On some nights Pi thinks he sees light in the distance, and he sends up a flare, but nothing ever comes of it. He recognizes that the area he can see is only a five-mile circle, so he has little hope of being rescued in the vast Pacific. The flares always smell like cumin to Pi, and they make him dream of Pondicherry.
Pi puts all his hope into reaching land instead of looking for a ship. In the brain smells can be closely related to strong memories, so the flares (which smell of cumin, a spice often used in Indian food) conjure up Pi’s childhood at Pondicherry.