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.
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 Several share similar experiences of struggling with outdated methods or incomplete information in older papers.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.
The symbol 'c' for the speed of light likely comes from the Latin word "celeritas," meaning swiftness or speed. While sometimes attributed to Einstein, he used 'V' in his early work. 'c' became the standard symbol later, possibly arising from the study of electromagnetic waves where 'c' represented a constant in Maxwell's equations. Its precise origin remains somewhat uncertain, but the connection to "celeritas" and the established use of 'c' for wave propagation constants are the most probable explanations.
The Hacker News comments discuss the origin of "c" for the speed of light, with most agreeing it likely comes from "constant" or the Latin "celeritas" (swiftness). Some debate whether Maxwell originally used "V" or another symbol, and whether "c" became standard before Einstein. A compelling comment highlights the difference between defining c as the speed of light versus recognizing it as a fundamental constant relating space and time, with implications beyond just light. Another interesting point raised is that "c" represents the speed of causality, the fastest rate at which information can propagate, regardless of the medium. There's also brief discussion of the historical context of measuring the speed of light and the development of electromagnetic theory.
Solar energy harnesses sunlight using photovoltaic (PV) panels or concentrated solar power (CSP) systems. PV panels directly convert sunlight into electricity via the photovoltaic effect, while CSP uses mirrors to focus sunlight, heating a fluid to generate electricity through conventional turbines. Factors influencing solar energy production include solar irradiance, panel efficiency, temperature, shading, and the system's angle and orientation relative to the sun. While solar offers numerous benefits like reduced reliance on fossil fuels and decreased greenhouse gas emissions, challenges remain, such as intermittency, storage limitations, and the environmental impact of manufacturing and disposal.
Hacker News users generally praised the clarity and comprehensiveness of the linked article on solar energy. Several commenters highlighted the helpful explanations of concepts like energy payback time (EPT) and the levelized cost of energy (LCOE). Some discussed the declining costs of solar and its increasing competitiveness with other energy sources. A few users pointed out the article's focus on crystalline silicon panels while briefly mentioning other technologies like thin-film. There was also discussion around the importance of considering the full lifecycle impacts of solar, including manufacturing and disposal. One compelling comment thread debated the realistic lifespan of solar panels and the factors that might influence their degradation over time. Another interesting exchange focused on the potential for integrating solar into existing infrastructure and the challenges related to energy storage.
Nature reports that Microsoft's claim of creating a topological qubit, a key step towards fault-tolerant quantum computing, remains unproven. While Microsoft published a paper presenting evidence for the existence of Majorana zero modes, which are crucial for topological qubits, the scientific community remains skeptical. Independent researchers have yet to replicate Microsoft's findings, and some suggest that the observed signals could be explained by other phenomena. The Nature article highlights the need for further research and independent verification before Microsoft's claim can be validated. The company continues to work on scaling up its platform, but achieving a truly fault-tolerant quantum computer based on this technology remains a distant prospect.
Hacker News users discuss Microsoft's quantum computing claims with skepticism, focusing on the lack of peer review and independent verification of their "majorana zero mode" breakthrough. Several commenters highlight the history of retracted papers and unfulfilled promises in the field, urging caution. Some point out the potential financial motivations behind Microsoft's announcements, while others note the difficulty of replicating complex experiments and the general challenges in building a scalable quantum computer. The reliance on "future milestones" rather than present evidence is a recurring theme in the criticism, with commenters expressing a "wait-and-see" attitude towards Microsoft's claims. Some also debate the scientific process itself, discussing the role of preprints and the challenges of validating groundbreaking research.
The "Whoosh Rocket" is a simple experiment demonstrating Newton's Third Law of Motion (for every action, there's an equal and opposite reaction). A plastic bottle, partially filled with water and pressurized with air, launches upwards when the air is released. The compressed air exerts force equally in all directions inside the bottle. When the stopper is removed, the air rushes out the opening, creating thrust. This downward force of the escaping air creates an equal and opposite upward force on the bottle, propelling it skyward. The amount of water affects the rocket's performance – too little and there isn't enough mass to be propelled efficiently; too much and the extra weight hinders its flight.
The Hacker News comments on the NASA "Whoosh Rocket" article largely focus on the surprising amount of thrust generated by this simple demonstration. Several commenters express fascination with the physics involved and the counterintuitive nature of the thrust being independent of the surrounding air pressure. Some discuss the educational value of the experiment, highlighting its simplicity and effectiveness in illustrating fundamental principles of rocket propulsion. One commenter provides further context by linking to a video demonstrating the experiment in a vacuum chamber, reinforcing the concept of thrust being generated solely by the expelled propellant. Another points out the historical significance of the experiment, linking it to a similar demonstration performed by Robert Goddard, considered the father of modern rocketry. There's a brief discussion comparing this type of rocket to other propulsion systems, and one user asks a clarifying question about the relevance of nozzle shape.
The question of whether a particle goes through both slits in the double-slit experiment is a misleading one, rooted in classical thinking. Quantum objects like electrons don't have definite paths like marbles. Instead, their behavior is described by a wave function, which evolves according to the Schrödinger equation and spreads through both slits. It's the wave function, not the particle itself, that interferes, creating the characteristic interference pattern. When measured, the wave function "collapses," and the particle is found at a specific location, but it's not meaningful to say which slit it "went through" before that measurement. The particle's position becomes definite only upon interaction, and retroactively assigning a classical trajectory is a misinterpretation of quantum mechanics.
Hacker News users discussed the nature of wave-particle duality and the interpretation of quantum mechanics in the double-slit experiment. Some commenters emphasized that the wave function is a mathematical tool to describe probabilities, not a physical entity, and that the question of "which slit" is meaningless in the quantum realm. Others pointed to the role of the measurement apparatus in collapsing the wave function and highlighted the difference between the wave function of the particle and the electromagnetic field wave. A few mentioned alternative interpretations like pilot-wave theory and many-worlds interpretation. Some users expressed frustration with the ongoing ambiguity surrounding quantum phenomena, while others found the topic fascinating and appreciated Strassler's explanation. A few considered the article too simplistic or misleading.
This paper provides a comprehensive overview of percolation theory, focusing on its mathematical aspects. It explores bond and site percolation on lattices, examining key concepts like critical probability, the existence of infinite clusters, and critical exponents characterizing the behavior near the phase transition. The text delves into various methods used to study percolation, including duality, renormalization group techniques, and series expansions. It also discusses different percolation models beyond regular lattices, like continuum percolation and directed percolation, highlighting their unique features and applications. Finally, the paper connects percolation theory to other areas like random graphs, interacting particle systems, and the study of disordered media, showcasing its broad relevance in statistical physics and mathematics.
HN commenters discuss the applications of percolation theory, mentioning its relevance to forest fires, disease spread, and network resilience. Some highlight the beauty and elegance of the theory itself, while others note its accessibility despite being a relatively advanced topic. A few users share personal experiences using percolation theory in their work, including modeling concrete porosity and analyzing social networks. The concept of universality in percolation, where different systems exhibit similar behavior near the critical threshold, is also pointed out. One commenter links to an interactive percolation simulation, allowing others to experiment with the concepts discussed. Finally, the historical context and development of percolation theory are briefly touched upon.
In 1964, John Stewart Bell published a groundbreaking theorem demonstrating that quantum mechanics fundamentally differs from classical physics, even when allowing for hidden variables. His theorem, now known as Bell's theorem, showed that the predictions of quantum mechanics concerning entangled particles could not be replicated by any local realistic theory. This work provided a testable inequality that allowed experimental physicists to investigate the foundations of quantum theory, ushering in a new era focused on experimental tests of quantum mechanics and the exploration of its nonlocal nature. Bell's seemingly simple paper revolutionized the understanding of quantum mechanics, highlighting the radical departure from classical notions of locality and realism and paving the way for fields like quantum information science.
HN commenters discuss Bell's theorem's profound impact, highlighting its shift from philosophical debate to testable science. Several note the importance of Clauser, Horne, Shimony, and Holt's (CHSH) refinement for making experimental verification possible. Some commenters delve into the implications of Bell's theorem, debating superdeterminism versus non-locality, and the nature of reality itself. A few provide helpful resources, linking to explanations and videos further clarifying the concepts. Others express admiration for Bell's work, describing its elegance and simplicity. There's also a short discussion on the accessibility of the APS Physics article to non-physicists, with some finding it surprisingly readable.
Tufts University researchers have developed an open-source software package called "OpenSM" designed to simulate the behavior of soft materials like gels, polymers, and foams. This software leverages state-of-the-art numerical methods and offers a user-friendly interface accessible to both experts and non-experts. OpenSM streamlines the complex process of building and running simulations of soft materials, allowing researchers to explore their properties and behavior under different conditions. This freely available tool aims to accelerate research and development in diverse fields including bioengineering, materials science, and manufacturing by enabling wider access to advanced simulation capabilities.
HN users discussed the potential of the open-source software, SOFA, for various applications like surgical simulations and robotics. Some highlighted its maturity and existing use in research, while others questioned its accessibility for non-experts. Several commenters expressed interest in its use for simulating specific materials like fabrics and biological tissues. The licensing (LGPL) was also a point of discussion, with some noting its permissiveness for commercial use. Overall, the sentiment was positive, with many seeing the software as a valuable tool for research and development.
A new mathematical framework called "next-level chaos" moves beyond traditional chaos theory by incorporating the inherent uncertainty in our knowledge of a system's initial conditions. Traditional chaos focuses on how small initial uncertainties amplify over time, making long-term predictions impossible. Next-level chaos acknowledges that perfectly measuring initial conditions is fundamentally impossible and quantifies how this intrinsic uncertainty, even at minuscule levels, also contributes to unpredictable outcomes. This new approach provides a more realistic and rigorous way to assess the true limits of predictability in complex systems like weather patterns or financial markets, acknowledging the unavoidable limitations imposed by quantum mechanics and measurement precision.
Hacker News users discuss the implications of the Quanta article on "next-level" chaos. Several commenters express fascination with the concept of "intrinsic unpredictability" even within deterministic systems. Some highlight the difficulty of distinguishing true chaos from complex but ultimately predictable behavior, particularly in systems with limited observational data. The computational challenges of accurately modeling chaotic systems are also noted, along with the philosophical implications for free will and determinism. A few users mention practical applications, like weather forecasting, where improved understanding of chaos could lead to better predictive models, despite the inherent limits. One compelling comment points out the connection between this research and the limits of computability, suggesting the fundamental unknowability of certain systems' future states might be tied to Turing's halting problem.
Dr. Drang poses a puzzle from the March 2025 issue of Scientific American, involving a square steel plate with a circular hole and a matching square-headed bolt. The challenge is to determine how much the center of the hole moves relative to the plate's center when the bolt is tightened, pulling the head flush against the plate. He outlines his approach using vector analysis, trigonometric identities, and small-angle approximations to derive a simplified solution. He compares this to a purely geometric approach, also presented in the magazine, and finds it both more elegant and more readily generalizable to different hole/head sizes.
HN users generally found the puzzle trivial, with several pointing out the quick solution of simply measuring the gap between the bolts to determine which one is missing. Some debated the practicality of such a solution, suggesting calipers would be necessary for accuracy, while others argued a visual inspection would suffice. A few commenters explored alternative, more complex approaches involving calculating the center of mass or using image analysis software, but these were generally dismissed as overkill. The discussion also briefly touched on manufacturing tolerances and the real-world implications of such a scenario.
Roger Penrose argues that Gödel's incompleteness theorems demonstrate that human mathematical understanding transcends computation and therefore, strong AI, which posits that consciousness is computable, is fundamentally flawed. He asserts that humans can grasp the truth of Gödelian sentences (statements unprovable within a formal system yet demonstrably true outside of it), while a computer bound by algorithms within that system cannot. This, Penrose claims, illustrates a non-computable element in human consciousness, suggesting we understand truth through means beyond mere calculation.
Hacker News users discuss Penrose's argument against strong AI, with many expressing skepticism. Several commenters point out that Gödel's incompleteness theorems don't necessarily apply to the way AI systems operate, arguing that AI doesn't need to be consistent or complete in the same way as formal mathematical systems. Others suggest Penrose misinterprets or overextends Gödel's work. Some users find Penrose's ideas intriguing but remain unconvinced, while others find his arguments simply wrong. The concept of "understanding" is a key point of contention, with some arguing that current AI models only simulate understanding, while others believe that sophisticated simulation is indistinguishable from true understanding. A few commenters express appreciation for Penrose's thought-provoking perspective, even if they disagree with his conclusions.
The article proposes a new theory of consciousness called "assembly theory," suggesting that consciousness arises not simply from complex arrangements of matter, but from specific combinations of these arrangements, akin to how molecules gain new properties distinct from their constituent atoms. These combinations, termed "assemblies," represent information stored in the structure of molecules, especially within living organisms. The complexity of these assemblies, measurable by their "assembly index," correlates with the level of consciousness. This theory proposes that higher levels of consciousness require more complex and diverse assemblies, implying consciousness could exist in varying degrees across different systems, not just biological ones. It offers a potentially testable framework for identifying and quantifying consciousness through analyzing the complexity of molecular structures and their interactions.
Hacker News users discuss the "Integrated Information Theory" (IIT) of consciousness proposed in the article, expressing significant skepticism. Several commenters find the theory overly complex and question its practical applicability and testability. Some argue it conflates correlation with causation, suggesting IIT merely describes the complexity of systems rather than explaining consciousness. The high degree of abstraction and lack of concrete predictions are also criticized. A few commenters offer alternative perspectives, suggesting consciousness might be a fundamental property, or referencing other theories like predictive processing. Overall, the prevailing sentiment is one of doubt regarding IIT's validity and usefulness as a model of consciousness.
John Siracusa reflects on twenty years of Hypercritical, his influential tech podcast. He acknowledges the show's impact, driven by his rigorous approach to analysis and honest, often critical, perspectives. He also discusses the personal toll of maintaining this level of scrutiny and the evolution of the tech landscape, which has made it increasingly difficult to cover everything with the desired depth. Ultimately, he concludes that it's time to end Hypercritical, emphasizing the need for a break and a shift in focus. He expresses gratitude for his listeners and reflects on the satisfaction derived from producing the show for so long.
Hacker News users discussed Gruber's Hyperspace announcement with cautious optimism. Some expressed excitement about the potential for a truly native Mac writing app built with modern technologies, praising its speed and minimalist design. Several commenters, however, raised concerns about vendor lock-in to Markdown and the subscription model, particularly given Gruber's past stance on subscriptions. Others questioned the long-term viability of relying on iCloud syncing and the lack of collaboration features. A few users pointed out the irony of Gruber creating a closed-source, subscription-based app after his criticisms of similar practices in the past, while others defended his right to change his business model. The lack of an iOS version was also a common complaint. Several commenters compared Hyperspace to other Markdown editors and debated its potential market fit given the existing competition.
This study demonstrates a significant advancement in magnetic random-access memory (MRAM) technology by leveraging the orbital Hall effect (OHE). Researchers fabricated a device using a topological insulator, Bi₂Se₃, as the OHE source, generating orbital currents that efficiently switch the magnetization of an adjacent ferromagnetic layer. This approach requires substantially lower current densities compared to conventional spin-orbit torque (SOT) MRAM, leading to improved energy efficiency and potentially faster switching speeds. The findings highlight the potential of OHE-based SOT-MRAM as a promising candidate for next-generation non-volatile memory applications.
Hacker News users discussed the potential impact of the research on MRAM technology, expressing excitement about its implications for lower power consumption and faster switching speeds. Some questioned the practicality due to the cryogenic temperatures required for the observed effect, while others pointed out that room-temperature operation might be achievable with further research and different materials. Several commenters delved into the technical details of the study, discussing the significance of the orbital Hall effect and its advantages over the spin Hall effect for generating spin currents. There was also discussion about the challenges of scaling this technology for mass production and the competitive landscape of next-generation memory technologies. A few users highlighted the complexity of the physics involved and the need for simplified explanations for a broader audience.
The post "But good sir, what is electricity?" explores the challenge of explaining electricity simply and accurately. It argues against relying solely on analogies, which can be misleading, and emphasizes the importance of understanding the underlying physics. The author uses the example of a simple circuit to illustrate the flow of electrons driven by an electric field generated by the battery, highlighting concepts like potential difference (voltage), current (flow of charge), and resistance (impeding flow). While acknowledging the complexity of electromagnetism, the post advocates for a more fundamental approach to understanding electricity, moving beyond simplistic comparisons to water flow or other phenomena that don't capture the core principles. It concludes that a true understanding necessitates grappling with the counterintuitive aspects of electromagnetic fields and their interactions with charged particles.
Hacker News users generally praised the article for its clear and engaging explanation of electricity, particularly its analogy to water flow. Several commenters appreciated the author's ability to simplify complex concepts without sacrificing accuracy. Some pointed out the difficulty of truly understanding electricity, even for those with technical backgrounds. A few suggested additional analogies or areas for exploration, such as the role of magnetism and electromagnetic fields. One commenter highlighted the importance of distinguishing between the physical phenomenon and the mathematical models used to describe it. A minor thread discussed the choice of using conventional current vs. electron flow in explanations. Overall, the comments reflected a positive reception to the article's approach to explaining a fundamental yet challenging concept.
Richard Feynman's blackboard, preserved after his death in 1988, offers a glimpse into his final thoughts and ongoing work. It features a partially completed calculation related to the quantum Hall effect, specifically concerning the motion of a single electron in a magnetic field. The board also displays a quote from "King Lear" – "What art thou that dost torment me in this world" – alongside a drawing and some seemingly unrelated calculations, hinting at the diverse range of topics occupying his mind. The preserved blackboard serves as a poignant reminder of Feynman's relentless curiosity and enduring engagement with physics.
HN users discuss the contents of Feynman's blackboard, focusing on the cryptic nature of "Know how to solve every problem that has been solved." Some interpret it as a reminder to understand fundamental principles rather than memorizing specific solutions, while others see it as highlighting the importance of studying existing solutions before tackling new problems. A few users point out the irony of the seemingly unfinished thought next to it, "What I cannot create, I do not understand," speculating on what Feynman might have intended to add. Others comment on the more mundane items, like the phone numbers and grocery list, offering a glimpse into Feynman's everyday life. Several express appreciation for the preservation of the blackboard as a historical artifact, providing insight into the mind of a brilliant physicist.
The French tokamak WEST (Tungsten Environment in Steady-state Tokamak) has set a new world record for plasma duration in a fusion reactor, achieving a plasma discharge lasting 390 seconds. This surpasses the previous record and represents a significant milestone in the development of sustainable fusion energy. The long duration demonstrates WEST's ability to handle the extreme heat and power fluxes associated with fusion reactions, crucial for future reactors like ITER and ultimately, the production of clean energy. This achievement validates design choices and material selections, particularly the tungsten walls, paving the way for longer, higher-performance plasma discharges.
HN commenters discuss the significance of the WEST tokamak achieving a 100+ second plasma discharge, emphasizing that while it's a step forward in sustained fusion, it's far from achieving net energy gain. Several point out that maintaining plasma temperature and stability for extended periods is crucial but distinct from generating more energy than is input. Some debate the true meaning of "world record," noting that other reactors have achieved higher temperatures or different milestones. Others express skepticism about the overall viability of fusion energy due to the ongoing technical challenges and massive resource requirements. There's also some discussion of alternative fusion approaches like stellarators and inertial confinement. Overall, the sentiment is cautious optimism tempered by a realistic understanding of the long road ahead for fusion power.
Researchers at the University of Surrey have theoretically demonstrated that two opposing arrows of time can emerge within specific quantum systems. By examining the evolution of entanglement within these systems, they found that while one subsystem experiences time flowing forward as entropy increases, another subsystem can simultaneously experience time flowing backward, with entropy decreasing. This doesn't violate the second law of thermodynamics, as the overall combined system still sees entropy increase. This discovery offers new insights into the foundations of quantum mechanics and its relationship with thermodynamics, particularly in understanding the flow of time at the quantum level.
HN users express skepticism about the press release's interpretation of the research, questioning whether the "two arrows of time" are a genuine phenomenon or simply an artifact of the chosen model. Some suggest the description is sensationalized and oversimplifies complex quantum behavior. Several commenters call for access to the actual paper rather than relying on the university's press release, emphasizing the need to examine the methodology and mathematical framework to understand the true implications of the findings. A few commenters delve into the specifics of microscopic reversibility and entropy, highlighting the challenges in reconciling these concepts with the claims made in the article. There's a general consensus that the headline is attention-grabbing but potentially misleading without deeper analysis of the underlying research.
Researchers have developed a new technique to create topological structures in water waves using a sort of "acoustic tweezer." By strategically placing vibrating sources beneath a water tank, they generate specific wave patterns that exhibit topological properties, meaning certain features are protected and robust against perturbations. This method allows for the precise control and manipulation of these topological gravity waves, potentially opening new avenues for studying wave phenomena and their interactions in fluids.
Hacker News users discussed the limitations of the "topological gravity" created with water waves, emphasizing that it's an analog simulation, not true gravity. Several commenters pointed out that while interesting, this doesn't offer new insights into actual gravity or quantum gravity. The analogy was compared to using water waves to simulate traffic flow – insightful for specific behaviors, but not fundamentally altering our understanding of cars. Some questioned the use of "topological" and "gravity" in the title, finding it misleadingly sensationalized. A few appreciated the elegance of the experiment, acknowledging the challenges of simulating complex physics, even in analog form. There was also brief discussion on the potential applications of such simulations in other fields.
Classical physics is generally considered deterministic, meaning the future state of a system is entirely determined by its present state. However, certain situations appear non-deterministic due to our practical limitations. These include chaotic systems, where tiny uncertainties in initial conditions are amplified exponentially, making long-term predictions impossible, despite the underlying deterministic nature. Other examples involve systems with a vast number of particles, like gases, where tracking individual particles is infeasible, leading to statistical descriptions and probabilistic predictions, even though the individual particle interactions are deterministic. Finally, systems involving measurement with intrinsic limitations also exhibit apparent non-determinism, arising from our inability to perfectly measure the initial state. Therefore, non-determinism in classical physics is often a result of incomplete knowledge or practical limitations rather than a fundamental property of the theory itself.
Hacker News users discuss deterministic chaos and how seemingly simple classical systems can exhibit unpredictable behavior due to sensitivity to initial conditions. They mention examples like the double pendulum, dripping faucets, and billiard balls, highlighting how minute changes in starting conditions lead to vastly different outcomes, making long-term prediction impossible. Some argue that while these systems are technically deterministic, the practical limitations of measurement render them effectively non-deterministic. Others point to the three-body problem and the chaotic nature of weather systems as further illustrations. The role of computational limitations in predicting chaotic systems is also discussed, along with the idea that even if the underlying laws are deterministic, emergent complexity can make systems appear unpredictable. Finally, the philosophical implications of determinism are touched upon, with some suggesting that quantum mechanics introduces true randomness into the universe.
Hans Bethe, renowned for calculating stellar energy production, surprisingly found success by applying simplifying assumptions to complex quantum problems. He tackled seemingly intractable calculations, like the splitting of energy levels in magnetic fields (Zeeman effect) and the behavior of crystals, by focusing on the most dominant interactions and ignoring smaller effects. This approach, though approximate, often yielded surprisingly accurate and insightful results, showcasing Bethe's knack for identifying the essential physics at play. His ability to "see through" complicated equations made him a pivotal figure in 20th-century physics, influencing generations of scientists.
Hacker News users discussed Bethe's pragmatic approach to physics, contrasting it with more mathematically driven physicists. Some highlighted his focus on getting usable results and his ability to simplify complex problems, exemplified by his work on the Lamb shift and stellar nucleosynthesis. Others commented on the article's portrayal of Bethe's personality, describing him as humble and approachable, even when dealing with complex subjects. Several commenters shared anecdotes about Bethe, emphasizing his teaching ability and the impact he had on their understanding of physics. The importance of approximation and "back-of-the-envelope" calculations in theoretical physics was also a recurring theme, with Bethe presented as a master of these techniques.
"Anatomy of Oscillation" explores the ubiquitous nature of oscillations in various systems, from physics and engineering to biology and economics. The post argues that these seemingly disparate phenomena share a common underlying structure: a feedback loop where a system's output influences its own input, leading to cyclical behavior. It uses the example of a simple harmonic oscillator (a mass on a spring) to illustrate the core principles of oscillation, including the concepts of equilibrium, displacement, restoring force, and inertia. The author suggests that understanding these basic principles can help us better understand and predict oscillations in more complex systems, ultimately offering a framework for recognizing recurring patterns in seemingly chaotic processes.
Hacker News users discussed the idea of "oscillation" presented in the linked Substack article, primarily focusing on its application in various fields. Some commenters questioned the novelty of the concept, arguing that it simply describes well-known feedback loops. Others found the framing helpful, highlighting its relevance to software development processes, personal productivity, and even biological systems. A few users expressed skepticism about the practical value of the framework, while others offered specific examples of oscillation in their own work, such as product development cycles and the balance between exploration and exploitation in learning. The discussion also touched upon the optimal frequency of oscillations and the importance of recognizing and managing them for improved outcomes.
The original poster is deciding between Physics PhD programs at Stanford and UC Berkeley, having been accepted to both. They're leaning towards Stanford due to perceived stronger faculty in their specific research interest (quantum computing/AMO physics) and the potential for better industry connections post-graduation. However, they acknowledge Berkeley's prestigious physics department and are seeking further input from the Hacker News community to solidify their decision. Essentially, they are asking for perspectives on the relative strengths and weaknesses of each program, particularly regarding career prospects in quantum computing.
The Hacker News comments on the "Ask HN: Physics PhD at Stanford or Berkeley" post largely revolve around the nuances of choosing between the two prestigious programs. Commenters emphasize that both are excellent choices, and the decision should be based on individual factors like specific research interests, advisor fit, and departmental culture. Several commenters suggest visiting both departments and talking to current students to gauge the environment. Some highlight Stanford's stronger connections to industry and Silicon Valley, while others point to Berkeley's arguably stronger reputation in certain subfields of physics. The overall sentiment is that the OP can't go wrong with either choice, and the decision should be based on personal preference and research goals rather than perceived prestige. A few commenters also caution against overemphasizing the "prestige" factor in general, encouraging the OP to prioritize a supportive and stimulating research environment.
Noether's theorem, proven by mathematician Emmy Noether in 1915, reveals a profound connection between symmetries in nature and conservation laws. It states that every continuous symmetry in a physical system corresponds to a conserved quantity. For example, the symmetry of physical laws over time leads to the conservation of energy, and the symmetry of laws across space leads to the conservation of momentum. This theorem has become a cornerstone of modern physics, providing a powerful tool for understanding and predicting the behavior of physical systems, from classical mechanics and electromagnetism to quantum field theory and general relativity. It unified seemingly disparate concepts and drastically simplified the search for new laws of physics.
HN commenters generally praised the Quanta article for its clear explanation of Noether's theorem, with several sharing personal anecdotes about learning it. Some discussed the theorem's implications, highlighting its connection to symmetries in physics and its importance in modern theories like quantum field theory and general relativity. A few commenters delved into more technical details, mentioning Lagrangian and Hamiltonian mechanics, gauge theories, and the relationship between conservation laws and symmetries. One commenter pointed out the importance of differentiating between global and local symmetries, while others appreciated the article's accessibility even for those without a deep physics background. The overall sentiment was one of appreciation for both Noether's work and the article's elucidation of it.
Researchers have demonstrated that antimony atoms implanted in silicon can function as qubits with impressive coherence times—a key factor for building practical quantum computers. Antimony's nuclear spin is less susceptible to noise from the surrounding silicon environment compared to electron spins typically used in silicon qubits, leading to these longer coherence times. This increased stability could simplify error correction procedures, making antimony-based qubits a promising candidate for scalable quantum computing. The demonstration used a scanning tunneling microscope to manipulate individual antimony atoms and measure their quantum properties, confirming their potential for high-fidelity quantum operations.
Hacker News users discuss the challenges of scaling quantum computing, particularly regarding error correction. Some express skepticism about the feasibility of building large, fault-tolerant quantum computers, citing the immense overhead required for error correction and the difficulty of maintaining coherence. Others are more optimistic, pointing to the steady progress being made and suggesting that specialized, error-resistant qubits like those based on antimony atoms could be a promising path forward. The discussion also touches upon the distinction between logical and physical qubits, with some emphasizing the importance of clearly communicating this difference to avoid hype and unrealistic expectations. A few commenters highlight the resource intensiveness of current error correction methods, noting that thousands of physical qubits might be needed for a single logical qubit, raising concerns about scalability.
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https://news.ycombinator.com/item?id=43639253
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.
The Hacker News post linked has a moderate number of comments, discussing various aspects related to Prince Rupert's drops. Several commenters delve deeper into the physics behind the drop's unusual strength and explosive shattering.
One compelling comment thread discusses the different failure modes of the head and tail of the drop. Commenters explain that the head's strength is due to compressive stress, making it incredibly resistant to external force. However, the tail is highly susceptible to tensile stress, meaning even a slight nick can initiate catastrophic shattering. This difference in stress distribution explains why breaking the tail releases the stored energy and causes the entire drop to explode.
Another interesting point raised is the historical context of Prince Rupert's drops. One commenter notes that despite being named after Prince Rupert of the Rhine, the drops were likely discovered in Germany in the early 17th century. Prince Rupert simply popularized them within the Royal Society in England. This historical clarification adds a layer of nuance to the commonly known story.
Some users share personal experiences with making and breaking the drops, offering practical advice on safety precautions. They emphasize the importance of eye protection due to the high-speed glass shards produced during the explosion.
One comment provides a link to a slow-motion video that vividly demonstrates the propagation of fractures throughout the drop upon breaking the tail. This visual aid helps to illustrate the rapid and comprehensive nature of the shattering process.
Finally, a few comments touch upon the practical applications of Prince Rupert's drops, while limited. They mention its use in demonstrating material science principles and its historical role in sparking scientific curiosity. Some also speculate on potential, though likely impractical, applications in material strengthening.
Overall, the comments section provides a valuable extension to the original article, offering deeper insights into the physics, history, and practical considerations related to Prince Rupert's drops, while avoiding speculation and focusing on factual information and personal experiences.