Suppose that a scientist finds this dinosaur fossil that has a tooth broken off in it’s spine. It also has several snapped bones. The tooth that is broken off in the dinosaur spine is a pretty large tooth. From this what can you figure must have happened? Another dinosaur that was bigger than the one that had the broken bones and tooth in it must have attacked and killed the other dinosaur. That is a simplified example of how scientists get their ideas of what happened.
Another example is this: A scientist is exploring a new area, when he goes over a hill. Over the hill is a small canyon, there are many layers and kinds of dirt on each steep wall. The edges are jagged and it is fairly deep. What do you think happened here? What must have happened is that this was a river bed but then a huge amount of water or mud probably rushed down this river bed carrying trees and rocks hurtling down the river with it. This then carved a canyon.
These are examples of how a scientist might explain what happened. No one was there or saw it happen, but scientist can get an idea of how it happened by looking at the leftovers from the incident. But sometimes the scientist looks at the leftovers and gets an idea, but it is the wrong idea. What happens at each incident is that many scientists look at what happened and come up with what they think happened. For example a different scientist could look at what happened at the canyon and see something totally different. His theory might be that over millions of years the canyon was carved by the water until it became as it is now. Now we have two different views. What are we going to do? We must examine the facts of both stories and figure out which way makes the most sense to us.
That is what we try to do in this website. We examine both stories and then come up with the best explanation.