This image shows the nebula in the constellation Orion. Within this nebula, new suns are forming as the dust cloud slowly condenses. These proplyds as they are called will theoretically condense even further to form planetary systems surrounding the star. Studies of meteorites tell geologists and astrophysicists about the age of our solar system. Whatever the origin, they are materials from the beginnings of our solar system that have changed relatively little since their original formation as rocks.
Geologists use radioactive age dating methods to determine the ages of rocks.
Certain atoms in the rock spontaneously change into different atoms over time through radioactive decay. This is a tremendous simplification, but basically it is somewhat like counting rings in a tree to see how old it is. Many meteorites age-date at about 4.6 billion years. This is the currently accepted age of the Earth. To give you an idea of just how big this number is, let's pretend that you wanted to count to 4.6 billion.