Age of meteorites and the earth

Within experimental error, meteorites have one age as determined by three independent radiometric methods. The most accurate method (Pb ²⁰⁷/Pb ²⁰⁶ gives an age of 4.55 ± 0.07 × 10 ⁹yr. Using certain assumptions which are apparently justified, one can define the isotopic evolution of lead for any meteoritic body. It is found that earth lead meets the requirements of this definition. It is therefore believed that the age for the earth is the same as for meteorites. This is the time since the earth attained its present mass