(Correct me if I am wrong as I am a novice in the area of chemistry) - If an element has a half-life of 10 years, half of its mass would turn into a daughter element. After another ten years, another half of it would decay, so that after 30 years only 12.5% of the mass of the original element remains. Therefore, the rate of decay slows down. If we have a 15 kg sample of that element, we know that 7.5 grams will mutate after a decade. However, what if we managed to make a pure planet sized (diameter = 8000 km) sample of that element? How can half of that huge mass decay in the same amount of time (only ten years)? Because there is so little time to mutate so much mass, wouldn't the transformation be visible? Additionally, if the planet is fragmented, would the rate of decay change?