Zircon is special because it rejects lead (Pb) when hot, but has no issue incorporating radioactive uranium. A zircon crystal is extracted from a meteorite that fell to Earth. In the zircon, we find about 1 million 235U atoms and 127 million 207Pb atoms. Assume 235U decays to 207Pb with a half-life of 0.6 billion years. How long has it been since the meteorite cooled