Music: Chakwal Group & Meesha Shafi — ‘Ishq Aap Bhe Awalla’
Author Archives: Attention to the Unseen
New support for an alternative formulation of quantum mechanics
Dan Falk writes: Of the many counterintuitive features of quantum mechanics, perhaps the most challenging to our notions of common sense is that particles do not have locations until they are observed. This is exactly what the standard view of quantum mechanics, often called the Copenhagen interpretation, asks us to believe. Instead of the clear-cut positions and movements of Newtonian physics, we have a cloud of probabilities described by a mathematical structure known as a wave function. The wave function, meanwhile, evolves over time, its evolution governed by precise rules codified in something called the Schrödinger equation. The mathematics are clear enough; the actual whereabouts of particles, less so. Until a particle is observed, an act that causes the wave function to “collapse,” we can say nothing about its location. Albert Einstein, among others, objected to this idea. As his biographer Abraham Pais wrote: “We often discussed his notions on objective reality. I recall that during one walk Einstein suddenly stopped, turned to me and asked whether I really believed that the moon exists only when I look at it.”
But there’s another view — one that’s been around for almost a century — in which particles really do have precise positions at all times. This alternative view, known as pilot-wave theory or Bohmian mechanics, never became as popular as the Copenhagen view, in part because Bohmian mechanics implies that the world must be strange in other ways. In particular, a 1992 study claimed to crystalize certain bizarre consequences of Bohmian mechanics and in doing so deal it a fatal conceptual blow. The authors of that paper concluded that a particle following the laws of Bohmian mechanics would end up taking a trajectory that was so unphysical — even by the warped standards of quantum theory — that they described it as “surreal.”
Nearly a quarter-century later, a group of scientists has carried out an experiment in a Toronto laboratory that aims to test this idea. And if their results, first reported earlier this year, hold up to scrutiny, the Bohmian view of quantum mechanics — less fuzzy but in some ways more strange than the traditional view — may be poised for a comeback.
Bohmian mechanics was worked out by Louis de Broglie in 1927 and again, independently, by David Bohm in 1952, who developed it further until his death in 1992. (It’s also sometimes called the de Broglie–Bohm theory.) As with the Copenhagen view, there’s a wave function governed by the Schrödinger equation. In addition, every particle has an actual, definite location, even when it’s not being observed. Changes in the positions of the particles are given by another equation, known as the “pilot wave” equation (or “guiding equation”). The theory is fully deterministic; if you know the initial state of a system, and you’ve got the wave function, you can calculate where each particle will end up.
That may sound like a throwback to classical mechanics, but there’s a crucial difference. Classical mechanics is purely “local” — stuff can affect other stuff only if it is adjacent to it (or via the influence of some kind of field, like an electric field, which can send impulses no faster than the speed of light). Quantum mechanics, in contrast, is inherently nonlocal. The best-known example of a nonlocal effect — one that Einstein himself considered, back in the 1930s — is when a pair of particles are connected in such a way that a measurement of one particle appears to affect the state of another, distant particle. The idea was ridiculed by Einstein as “spooky action at a distance.” But hundreds of experiments, beginning in the 1980s, have confirmed that this spooky action is a very real characteristic of our universe.
In the Bohmian view, nonlocality is even more conspicuous. The trajectory of any one particle depends on what all the other particles described by the same wave function are doing. And, critically, the wave function has no geographic limits; it might, in principle, span the entire universe. Which means that the universe is weirdly interdependent, even across vast stretches of space. The wave function “combines — or binds — distant particles into a single irreducible reality,” as Sheldon Goldstein, a mathematician and physicist at Rutgers University, has written. [Continue reading…]
Music: Meesha Shafi — ‘Chori Chori’
Why physics is not a discipline
Philip Ball writes: Have you heard the one about the biologist, the physicist, and the mathematician? They’re all sitting in a cafe watching people come and go from a house across the street. Two people enter, and then some time later, three emerge. The physicist says, “The measurement wasn’t accurate.” The biologist says, “They have reproduced.” The mathematician says, “If now exactly one person enters the house then it will be empty again.”
Hilarious, no? You can find plenty of jokes like this — many invoke the notion of a spherical cow — but I’ve yet to find one that makes me laugh. Still, that’s not what they’re for. They’re designed to show us that these academic disciplines look at the world in very different, perhaps incompatible ways.
There’s some truth in that. Many physicists, for example, will tell stories of how indifferent biologists are to their efforts in that field, regarding them as irrelevant and misconceived. It’s not just that the physicists were thought to be doing things wrong. Often the biologists’ view was that (outside perhaps of the well established but tightly defined discipline of biophysics) there simply wasn’t any place for physics in biology.
But such objections (and jokes) conflate academic labels with scientific ones. Physics, properly understood, is not a subject taught at schools and university departments; it is a certain way of understanding how processes happen in the world. When Aristotle wrote his Physics in the fourth century B.C., he wasn’t describing an academic discipline, but a mode of philosophy: a way of thinking about nature. You might imagine that’s just an archaic usage, but it’s not. When physicists speak today (as they often do) about the “physics” of the problem, they mean something close to what Aristotle meant: neither a bare mathematical formalism nor a mere narrative, but a way of deriving process from fundamental principles.
This is why there is a physics of biology just as there is a physics of chemistry, geology, and society. But it’s not necessarily “physicists” in the professional sense who will discover it. [Continue reading…]
New evidence that humans settled in southeastern U.S. far earlier than previously believed
Phys.org reports: The discovery of stone tools found in a Florida river show that humans settled the southeastern United States far earlier than previously believed — perhaps by as much as 1,500 years, according to a team of scientists that includes a University of Michigan paleontologist.
Michael Waters of Texas A&M University and Jessi Halligan of Florida State University led a research team that also included U-M’s Daniel Fisher and scientists from the University of Minnesota, University of Texas, University of Arizona, Stafford Research Laboratories in Colorado, Aucilla Research Institute in Florida, and Exeter and Cambridge universities in the United Kingdom.
A report on the team’s findings appears in Science Advances. [Continue reading…]
The long history of a short form
Ryan Ruby writes: For a word that literally means definition, the aphorism is a rather indefinite genre. It bears a family resemblance to the fragment, the proverb, the maxim, the hypomnema, the epigram, the mantra, the parable, and the prose poem. Coined sometime between the fifth and third centuries BC as the title for one of the books of the Corpus Hippocraticum, the Aphorismi were originally a compendium of the latest medical knowledge. The penultimate aphorism, “In chronic disease an excessive flux from the bowels is bad,” is more representative of the collection’s contents than the first — “Life is short, art is long” — for which it is best known.
But in those six words lies a clue to the particular space aphorisms were supposed to define. Thanks to a semantic slippage between the Greek word techne and its English translation (via the Latin ars), the saying is often taken to mean that the works of human beings outlast their days. But in its original context, Hippocrates or his editors probably intended something more pragmatic: the craft of medicine takes a long time to learn, and physicians have a short time in which to learn it. Although what aphorisms have in common with the forms listed above is their brevity, what is delimited by the aphorism is not the number of words in which ideas are expressed but the scope of their inquiry. Unlike Hebrew proverbs, in which the beginning of wisdom is the fear of God, the classical aphorism is a secular genre concerned with the short span of time we are allotted on earth. Books of aphorisms are also therapeutic in nature, collections of practical wisdom through which we can rid ourselves of unnecessary suffering and achieve what Hippocrates’ contemporary Socrates called eudaimonia, the good life.
This is certainly what the Stoic philosopher Arrian had in mind when he whittled down the discourses of his master, Epictetus, into a handbook of aphorisms. The Enchiridion is composed of that mixture of propositional assertion and assertive imperative that is now a hallmark of the form. In it, Epictetus, a former slave, outlines the Stoic view that, while “some things are in our control,” most things are ruled by fate. The way to the good life is to bring what is up to us — our attitudes, judgments, and desires — into harmony with what is not up to us: what happens to our bodies, possessions, and reputations. If we accept that what does happen must happen, we will never be disappointed by vain hopes or sudden misfortunes. Our dispositions, not our destinies, are the real source of our unhappiness. [Continue reading…]
Music: Klaus Paier & Asja Valcic — ‘Oblivion’
‘Nobody knew what you would see on the other side of a mountain’
Carl Zimmer writes: As a boy growing up in Denmark, Eske Willerslev could not wait to leave Gentofte, his suburban hometown. As soon as he was old enough, he would strike out for the Arctic wilderness.
His twin brother, Rane, shared his obsession. On vacations, they retreated to the woods to teach themselves survival skills. Their first journey would be to Siberia, the Willerslev twins decided. They would make contact with a mysterious group of people called the Yukaghir, who supposedly lived on nothing but elk and moose.
When the Willerslev twins reached 18, they made good on their promise. They were soon paddling a canoe up remote Siberian rivers.
“Nobody knew what you would see on the other side of a mountain,” said Eske Willerslev, who is now 44. “There were villages on the maps, and you wouldn’t even see a trace of them.”
Dr. Willerslev spent much of the next four years in Siberia, hunting moose, traveling across empty tundra and meeting the Yukaghirs and other people of the region. The experience left him wondering about the history of ethnic groups, about how people spread across the planet.
A quarter of a century later, Dr. Willerslev is still asking those questions, but now he’s getting some eye-opening answers.
As the director of the Center for GeoGenetics at the University of Copenhagen, Dr. Willerslev uses ancient DNA to reconstruct the past 50,000 years of human history. The findings have enriched our understanding of prehistory, shedding light on human development with evidence that can’t be found in pottery shards or studies of living cultures. [Continue reading…]
Animals are us
Tania Lombrozo writes: Researchers have studied how people think about humans in relation to the natural world, and how the way we reason about humans and other animals changes over the course of development and as a function of education and culture.
The findings from this body of work suggest that by age 5, Western children growing up in urban environments are anomalous in the extent to which they regard humans as central to the biological world. Much of the rest of the world — including 3-year-olds, 5-year-olds in rural environments and adults from indigenous populations in South America — are more inclined to think about humans as one animal species among others, at least when it comes to reasoning about the properties that human and non-human animals are likely to possess.
To illustrate, consider a study by Patricia Herrmann, Sandra Waxman and Douglas Medin published in the Proceedings of the National Academy of Sciences in 2010. In one experiment, 64 urban children, aged 3 or 5, were asked a series of questions that assessed their willingness to generalize an unknown property from one object to another. For instance, they might be told that people “have andro inside,” and would then have to guess whether it’s right or wrong to say that dogs “have andro inside.”
The findings with 5-year-olds replicated classic work in developmental psychology and suggested a strong “anthropocentric” bias: The children were more likely to generalize from humans to non-humans than the other way around, consistent with a privileged place for humans in the biological world. The 3-year-olds, by contrast, showed no signs of this bias: They generalized from humans to non-humans and from non-humans to humans in just the same way. These findings suggest that an anthropocentric perspective isn’t a necessary starting point for human reasoning about the biological world, but rather a perspective we acquire through experience.
So what happens between the ages of 3 and 5 to induce an anthropocentric bias?
Perhaps surprisingly, one influence seems to be anthropomorphism in storybooks. [Continue reading…]
The birth and death of a landscape
Justin Nobel writes: To reach the youngest land in the United States you need a boat. Robert Twilley still vividly remembers the first time he made the trip. The Louisiana State University coastal ecologist piled into a 24-foot Boston Whaler with a bunch of geomorphologists from Minnesota and motored out to an arc of spongy islands along the central coast of Louisiana called the Wax Lake Delta. It was the best place to learn about how a delta develops. The way the land eventually stabilizes and becomes home to a unique ecosystem that changes as the delta gets older is a process that ecologists call succession. “Succession is one of the most fascinating concepts in ecology,” said Twilley, “though one of the hardest to study. But in the Wax Lake Delta you can see it all. Biologic communities link up A to Z; it is the holy grail of ecosystem succession.”
What is remarkable for scientists like Twilley is that with good muck boots, a small boat, and a non-aversion to intense sun, freak thunderstorms, biting insects, and devastating humidity, the aging process of this new land can be studied in a human lifespan. In just over 40 years, the Wax Lake Delta has grown from nothing to an area twice the size of Manhattan. Meanwhile, since the European settlement of North America, the Mississippi River Delta has lost approximately one-third of its original wetland area. A delta that was once about twice the size of Delaware and on maps resembled a head of cauliflower now looks more like a string bean. The slow death of the Mississippi River Delta has severe consequences, including reduced hurricane protection for cities like New Orleans. Not only an important food source for humans and wildlife, this rich habitat also helps filter pollutants and absorb excess nutrients that would deplete the oxygen in the Gulf of Mexico’s water.
As one delta dies, another one grows. The budding Wax Lake Delta has allowed Twilley and his team of researchers to study how a delta ages. First, the nascent delta takes shape as lobes of sediment accumulate below the water. The delta is born when it breaches the surface of the water. Colonized by plants that gradually enhance the soil’s organic content and raise its elevation, it rolls through childhood. And eventually, it grows into a landscape able to support large shrubs and black willow trees. “The delta is almost like an organism,” says Twilley, “There is a birthing, there is an aging process, and there is a death.” [Continue reading…]
Music: Snarky Puppy — ‘Alma’
‘Children today are less free than they have ever been’
Jenny Anderson writes: “Something in modern life is undermining mental health,” Jean Twenge, a professor of psychology at San Diego State University, wrote in a recent paper.
Specifically, something is undermining young people’s mental health, especially girls.
In her paper, Twenge looks at four studies covering 7 million people, ranging from teens to adults in the US. Among her findings: high school students in the 2010s were twice as likely to see a professional for mental health issues than those in the 1980s; more teens struggled to remember things in 2010-2012 compared to the earlier period; and 73% more reported trouble sleeping compared to their peers in the 1980s. These so-called “somatic” or “of-the-body” symptoms strongly predict depression.
“It indicates a lot of suffering,” Twenge told Quartz.
It’s not just high school students. College students also feel more overwhelmed; student health centers are in higher demand for bad breakups or mediocre grades, issues that previously did not drive college kids to seek professional help. While the number of kids who reported feeling depressed spiked in the 1980s and 1990s, it started to fall after 2008. It has started rising again:
Kids are being diagnosed with higher levels of attention-deficit hyperactivity disorder (ADHD), and everyone aged 6-18 is seeking more mental health services, and more medication.
The trend is not a uniquely American phenomenon: In the UK, the number of teenagers (15-16) with depression nearly doubled between the 1980s and the 2000s and a recent survey found British 15-year-olds were among the least happy teenagers in the world (those in Poland and Macedonia were the only ones who were more unhappy).
“We would like to think of history as progress, but if progress is measured in the mental health and happiness of young people, then we have been going backward at least since the early 1950s,” Peter Gray, a psychologist and professor at Boston College, wrote in Psychology Today.
Researchers have a raft of explanations for why kids are so stressed out, from a breakdown in family and community relationships, to the rise of technology and increased academic stakes and competition. Inequality is rising and poverty is debilitating.
Twenge has observed a notable shift away from internal, or intrinsic goals, which one can control, toward extrinsic ones, which are set by the world, and which are increasingly unforgiving.
Gray has another theory: kids aren’t learning critical life-coping skills because they never get to play anymore.
“Children today are less free than they have ever been,” he told Quartz. And that lack of freedom has exacted a dramatic toll, he says.
“My hypothesis is that the generational increases in externality, extrinsic goals, anxiety, and depression are all caused largely by the decline, over that same period, in opportunities for free play and the increased time and weight given to schooling,” he wrote. [Continue reading…]
Scientists map brain’s thesaurus to help decode inner thoughts
UC Berkeley reports: What if a map of the brain could help us decode people’s inner thoughts?
UC Berkeley scientists have taken a step in that direction by building a “semantic atlas” that shows in vivid colors and multiple dimensions how the human brain organizes language. The atlas identifies brain areas that respond to words that have similar meanings.
The findings, published in the journal Nature, are based on a brain imaging study that recorded neural activity while study volunteers listened to stories from the “Moth Radio Hour.” They show that at least one-third of the brain’s cerebral cortex, including areas dedicated to high-level cognition, is involved in language processing.
Notably, the study found that different people share similar language maps: “The similarity in semantic topography across different subjects is really surprising,” said study lead author Alex Huth, a postdoctoral researcher in neuroscience at UC Berkeley. Click here for Huth’s online brain viewer. [Continue reading…]
Music: Snarky Puppy feat. Salif Keïta, Carlos Malta, & Bernardo Aguiar — ‘Soro’
200 years ago, the sky went dark and there was no summer
Ishaan Tharoor writes: As summer approaches, many in the United States will be awaiting warmer, balmier days. It’s a prospect keenly felt right now by those in the nation’s capital, which has endured two weeks of ceaseless rain.
But things could be much worse. Two hundred years ago, the U.S. Eastern Seaboard registered record-low temperatures. On June 6, 1816, six inches of snow fell across wide swaths of New England. “The heads of all the mountains on every side were crowned with snow,” one area farmer wrote. “The most gloomy and extraordinary weather ever seen.”
A Connecticut clockmaker recalled at the time having to wear an overcoat and mittens for much of the summer; another bookkeeper noted in his diary that “the vegetation does not seem to advance at all.” Frosts set in and crops failed. In Montreal, there were reports of frozen birds dropping dead on the city streets. Denizens of Vermont were forced to subsist on “nettles, wild turnips and hedgehogs.”
These early Americans probably did not know the cause of the epic cold spell: A year prior, after months of rumbling, a colossal eruption occurred at Mount Tambora, on a small island in what was then the Dutch East Indies and is now Indonesia. Millions of tons of ash and sulfurous gas went dozens of miles up into the stratosphere, creating a kind of dusty veil around the planet and plunging part of Asia in darkness. [Continue reading…]
Missing mitochondria show life doesn’t relentlessly pursue complexity
Sarah Kaplan writes: Life on Earth used to be simple.
Once upon a time, every organism on the planet was a single, simple cell. Scientists call them prokaryotes. They are about as basic as a living thing can be — just little balloons of DNA and protein, with no grander goals in life than to swim around, eat and occasionally duplicate themselves to produce more swimmers and eaters.
Then, about 1.5 billion years ago, something strange and spectacular happened. One prokaryote engulfed another, and instead of digesting it, he put the little guy to work. They established an endosymbiotic relationship: The smaller internal cell performed lots of helpful tasks — such as making energy and building proteins — and in exchange, the bigger cell kept it safe and well-fed. This lucky bit of teamwork gave rise to the complex (a.k.a. eukaryotic) cell that exists today, from curious single-celled protists to the cells that make up all plants, fungi and animals — including us.
The eukaryotes are a weird and diverse lot, but at the cellular level we’ve all got the same basic components: a nucleus to store our DNA, and mitochondria — the descendants of that ancient swallowed organism — to make energy and perform other essential functions. Other internal structures, called organelles, may vary, but those two are so universal that biologists assumed we couldn’t exist without them.
“They’re part of the definition of eukaryotic cell,” said Anna Karnkowska, an evolutionary biologist at the University of British Columbia. “If you open a biology textbook to a picture of a eukaryotic cell, that’s what you’ll see.”
Which is why she was so shocked to find a eukaryote that didn’t have any mitochondria at all: a single-celled relative of the giardia parasite called Monocercomonoides.
The discovery, which Karnkowska made with other biologists when she was a post-doctoral fellow at Charles University in Prague, seems to rip up that textbook illustration. One of her co-authors compared it to finding a city with no utilities or public works department.
“This is the first example of a eukaryote lacking any form of a mitochondrion,” the researchers write in their study, which was published Thursday in the journal Current Biology, “demonstrating that this organelle is not absolutely essential for the viability of a eukaryotic cell.” [Continue reading…]
Music: Omar Sosa — ‘Ternura’
How do we know the distance to the stars?
Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars. — Carl Sagan
Ethan Siegel writes: To look out at the night sky and marvel at the seemingly endless canopy of stars is one of the oldest and most enduring human experiences we know of. Since antiquity, we’ve gazed towards the heavens and wondered at the faint, distant lights in the sky, curious as to their nature and their distance from us. As we’ve come to more modern times, one of our cosmic goals is to measure the distances to the faintest objects in the Universe, in an attempt to uncover the truth about how our Universe has expanded from the Big Bang until the present day. Yet even that lofty goal depends on getting the distances right to our nearest galactic neighbors, a process we’re still refining. We’ve taken three great steps forward in our quest to measure the distance to the stars, but we’ve still got further to go.
The story starts in the 1600s with the Dutch scientist, Christiaan Huygens. Although he wasn’t the first to theorize that the faint, nighttime stars were Suns like our own that were simply incredibly far away, he was the first to attempt to measure their distance. An equally bright light that was twice as far away, he reasoned, would only appear one quarter as bright. A light ten times as distant would be just one hundredth as bright. And so if he could measure the brightness of the brightest star in the night sky — Sirius — as a fraction of the brightness of the Sun, he could figure out how much more distant Sirius was than our parent star. [Continue reading…]
