Posts Tagged ‘quantum physics’
“A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux … is that the vast majority of the mass of the universe seems to be missing”*…
Quantum effects may not be just subatomic, Sabine Hossenfelder suggests; they might be expressed across galaxies, and solve the puzzle of dark matter…
Most of the matter in the Universe is invisible, composed of some substance that leaves no mark as it breezes through us – and through all of the detectors the scientists have created to catch it. But this dark matter might not consist of unseen particle clouds, as most theorists have assumed. Instead, it might be something even stranger: a superfluid that condensed to puddles billions of years ago, seeding the galaxies we observe today.
This new proposal has vast implications for cosmology and physics. Superfluid dark matter overcomes many of the theoretical problems with the particle clouds. It explains the long-running, increasingly frustrating failure to identify the individual constituents within these clouds. And it offers a concrete scientific path forward, yielding specific predictions that could soon be testable.
Superfluid dark matter has important conceptual implications as well. It suggests that the common picture of the Universe as a mass of individual particles bound together by forces – almost like a tinker toy model – misses much of the richness of nature. Most of the matter in the Universe might be utterly unlike the matter in your body: not composed of atoms, and not even built of particles as we normally understand them, but instead a coherent whole of vast extension…
Is dark matter composed of particles? Is it a fluid? Or is it both? Read On: “The superfluid Universe,” from @skdh in @aeonmag.
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As we deconstruct the dark, we might spare a thought for Richard Philips Feynman; he died on this date in 1988. A theoretical physicist, Feynman was probably the most brilliant, influential, and iconoclastic figure in his field in the post-WW II era.
Richard Feynman was a once-in-a-generation intellectual. He had no shortage of brains. (Relevantly to the piece above, in 1965 he won the Nobel Prize in Physics for his work on quantum electrodynamics.) He had charisma. (Witness this outtake [below] from his 1964 Cornell physics lectures [available in full here].) He knew how to make science and academic thought available, even entertaining, to a broader public. (See, for example, these two public TV programs hosted by Feynman here and here.) And he knew how to have fun.
– From Open Culture (where one can also find Feynman’s elegant and accessible 1.5 minute explanation of “The Key to Science.”)
“To create something from nothing is one of the greatest feelings”*…
Something from nothing? Not exactly. As Charlie Wood explains, it’s even weirder…
For their latest magic trick, physicists have done the quantum equivalent of conjuring energy out of thin air. It’s a feat that seems to fly in the face of physical law and common sense.
“You can’t extract energy directly from the vacuum because there’s nothing there to give,” said William Unruh, a theoretical physicist at the University of British Columbia, describing the standard way of thinking.
But 15 years ago, Masahiro Hotta, a theoretical physicist at Tohoku University in Japan, proposed that perhaps the vacuum could, in fact, be coaxed into giving something up.
At first, many researchers ignored this work, suspicious that pulling energy from the vacuum was implausible, at best. Those who took a closer look, however, realized that Hotta was suggesting a subtly different quantum stunt. The energy wasn’t free; it had to be unlocked using knowledge purchased with energy in a far-off location. From this perspective, Hotta’s procedure looked less like creation and more like teleportation of energy from one place to another — a strange but less offensive idea.
“That was a real surprise,” said Unruh, who has collaborated with Hotta but has not been involved in energy teleportation research. “It’s a really neat result that he discovered.”
Now in the past year, researchers have teleported energy across microscopic distances in two separate quantum devices, vindicating Hotta’s theory. The research leaves little room for doubt that energy teleportation is a genuine quantum phenomenon.
“This really does test it,” said Seth Lloyd, a quantum physicist at the Massachusetts Institute of Technology who was not involved in the research. “You are actually teleporting. You are extracting energy.”…
“Physicists Use Quantum Mechanics to Pull Energy out of Nothing,” from @walkingthedot in @QuantaMagazine.
Vaguely related (and fascinating): “The particle physics of you.”
* Prince
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As we demolish distance, we might send insightful birthday greetings to Brain Cox; he was born on this date in 1968. A physicist and former musician (he was keyboardist for Dare and D:Ream), he is a professor of particle physics in the School of Physics and Astronomy at the University of Manchester, and a fellow at CERN (where he works on the ATLAS experiment, studying the forward proton detectors for the Large Hadron Collider there).
But Cox is most widely known as the host/presenter of science programs, perhaps especially the BBC’s Wonders of the Universe series, and for popular science books, such as Why Does E=mc²? and The Quantum Universe— which (he avers) were inspired by Carl Sagan and for which Cox has earned recognition as the natural successor to David Attenborough and Patrick Moore.
Science is too important not to be a part of a popular culture.
“There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”*…
Some observations are best considered “interesting, if true”; some, a la Karl Popper, “true, until false”… Consider this very recent paper in Nature…
Theories of scientific and technological change view discovery and invention as endogenous processes, wherein previous accumulated knowledge enables future progress by allowing researchers to, in Newton’s words, ‘stand on the shoulders of giants.’ Recent decades have witnessed exponential growth in the volume of new scientific and technological knowledge, thereby creating conditions that should be ripe for major advances. Yet contrary to this view, studies suggest that progress is slowing in several major fields. Here, we analyse these claims at scale across six decades, using data on 45 million papers and 3.9 million patents from six large-scale datasets, together with a new quantitative metric—the CD index—that characterizes how papers and patents change networks of citations in science and technology. We find that papers and patents are increasingly less likely to break with the past in ways that push science and technology in new directions. This pattern holds universally across fields and is robust across multiple different citation- and text-based metrics. Subsequently, we link this decline in disruptiveness to a narrowing in the use of previous knowledge, allowing us to reconcile the patterns we observe with the ‘shoulders of giants’ view. We find that the observed declines are unlikely to be driven by changes in the quality of published science, citation practices or field-specific factors. Overall, our results suggest that slowing rates of disruption may reflect a fundamental shift in the nature of science and technology.
The full paper: “Papers and patents are becoming less disruptive over time” @Nature
One notes that the quote above– from Lord Kelvin, at the turn of the twentieth century– immediately preceded a couple of decades in which physics was radically redefined and advanced by Planck, Einstein, Bohr, et al. (In fairness to Kelvin, consider this suggestion that his point was more subtle.) As we look forward, we might ponder the ways in which the reorganization of disciplines, the rise of research in other cultures (less constrained by the mores of “conventional” research), the use of AI, and/or some as yet unknown dynamic could challenge the phenomenon– “a narrowing in the use of previous knowledge”– to which the authors attribute diminishing disruption.
[Source of the image above]
* Lord Kelvin, in an address to the the Royal Institution in April of 1900
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As we ponder progress, we might send advanced birthday greetings to Wilhelm Wien; he was born on this date in 1864. A physicist, his work helped move past Kelvin’s log-jam. In 1893, he used theories about heat and electromagnetism to deduce Wien’s displacement law, which calculates the emission of a blackbody (a surface that absorbs all radiant energy falling on it) at any temperature from the emission at any one reference temperature. His colleague Max Planck colaborated with Wien, then extended the thinking in what we now know as Planck’s law, which led to the development of quantum theory.
Wien received the 1911 Nobel Prize for his work on heat radiation.
Just before Kelvin’s speech (in 1898) Wien identified a positive particle equal in mass to the hydrogen atom– what we now know as a proton. Wien, in the techniques he used, laid the foundation of mass spectrometry.
“Taxonomy is described sometimes as a science and sometimes as an art, but really it’s a battleground”*…
The periodic table of elements, in the form introduced by Dmitri Mendeleev, is something that many of us take for granted. But as Philip Ball explains, there are a number of different visualizations making claims for our attention…
The Periodic Table was conceived as a scheme for bringing order to the elements. When there were deemed to be only four of these—the earth, air, fire, and water of the Greek philosopher Empedocles (it was just one of the elemental systems proposed in ancient times, but enjoyed the weighty advocacy of Plato and Aristotle)—things seemed simple enough. But during the Renaissance, natural philosophers were increasingly forced to accept that the metals then known—copper, iron, lead, tin, mercury, silver and gold—were not as interconvertible as the alchemists believed, but seemed to have an elemental primacy about them, too. More and more of these became recognized—zinc, bismuth, cobalt, and others—along with other new elements such as sulfur, phosphorus, carbon, and, in the late eighteenth century, gaseous elements like nitrogen, hydrogen and oxygen. When the French chemist Antoine Lavoisier (who named those latter two) drew up a list of known elements for his seminal textbook Traité élémentaire de chemie in 1789, he counted 33—including light and heat, which he called caloric.
The list didn’t seem to be arbitrary though. In the early nineteenth century, several scientists noted that some elements seemed to come in families, resembling one another in the kinds of reactions they engaged in and the compounds they formed. Some claimed to see triads: the halogens chlorine, bromine and iodine for example, or the reactive metals sodium, potassium (both discovered by English chemist Humphry Davy in 1807) and lithium (identified in 1817). Was there a hidden pattern to the elements?
The Russian chemist Dmitri Mendeleev, working at Saint Petersburg University, is usually credited with discovering that pattern. A Siberian by birth, with Rasputin-like dishevelled hair and an irascible manner, he published his first Periodic Table in 1869. It is “periodic” because, if you list the elements in order of their mass, certain chemical properties seem to recur periodically along the list. The table is produced by folding that linear list so that elements with shared properties sit in vertical columns (although Mendeleev’s first table had them instead in rows, effectively turning today’s table on its side)…
Still, it’s a weird kind of periodicity. At first, chemical properties seemed to recur every eight elements. But in the row that starts with potassium, there’s an interlude of ten metals—the transition metals—and so it continues thereafter, creating a periodicity of 18. And after lanthanum (element 57), chemists discovered a whole series of 14 metallic elements with almost identical properties that have to be squeezed in too—frankly, these elements, called the lanthanides after the first of their ilk, all seem a bit redundant. There’s another block like this after radioactive actinium (element 89), called the actinides. In most Periodic Tables, the lanthanide and actinide blocks are left floating freely underneath so the table doesn’t get stretched beyond the confines of the page. (Some insist that this long-form table is the only proper one.) Why this odd structure?
The answer became clear with the invention of quantum mechanics in the early twentieth century. The chemical properties of New Zealander Ernest Rutherford showed that atoms comprise a central, very dense nucleus with a positive electrical charge, surrounded by enough negatively charged electrons to perfectly balance that charge. Rutherford imagined the electrons orbiting the nucleus like moons, but in the quantum-mechanical description they occupy nebulous, smeared-out clouds called orbitals. Using quantum mechanics to describe the disposition of electrons shows that they are arrayed in shells. The first of these can contain just two electrons—this is the only shell possessed by hydrogen and helium, the two lone elements at the tops of the towers—while the next has eight, and then 18. The shape of the periodic table thus encodes the character of the quantum atom.
All clear? Not quite. Even now, there’s no consensus about how to draw the Periodic Table…
Read on to explore some fascinating alternative depictions: “Picture This: The Periodic Table,” by @philipcball in @PioneerWorks_.
* Bill Bryson, A Short History of Nearly Everything
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As we ruminate on relationships, we might spare a thought for Vladimir Vernadsky; he died on this date in 1945. A Ukrainian mineralogist and geochemist, he is considered one of the founders of geochemistry, biogeochemistry, and radiogeology. He also co-founded and served as the first President of the Ukrainian Academy of Sciences (now National Academy of Sciences of Ukraine).
Vernadsky is probably best remembered for his 1926 book Biosphere, in which he popularized the concepts of the biosphere and the noosphere, arguing (after Eduard Suess) that in the Earth’s development, the noosphere (cognitive life) is the third stage in the earth’s development, after the geosphere (inanimate matter) and the biosphere (biological life). Just as the emergence of life fundamentally transformed the geosphere, the emergence of human cognition will fundamentally transform the biosphere. In this theory, the principles of both life and cognition are essential features of the Earth’s evolution, and must have been implicit in the earth all along (a position Vernadsky held was complementary to Darwin’s theory of evolution). Indeed, within the last 200 years, humanity has been a powerful geologic force, moving more mass upon the earth than has the biosphere.
“Consciousness cannot be accounted for in physical terms. For consciousness is absolutely fundamental. It cannot be accounted for in terms of anything else.”*…
Representation of consciousness from the seventeenth century by Robert Fludd, an English Paracelsian physician (source)
… but that doesn’t mean that we won’t attempt to answer “the hard problem of consciousness.” Indeed, as Elizabeth Fernandez notes, some scientists are using Schrödinger’s own work to try…
Supercomputers can beat us at chess and perform more calculations per second than the human brain. But there are other tasks our brains perform routinely that computers simply cannot match — interpreting events and situations and using imagination, creativity, and problem-solving skills. Our brains are amazingly powerful computers, using not just neurons but the connections between the neurons to process and interpret information.
And then there is consciousness, neuroscience’s giant question mark. What causes it? How does it arise from a jumbled mass of neurons and synapses? After all, these may be enormously complex, but we are still talking about a wet bag of molecules and electrical impulses.
Some scientists suspect that quantum processes, including entanglement, might help us explain the brain’s enormous power, and its ability to generate consciousness. Recently, scientists at Trinity College Dublin, using a technique to test for quantum gravity, suggested that entanglement may be at work within our brains. If their results are confirmed, they could be a big step toward understanding how our brain, including consciousness, works…
More on why maybe the brain isn’t “classical” after all: “Brain experiment suggests that consciousness relies on quantum entanglement,” from @SparkDialog in @bigthink.
For an orthogonal view: “Why we need to figure out a theory of consciousness.”
* Erwin Schrödinger
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As we think about thinking, we might spare a thought for Alexius Meinong; he died on this date in 1920. A philosopher, he is known for his unique ontology and for contributions to the philosophy of mind and axiology– the theory of value.
Meinong’s ontology is notable for its belief in nonexistent objects. He distinguished several levels of reality among objects and facts about them: existent objects participate in actual (true) facts about the world; subsistent (real but non-existent) objects appear in possible (but false) facts; and objects that neither exist nor subsist can only belong to impossible facts. See his Gegenstandstheorie, or the Theory of Abstract Objects.
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