Traffic is the expression of human purpose.
--Tom Vanderbilt, Traffic

On residential streets, engineers attempt to control car speeds by installing traffic-calming devices . You probably know all about the venerable speed bump , but these days you’re more likely to drive over the lower and wider speed hump or the even wider speed table . Many people refer to these generally as sleeping policemen , a richly evocative, perhaps even poetic locution.

In 1861, when the few steam-powered automobiles around were known as road locomotives (or light locomotives), the British Parliament established the world’s first speed limit of 10 miles per hour (16 kilometers per hour). In 1865 a revised law slashed it to 4 mph in the country and 2 mph in towns and villages. Apparently alarmed by even these modest speeds, Parliament also decreed the world’s first traffic-­calming devices: each vehicle had to be preceded by a person walking 60 yards (about 55 meters) ahead and waving a red flag to warn others of the vehicle’s approach.

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The Future of Deep Learning Is Photonic

Computing with light could slash the energy needs of neural networks

10 min read

This computer rendering depicts the pattern on a photonic chip that the author and his colleagues have devised for performing neural-network calculations using light.

Alexander Sludds

Think of the many tasks to which computers are being applied that in the not-so-distant past required human intuition. Computers routinely identify objects in images, transcribe speech, translate between languages, diagnose medical conditions, play complex games, and drive cars.

The technique that has empowered these stunning developments is called deep learning, a term that refers to mathematical models known as artificial neural networks. Deep learning is a subfield of machine learning, a branch of computer science based on fitting complex models to data.

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