Posts Tagged ‘Physics’
“Reality is that which, when you stop believing in it, doesn’t go away”*…
Reality is tough. Everything eats and is eaten. Everything destroys and is destroyed.
In a way that challenges lots of our deeply-seated conceptions (your correspondent’s, anyway), philosopher (and self-proclaimed pessimist) Drew Dalton invokes the laws of thermodynamics to argue that it is our moral duty to strike back at the Universe…
Reality is not what you think it is. It is not the foundation of our joyful flourishing. It is not an eternally renewing resource, nor something that would, were it not for our excessive intervention and reckless consumption, continue to harmoniously expand into the future. The truth is that reality is not nearly so benevolent. Like everything else that exists – stars, microbes, oil, dolphins, shadows, dust and cities – we are nothing more than cups destined to shatter endlessly through time until there is nothing left to break. This, according to the conclusions of scientists over the past two centuries, is the quiet horror that structures existence itself.
We might think this realisation belongs to the past – a closed chapter of 19th-century science – but we are still living through the consequences of the thermodynamic revolution. Just as the full metaphysical implications of the Copernican revolution took centuries to unfold, we have yet to fully grasp the philosophical and existential consequences of entropic decay. We have yet to conceive of reality as it truly is. Instead, philosophers cling to an ancient idea of the Universe in which everything keeps growing and flourishing. According to this view, existence is good. Reality is good.
But what would our metaphysics and ethics look like if we learned that reality was against us?…
Read on for his provocative argument that philosphers must grapple with the meaning of thermodynamics: “Reality is evil,” from @dmdalton.bsky.social in @aeon.co.
Dalton further explores these ideas in his book The Matter of Evil: From Speculative Realism to Ethical Pessimism (2023)
* Philip K. Dick
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As we wrestle with reality, we might send somewhat sunnier birthday greetings to Stephen William Hawking CH CBE FRS FRSA; he was born on this date in 1942. A theoretical physicist and cosmologist, he is probably best known in his professional circles for his work with Roger Penrose on gravitational singularity theorems in the framework of general relativity, for his theoretical prediction that black holes emit radiation (now called Hawking radiation), and for his support of the many-worlds interpretation of quantum mechanics.
But Hawking is more broadly known as a popularizer of science. His A Brief History of Time stayed on the British Sunday Times best-seller list for over four years (a record-breaking 237 weeks), and has sold over 10 million copies worldwide.
“We have this one life to appreciate the grand design of the universe, and for that, I am extremely grateful.”
“If geometry is dressed in a suit coat, topology dons jeans and a T-shirt”*…
Paulina Rowińska on how, in the mid-19th century, Bernhard Riemann conceived of a new way to think about mathematical spaces, providing the foundation for modern geometry and physics…
Standing in the middle of a field, we can easily forget that we live on a round planet. We’re so small in comparison to the Earth that from our point of view, it looks flat.
The world is full of such shapes — ones that look flat to an ant living on them, even though they might have a more complicated global structure. Mathematicians call these shapes manifolds. Introduced by Bernhard Riemann in the mid-19th century, manifolds transformed how mathematicians think about space. It was no longer just a physical setting for other mathematical objects, but rather an abstract, well-defined object worth studying in its own right.
This new perspective allowed mathematicians to rigorously explore higher-dimensional spaces — leading to the birth of modern topology, a field dedicated to the study of mathematical spaces like manifolds. Manifolds have also come to occupy a central role in fields such as geometry, dynamical systems, data analysis and physics.
Today, they give mathematicians a common vocabulary for solving all sorts of problems. They’re as fundamental to mathematics as the alphabet is to language. “If I know Cyrillic, do I know Russian?” said Fabrizio Bianchi, a mathematician at the University of Pisa in Italy. “No. But try to learn Russian without learning Cyrillic.”
So what are manifolds, and what kind of vocabulary do they provide?…
[Rowińska explains manifolds and the history of the development of our understanding of them, concentrating on the pivotal role of Riemann…]
… Manifolds are crucial to our understanding of the universe… In his general theory of relativity, Einstein described space-time as a four-dimensional manifold, and gravity as that manifold’s curvature. And the three-dimensional space we see around us is also a manifold — one that, as manifolds do, appears Euclidean to those of us living within it, even though we’re still trying to figure out its global shape.
Even in cases where manifolds don’t seem to be present, mathematicians and physicists try to rewrite their problems in the language of manifolds to make use of their helpful properties. “So much of physics comes down to understanding geometry,” said Jonathan Sorce, a theoretical physicist at Princeton University. “And often in surprising ways.”
Consider a double pendulum, which consists of one pendulum hanging from the end of another. Small changes in the double pendulum’s initial conditions lead it to carve out very different trajectories through space, making its behavior hard to predict and understand. But if you represent the configuration of the pendulum with just two angles (one describing the position of each of its arms), then the space of all possible configurations looks like a doughnut, or torus — a manifold. Each point on this torus represents one possible state of the pendulum; paths on the torus represent the trajectories the pendulum might follow through space. This allows researchers to translate their physical questions about the pendulum into geometric ones, making them more intuitive and easier to solve. This is also how they study the movements of fluids, robots, quantum particles and more.
Similarly, mathematicians often view the solutions to complicated algebraic equations as a manifold to better understand their properties. And they analyze high-dimensional datasets — such as those recording the activity of thousands of neurons in the brain — by looking at how those data points might sit on a lower-dimensional manifold.
Asking how scientists use manifolds is akin to asking how they use numbers, Sorce said. “They are at the foundation of everything.”…
“What Is a Manifold?” from @quantamagazine.bsky.social.
Apposite: Rowińska in conversation with Ira Flatow on Science Friday: “How Math Helps Us Map The World.”
* David S. Richeson, Euler’s Gem: The Polyhedron Formula and the Birth of Topology (Riemann’s work was an advance on the foundation that Euler laid in his 1736 paper on the Seven Bridges of Königsberg, which led to his polyhedron formula)
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As we get down with geometry, we might spare a thought for John Wallis; he died on this date in 1703. A clergyman and mathematician, he served as chief cryptographer for Parliament (decoding Royalist messages during the Civil War) and, later (as Savilian Chair of geometry at Oxford after the hostilities), for the the royal court. Wallis is credited with introducing the symbol ∞ to represent the concept of infinity, and used 1/∞ for an infinitesimal… which earned him (along with his contemporaries Isaac Newton and Gottfried Wilhelm Leibniz) a share of the credit for the development of infinitesimal calculus. He was a founding member of the Royal Society and one of its first Fellows.
“We are the first generation to feel the effect of climate change and the last generation who can do something about it”*…
One of the issues that vexes coordinated response is a paradox that lies at the heart of the phenomenon: Earth’s climate is chaotic and volatile. Climate change is simple and predictable. How can both be true? Joseph Howlett explains…
The Earth’s atmosphere is nothing but freely roaming molecules. Left alone, they would drift and collide, and eventually even out into a mixture that’s dynamic, yet stable and broadly unchanging.
The sun’s rays complicate things. Energy enters the Earth system in daily cycles, the bulk of it going to whichever half of the planet is tilted toward the sun (and experiencing summer). The molecules in that half acquire more energy than others, which sets the global atmosphere steadily swirling. Depending on the season and location, molecules in our atmosphere might traverse warm land, then cold seas. They might encounter a mountain range that forces them to high altitudes, where the air pressure is low and water condenses. Then they might become part of large-scale phenomena, such as currents, atmospheric rivers, turbulent jet streams and continental fronts.
These phenomena are erratic. They interact at every scale and manifest as weather, from clear sunny days to blustery blizzards and the anomalous events — from hurricanes and polar vortices to hailstorms and tornadoes — that are happening with increasing intensity. Any thought of stability is illusory; no patch of molecules dances in isolation.
The result, from seemingly simple inputs of molecules and energy, is emergent, incalculable chaos. Some individual molecule in the room you are sitting in is careening about blindly and colliding with its immediate neighbors. Zoom out — block to city, field to landscape, region to continent — and patterns appear and intermix. Complexity abounds and compounds. Nothing in the atmosphere is untethered from the rest of the global picture.
We live with this unpredictable mess of an atmosphere every day. We tote around unopened umbrellas, or refresh weather apps and watch our weekend plans dissolve. Anticipating conditions any further out than a week or two is a fool’s errand. The Earth is a complex dynamical system — an interwoven mass of moving parts, each of which requires a different branch of science to understand. Even with advanced knowledge, sophisticated algorithms and modern instruments, it defies and eludes us.
Yet this engine of chaos is now under our influence. It is incontrovertible fact that we are changing the Earth’s temperature by adding more carbon dioxide to the atmosphere. We know exactly how we are changing it — that when we double the proportion of carbon dioxide in the thin layer that rests over the surface of the Earth, the planet will become 2 to 4 degrees Celsius warmer, overall, than it is today. This conclusion has remained essentially unchanged since 1896, when the Swedish scientist Svante Arrhenius arrived at an estimate of 2 to 5 degrees. (Using an extraordinarily simplified picture of Earth, he made a number of mistakes that, in the end, balanced out.) Some details may remain uncertain, some chaos untamable, but the basic conclusion is a matter of unwavering scientific agreement — 97% is a rare degree of consensus on almost any subject. We are nearly as sure of this as we are of the causes of infectious disease, or how stars form, or the fact that life evolves through natural selection.
oth things are true: The climate system is vastly complex, and we’re certain about what we are doing to it. How can we be so confident in a hundred-year projection when we can’t predict the weather with any reliability more than a week out?
“How can it be that both are true?” said Nadir Jeevanjee, an atmospheric physicist at NOAA’s Geophysical Fluid Dynamics Laboratory, a leading institution for cutting-edge simulations of the atmosphere. “It’s a huge tension that’s lurking behind the whole conversation.”
It turns out that complexity can be a veil concealing more basic truths. An enormously complicated system can yield simple answers. You just have to ask a simple enough question…
Read on for Howlett’s fascinating– and important– explanation: “The Climate Change Paradox,” from @quantamagazine.bsky.social.
And for a reminder that this matters (as though we need one…): “Human-Caused Warming Tripled the Death Toll of European Heat Waves This Summer, New Report Shows,” from @insideclimatenews.org.
* Barack Obama
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As face reality, we might recall that on this date in 1988, the #1 song in the U.S. was Bobby McFerrin‘s “Don’t Worry, Be Happy,” the first a cappella song to reach the top of the Billboard Hot 100 chart, a position it held for two weeks.
(Produced by Colossal Pictures, Directed by Drew Takahashi)
“The universe is under no obligation to make sense to you”*…
Still, we try… In a consideration of three new books, the estimable Sean Carroll brings us up to date on the state of play…
Should scientists be embarrassed that they can’t settle on a definition for the Big Bang? The cosmologist Will Kinney describes it as the “physical theory of the hot infant universe,” while Wikipedia goes for the more elaborate “a physical theory that describes how the universe expanded from an initial state of high density and temperature.” The first refers only to early times, while the latter seems to extend to subsequent times as well. The physicist and science writer Tony Rothman offers the pithier “the universe’s origin,” the theoretical physicist Thomas Hertog suggests that it is the “primeval state” of cosmic history, and a NASA website gives us “the idea that the universe began as just a single point.” These seem to refer to one moment at the start of things, rather than the universe’s life since then.
All of these sources (except NASA, unfortunately) capture something correct. The confusion stems both from the inherent ambiguity of using ordinary language to describe novel scientific concepts and from the state of modern cosmology itself. Cosmology is the study of the universe on the largest scales. So it ignores details of stars and planets, focusing on galaxies and even bigger structures, up to the universe as a whole. Modern cosmology is only about a century old, as it wasn’t until the 1920s that astronomers determined that our own Milky Way is just one of a large number of galaxies and the origin and evolution of them all could be studied together. And it wasn’t until the 1990s that the field matured into the one that exists today, featuring precision measurements and ultralarge datasets.
Dealing as it does with some of the most profound questions about the nature of the cosmos, cosmological research has always involved a vigorous give-and-take between rampant speculation and unanticipated discoveries. Its practitioners have long been fond of spinning purportedly inviolate physical principles from their personal intuitions about how reality should work. But cosmology remains an empirical science—a cherished belief can be quickly swept away by a solid measurement.
The present moment in the science of cosmology is one of consolidation, as we have successfully incorporated the lessons of some impressive discoveries made near the turn of the twenty-first century. Yet crucially important questions remain unanswered, especially about what exactly happened at the onset of the expanding space that evolved into our contemporary universe. It is therefore a good time for books that take stock of where we are and what might come next, and that illustrate which puzzles modern physicists choose to take seriously.
This much we know: we live in a galaxy, the Milky Way, containing around 200 billion stars. There are something like a trillion galaxies in our observable universe, distributed almost uniformly through space. Stars and galaxies condensed out of an originally nearly smooth distribution of matter. Distant galaxies are moving apart from one another. Extrapolating backward, we reach a hot, densely packed configuration about 13.8 billion years ago. We can observe the remnants of this early period in nearly uniform cosmic background radiation coming from every direction in the sky.
The Big Bang model is precisely this general picture, of a universe that expands and cools out of a smooth, hot primordial state. It is well understood and almost universally accepted among modern cosmologists. The Big Bang event is a hypothetical moment when the whole thing might have started, at which the temperature and density are supposed to have been literally infinite—a “singularity,” in physics parlance. This is why the NASA definition above is unambiguously wrong: the Big Bang event has nothing to do with “a single point” in space—it refers to a moment in time.
Nobody knows whether there actually was such an event. To be honest, there probably wasn’t. Einstein’s theory of general relativity predicts that such a singularity would have happened, but most physicists think this signals a breakdown in the theory rather than being an accurate description of the physical world. A prediction of infinitely big physical quantities is apt to be a sign that we don’t have the right theoretical understanding…
[Starting with Einstein’s unification of space-time in 1905, Carroll explains the implications of quantum theory, in particular on the question of the expansion of the universe. Using the three (very different, but complementary) books under consideration, he unpacks the issues and demonstrates the way in which scientific theories about the origin of the universe often involve a vigorous give-and-take between speculation and discovery…]
… Taken together, these three books provide an illuminating view of the state of modern cosmology. There are established results, laudable efforts to connect promising hypotheses to a flood of incoming data, and brave speculations about the physical and metaphysical unknown. They are all notably well written for the genre and will keep readers entertained as they are educated. We can marvel at both how much scientists have learned about the universe and how much we have yet to understand.
The state of cosmology (and a look at science at work): “A First Time for Everything,” from @seanmcarroll.bsky.social in @nybooks.com.
* Neil deGrasse Tyson
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As we wrestle with reality, we might spare a thought for a major (if, in the end, incorrect) character in tale that Carroll tells: Fred Hoyle; he died on this date in 2001. A prominent astronomer, he formulated the theory of stellar nucleosynthesis. But he is rather better remembered for his controversial stances on other scientific matters—in particular his rejection of the (as Carroll observes, now widely-accepted) “Big Bang” theory– a term he coined, derisively, in an episode of his immensely-popular series The Nature of the Universe on BBC radio– and his promotion of panspermia as the source of life on Earth (or maybe the traffic was in the other direction?).
“Anyone not shocked by quantum mechanics has not yet understood it”*…
In the summer of 1925, a young Werner Heisenberg retreated to Helgoland in the North Sea and reemerged with the first full-fledged version of quantum mechanics. A century later, the theory’s meaning remains unsettled. Charlie Wood joined a group of physicists in Helgoland to take stock of the theory on its centennial…
Happy 100th birthday, quantum mechanics!” a physicist bellowed into a microphone one evening in June, and the cavernous banquet hall of Hamburg’s Hotel Atlantic erupted into cheers and applause. Some 300 quantum physicists had traveled from around the world to attend the opening reception of a six-day conference marking the centennial of the most successful theory in physics. The crowd included well-known pioneers of quantum computing and quantum cryptography, and four Nobel Prize winners.
“I feel like I’m at Woodstock,” Daniel Burgarth of the University of Erlangen-Nuremberg in Germany told me. “It’s my only chance to see them all in one place.”
One hundred years to the month had passed since a 23-year-old postdoc named Werner Heisenberg was driven by a case of hay fever to Helgoland, a barren, windswept island in the North Sea. There, Heisenberg completed a calculation that would become the heart of quantum mechanics, a radical new theory of the atomic and subatomic world.
The theory remains radical.
Before quantum mechanics hit the scene, “classical” physics theories dealt directly with the stuff of the world and its properties: the orbits of planets, say, and the speeds of pendulums. Quantum mechanics deals in something more abstract: possibilities. It predicts the chances that we’ll observe an atom doing this or that, or being here or there. It gives the impression that particles can engage in multiple possible behaviors at once, that they have no fixed reality. So physicists have spent the last century grappling with questions like: What is real? And where does our reality come from?…
Wood recounts the genesis and development of the theory and considers some of the vexing questions that remain: e.g., the many-world interpretation, the place (?) of gravity in the theory, et al. He concludes with a quote from Robert Spekkens, a physicist at the Perimeter Institute (whose work illustrates Lawrence Krause‘s observation that “At the heart of quantum mechanics is a rule that sometimes governs politicians or CEOs – as long as no one is watching, anything goes”): “We’re privileged to live at a time when the great prize of making sense of quantum theory is still there for the taking.”
Eminently worth reading in full: “‘It’s a Mess’: A Brain-Bending Trip to Quantum Theory’s 100th Birthday Party” from @walkingthedot.bsky.social in @quantamagazine.bsky.social.
See also: “Physicists Can’t Agree on What Quantum Mechanics Says about Reality“
* Niels Bohr
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As we wrestle with reality, we might send relativistic birthday greetings to one of quantum theory’s pioneers, Erwin Schrödinger; he was born on this date in 1887. A physicist, Schrödinger took Louis de Broglie‘s concept of atomic particles as having wave-like properties, and modified the earlier Bohr model of the atom to accommodate the wave nature of the electrons, which he instantiated in the Schrödinger equation, which provides a way to calculate the wave function of a system and how it changes dynamically in time. It was the basis of the work that earned him the Nobel Prize in 1933. And he coined the term “quantum entanglement” in 1935.
But surely Schrödinger is most widely known for creating the thought experiment we all know as “Schrödinger’s Cat” (and here).
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