Quanta Magazine

For evolutionary biologists, what most distinguishes the marine creatures called cnidarians and ctenophores is not the peculiar spelling of their names, nor the fact that they tend to be beautiful, but that they are among the oldest known groups of complex animals. Cnidarians (the “c” is silent) include jellyfish, corals and sea anemones, and their colorful tendrils and fronds adorn oceans all over the globe. Ctenophores (another silent “c”), otherwise known as comb jellies, are mostly translucent and gelatinous, and they pulse through the marine world like ectoplasm.

Thought to have arisen between about 740 million and 520 million years ago, both phyla of marine invertebrates were among the first multicellular animals to evolve several different tissue types. Their appearance ramped up the complexity of the animal world: They are more similar to us in terms of size and organization than they are to the single-celled organisms that came before them. The evolutionary debut of cnidarians and ctenophores thus represented one of the most significant steps in the journey from primordial slime to humans.

What made it possible?

Sebé-Pedrós and his colleagues believe that what made these new patterns of gene regulation and expression possible in the earliest complex animals was a rather bizarre gambit that all multicellular creatures now employ. It involves pulling loops of DNA out of the tangled mass of the chromosomes, and letting the loops undergo topologically complicated contortions to put one part of the chromosome in contact with other parts far away. The origin of animal complexity might literally have been loopy.

🧬 Read the full story: www.quantamagazine.org/loops-of-dna-equipped-ancie…

🎨 Myriam Wares for Quanta Magazine

4 days ago | [YT] | 784

Quanta Magazine

If there’s one law of physics that seems easy to grasp, it’s the second law of thermodynamics: Heat flows spontaneously from hotter bodies to colder ones. But now, gently and almost casually, Alexssandre de Oliveira Jr. has just shown me I didn’t truly understand it at all. 
 
Take this hot cup of coffee and this cold jug of milk, the Brazilian physicist said as we sat in a café in Copenhagen. Bring them into contact and, sure enough, heat will flow from the hot object to the cold one, just as the German scientist Rudolf Clausius first stated formally in 1850. However, in some cases, de Oliveira explained, physicists have learned that the laws of quantum mechanics can drive heat flow the opposite way: from cold to hot. 
 
This doesn’t really mean that the second law fails, he added as his coffee reassuringly cooled. It’s just that Clausius’ expression is the “classical limit” of a more complete formulation demanded by quantum physics.
 
Physicists began to appreciate the subtlety of this situation more than two decades ago and have been exploring the quantum mechanical version of the second law ever since. Now, de Oliveira, a postdoctoral researcher at the Technical University of Denmark, and colleagues have shown that the kind of “anomalous heat flow” that’s enabled at the quantum scale could have a convenient and ingenious use. 
 
It can serve, they say, as an easy method for detecting “quantumness” — sensing, for instance, that an object is in a quantum “superposition” of multiple possible observable states, or that two such objects are entangled, with states that are interdependent — without destroying those delicate quantum phenomena. Such a diagnostic tool could be used to ensure that a quantum computer is truly using quantum resources to perform calculations. It might even help to sense quantum aspects of the force of gravity, one of the stretch goals of modern physics. 

🔗 Keep reading: www.quantamagazine.org/a-thermometer-for-measuring…

🎨 Daniel Garcia for Quanta Magazine

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1 week ago (edited) | [YT] | 812

Quanta Magazine

In 2010, biologists made a shocking discovery. Living in the mud of the North Sea were microorganisms whose genes looked a lot like ours. Genetic analysis revealed that humans, oak trees, blue whales — any living things whose cells have nuclei and mitochondria — are related to these microbes, which were named the Asgard archaea after the home of the Norse gods. Two billion years ago, it was an ancestor of an Asgard that diverged from its kin and eventually became us.

No one knows precisely how that happened, and for a long time, no one even knew what these long-lost cousins looked like. Asgard DNA could be fished out of the mud and studied, but the cells themselves were so rare and hard to grow in the lab that no one could scrutinize them under the microscope. There was an explosion of speculation among scientists about what they would be like. Would they be big? Small? Covered with tentacles, shaped like rods, perfectly spherical? Do their cells look like ours inside, or are they completely different?

Little by little, researchers have worked out ways to grow them and watch as they go about their lives. Now, some of the first reports about the biology of certain Asgards are revealing new, provocative details about the interior lives of these cells. The latest paper, from the labs of Martin Pilhofer at ETH Zurich and Christa Schleper at the University of Vienna, describes how a portion of their cytoskeleton — the set of cellular structures that give a cell its shape — is surprisingly similar to what can be found in more complex organisms such as ourselves.

🔗 Read the full story: www.quantamagazine.org/tiny-tubes-reveal-clues-to-…

🎨 Credit
1, 2: Torsten Wittmann/Science Source
3: Vera Hartmann; Courtesy of Schleper Lab

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1 month ago | [YT] | 1,077

Quanta Magazine

All the activity on Earth’s surface — erupting volcanoes, shifting tectonic plates, restless seas and myriad forms of life — depends on the two-part engine under the hood. Directly beneath Earth’s crust lies the mantle: rock that melts, churns and flows like putty, driving the volcanic and tectonic activity at the surface. And below that, there’s the outer core, a liquid-metal ocean whose swirling streams surround the planet with a protective magnetic field.

A longtime assumption of geoscientists is that the boundary between the mantle and the outer core is clear and severe. After all, lighter mantle rock should essentially float atop the denser metallic core. But a recently published pair of studies tells a surprising story, one that was already suspected: Earth’s core is leaking material. This stuff is making its way right up to the surface, potentially ferried through two monster-size blobs sitting at the core-mantle boundary.

This “is kind of crazy,” said Harriet Lau, a geodynamicist at Brown University who was not involved with either study. If material is effusing from the core into the mantle, is the boundary between them “as distinct as we think?”

The research concludes that this abyssal wall has doorways.

🌋 Keep reading: www.quantamagazine.org/earths-core-appears-to-be-l…

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2 months ago | [YT] | 802

Quanta Magazine

Take a deep breath. A flow of oxygenated air has rushed into your lungs and bloodstream, fueling metabolic fires in cells throughout your body. You, being an aerobic organism, use oxygen as the cellular spark that frees molecular energy from the food you eat. But not all organisms on the planet live or breathe this way. Instead of using oxygen to harvest energy, many single-celled life forms that live in environments far from oxygen’s reach, such as deep-sea hydrothermal vents or stygian crevices in the soil, wield other elements to respire and unlock energy.

This physical separation of the oxygen-rich and oxygen-free worlds is not merely a matter of life utilizing available resources; it’s a biochemical necessity. Oxygen doesn’t play nice with the metabolic pathways that make it possible to respire with the use of other elements, such as sulfur or manganese. It gives aerobes like us life, but for many anaerobes, or creatures that respire without oxygen, it is a toxin that reacts with and damages their specialized molecular machinery.

“Oxygen — we love it, of course,” said Courtney Stairs, an evolutionary biologist at Lund University in Sweden. “But it’s actually a pretty harmful molecule for most of life on our planet, and even ourselves. We have ways to mitigate the negative effects of oxygen. So we can’t imagine life without it, but life is actually quite hard with it.”

For the first couple billion years of life on Earth, organisms avoided this predicament altogether. Back then, the air and oceans were mostly devoid of oxygen, so life was almost entirely anaerobic. Then, around 2.7 billion years ago, the seas filled with industrious, photosynthetic cyanobacteria. They had invented a way to turn sunlight into sugar and oxygen, and they flourished. Over hundreds of millions of years, their accumulated breathing filled the atmosphere and oceans with oxygen. This so-called Great Oxidation Event was a pivotal transformation in the biosphere and the physical chemistry of Earth’s atmosphere and oceans. In this new environment, aerobic respiration evolved to dominate the world.

An ongoing mystery for researchers is how life navigated the shift from anaerobic to aerobic respiration; so much microbial biodiversity had to adapt to a world filled with what was once a biochemical bane. Now researchers have fresh insight into what that transition could have looked like billions of years ago, gleaned from an organism living today. A bacterium that researchers collected from the cauldron of a Yellowstone National Park hot spring does something that life really shouldn’t be able to do: It runs aerobic and anaerobic metabolisms simultaneously. It breathes oxygen and sulfur at the same time.

🔗 Keep reading: www.quantamagazine.org/the-cells-that-breathe-two-…
📸 Eric Boyd

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2 months ago | [YT] | 655

Quanta Magazine

There are precision measurements, and then there’s the Laser Interferometer Gravitational-Wave Observatory. In each of LIGO’s twin gravitational wave detectors (one in Hanford, Washington, and the other in Livingston, Louisiana), laser beams bounce back and forth down the four-kilometer arms of a giant L. When a gravitational wave passes through, the length of one arm changes relative to the other by less than the width of a proton. It’s by measuring these minuscule differences — a sensitivity akin to sensing the distance to the star Alpha Centauri down to the width of a human hair — that discoveries are made.

The design of the machine was decades in the making, as physicists needed to push every aspect to its absolute physical limits. Construction began in 1994 and took more than 20 years, including a four-year shutdown to improve the detectors, before LIGO detected its first gravitational wave in 2015: a ripple in the space-time fabric coming from the faraway collision of a pair of black holes.

Physicist Rana Adhikari led the detector optimization team in the mid-2000s. He and a handful of collaborators painstakingly honed parts of the LIGO design, exploring the contours of every limit that stood in the way of a more sensitive machine.

But after the 2015 detection, Adhikari wanted to see if they could improve upon LIGO’s design, enabling it, for instance, to pick up gravitational waves in a broader band of frequencies. Such an improvement would enable LIGO to see merging black holes of different sizes, as well as potential surprises. “What we’d really like to discover is the wild new astrophysical thing no one has imagined,” Adhikari said. “We should have no prejudice about what the universe makes.”

He and his team turned to AI. Initially, the AI’s designs seemed outlandish. “The outputs that the thing was giving us were really not comprehensible by people,” Adhikari said. “They were too complicated, and they looked like alien things or AI things. Just nothing that a human being would make, because it had no sense of symmetry, beauty, anything. It was just a mess.” But the design was clearly effective.

🔗 Keep reading: www.quantamagazine.org/ai-comes-up-with-bizarre-ph…

Art Credit
🎨 1, 3: Señor Salme for Quanta Magazine
📸 2: Steve Babuljak

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2 months ago | [YT] | 880

Quanta Magazine

The universe is not always smooth — at the centers of black holes, for instance, the curvature of space-time explodes to infinity, forming a singularity., Whenever space-time isn’t sufficiently smooth, the 10 interconnected differential equations underlying Albert Einstein’s general theory of relativity stop working.

In October 2015, a young mathematician named Clemens Sämann was flying home to Austria from a conference in Turin, Italy, when he had a chance encounter. He found himself seated beside Michael Kunzinger, another conference attendee. Kunzinger was a math professor at the University of Vienna, where Sämann had just started his postdoctoral research. They soon got to talking, and landed on Einstein’s general theory of relativity and its limitation to smooth space-times. They wondered whether there was a mathematical way to get around this limitation.

The pair wouldn’t start working on the problem in earnest for another year. But since then, they’ve made significant advances toward their goal. They’ve found new ways to estimate curvature and other geometric properties without relying on the assumption that space-time is smooth. In collaboration with other researchers, they’ve used their methods to rederive (and sometimes strengthen) core theorems about the universe without depending on Einstein’s equations, putting those theorems on even firmer mathematical footing.

And they’re now part of an ambitious new program — launched last year under the direction of Roland Steinbauer, another University of Vienna mathematician — that aims to provide “a new geometry for Einstein’s theory of relativity and beyond.”

“Standard general relativity talks about geometric objects, namely space-times, but only if they behave nicely enough,” Steinbauer said. “With this new framework, we can go beyond that. We can handle very edgy objects, very badly behaved objects.”

Read the full story: www.quantamagazine.org/a-new-geometry-for-einstein…

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1: @harolbustos for Quanta Magazine
3: Der Knopfdrücker; Joseph Krpelan
4: @artscistudios/Quanta Magazine

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2 months ago | [YT] | 1,180

Quanta Magazine

Climate models have changed the way we view the world. While effective, these models are imperfect, and scientists are constantly looking at ways to improve their accuracy and predictability.

MIT professor Elfatih Eltahir has spent decades developing complex models to understand how climate change affects vulnerable regions like the Nile Basin and Singapore. In this episode of The Joy of Why, Eltahir tells co-host Steven Strogatz how growing up near the Nile in Sudan helped him realize that climate change doesn’t occur in isolation. To better understand climate-related impacts and to create more effective adaptation strategies, Eltahir says we need regional models that incorporate contextual data like disease spread and population growth. Eltahir also discusses his “Equation of the Future of Africa,” and he introduces the concept of “outdoor days,” which he hopes can improve public perception about climate change.

🎧 Listen to the episode: www.quantamagazine.org/how-can-regional-models-adv…

🎨 Peter Greenwood for Quanta Magazine; Logo by Jaki King for Quanta Magazine

3 months ago | [YT] | 435

Quanta Magazine

Randomness is a source of power. From the coin toss that decides which team gets the ball to the random keys that secure online interactions, randomness lets us make choices that are fair and impossible to predict. 

So instead, programmers often rely on things called hash functions, which swirl data around and extract some small portion in a way that looks random. For decades, many computer scientists have presumed that for practical purposes, the outputs of good hash functions are generally indistinguishable from genuine randomness — an assumption they call the random oracle model.

“It’s hard to find today a cryptographic application… whose security analysis does not use this methodology,” said Ran Canetti of Boston University.

Now, a new paper has shaken that bedrock assumption. It demonstrates a method for tricking a commercially available proof system into certifying false statements, even though the system is demonstrably secure if you accept the random oracle model. Proof systems related to this one are essential for the blockchains that record cryptocurrency transactions, where they are used to certify computations performed by outside servers.

There’s “a lot of money relying on this stuff,” said Eylon Yogev of Bar-Ilan University in Israel. For blockchain proof protocols, “there’s a huge motivation for attackers to break the security of the system.”

In the new paper — by Dmitry Khovratovich of the Ethereum Foundation, Ron Rothblum of the zero-knowledge proof technology company Succinct and the Technion in Haifa, Israel, and Lev Soukhanov of the blockchain-focused start-up [[alloc] init] — the researchers are able to prove lies no matter which hash function is used to generate the “randomness” the proof system relies upon.

When Yogev heard about the team’s result, he said, “I had the feeling that someone is pulling the carpet from under my feet.” He and others have been working to patch up these vulnerabilities. But “it’s far from being a solved issue,” he said.

More broadly, the new result is forcing a reckoning about the random oracle model. “This is a time to rethink,” Canetti said.

🎨 Wei-An Jin/Quanta Magazine

🔗 Read the full story: www.quantamagazine.org/computer-scientists-figure-…

3 months ago | [YT] | 677

Quanta Magazine

When Thomas Hummel gets a whiff of an unripe, green tomato, he finds himself in his childhood home in Bavaria. Under the tilted ceilings of the bedroom that he shared with his two older brothers, there were three beds, a simple table and a cupboard. “My mother put those green tomatoes on the cupboard for them to ripen,” said Hummel, an olfaction researcher at the Carl Gustav Carus University Hospital in Germany. “They have this very specific smell.”

It’s grassy, green, pungent, rough and bitter, he said. When he passes by a bin of tomatoes at the market today, “it is always to some degree emotional,” he said, “like every smell is emotional.”

Smell is deeply tied with the emotion and memory centers of our brain. Lavender perfume might evoke memories of a close friend. A waft of cheap vodka, a relic of college days, might make you grimace. The smell of a certain laundry detergent, the same one your grandparents used, might bring tears to your eyes.

Smell is also our most ancient sense, tracing back billions of years to the first chemical-sensing cells. But scientists know little about it compared to other senses — vision and hearing in particular. That’s in part because smell has not been deemed critical to our survival; humans have been wrongly considered “bad smellers” for more than a century. It’s also not easy to study.

“It’s a highly dimensional sense,” said Valentina Parma, an olfactory researcher at the Monell Chemical Senses Center in Philadelphia. “We don’t know exactly how chemicals translate to perception.” But scientists are making progress toward systematically characterizing and quantifying what it means to smell by breaking the process down to its most fundamental elements — from the odor molecules that enter your nose to the individual neurons that process them in the brain.

Several new databases, including one recently published in the journal 𝘚𝘤𝘪𝘦𝘯𝘵𝘪𝘧𝘪𝘤 𝘋𝘢𝘵𝘢, are attempting to establish a shared scientific language for the perception of molecular scents — what individual molecules “smell like” to us. And on the other end of the pathway, researchers recently published a study in 𝘕𝘢𝘵𝘶𝘳𝘦 describing how those scent molecules are translated into a neural language that triggers emotions and memories.

Together, these efforts are painting a richer picture of our strongest memory-teleportation device. This higher-resolution look is challenging the long-held assumption that smell is our least important sense.

👃Read the full story: www.quantamagazine.org/how-smell-guides-our-inner-…

🎨 Michael Waraksa for Quanta Magazine

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3 months ago | [YT] | 601