If you collect up chondrite samples from around the world they can be dated. Using the Rb-Sr method we gain a remarkable result. All the chondrites plot on a straight line - an isochron. Therefore all chondrites formed at the same time out in space. The age of 4.5 billion years dates the formation of the solar system. It means that the formation was not protracted over 100s million years otherwise chondrites would give more scatter. Note that the Rb-Sr system is used here because it is less prone to leaking than , for example potassium - argon. Isotopes could leak during heating that accompanies entry of the meteorite through Earth's atmosphere. For more on meteorites, click here.
