One interesting thing about this is that it represents a race, between the concentration of Uranium in high-grade ores through geological processes (which requi

One interesting thing about this is that it represents a race, between the concentration of Uranium in high-grade ores through geological processes (which requires the Earth to have formed, and so on and so on) on the one hand and the reduction in abundance of U-235 in natural Uranium over time due to radioactive decay.