The mathematician John Conway didn’t fit into a box.

🧵 Conway’s first love was geometry. In 1966, he discovered the symmetries of the Leech lattice, a 24-dimensional structure with lots of applications. Mathematicians later proved that it gave the densest possible way to pack spheres in 24-dimensional space — each sphere touches 196,560 others.

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In chaotic systems, the smallest fluctuations get amplified. As scientist Edward Lorenz put it in the 1960s and 70s, even a seagull flapping its wings might eventually make a big difference to the weather. Here's how scientists came to understand what chaos is, and how to wrangle it:

🧵 350 BC: Even the ancients knew that small changes can have large and seemingly unpredictable effects. In On The Heavens, Aristotle wrote, “The least initial deviation from the truth is multiplied later a thousandfold.”

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Cosmic forces interact with our bodies every day, sometimes in surprising ways.

🧵 The universe is ruled by four forces:
1. The electromagnetic force, which guides the behavior of light and charged particles
2. The weak force, which rules radioactive decay
3. The strong force, which holds nuclei together
4. Gravity, which causes objects to attract

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Andrew Barto and Richard Sutton have won the A.M. Turing Award for developing the theoretical foundations of reinforcement learning, a key method behind many major breakthroughs in artificial intelligence. 🧵
In reinforcement learning, AI systems are trained to accomplish tasks using “reward” signals that steer them toward useful actions. In the 1980s, Barto and Sutton devised mathematical techniques that made this basic idea applicable to many different problems. 2/6 buff.ly/mLfJu3M

Why were the first drawings of neurons defaced?

🧵1/9 At the turn of the 20th century, Spanish pathologist and artist Santiago Ramón y Cajal became the first person to realize that every neuron in the brain is a separate cell. For this work, he was awarded the 1906 Nobel Prize.

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What is space dust?

🧵 (1/11) Tiny rocks, known as space or cosmic dust, speckle the otherwise empty space between planets and stars. Some float to Earth from hundreds of millions of miles away, falling to the ground as micrometeorites. Round and multicolored like tiny marbles, each bears
a distinctive message.

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Here are some of the biggest breakthroughs in physics this year 🧵 The largest-ever 3D map of the cosmos has sent theoretical physicists to their blackboards. The data hinted that dark energy — a mysterious, repulsive form of energy that permeates the universe — may be weakening. quantamagazine.org/dark-energy-ma…

Albert Einstein upended our view of the universe by merging space and time into a single dynamic fabric. Now, many physicists are coming to their own radical realization: The fabric of space-time seems to emerge from something else. 🧵 What does it mean for nature’s fundamental building blocks to exist outside of space and time?

How could such entities ever be described?

And why do physicists think it’s true?

Today, Quanta is wrangling with these questions in “The Unraveling of Space-Time,” a collection of articles, graphics, explainers, interviews and a video exploring physicists’ quest for the fundamental nature of reality.

Here’s what you’ll find:

2/quantamagazine.org/the-unraveling…

New brain imaging research, published today in @Nature, suggests that psilocybin, the active compound in “magic mushrooms,” generates psychedelic experience by disrupting the brain's default mode network. But what is the default mode network? 🧵nature.com/articles/s4158… It was first characterized in 2001 when the neurologist Marcus Raichle studied people’s brain activity while they weren’t doing anything in particular — they let their minds wander. He dubbed the active areas the “default mode” of the brain.

2/6quantamagazine.org/what-your-brai…

Proteins do it all. Hemoglobin ferries oxygen around the body. Keratin structures hair, nails and skin. Insulin helps glucose convert into energy.

The fold of a protein is critical to its function. Yet no one really knows specifically how protein folding happens.

1/15 It’s the early 1960s. Biologists are growing proteins into crystals, bombarding them with X-rays and measuring how the rays bend — a technique known as X-ray crystallography.

From there, they create ball and stick models. Every finished model represents years of work.

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Today, we published our annual list of the year’s biggest discoveries in computer science. Here are a few of the stories that we included 🧵 Why is it hard to understand what makes hard problems hard? The mission to quantify practical solvability defines a field of computer science called meta-complexity. This year, Quanta dove into this puzzle in an extended article and short documentary. quantamagazine.org/complexity-the…

Computer scientists often study how difficult certain problems are to solve. But a subset of them are fascinated by a more complex question: How hard is it to determine how hard those problems are?

This field is known as meta-complexity. 🧵 Meta-complexity focuses on the differences in difficulty between certain types of computational problems. For example, Hamiltonian paths (paths that pass through every point of a graph) become exponentially harder to compute as the graphs grow larger.

Yesterday we published an article with the headline “Physicists Create a Wormhole Using a Quantum Computer.” It described the efforts by a team of physicists led by Maria Spiropulu of Caltech to implement a “wormhole teleportation protocol” on a quantum computer. (1/10) As the article details, the work is an experimental exploration of “holographic duality,” which for two decades has been the dominant research thrust in efforts to reconcile quantum mechanics and general relativity. (2/10)

2022 is almost here. Did this year feel like it went by quickly for you, or slowly?

Will you use a clock, a slowly descending mirrorball or three entangled atoms to know when it’s the new year? This is a good time for a thread about time: 🧵⏰ Over the millennia, our clever methods for timekeeping have included sundials, pendulums and strontium lattice clocks. Here’s how inventions to measure time have paralleled efforts to understand what time actually is:

quantamagazine.org/what-is-time-a…

The discoveries covered in Quanta come from real people driven by curiosity, passion and problem solving. Here’s an overview of some of the researchers we interviewed in the magazine and on our YouTube channel this year: 🧵🔬 Millions of years ago, a massive volcanic plume propelled the Indian microcontinent into Eurasia, forming the Himalayas — or so the theory went. In this interview, geologist Lucía Pérez-Díaz explains how she disproved this theory.
quantamagazine.org/the-new-histor…

How do scientists make predictions about systems with millions of different variables? How do relationships between these variables impact a system as a whole? What can these dynamics tell us about Earth?

Here’s more on the winners of the 2021 Nobel Prize in Physics: 🧵 More than a century ago, Svante Arrhenius, a Swedish physicist, developed a climate model that showed the influence of carbon dioxide on Earth’s atmosphere. Arrhenius aspired to strip the planet’s climate down to its essence.

Many have tried and failed to build a perpetual motion machine. That device remains impossible, but physicists now say they’ve built a genuine “time crystal” inside a quantum computer that forever cycles between states without burning energy. (Thread) quantamagazine.org/first-time-cry… A time crystal is the first of a new category of phases of matter, expanding the definition of what a phase is. Its atoms are ordered and perfectly stable, but they exist in an excited and evolving state.

The most ambitious project in math seeks to answer fundamental questions by connecting disparate branches of the field, like calculus and geometry. This effort, known as the Langlands program, recently received a rare gift that has vastly expanded its potential. (Thread) The Langlands program seeks to assemble a mathematical dictionary that uses objects from calculus to investigate polynomials. An adjacent effort seeks to do something similar in geometric terms.

In 1873, the mathematician Georg Cantor shook math to the core when he discovered that infinity comes in many sizes. Setting out to climb the tower of infinities that he created, a mystery stopped him in his tracks. (Thread) There exist an infinite amount of “natural” numbers, like 1, 2 and 3, but Cantor proved that there are even more “real” numbers that sit between the natural numbers on the number line — most with never-ending digits, like 3.14159…. In other words, a larger infinity.

THREAD: The researchers developing epidemiological models are often expected to provide answers where there are none, with a certainty they can’t guarantee. Here is how these models are made, and where their uncertainties lie. (Reporting by @jordanacep) To understand pandemics and other disease outbreaks, scientists turn to two well-established approaches to quantitative epidemiological modeling. Today’s models usually fall on a spectrum between the two.

In the 1970s, Steven Hawking proposed that information that falls into a black hole gets destroyed, never to be retrieved. A series of breakthrough papers have now shown that’s not correct. Here’s a thread about the famous black hole information paradox: According to Einstein’s general theory of relativity, the gravity of a black hole is so intense that nothing can escape it. Hawking’s “semiclassical” approach brought together quantum mechanics and relativity and predicted the famous information paradox.