Can I Crush my capsules?

What stops water moving through a tiny hole, are ground up tablets safe to swallow, what are freckles, how fast can a human heart beat, what happens when a cataract is removed, where do fat flies come from and how does the moon influence the Earth? Join Dr Chris as he pits his wits against this week's round up of science questions from South Africa... Like this podcast? Please help us by supporting the Naked Scientists