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A Brief History of Money

Or, how we learned to stop worrying and embrace the abstraction

14 min read
Photo: Levi Brown; Prop Stylist: Ariana Salvato
Photo: Levi Brown; Prop Stylist: Ariana Salvato

In the 13th century, the Chinese emperor Kublai Khan embarked on a bold experiment. China at the time was divided into different regions, many of which issued their own coins, discouraging trade within the empire. So Kublai Khan decreed that henceforth money would take the form of paper.

It was not an entirely original idea. Earlier rulers had sanctioned paper money, but always alongside coins, which had been around for centuries. Kublai's daring notion was to make paper money (the chao) the dominant form of currency. And when the Italian merchant Marco Polo visited China not long after, he marveled at the spectacle of people exchanging their labor and goods for mere pieces of paper. It was as if value were being created out of thin air.

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Quantum Computing for Dummies

New guide helps beginners run quantum algorithms on IBM's quantum computers over the cloud

3 min read
An image of the inside of an IBM quantum computer.
IBM

Quantum computers may one day rapidly find solutions to problems no regular computer might ever hope to solve, but there are vanishingly few quantum programmers when compared with the number of conventional programmers in the world. Now a new beginner's guide aims to walk would-be quantum programmers through the implementation of quantum algorithms over the cloud on IBM's publicly available quantum computers.

Whereas classical computers switch transistors either on or off to symbolize data as ones or zeroes, quantum computers use quantum bits, or "qubits," which because of the peculiar nature of quantum physics can exist in a state called superposition where they are both 1 and 0 at the same time. This essentially lets each qubit perform two calculations at once. The more qubits are quantum-mechanically linked, or entangled (see our explainer), within a quantum computer, the greater its computational power can grow, in an exponential fashion.

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This Wearable Neck Patch Can Diagnose Concussions

Self-powered sensors convert neck strain into electrical pulses to detect head trauma in athletes

4 min read
image of back of man's head and shoulders with a patch taped to his lower neck; right image is a time lapse image of a man's head extending far forward and back, simulating a case of whiplash

The prototype patch in this research is shown in (a) on the left; on the right (b) is the kind of head rotation that can yield an electrical response from the patch.

Juan Pastrana

Nelson Sepúlveda was sitting in the stands at Spartan Stadium, watching his hometown Michigan State players bash heads with their cross-state football rivals from the University of Michigan, when he had a scientific epiphany.

Perhaps the nanotechnologies he had been working on for years—paper-thin devices known as ferroelectret nanogenerators that convert mechanical energy into electrical energy—could help save these athletes from the ravages of traumatic brain injury.

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Get the Coursera Campus Skills Report 2022

Download the report to learn which job skills students need to build high-growth careers

1 min read

Get comprehensive insights into higher education skill trends based on data from 3.8M registered learners on Coursera, and learn clear steps you can take to ensure your institution's engineering curriculum is aligned with the needs of the current and future job market. Download the report now!