Naked Scientists Podcast -17th Jun 2012 - Why does a head injury, or standing up too quickly, make us "see stars"? Are slug pellets painful? How do flies fly in an elevator? We take on your science questions this week, and find out why we should let food ferment, what makes batteries get hot and if the strings in string theory are real. Plus, a new drive to improve science education, new vistas for Voyager 1 and new veins from stem cells.