Posts Tagged ‘quantum physics’
“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.
“I have not yet lost a feeling of wonder, and of delight, that the delicate motion should reside in all the things around us”*…
The proton, the positively charged particle at the heart of the atom, is an object of unspeakable complexity, one that changes its appearance depending on how it is probed…
“This is the most complicated thing that you could possibly imagine,” said Mike Williams, a physicist at the Massachusetts Institute of Technology. “In fact, you can’t even imagine how complicated it is.”
The proton is a quantum mechanical object that exists as a haze of probabilities until an experiment forces it to take a concrete form. And its forms differ drastically depending on how researchers set up their experiment. Connecting the particle’s many faces has been the work of generations. “We’re kind of just starting to understand this system in a complete way,” said Richard Milner, a nuclear physicist at MIT.
As the pursuit continues, the proton’s secrets keep tumbling out. Most recently, a monumental data analysis published in August found that the proton contains traces of particles called charm quarks that are heavier than the proton itself.
The proton “has been humbling to humans,” Williams said. “Every time you think you kind of have a handle on it, it throws you some curveballs.”
Recently, Milner, together with Rolf Ent at Jefferson Lab, MIT filmmakers Chris Boebel and Joe McMaster, and animator James LaPlante, set out to transform a set of arcane plots that compile the results of hundreds of experiments into a series of animations of the shape-shifting proton…
Charlie Wood (and Merrill Sherman) have incorporated that work into an attempt to unveil the particle’s secrets: “Inside the Proton, the ‘Most Complicated Thing You Could Possibly Imagine’,” from @walkingthedot in @QuantaMagazine.
* Edmund Burke
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As we ponder presumptive paradoxes, we might send insightful birthday greetings to David Schramm; he was born on this date in 1945. A theoretical astrophysicist, he established the field of particle astrophysics, a branch of particle physics that studies elementary particles of astronomical origin and their relation to astrophysics and cosmology. He was particularly well known for the study of Big Bang nucleosynthesis and its use as a probe of dark matter and of neutrinos. And he made important contributions to the study of cosmic rays, supernova explosions, heavy-element nucleosynthesis, and nuclear astrophysics generally.
“Horror vacui”*…
Recently, (Roughly) Daily took a look at nothing– and the perplexing philosophical questions that it raises. Today, Charlie Wood examines nothing’s physical manifestation, the vacuum, and the similarly perplexing questions it raises for physicists…
Millennia ago, Aristotle asserted that nature abhors a vacuum, reasoning that objects would fly through truly empty space at impossible speeds. In 1277, the French bishop Etienne Tempier shot back, declaring that God could do anything, even create a vacuum.
Then a mere scientist pulled it off. Otto von Guericke invented a pump to suck the air from within a hollow copper sphere, establishing perhaps the first high-quality vacuum on Earth. In a theatrical demonstration in 1654, he showed that not even two teams of horses straining to rip apart the watermelon-size ball could overcome the suction of nothing. [See illustration above.]
Since then, the vacuum has become a bedrock concept in physics, the foundation of any theory of something. Von Guericke’s vacuum was an absence of air. The electromagnetic vacuum is the absence of a medium that can slow down light. And a gravitational vacuum lacks any matter or energy capable of bending space. In each case the specific variety of nothing depends on what sort of something physicists intend to describe. “Sometimes, it’s the way we define a theory,” said Patrick Draper, a theoretical physicist at the University of Illinois.
As modern physicists have grappled with more sophisticated candidates for the ultimate theory of nature, they have encountered a growing multitude of types of nothing. Each has its own behavior, as if it’s a different phase of a substance. Increasingly, it seems that the key to understanding the origin and fate of the universe may be a careful accounting of these proliferating varieties of absence.
“We’re learning there’s a lot more to learn about nothing than we thought,” said Isabel Garcia Garcia, a particle physicist at the Kavli Institute for Theoretical Physics in California. “How much more are we missing?”
So far, such studies have led to a dramatic conclusion: Our universe may sit on a platform of shoddy construction, a “metastable” vacuum that is doomed — in the distant future — to transform into another sort of nothing, destroying everything in the process.
Nothing started to seem like something in the 20th century, as physicists came to view reality as a collection of fields: objects that fill space with a value at each point (the electric field, for instance, tells you how much force an electron will feel in different places). In classical physics, a field’s value can be zero everywhere so that it has no influence and contains no energy. “Classically, the vacuum is boring,” said Daniel Harlow, a theoretical physicist at the Massachusetts Institute of Technology. “Nothing is happening.”
But physicists learned that the universe’s fields are quantum, not classical, which means they are inherently uncertain. You’ll never catch a quantum field with exactly zero energy…
For an explanation of how key to understanding the origin and fate of the universe may be a more complete understanding of the vacuum: “How the Physics of Nothing Underlies Everything,” from @walkingthedot in @QuantaMagazine.
* attributed to Aristitole, and usually “translated,” as above, “Nature abhors a vacuum”
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As we noodle on nought, we might spare a thought for Hugo Gernsback, a Luxemborgian-American inventor, broadcast pioneer, writer, and publisher; he died on this date in 1967 at the age of 83.
Gernsback held 80 patents at the time of his death; he founded radio station WRNY, was involved in the first television broadcasts and is considered a pioneer in amateur radio. But it was a writer and publisher that he probably left his most lasting mark: In 1926, as owner/publisher of the magazine Modern Electrics, he filled a blank spot in his publication by dashing off the first chapter of a series called “Ralph 124C 41+.” The twelve installments of “Ralph” were filled with inventions unknown in 1926, including “television” (Gernsback is credited with introducing the word), fluorescent lighting, juke boxes, solar energy, television, microfilm, vending machines, and the device we now call radar.
The “Ralph” series was an astounding success with readers; and later that year Gernsback founded the first magazine devoted to science fiction, Amazing Stories. Believing that the perfect sci-fi story is “75 percent literature interwoven with 25 percent science,” he coined the term “science fiction.”
Gernsback was a “careful” businessman, who was tight with the fees that he paid his writers– so tight that H. P. Lovecraft and Clark Ashton Smith referred to him as “Hugo the Rat.”
Still, his contributions to the genre as publisher were so significant that, along with H.G. Wells and Jules Verne, he is sometimes called “The Father of Science Fiction”; in his honor, the annual Science Fiction Achievement awards are called the “Hugos.”
(Coincidentally, today is also the birthday– in 1906– of Philo T. Farnsworth, the man who actually did invent television…)
“Why, sometimes I’ve believed as many as six impossible things before breakfast”*…
Imaginary numbers were long dismissed as mathematical “bookkeeping.” But now, as Karmela Padavic-Callaghan explains, physicists are proving that they describe the hidden shape of nature…
Many science students may imagine a ball rolling down a hill or a car skidding because of friction as prototypical examples of the systems physicists care about. But much of modern physics consists of searching for objects and phenomena that are virtually invisible: the tiny electrons of quantum physics and the particles hidden within strange metals of materials science along with their highly energetic counterparts that only exist briefly within giant particle colliders.
In their quest to grasp these hidden building blocks of reality scientists have looked to mathematical theories and formalism. Ideally, an unexpected experimental observation leads a physicist to a new mathematical theory, and then mathematical work on said theory leads them to new experiments and new observations. Some part of this process inevitably happens in the physicist’s mind, where symbols and numbers help make invisible theoretical ideas visible in the tangible, measurable physical world.
Sometimes, however, as in the case of imaginary numbers – that is, numbers with negative square values – mathematics manages to stay ahead of experiments for a long time. Though imaginary numbers have been integral to quantum theory since its very beginnings in the 1920s, scientists have only recently been able to find their physical signatures in experiments and empirically prove their necessity…
Learn more at “Imaginary numbers are real,” from @Ironmely in @aeonmag.
* The Red Queen, in Lewis Carroll’s Through the Looking Glass
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As we get real, we might spare a thought for two great mathematicians…
Georg Friedrich Bernhard Riemann died on this date in 1866. A mathematician who made contributions to analysis, number theory, and differential geometry, he is remembered (among other things) for his 1859 paper on the prime-counting function, containing the original statement of the Riemann hypothesis, regarded as one of the most influential papers in analytic number theory.
Andrey (Andrei) Andreyevich Markov died on this date in 1922. A Russian mathematician, he helped to develop the theory of stochastic processes, especially those now called Markov chains: sequences of random variables in which the future variable is determined by the present variable but is independent of the way in which the present state arose from its predecessors. (For example, the probability of winning at the game of Monopoly can be determined using Markov chains.) His work on the study of the probability of mutually-dependent events has been developed and widely applied to the biological, physical, and social sciences, and is widely used in Monte Carlo simulations and Bayesian analyses.
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