El reloj de arena magnético

Inside a normal egg timer the grains will always form a shallow conical mound in the lower bulb. The new grains then fall onto the tip of the cone before they slide down the side. If you put your Magnetic Egg Timer onto its wooden stand, something completely different happens: although the grains fall through the hole as usual, they form a spiky, hedgehog-like structure at the bottom of the lower bulb. Only when you lift the egg timer off its stand, the spiky structure disappears and turns into the normal cone.