Take for example the extinction of dinosaurs; no one really knows what happened so that is then scientific theory.
You might find them all disagreeing with each other as to what really happened. It will have the same shape as the original object, but is actually more like rock.
From these fossils, they’re also able to create models of stuff they’ve found, so that we can see what they looked like.
They study those fossils very, very carefully and it helps them to understand how Earth has changed, for example, how climate has changed.
Was it a comet, was it a volcano…they all believe different things. The fossils of bones don’t actually have any bones in them. No one knows for sure when the first fossils were found, but it is thought that the Greeks and Romans might even have found fossils.