Call it the audacity of youth. Some 8 million tons of plastic get tossed in the ocean each year, and many experts have given up on the prospect of cleaning it up. But sometimes intractable problems need a dose of crazy thinking. Cue 20-year-old Boyan Slat, who in high school hypothesized that a system of floating barriers would do the trick — and then raised millions of dollars for his idea. Critics may have qualms, but Slat and his team are set to map the ocean’s plastic debris next month. I wish them great luck.