Wildfires worldwide, and algae microbots for drug delivery

In this week's show, wildfires continue to race across the world in Canada, Ireland, Scotland and Italy. Why are they happening, and what can we do to prevent them? Plus, scientists track neighbourhood food consumption from DNA in sewage, the first evidence of an "exomoon" orbiting a planet outside our solar system, and how tiny "algebots" can deliver cancer chemotherapy in the bladder. What makes…