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I recently saw vodka in the supermarket with real gold leaf flakes in it. What caught my eye was that the gold flakes were distributed uniformly throughout the bottle. Gold is much denser than water, so why don鈥檛 they sink to the bottom?

鈥� Left long enough, the gold flakes will fall to the bottom of the bottle. The reason they remain fairly evenly distributed is that they are small and light enough to keep floating. Gold is incredibly malleable, meaning it can easily be worked into flakes a thousandth of a millimetre thick.

Energy from the bottles being moved around periodically, or from floor vibrations as people walk past, and convection currents from temperature changes in the liquid are enough to disturb the flakes and set them floating. The same effect applies to dust, soot and smoke particles in the air.

Ian Gordon, Camberley, Surrey, UK

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