In which a long-standing and puzzling question is answered [but is also Stuff On My Phone (22)]

When I know I'm going to be stuck on a ferry for a while, journeying between islands or archipelagos, I try to remember to download some radio programmes to my phone, so that I can spend the time catching up on stuff I didn't have the opportunity to listen to live. I'm quite partial to BBC Radio 4's The Life Scientific, The News Quiz and Saturday Live, none of which I'm organised enough to hear when they are originally broadcast.

This Friday evening was no exception, returning to Kirkwall from Lerwick in Shetland, stuck on a ferry for upwards of six hours. After drafting a blogpost (Small Year, Part 2), reading a bit of Barbara Kingsolver non-fiction, having a meal and then tapping my feet to various tunes on my phone, I fired up iPlayer Radio and listened to an edition of Saturday Live from November.

The guests included comedian, writer and presenter Sandi Toksvig, physicist Helen Czerski, reformed armed robber and now professional athlete John McAvoy and Ben Hewett, chair of Harmonica UK. Add into this mix the most lovable presenting duo in entertainment, the cuddly (but sharp as a new pin) Reverend Richard Coles and the most gorgeous laugh in radio, Aasmah Mir, and my troubles just melt away.

This particular episode is quite possibly the best 90 minutes of radio I've ever heard (and there's been several Test Match Special moments to give it a run for its money). The chat and banter was by turns interesting, funny, educational, heart-breaking and uplifting. But, for me, one particular snippet stood out. Helen Czerski was explaining how physics can be a very ordinary, everyday subject, not the confusing, impenetrable science which we often believe it to be. To illustrate this point, she mentioned making a mug of instant coffee and listening to the changing pitch of the sound as we stir the liquid in the mug (at 1 hour and 15 minutes into the programme). From being a very small Tenselet, I have always wondered why this was so! Wow! Fantastic! It's bubbles, apparently, introduced into the mixture by the coffee granules. The bubbles are released when the boiling water is added and sound travels slower through bubbly water, hence the pitch drops as we clang the side of the mug with a spoon. Then, as the bubbles make their way to the surface and escape out into the atmosphere and the liquid becomes less bubbly, the pitch gradually increases back to its original starting point. Yay! Explained! You cannot imagine how thrilled I was to receive this piece of wisdom (albeit two months later than the rest of the Radio 4 listening audience).