A 2,000-foot-long floating boom just left San Francisco on its way to the Pacific Garbage Patch, a gyre of trash between California and Hawaii, with 1.8 trillion pieces of garbage, including 87,000 tons of plastic. The Pacific Garbage Patch is about three times the size of France. The unmanned boom was towed by a ship from the nonprofit Ocean Cleanup, an organization founded by Boyan Slat, a 24-year-old Dutch inventor. Once on site, the boom will detach from the towing vessel. The current is expected to pull it into a U shape, which will trap the plastic as it is…