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:

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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.

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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:

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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.
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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.

Here’s a thread about the fundamental constituents of the universe, as explained by @nattyover, with graphics by Samuel Velasco and @LucyIkkanda. In the 1970s, physicists formed a framework that encapsulates our best understanding of nature’s fundamental order. Yet most visualizations of the Standard Model of particle physics are too simple, ignore important interconnections or are overwhelming.

Time has fascinated the human mind for millennia. Through the vantage points of culture, physics, timekeeping and biology, we have compiled a special timeline organizing some of the efforts that humans have made to understand time. (thread) quantamagazine.org/what-is-time-a… Western culture tends to emphasize a linear conception of time, but the ancestors of today’s Australian aboriginal peoples embraced a timeless view of nature. In Asia, followers of Hinduism and Buddhism adopted a cyclic view.

The revered condensed matter physicist Philip Anderson passed away yesterday at the age of 97. Here is a sampling of some of Anderson’s ideas that have propelled modern physics. (Thread) Anderson won the 1977 Nobel Prize in Physics for his discovery of what is now called Anderson localization, a phenomenon in which some waves stay within a given “local” region rather than advancing freely.

Most of us imagine the universe as extending forever in all directions. Does it have to be so? (Thread)
quantamagazine.org/what-is-the-ge… After all, because of the planet’s very subtle curvature, everyone once thought that the Earth was flat. Now, of course, we know it’s shaped like a sphere.

Rock-paper-scissors is a classic problem in game theory that’s also a touchstone concept in biology because of its relevance to evolution and ecology. ✊🤚✌️
Here’s why.
A thread: (1/9) Since 1960, biologists have pondered “the paradox of the plankton”: How can ecosystems stably hold so many competing species? Why doesn’t the fittest eliminate the rest? (2/9)