This post discusses a common problem in game physics: preventing jittering and instability in stacked rigid bodies. It introduces a technique called "speculative contacts," where potential collisions in the next physics step are predicted and pre-emptively resolved. This allows for stable stacking by ensuring the bodies are prepared for contact, rather than reacting impulsively after penetration occurs. The post emphasizes the improved stability and visual quality this method offers compared to traditional solutions like increasing solver iterations, which are computationally expensive. It also highlights the importance of efficiently identifying potential contacts to maintain performance.
The "Blowtorch Theory" proposes a new cosmological model where structure formation is driven by highly collimated jets emitted from supermassive black holes, dubbed "blowtorches." These blowtorches inject energy and matter into the intergalactic medium, heating and ionizing it, which in turn influences the formation of galaxies and galaxy clusters. Unlike standard models that rely on dark matter and inflation, this theory suggests that the observed large-scale structures, cosmic voids, and filaments are sculpted by these powerful jets, potentially eliminating the need for these currently unexplained phenomena. The theory also offers an alternative explanation for the accelerating expansion of the universe, attributing it to the cumulative effect of these blowtorches pushing matter outwards over cosmic time.
Hacker News users discussed the plausibility and implications of the "Blowtorch Theory." Some expressed skepticism about its scientific rigor, noting the lack of peer review and the author's apparent outsider status. Others were intrigued by the novelty of the idea, but questioned its underlying assumptions and the feasibility of testing its predictions. Several commenters compared it to other non-standard cosmological models like Electric Universe theory, highlighting the challenges of gaining acceptance within the established scientific community. A few users requested clarification on specific aspects of the theory, while others debated the value of exploring alternative explanations for cosmological phenomena.
Dropping an egg on its side significantly increases its chances of surviving a fall, according to physics simulations. The curved shape of the egg distributes the impact force over a larger area than if it landed on one end, reducing pressure and the likelihood of cracking. Specifically, the side-landing allows the egg to rotate, further dissipating energy and lessening the shock. While cushioning materials are typically used in egg drop experiments, this research suggests the egg's shape itself can be exploited for protection.
Hacker News users generally agreed with the article's premise that dropping an egg on its side distributes the force more evenly, increasing the chances of survival. Several commenters shared their own egg-drop experiment experiences, emphasizing the importance of proper padding and the sometimes unpredictable nature of such experiments. Some debated the merits of different padding materials, with mentions of Styrofoam peanuts, bubble wrap, and even Jell-O. A few users pointed out the real-world applications of these principles in packaging design and impact absorption. One commenter offered a counterintuitive approach, suggesting dropping the egg from a very short distance to minimize impact force, regardless of orientation. Others discussed the importance of considering the egg's center of gravity and the potential for cracks to propagate even with seemingly successful landings.
"Strange metals," materials that exhibit unusual electrical resistance, defy conventional explanations of conductivity. Instead of resistance linearly increasing with temperature, as in normal metals, it increases in direct proportion, even at extremely low temperatures. This behavior suggests a fundamental shift in our understanding of how electrons move through these materials, potentially involving entanglement and collective, fluid-like behavior rather than independent particle motion. Researchers are exploring theoretical frameworks, including those borrowed from black hole physics, to explain this phenomenon, which could revolutionize our understanding of electricity and pave the way for new technologies.
HN commenters discuss the difficulty of understanding the article without a physics background, highlighting the challenge of explaining complex scientific concepts to a wider audience. Several express a desire for a more accessible explanation of strange metals and their potential implications. Some question the revolutionary nature of the research, while others speculate about potential applications in areas like superconductivity and quantum computing. The discussion also touches on the role of Planck's constant and its significance in understanding these unusual materials, with some commenters trying to offer simplified explanations of the underlying physics. A few highlight the importance of basic research and the potential for unexpected discoveries.
Researchers at the University of Arizona have developed a phototransistor capable of operating at petahertz speeds under ambient conditions. This breakthrough utilizes a unique semimetal material and a novel design exploiting light-matter interactions to achieve unprecedented switching speeds. This advancement could revolutionize electronics, enabling significantly faster computing and communication technologies in the future.
Hacker News users discuss the potential impact and feasibility of a petahertz transistor. Some express skepticism about the claims, questioning if the device truly functions as a transistor and highlighting the difference between demonstrating light modulation at petahertz frequencies and creating a usable electronic switch. Others discuss the challenges of integrating such a device into existing technology, citing the need for equally fast supporting components and the difficulty of generating and controlling signals at these frequencies. Despite the skepticism, there's general excitement about the potential of such a breakthrough, with discussions ranging from potential applications in communication and computing to its implications for fundamental scientific research. Some users also point out the ambiguity around "ambient conditions," speculating about the true operating environment. Finally, a few comments provide further context by linking to related research and patents.
Earth experiences two high-tide bulges, one directly facing the Moon and another on the opposite side. The bulge facing the Moon is caused by the Moon's gravitational pull being strongest on that side, pulling the water towards it. The opposite bulge is a result of inertia. The Moon's gravity also pulls on the Earth itself, and this pull is stronger on the side closer to the Moon. This difference in gravitational pull effectively stretches the Earth, causing the ocean on the far side to bulge outwards as if being flung away. So, while the near-side bulge is due to direct gravitational attraction, the far-side bulge is due to the residual effect of the Earth being pulled towards the Moon more strongly on the near side.
Hacker News users discuss the physics behind the double-bulge high tide phenomenon, generally agreeing with the Stack Exchange explanation. Some emphasize the importance of frames of reference, pointing out that the bulge opposite the moon is due to inertia in a rotating frame, effectively being "left behind" as the Earth and Moon orbit their barycenter. Several commenters use analogies, like swinging a bucket of water or a hula hoop, to visualize the forces at play. One clarifies the common misconception that the far-side bulge is solely due to the moon's gravity "pulling the Earth away from the water," explaining it's a combination of inertial effects and the gradient of the gravitational field. Some also discuss how the sun's gravity contributes to tides and the complexities of real-world tides beyond the simplified model.
Racketmeter is a tool that measures badminton racket string tension using sound frequency analysis. By recording the sound produced when plucking the strings with the Racketmeter app, the software analyzes the dominant frequency and converts it into tension using a physics-based algorithm. The app supports a wide range of rackets and strings, and aims to provide an affordable and accessible alternative to traditional tension measuring devices. It offers various features like tension history tracking, string recommendations, and data visualization to help players optimize their racket setup.
HN users generally expressed interest in Racketmeter, praising its innovative approach to string tension measurement. Some questioned the accuracy and consistency, particularly regarding the impact of string type and racket frame material. Several commenters with badminton experience suggested additional features, like storing measurements by racket and string, and incorporating tension recommendations based on player skill level or playing style. Others were curious about the underlying physics and the potential for expanding the technology to other racket sports like tennis or squash. There was also a brief discussion of the challenges in accurately measuring tension with traditional tools.
A new study suggests the universe could decay far sooner than previously estimated, in approximately 10⁷⁸ years, due to the hypothetical decay of the Higgs boson vacuum. This timeline, while still astronomically long, is significantly shorter than prior estimates focusing on proton decay. The research highlights the instability of the current vacuum state, proposing it could transition to a lower energy state, potentially leading to a bubble of "true vacuum" expanding at the speed of light and obliterating everything in its path. However, this remains theoretical and depends on confirming current assumptions about particle physics and cosmology, including the mass of the top quark and the Higgs boson.
HN commenters discuss the vast timescale involved, questioning the meaning of such predictions so far into the future. Several express skepticism about the underlying physics and the ability to extrapolate current understanding to such extremes. Some point out the limitations of current models and the potential for unknown factors to influence the universe's ultimate fate. The practicality of worrying about an event so distant in the future is also questioned, with some suggesting focusing on more immediate concerns. A few commenters delve into the theoretical mechanisms of decay, including proton decay and vacuum metastability, but overall the discussion leans towards the philosophical implications of such a distant and uncertain event.
Coffee stains exhibit a darker ring at their edge due to a phenomenon called the "coffee-ring effect." As a drop of coffee evaporates, the liquid flows outwards from the center to replenish the evaporating edge. This outward flow carries coffee particles, which then get deposited and accumulate at the perimeter, creating a denser, darker stain. The pinned contact line of the droplet prevents these particles from moving back inwards, further concentrating them at the edge.
Hacker News users discuss the linked article's explanation of the "coffee ring effect." Several commenters point out that the explanation, while commonly cited, isn't entirely accurate. The dominant factor isn't just faster evaporation at the edge, but also the outward capillary flow that carries suspended particles toward the perimeter as the droplet shrinks. Some discuss the implications for printing and coating technologies, where uniform drying is desirable. Others mention the role of particle shape and size in influencing the effect, with larger or elongated particles creating less pronounced rings. A few users suggest alternative explanations or contributing factors, like Marangoni flow and the changing contact angle of the droplet. Finally, some commenters simply appreciate the elegant simplicity of the original explanation, even if incomplete.
Researchers have developed a novel interferometer that can read text from a distance of over a mile. This device uses two telescopes to collect light scattered from a target, combining the light to create an interference pattern. By analyzing subtle changes in this pattern caused by the target's microscopic surface variations, the system effectively reconstructs an image. Demonstrated with retroreflectors and printed text at 1.6 kilometers, this technology opens possibilities for remote sensing and surveillance in challenging conditions where conventional imaging methods struggle.
Hacker News users discussed the potential applications and limitations of the interferometer described in the linked article. Several commenters questioned the practicality of the device, citing the need for extremely precise alignment and the susceptibility to atmospheric disturbances. Some highlighted the potential for use in surveillance, while others saw more benign applications like remote sensing in hazardous environments. A few users expressed skepticism about the claimed resolution and signal-to-noise ratio, requesting more technical details. The discussion also touched on the differences between this technology and lidar, and the possibility of using computational methods to improve image quality. Several commenters also discussed the history of similar technologies and their potential future development.
The ALICE experiment at CERN's Large Hadron Collider has observed the transformation of lead nuclei into gold. This doesn't involve alchemy, but rather a natural, albeit rare, radioactive decay process. When lead ions collide in the LHC, they can lose a proton, resulting in an isotope of gold. This gold nucleus is unstable and quickly decays further, but its brief existence has been confirmed by ALICE through precision measurements of the particle's momentum and mass-to-charge ratio. This observation provides valuable data for understanding the nuclear structure of heavy ions and the processes occurring during high-energy collisions.
Several commenters on Hacker News expressed skepticism about the title's phrasing, clarifying that the process described in the article involves creating a very small amount of gold from lead for an extremely short period, and that it is not a viable method for producing gold. They point out that the energy cost far exceeds the value of the gold produced. Some discussed the nuclear physics involved, explaining the difference between nuclear fission and fusion, and how this experiment relates to neither. The impracticality of the process for gold production was a recurring theme. Others mentioned the difficulties of separating the gold from the lead target, further emphasizing the lack of practical application. A few comments jokingly referred to alchemy, contrasting the reality of the experiment with the historical pursuit of transmuting base metals into gold.
A Science article raises concerns about potential data manipulation in a 2018 Nature paper that claimed evidence for Majorana zero modes, a key component for Microsoft's topological quantum computing approach. Critics allege that the authors selectively presented data, omitting measurements that contradicted their claims and potentially adjusted image parameters to enhance desired features. This controversy casts doubt on the original findings and raises questions about the validity of Microsoft's pursuit of this specific type of quantum computer. An investigation by Delft University of Technology, where the research originated, is currently underway.
Hacker News users discuss the implications of the alleged data manipulation, focusing on the damage to scientific integrity and Microsoft's reputation. Several commenters express skepticism about Majorana fermion-based quantum computing in general, viewing Microsoft's approach as a long shot. Some highlight the pressure to publish groundbreaking results, potentially incentivizing misconduct. The lack of clear evidence and the ongoing investigation are also noted, with some advocating caution before drawing definitive conclusions. A few commenters mention the potential impact on funding for the field and the need for rigorous review processes.
NIST has added a new atomic fountain clock, NIST-F2, to its timekeeping ensemble. This clock, based on cesium atoms, joins NIST-F1 and contributes to the official U.S. civilian time standard. NIST-F2 boasts an improved design and lower uncertainty than its predecessor, enhancing the accuracy and stability of the nation's timekeeping and impacting applications like navigation, communication, and scientific research. The addition of NIST-F2 strengthens the overall resilience of the timekeeping system.
Several commenters on Hacker News discussed the new NIST-F2 atomic fountain clock and its implications. Some highlighted the incredible accuracy of the clock, noting it would only lose or gain one second every 300 million years. Others focused on the practical applications of such precise timekeeping, including improved GPS accuracy, synchronization in telecommunications, and advancements in scientific research. A few commenters delved into the technical details of how atomic fountain clocks work, explaining the laser cooling and trapping of atoms. There was also a brief discussion on the importance of maintaining multiple atomic clocks for redundancy and cross-validation. Finally, some commenters expressed awe and appreciation for the scientific achievement represented by the new clock.
"Induced atmospheric vibration" refers to the phenomenon where seismic waves from earthquakes or underground explosions cause the ground to vibrate, which in turn pushes on the air above it, generating low-frequency sound waves (infrasound). These infrasound waves can travel long distances through the atmosphere and be detected by specialized sensors. While the term itself isn't standard scientific terminology, the process it describes is a recognized effect. These atmospheric pressure fluctuations are related to, but distinct from, the ground motion itself and can even be used to detect and characterize seismic events.
Hacker News users discussed the Stack Exchange question about "induced atmospheric vibration," largely focusing on whether the phenomenon is real or misinterpretation. Several commenters expressed skepticism, suggesting the perceived vibrations could be explained by more mundane phenomena like wind gusts, ground vibrations, or infrasound interacting with structures. One commenter pointed out the lack of credible scientific literature on the topic, reinforcing the idea that "induced atmospheric vibration" may not be a recognized scientific concept. Others debated the potential role of temperature gradients and air density fluctuations. A few commenters offered alternative explanations, such as the movement of large vehicles or industrial equipment causing vibrations that propagate through the ground and air. The overall sentiment suggests a healthy dose of skepticism toward the original question's premise.
David Tong's webpage provides a collection of freely available lecture notes covering various topics in theoretical physics, aimed primarily at advanced undergraduate and beginning graduate students. The subjects range from classical mechanics and electromagnetism to quantum field theory, general relativity, string theory, and solitons, each offering a comprehensive and pedagogical approach. The notes are based on lectures Tong has delivered at the University of Cambridge and are continually updated. They include problem sets, further reading suggestions, and, in some cases, accompanying video lectures.
Hacker News users generally praised David Tong's lecture notes for their clarity, comprehensiveness, and accessibility. Several commenters highlighted the notes as an excellent resource for both students and those seeking to refresh their knowledge of physics. Some pointed out specific strengths, such as the clear explanations of challenging concepts like quantum field theory and general relativity. A few users mentioned minor typos or areas for improvement, but the overall sentiment was overwhelmingly positive, with many thanking Tong for making these resources freely available. Several commenters also discussed their own experiences using the notes, either as students or for self-study, further reinforcing their value.
Physicists have created a theoretical "Quantum Rubik's Cube" where the colored squares exist in superimposed states. Unlike a classical Rubik's Cube, rotations can entangle the squares, making the puzzle significantly more complex. Researchers developed an algorithm to solve this quantum puzzle, focusing on maximizing the probability of reaching the solved state, rather than guaranteeing a solution in a specific number of moves. They discovered that counterintuitive moves, ones that seemingly scramble the cube, can actually increase the likelihood of ultimately solving it due to the nature of quantum superposition and entanglement.
HN commenters were generally skeptical of the article's framing. Several pointed out that the "quantum Rubik's cube" isn't a physical object, but a theoretical model using quantum states analogous to a Rubik's cube. They questioned the practicality and relevance of the research, with some suggesting it was a "solution in search of a problem." Others debated the meaning of "optimal solution" in a quantum context, where superposition allows for multiple states to exist simultaneously. Some commenters did express interest in the underlying mathematics and its potential applications, although these comments were less prevalent than the skeptical ones. A few pointed out that the research is primarily theoretical and explorations into potential applications are likely years away.
Researchers have developed a portable, handheld detector capable of identifying and measuring all major types of ionizing radiation, including alpha, beta, gamma, and neutron radiation. This advancement significantly improves radiation safety by providing a single, easy-to-use device for comprehensive radiation detection in various settings like nuclear power plants, hospitals, and environmental monitoring. The detector combines multiple sensing technologies and advanced algorithms to differentiate between radiation types and accurately quantify their intensity, enabling faster and more informed responses to potential radiation hazards.
HN commenters discuss the practicality and potential applications of the handheld radiation detector. Some express skepticism about its sensitivity and ability to differentiate between different types of radiation effectively, particularly at low levels. Others highlight its potential usefulness in specific scenarios like checking for radon or contaminated materials, while also noting the limitations for average consumers given the naturally occurring background radiation. The overall sentiment leans towards cautious optimism, acknowledging the device's potential while questioning its real-world performance and target audience. A few commenters also point out the importance of understanding background radiation levels and interpreting the readings accurately. Finally, the discussion touches upon the existing availability of similar devices, suggesting this new device isn't entirely revolutionary but rather a potential improvement on current technology.
This paper explores formulating electromagnetism solely in terms of spacetime geometry, eliminating the need for independent fields like the electromagnetic tensor. It achieves this by attributing electromagnetic effects to distortions in the connection of a five-dimensional Kaluza-Klein spacetime. Specifically, the authors show that a torsion-free connection in this higher-dimensional space, projected onto four dimensions, naturally produces the field equations of electromagnetism. This geometric interpretation avoids introducing external forces, instead describing electromagnetic interactions as a consequence of the geometry induced by charged particles in the extended spacetime. The electromagnetic four-potential emerges as part of the five-dimensional metric, further solidifying the purely geometric nature of this approach.
Hacker News users discuss the geometric interpretation of electromagnetism presented in the linked paper. Some express skepticism about the practical implications or novelty of this approach, questioning whether it offers new insights or simply rephrases existing knowledge in a different mathematical language. Others appreciate the elegance of the geometric perspective, finding it conceptually appealing and potentially useful for understanding the fundamental nature of electromagnetism. A few commenters delve into specific aspects of the theory, such as the role of the Hodge star operator and the relationship between this geometric framework and other formulations of electromagnetism. Several users request further explanation or resources to better grasp the concepts presented. The overall sentiment appears to be a mixture of curiosity, cautious optimism, and a desire for more concrete demonstrations of the theory's utility.
ArXiv, the preprint server that revolutionized scientific communication, faces challenges in maintaining its relevance and functionality amidst exponential growth. While its open-access model democratized knowledge sharing, it now grapples with scaling its infrastructure, managing the deluge of submissions, and ensuring quality control without stifling innovation. The article explores ArXiv's history, highlighting its humble beginnings and its current struggles with limited resources and a volunteer-driven moderation system. Ultimately, ArXiv must navigate the complexities of evolving scientific practices and adapt its systems to ensure it continues to serve as a vital tool for scientific progress.
Hacker News users discuss ArXiv's impact and challenges. Several commenters praise its role in democratizing scientific communication and accelerating research dissemination. Some express concern over the lack of peer review, leading to the spread of unverified or low-quality work, while acknowledging the tradeoff with speed and accessibility. The increasing volume of submissions is mentioned as a growing problem, making it harder to find relevant papers. A few users suggest potential improvements, such as enhanced search functionality and community-driven filtering or rating systems. Others highlight the importance of ArXiv's role as a preprint server, emphasizing that proper peer review still happens at the journal level. The lack of funding and the difficulty of maintaining such a crucial service are also discussed.
A proposed cosmic radio detector, outlined in a recent study, could potentially identify axion dark matter within the next 15 years. The detector would search for radio waves emitted when axions, a hypothetical dark matter particle, convert into photons in the magnetic fields of neutron stars. This new method leverages the strong magnetic fields around neutron stars to enhance the signal and improve the chances of detection, potentially providing a breakthrough in our understanding of dark matter. The approach focuses on a specific radio frequency band where the signal is expected to be strongest and distinguishes itself from other axion detection strategies.
Several Hacker News commenters express skepticism about the feasibility of distinguishing dark matter signals from foreground noise, particularly given the immense challenge of shielding the detector from terrestrial and solar radio interference. Some highlight the long timeframe (15 years) mentioned in the article, questioning whether more immediate, albeit less ambitious, projects might yield more valuable data sooner. Others note the inherent difficulty of detecting something unknown, particularly when relying on speculative models of dark matter interaction. A few commenters point out the exciting potential of such a discovery, but temper their enthusiasm with the acknowledgement of the substantial technical and theoretical hurdles involved.
The blog post explores the physics behind the distinctive "whoosh" sound created by passing objects like airplanes. It explains how this sound isn't simply the object's engine noise, but rather the Doppler-shifted frequencies of ambient noise—like wind, traffic, or conversations—being compressed as the object approaches and stretched as it recedes. This effect, similar to how a siren's pitch changes as it passes by, is most noticeable with fast-moving objects in relatively quiet environments. The post further delves into how our brains perceive these shifting frequencies, potentially misinterpreting them as the sound of the object itself and sometimes even creating phantom whooshing sensations when no physical source exists.
Hacker News users discuss various aspects of the "whoosh" sound phenomenon. Several commenters offer additional examples of sounds exhibiting similar characteristics, such as the Doppler shift observed with passing cars or the sound of a large truck passing a house. Some discuss the physics behind the phenomenon, including the role of air pressure changes and the shape of the object creating the sound. Others delve into the subjective experience of these sounds, noting how perception can be influenced by factors like background noise and individual sensitivity. One compelling comment highlights the prevalence of this effect in movies and its potential exaggeration for dramatic effect. Another interesting observation is the comparison to the "sonic boom" of a supersonic aircraft, contrasting the continuous whoosh with the sharp crack of the boom. Finally, a few commenters mention the psychological impact of these sounds, including their potential to be unsettling or even anxiety-inducing.
Sailboats harness the wind to generate propulsive force through aerodynamic principles. The sails, acting as airfoils, create a pressure difference, generating lift perpendicular to the wind. This lift force can be resolved into two components: one pushing the boat sideways (leeway), and the other propelling it forward. The keel or centerboard counteracts leeway, allowing the boat to move efficiently against the wind by sailing at an angle. Sail shape, hull design, and appendage configuration are crucial for optimizing performance, balancing stability and speed. Different sail types and trims are used depending on the wind direction and strength, allowing sailors to adjust to varying conditions and desired points of sail.
HN commenters largely praised the article for its clear explanations of complex sailing concepts like apparent wind, sail trim, and heeling forces. Several appreciated the interactive diagrams, highlighting their effectiveness in illustrating how these forces interact. Some commenters with sailing experience shared personal anecdotes and added further details, expanding upon points made in the article, such as the importance of sail shape and the challenges of heavy weather sailing. A few mentioned the site's outdated design but emphasized that the quality of the content outweighed the aesthetic shortcomings.
Entropy, in the context of information theory, quantifies uncertainty. A high-entropy system, like a fair coin flip, is unpredictable, as all outcomes are equally likely. A low-entropy system, like a weighted coin always landing on heads, is highly predictable. This uncertainty is measured in bits, representing the minimum number of yes/no questions needed to determine the outcome. Entropy also relates to compressibility: high-entropy data is difficult to compress because it lacks predictable patterns, while low-entropy data, with its inherent redundancy, can be compressed significantly. Ultimately, entropy provides a fundamental way to measure information content and randomness within a system.
Hacker News users generally praised the article for its clear explanation of entropy, particularly its focus on the "volume of surprise" and use of visual aids. Some commenters offered alternative analogies or further clarifications, such as relating entropy to the number of microstates corresponding to a macrostate, or explaining its connection to lossless compression. A few pointed out minor perceived issues, like the potential confusion between thermodynamic and information entropy, and questioned the accuracy of describing entropy as "disorder." One commenter suggested a more precise phrasing involving "indistinguishable microstates", while another highlighted the significance of Boltzmann's constant in relating information entropy to physical systems. Overall, the discussion demonstrates a positive reception of the article's attempt to demystify a complex concept.
Researchers have demonstrated a new form of light, called "rotatum," which carries transverse angular momentum along the propagation direction. Unlike circularly polarized light, where the electric and magnetic fields rotate transverse to the propagation direction, in rotatum, these fields rotate along the direction of travel, tracing a spiral trajectory. This unique property arises from a specific superposition of two vortex beams with opposite orbital angular momentum and opposite circular polarization. Experimental generation and characterization of rotatum using vectorially structured light confirms its theoretical predictions, opening new avenues for optical manipulation, quantum information, and high-dimensional light–matter interactions.
Several Hacker News commenters discuss the "Rotatum of Light" study, questioning its novelty and practical implications. Some argue the observed effect is simply circular polarization, a well-established concept, and that the "rotatum" terminology is unnecessary jargon. Others express confusion about the potential applications, wondering if it offers any advantages over existing polarization techniques. A few users attempt to clarify the research, suggesting it explores a specific type of structured light with potential uses in optical trapping, communication, and quantum computing, though these uses remain speculative. The overall sentiment seems skeptical, with many questioning the significance of the findings and the hype surrounding them.
Prince Rupert's Drops, formed by dripping molten glass into cold water, possess incredible compressive strength in their head due to rapid cooling creating a hardened outer layer squeezing a still-molten interior. This exterior endures hammer blows and even bullets. However, the tail is incredibly fragile; the slightest scratch disrupts the delicate balance of internal stresses, causing the entire drop to explosively disintegrate into powder. This dramatic difference in strength is due to how the internal stresses are distributed throughout the drop, concentrating tensile stress in the tail.
Hacker News users discuss the surprising strength of Prince Rupert's Drops, focusing on the rapid cooling process creating immense compressive stress on the surface while leaving the interior under tension. Several commenters delve into the specifics of this process, explaining how the outer layer solidifies quickly, while the inner portion cools slower, pulling inwards and creating a strong compressive layer. One commenter highlights the analogy to tempered glass, clarifying that the Prince Rupert's Drop is a more extreme example of this principle. The "tadpole tail" weakness is also explored, with users pointing out that disrupting this delicate equilibrium releases the stored energy, causing the explosive shattering. Some commenters mention other videos and experiments, including slow-motion footage and demonstrations involving bullets and hydraulic presses, further illustrating the unique properties of these glass formations. A few users express their fascination with the counterintuitive nature of the drops, noting how such a seemingly fragile object possesses such remarkable strength under certain conditions.
CERN has released a conceptual design report detailing the feasibility of the Future Circular Collider (FCC), a proposed successor to the Large Hadron Collider. The FCC would be a much larger and more powerful collider, with a circumference of 91-100 kilometers, capable of reaching collision energies of 100 TeV. The report outlines the technical challenges and potential scientific breakthroughs associated with such a project, which would significantly expand our understanding of fundamental physics, including the Higgs boson, dark matter, and the early universe. The ambitious project is estimated to cost around €24 billion and would involve several phases, starting with an electron-positron collider followed by a proton-proton collider in the same tunnel. The report serves as a roadmap for future discussions and decisions about the next generation of particle physics research.
HN commenters discuss the immense cost and potential scientific return of the proposed Future Circular Collider (FCC). Some express skepticism about the project's justification, given its price tag and the lack of guaranteed breakthroughs. Others argue that fundamental research is crucial for long-term progress and that the FCC could revolutionize our understanding of the universe. Several comments compare the FCC to the SSC, a similar project canceled in the US, highlighting the political and economic challenges involved. The potential for technological spin-offs and the inspirational value of such ambitious projects are also mentioned. A few commenters question the timing, suggesting that resources might be better spent on more immediate global issues like climate change.
The author recounts their frustrating experience trying to replicate a classic Hall effect experiment to determine the band structure of germanium. Despite meticulous preparation and following established procedures, their results consistently deviated significantly from expected values. This led them to suspect systematic errors stemming from equipment limitations or unforeseen environmental factors, ultimately concluding that accurately measuring the Hall coefficient in a basic undergraduate lab setting is far more challenging than textbooks suggest. The post highlights the difficulties of practical experimentation and the gap between theoretical ideals and real-world results.
Hacker News users discuss the linked blog post, which humorously details the author's struggles to reproduce a classic 1954 paper on germanium's band structure. Commenters generally appreciate the author's humor and relatable frustration with reproducing old scientific results. Several share similar experiences of struggling with outdated methods or incomplete information in older papers. Some highlight the difficulty in accessing historical computing resources and the challenge of interpreting old notations and conventions. Others discuss the evolution of scientific understanding and the value of revisiting foundational work, even if it proves difficult. A few commenters express admiration for the meticulous work done in the original paper, given the limitations of the time.
A recent paper claims Earth's rotation could be harnessed for power using a "gravity engine," theoretically generating terawatts of energy by raising and lowering massive weights as the Earth rotates. This concept, building on decades-old physics, hinges on the Coriolis effect. However, many physicists are skeptical, arguing that the proposed mechanism violates fundamental laws of physics, particularly conservation of angular momentum. They contend that any energy gained would be offset by a minuscule slowing of Earth's rotation, effectively transferring rotational energy rather than creating it. The debate highlights the complex interplay between gravity, rotation, and energy, with the practicality and feasibility of such a gravity engine remaining highly contested.
Hacker News users discuss a Nature article about a controversial claim that Earth's rotation could be harnessed for power. Several commenters express skepticism, pointing to the immense scale and impracticality of such a project, even if theoretically possible. Some highlight the conservation of angular momentum, arguing that extracting energy from Earth's rotation would necessarily slow it down, albeit imperceptibly. Others debate the interpretation of the original research, with some suggesting it's more about subtle gravitational effects than a large-scale power source. A few commenters mention existing technologies that indirectly utilize Earth's rotation, such as tidal power. The overall sentiment seems to be one of cautious curiosity mixed with doubt about the feasibility and significance of the proposed concept. A few users engage in more playful speculation, imagining the distant future where such technology might be relevant.
New research from the LHCb experiment at CERN reveals a greater than anticipated difference in how often the charm meson decays into a kaon and either a pion or a muon pair, depending on whether an up or down quark is involved. This asymmetry, which signifies a violation of charge-parity (CP) symmetry, is four times larger than the Standard Model of particle physics predicts. While not yet statistically definitive enough to claim a discovery, this substantial deviation hints at potential new physics beyond the Standard Model, possibly involving unknown particles or forces influencing these decays. Further data analysis is crucial to confirm these findings and explore the implications for our understanding of fundamental interactions.
HN commenters discuss potential implications of the discovery that the up/down quark mass difference is larger than previously thought. Some express excitement about the potential to refine the Standard Model and gain a deeper understanding of fundamental physics. Others are skeptical, pointing out the preliminary nature of the findings and questioning the significance of a small shift in already-known asymmetry. Several commenters delve into the technical details of lattice QCD calculations and the challenges involved in precisely determining quark masses. There's also discussion of the relationship between quark masses and the strong CP problem, with some suggesting this discovery might offer new avenues for exploration in that area.
The CERN Courier article "Beyond Bohr and Einstein" discusses the ongoing quest to understand the foundations of quantum mechanics, nearly a century after the famous Bohr-Einstein debates. While acknowledging the undeniable success of quantum theory in predicting experimental outcomes, the article highlights persistent conceptual challenges, particularly regarding the nature of measurement and the role of the observer. It explores alternative interpretations, such as QBism and the Many-Worlds Interpretation, which attempt to address these foundational issues by moving beyond the traditional Copenhagen interpretation championed by Bohr. The article emphasizes that these alternative interpretations, though offering fresh perspectives, still face their own conceptual difficulties and haven't yet led to experimentally testable predictions that could distinguish them from established quantum theory. Ultimately, the piece suggests that the search for a complete and intuitively satisfying understanding of quantum mechanics remains an open and active area of research.
HN commenters discuss interpretations of quantum mechanics beyond the Bohr-Einstein debates, focusing on the limitations of the Copenhagen interpretation and the search for a more intuitive or complete picture. Several express interest in alternatives like pilot-wave theory and QBism, appreciating their deterministic nature or subjective approach to probability. Some question the practical implications of these interpretations, wondering if they offer any predictive power beyond the standard model. Others emphasize the philosophical importance of exploring these foundational questions, even if they don't lead to immediate technological advancements. The role of measurement and the observer is a recurring theme, with some arguing that decoherence provides a satisfactory explanation within the existing framework.
Summary of Comments ( 4 )
https://news.ycombinator.com/item?id=44127173
HN users discuss various aspects of rigid body simulation, focusing on the challenges of achieving stable "rest" states. Several commenters highlight the inherent difficulties with numerical methods, especially in stacked configurations where tiny inaccuracies accumulate and lead to instability. The "fix" proposed in the linked tweet, of directly zeroing velocities below a threshold, is deemed by some as a hack, while others appreciate its pragmatic value in specific scenarios. A more nuanced approach of damping velocities based on kinetic energy is suggested, as well as a pointer to Bullet Physics' strategy for handling resting contacts. The overall sentiment leans towards acknowledging the complexity of robust rigid body simulation and the need for a balance between physical accuracy and computational practicality.
The Hacker News post "Putting Rigid Bodies to Rest" links to a tweet showcasing a demo of a physics engine. The comments section is relatively short, with a primary focus on the specifics of the demo and some broader discussion about physics engines and game development.
One commenter points out that the demo is not actually putting rigid bodies to rest in the traditional physics engine sense. Instead, it's cleverly using joints to create the illusion of stability. They explain that true resting behavior usually involves detecting minimal movement and then freezing the object to prevent further computation. This commenter's observation sparks a small discussion about the practicality and efficiency of this approach versus true resting implementations.
Another commenter highlights the nostalgic aspect of the demo, comparing it to early 3D games and demoscene productions. They express appreciation for the visual simplicity and the focus on a single, well-executed effect.
A further comment dives a bit deeper into the technical details, speculating on how the demo might be handling collision detection and response, given the jointed nature of the construction. They posit that a specialized collision detection algorithm might be used to optimize performance.
The rest of the comments are brief, mostly expressing general interest in the demo or agreeing with previous points. One commenter simply states their appreciation for the "satisfying" nature of the simulation. There's no extensive debate or deeply technical analysis, likely due to the limited scope of the original tweet and the straightforward nature of the demo itself.