Why don’t flames have shadows? It’s because a flame is a chemical salad full of wax and oxygen molecules that are burning, along with carbon dioxide, water vapor, hot air, and unburnt solid fuel particles that are so hot they’re glowing incandescently. The flame is only a quarter as dense as the surrounding air, so light can pass right through it. Whatever shadow is created can be easily filled in by the glow of the flame itself. When light passes from the hot flame to the cooler air, we get ghostly distortions of intensity that are the only evidence that anything’s there.