Resumen de Ask the experts.

Stephen Morris, Jeremy Claude Barnes

• This article offers questions from readers. One reader wants to know why stalagmite-like spikes form in ice cubes. Professor Stephen Morris explains the physics behind water freezing and says rapid cooling forms more spikes in the crystals. Another reader asks if sleeping after a meal leads to weight gain. Professor Jeremy Barnes says that sleeping itself is not a cause of weight gain but it is the balance of calories in and calories out.