "Gaian" feedback loops and temporal windows for the interaction of early life with its physical environment. Hereby we consider an alternative macroevolutionary pathway that may result in tight functional integration of all sub-planetary ecosystems, eventually giving rise to a true superorganism at the biospheric level. The blueprint for a possible outcome of this scenario has been masterfully provided by the great Polish novelist Stanis{\l}aw Lem in his 1961 novel Solaris. In fact, Solaris offers such a persuasive and powerful case for an "extremely strong" Gaia hypothesis that it is, arguably, high time to investigate it in a discursive astrobiological and philosophical context. In addition to novel predictions in the domain of potentially detectable biosignatures, some additional cognitive and heuristic benefits of studying such extreme cases of functional integration are briefly discussed., Comment: 20 pages, 1 figure; accepted in "Origins of Life and Evolution of Biospheres"

The plate trick or belt trick is a striking physical demonstration of properties of the double cover of the three-dimensional rotation group by the sphere of unit quaternions or spinors. The two ends of a flexible object are continuously rotated with respect to each other. Surprisingly, the object can be manipulated so as to avoid accumulating twists. We present a new mechanical linkage that implements this task. It consists of a sequence of rigid bodies connected by hinge joints, together with a purely mechanical control mechanism. It has one degree of freedom, and the motion is generated by simply turning a handle.

We assess the possibility of reducing the travel time of a crewed mission to Mars by examining four different propulsion methods and keeping the mass at departure under 2500 tonne, for a fixed architecture. We evaluated representative systems of three different state of the art technologies (chemical, nuclear thermal and electric) and one advance technology, the ``Pure Electro-Magnetic Thrust'' (PEMT) concept (proposed by Rubbia). A mission architecture mostly based on the Design Reference Architecture 5.0 is assumed in order to estimate the mass budget, that influences the performance of the propulsion system. Pareto curves of the duration of the mission and time of flight versus mass of mission are drawn. We conclude that the ion engine technology, combined with the classical chemical engine, yields the shortest mission times for this architecture with the lowest mass and that chemical propulsion alone is the best to minimise travel time. The results obtained using the PEMT suggest that it could be a more suitable solution for farther destinations than Mars., Change in title and review of paper body to clarify the main objectives and results. 14 pages, 7 figures and 2 tables

Next-generation missions designed to detect biosignatures on exoplanets will also be capable of placing constraints on technosignatures (evidence for technological life) on these same worlds. Here, I estimate the detectability of nightside city lights on habitable, Earth-like, exoplanets around nearby stars using direct-imaging observations from the proposed LUVOIR and HabEx observatories, assuming these lights come from high-pressure sodium lamps. I consider how the detectability scales with urbanization fraction: from Earth's value of 0.05%, up to the limiting case of an ecumenopolis -- or planet-wide city. Though an Earth analog would not be detectable by LUVOIR or HabEx, planets around M-dwarfs close to the Sun would show detectable signals at $3\,\sigma$ from city lights, using 300 hours of observing time, for urbanization levels of 0.4% to 3%, while city lights on planets around nearby Sun-like stars would be detectable at urbanization levels of $\gtrsim10\%$. The known planet Proxima b is a particularly compelling target for LUVOIR A observations, which would be able to detect city lights twelve times that of Earth in 300 hours, an urbanization level that is expected to occur on Earth around the mid-22nd-century. An ecumenopolis, or planet-wide city, would be detectable around roughly 30 to 50 nearby stars by both LUVOIR and HabEx, and a survey of these systems would place a $1\,\sigma$ upper limit of $\lesssim2\%$ to $\lesssim4\%$, and a $3\,\sigma$ upper limit $\lesssim10\%$ to $\lesssim15\%$, on the frequency of ecumenopolis planets in the Solar neighborhood assuming no detections., Comment: MNRAS in press. Updated based on comments received and referee report to reflect the accepted version

Background: A solar sail presents a large sheet of low areal density membrane and is the most elegant propellant-less propulsion system for the future exploration of the Solar System and beyond. By today the study on sail membrane deployment strategies has attracted considerable attention. Goal: In this work we present an idea of the deployment and stretching of the circular solar sail. We consider the superconducting current loop attached to the thin membrane %to develop a new (method) approach of deployment of a solar sail and and predict that a superconducting current loop can deploy and stretch the circular solar sail membrane. Method: In the framework of a strict mathematical approach based on the classical electrodynamics and theory of elasticity the magnetic field induced by the superconducting current loop and elastic properties of a circular solar sail membrane and wire loop are analyzed. The formulas for the wire and sail membrane stresses and strains caused by the current in the superconducting wire are derived. Results: The obtained analytical expressions can be applied to a wide range of solar sail sizes. Numerical calculations for the sail of radius of 5 m to 150 m made of CP1 membrane of the thickness of 3.5 $\mu m$ attached to Bi$-$2212 superconducting wire with the cross-section radius of 0.5 mm to 10 mm are presented. Calculations are performed for the engineering current densities of 100 A/mm$^{2}$ to 1000 A/mm$^{2}$. Conclusion: Our calculations demonstrate the feasibility of the proposed idea for the solar sail deployment for the future exploration of the deep space by means of the light pressure propellant., Comment: 17 pages, 9 figures

The Clausius-Clapeyron relation and its analogs in other first-order phase transitions, such as type-I superconductors, are derived using very elementary methods, without appealing to the more advanced concepts of entropy or Gibbs free energy. The reasoning is based on Kelvin's formulation of the second law of thermodynamics, and should be accessible to high school students. After recalling some basic facts about the Carnot cycle, we present two very different systems that undergo discontinuous phase transitions (ice/water and normal/superconductor), and construct engines that exploit the properties of these systems to produce work. In each case, we show that if the transition temperature $T_tr$ were independent of other parameters, such as pressure or magnetic field, it would be possible to violate Kelvin's principle, i.e., to construct a perpetuum mobile of the second kind. Since the proposed cyclic processes can be realized reversibly in the limit of infinitesimal changes in temperature, their efficiencies must be equal to that of an ordinary Carnot cycle. We immediately obtain an equation of the form $dT /dX = f(T, X)$, which governs how the transition temperature changes with the parameter $X$.

A very short, non-technical review of the main problems which are presently open in the context of the gravitational theory and of its cosmological applications, and which are currently under investigation and deep discussion. We will talk in particular about the equivalence principle, the dark matter and dark energy contributions, the cosmological constant, the quantisation of gravity, the dynamics of the very early Universe., 5 pages, no figures. To be published (in Italian language) on "Ithaca: Sfide", XXI (2023) ISSN: 2282-8079, ESE (Salento University Publishing), http://ithaca.unisalento.it/

In high-power applications, multiple power MOSFETs are connected in parallel and treated as a single switch in order to handle much larger total currents. In this paper, a parallel power MOSFETs model from the turnoff state until they reach their steady state is introduced. The model represents the relationship between each power MOSFET's gate voltage and the current distribution among them. The study's key purpose is to use the model for dealing with the asymmetry in sharing current and power loss between these semiconductor devices during the steady state region., 10 pages, 7 figures, The 2023 INTERNATIONAL SYMPOSIUM ON ADVANCED ENGINEERING (ISAE2023)

We explain that black holes are the most efficient capacitors of quantum information. It is thereby expected that all sufficiently advanced civilizations ultimately employ black holes in their quantum computers. The accompanying Hawking radiation is democratic in particle species. Due to this, the alien quantum computers will radiate in ordinary particles such as neutrinos and photons within the range of potential sensitivity of our detectors. This offers a new avenue for SETI, including the civilizations entirely composed of hidden particles species interacting with our world exclusively through gravity., 18 pages, 0 figures

In the past 15 years, the number of known planets outside of our solar system has grown from about 200 to more than 5000. During that time, we have conducted one of the longest crowdfunding campaigns in history, a nonprofit adopt a star program that supports astronomy research. The program includes the targets of NASA space telescopes that are searching for planets around other stars, and it uses the proceeds to help determine the properties of those stars and their planetary systems. I summarize how this innovative program has evolved over the years and engaged the public worldwide to support an international team of astronomers., 4 pages, 2 figures. Project website is at https://adoptastar.org

In this case study, we explore the capabilities and limitations of ChatGPT, a natural language processing model developed by OpenAI, in the field of string theoretical swampland conjectures. We find that it is effective at paraphrasing and explaining concepts in a variety of styles, but not at genuinely connecting concepts. It will provide false information with full confidence and make up statements when necessary. However, its ingenious use of language can be fruitful for identifying analogies and describing visual representations of abstract concepts., 10 pages, 2 figures

We propose here a proposal to connect neutrino and energy frontiers, by exploiting collimated muon beams for neutrino oscillations, which generate symmetric neutrino and antineutrino sources: $\mu^+\rightarrow e^+\,\bar{\nu}_{\mu}\, \nu_{e}$ and $\mu^-\rightarrow e^-\, \nu_{\mu} \,\bar{\nu}_{e}$. Interfacing with long baseline neutrino detectors such as DUNE and T2K, this experiment can be applicable to measure tau neutrino properties, and also to probe neutrino CP phase, by measuring muon electron (anti-)neutrino mixing or tau (anti-)neutrino appearance, and differences between neutrino and antineutrino rates. There are several significant benefits leading to large neutrino flux and high sensitivity on CP phase, including 1) collimated and manipulable muon beams, which lead to a larger acceptance of neutrino sources in the far detector side; 2) symmetric $\mu^+$ and $\mu^-$ beams, and thus symmetric neutrino and antineutrino sources, which make this proposal ideally useful for measuring neutrino CP violation. More importantly, $\bar{\nu}_{e,\mu}\rightarrow\bar{\nu}_\tau$ and $\nu_{e,\mu}\rightarrow \nu_\tau$, and, $\bar{\nu}_{e}\rightarrow\bar{\nu}_\mu$ and $\nu_{e}\rightarrow \nu_\mu$ oscillation signals can be collected simultaneously, with no needs for separate specific runs for neutrinos or antineutrinos. Furthermore, it is possible to exchange $\mu^+$ and $\mu^-$ flying routes, thus further reducing possible bias or systematic uncertainties. In an optimistic way, we estimate $10^4$ tau (anti-) neutrinos can be collected per year thus this proposal can serve as a brighter tau neutrino factory. Moreover, 5 standard deviations of sensitivity can be easily reached for CP phase as $|\pi/2|$, with only 1--2 years of data taking, by combining tau and muon (anti-) neutrino appearances., Comment: Updated version with additional applications and references added; Happy Mu Nu Year!

The wind blows stronger and more reliably over the sea than over land. Thus, offshore wind energy is expected to make a major contribution to the energy transition in Germany, especially in the German Bight. But what happens when a growing number of wind farms extract more and more wind energy from the atmosphere?, 10 pages, 6 figures

The Galactic Plane was searched for transient, monochromatic light at optical and near-IR wavelengths to detect pulses shorter than 1 sec. An objective-prism Schmidt telescope and CMOS camera were used to observe 973 square degrees along the Galactic Plane within a strip 2.1 deg wide. The non-detections of laser pulses from the Galactic Plane add to the non-detections from more than 5000 stars. The absence of extraterrestrial beacons reveals more of a SETI desert at optical and radio wavelengths., 24 pages

We present multi-wavelength data and analysis, including new FUV AstroSat/UVIT observations of the spiral galaxy UGC 10420 (z=0.032), a member of the cluster Abell 2199. UGC 10420 is present on the edge of the X-ray emitting region of the cluster at a distance of ~ 680 kpc from the centre. The FUV data shows intense knots of star formation on the leading edge of the galaxy, accompanied by a tail of the same on the diametrically opposite side. Our analysis shows that the images of the galaxy disk in the optical and mid-infrared are much smaller in size than that in the FUV. While the broadband optical colours of UGC 10420 are typical of a post-starburst galaxy, the SFR derived from a UV-to-IR spectral energy distribution is at least a factor of nine higher than that expected for a star-forming field galaxy of similar mass at its redshift. A careful removal of the contribution of the diffuse intracluster gas shows that the significant diffuse X-ray emission associated with the inter-stellar medium of UGC 10420 has a temperature, T_X = 0.24^{+0.09}_{-0.06} keV (0.4-2.0 keV) and luminosity, L_X = 1.8+/-0.9 x 10^{40} erg/s, which are typical of the X-ray emission from late-type spiral galaxies. Our analysis favours a scenario where the interaction of a galaxy with the hot intra-cluster medium of the cluster, perturbs the gas in the galaxy causing starburst in the leading edge of the disk. On the other hand, the turbulence thus developed may also push some of the gas out of the disk. Interactions between the gas ejected from the galaxy and the intracluster medium can then locally trigger star formation in the wake of the galaxy experiencing ram-pressure stripping. Our data however does not rule out the possibility of a flyby encounter with a neighbouring galaxy, although no relevant candidates are observed in the vicinity of UGC 10420. (abridged), Comment: Accepted for publication in the Publication of the Astronomical Society of Australia (PASA). 16 pages, 11 figures