No Breakthrough Yet: Stephen Hawking's Interstellar 'Starshot' Faces Challenges

On Tuesday (April 12), a group of scientists, engineers and investors announced Breakthrough Starshot, a$100 million initiative to study sending tiny robotic probes to the nearest starsystem beyond the sun, Alpha Centauri, within a generation. The project's architects envision building numerous spacecraft, each the size of a postage stamp and each equipped with a gossamer sail made of reflective material. A giant array of ground-based lasers would fire pulses at these miniprobes, whose sails wou