Rock Clocks

You can think of the Solar System as a great big building site. Most of the building finished billion years ago but since then the inhabitants have been indulging in a bit of wear and tear.

The Solar System building site started operations about 4.56 billion years ago. It was then that a star that had been cooking atoms in its nuclear reactor core ran out of fuel and blew up; blasting building materials into the area of space that would become the Solar System.

It can be easy to work out the age of some historic buildings because they have the date they were built carved on one of their stones in a prominent place. Rocks come with their own manufacturing date recorded in the minerals they are made of. It comes in the form of an atomic clock. Some atoms are unstable and decay into different elements at a steady rate. So as soon as rocks solidify, their clocks are set and their unstable atoms start to mark time. By looking at what atoms have disappeared and what have formed, scientists can work out when the rock was made.

Dating a Meteorite

Click the rock on the left to go on the date

Extra resource

Another decay series questions and answer sheet (Word docs), includes use of the concepts - isotope, alpha decay, beta decay, mass number, proton number, half life