Will Japan retrieve an asteroid sample?

The Japanese mission to bring back a sample of an asteroid, are changes in Earth's magnetic field linked to climate change, what causes tip-of-the-tongue experiences when you cannot remember a word, why does the Moon look much larger on the horizon, how do farts form and can farts be harnessed to power things? And is a TV screen next to my bed bad for me? Will mobile phone use do me harm? Why flowers and chocolates for Valentine's Day? Join Dr Chris for this week's crop of questions and answers...