Safecast is a network of volunteers who came together to map radiation levels throughout Japan after the Fukushima Diiachi nuclear power plant disaster in 2011. They soon realized radiation readings varied widely, with some areas close to the disaster facing light contamination, depending on wind and geography, while others much further away showed higher readings. Safecast volunteers use Geiger counters and open-source software to measure the radiation, and then post the data online for anyone to access. Broadcasting from Tokyo, we are joined by Pieter Franken, co-founder of Safecast. “The first trip we made into Fukushima, it was an eye-opener, first of all, the radiation levels we encountered were way higher than what we had seen on television,” Franken says. “We decided to focus on measuring every single street as our goal in Safecast, so for the last three years we have been doing that, and this month we are passing the 15 millionth location we have measured, and basically every street in Japan has been at least measured once, if not many, many more times.”