Why do boats have round portholes?

Shortages of cooking oil, risks of being hit by lightning and can lightning travel through your plumbing; why boats have round portholes; what's the memory capacity of a human brain; can we measure happiness; do animals feel happy and sad like we do; what gives farts their unique characteristics, and why do stars twinkle? Lester and Dr Chris have the answers... Like this podcast? Please help us by supporting the Naked Scientists